2019-12-13

会话(session)

会话他是一个作用域，可以存值，可以取值，session的id一样，就是同一个会话，不一样，就不是同一个会话

实现session有两种形式

cookies(默认)

cookie被禁用，url重写

当cookie被禁用，session不好使了,在提交的后面加一个；jsessionid=session.getid

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n128" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//获取session</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">HttpSession session = request.getSession();</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n129" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.isNew()</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">返回值true,false,判断这个session是不是新的会话</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n130" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//session设置会话有效时间</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.setMaxInactiveInterval(60*60);</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n131" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//会话最后访问时间</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.getLastAccessedTime()</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n132" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//会话创建时间</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.getCreationTime()</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n133" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//获取会话有效时间</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.getMaxInactiveInterval()</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n134" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//获取Id</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.getId()</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n135" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//添加，第二个值是object类型</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.setAttribute("count",count);</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n136" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//获取返回值object</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">session.getAttribute("count")</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

</pre>

servlet2.5,3.0区别

2.5要在web.xml中配置，3.0不用，但得写注解，2.5配置文件会越来越多

jsp

servlet缺点：写html代码费劲，写java代码方便(java代码里嵌入html)

jsp:就是一个servlet，是servlet升级版，写html方便(html里嵌入java代码)

嵌入java代码用<% %>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n151" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><%</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> Date time=new Date();</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">out.print("<h3>time:"+time+"<h3>");</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">%></pre>

</pre>

当你第一次使用jsp时，速度略微慢点

jsp编译过程:先编译成servlet，在编译成.class文件，在运行在虚拟机上.

jsp注释:

使用“//”对单行代码进行注释

使用“/* */”方式对多行代码进行注释

使用“/** */”方式对多行代码进行注释

使用“<%-- --%>”对多行代码进行注释(客户端不能查看到 )

使用“”对多行HTML代码进行注释这(客户端可以查看到)

指令

page指令:

include指令

include 指令用于在运行时将 HTML文件或 JSP页面嵌入到另一个 JSP页面 "

<%@ include file = "/foot.jsp" %>

声明的概念

JSP声明就是在JSP页面中声明Java方法

1：<%!public int x=10;%>(声明标记:声明一个属性,方法，以后不用，用了就错了)

2：标记：书写java代码的地方

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n185" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><% </pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">String name="哈哈";</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">int count=100;</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">%></pre>

</pre>

3:输出标记

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n188" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h1>输出标记:</h1></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>name:<%=name %></h3></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>count:<%=count+10 %></h3></pre>

</pre>

jsp隐式对象

request

也是一个域，可以传值到jsp

request.setAttribute()

第一个参数字符串，第二个object类型

request.getAttribute()

参数是字符串，返回值是object类型

request.getContextPath()工程目录

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n205" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><%=request.getContextPath() %>/index.jsp</pre>

</pre>

2种跳转页面方法，第二种request值可以传过去this.findAll(request, response);

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n209" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//跳转url地址栏不是最终地址，是servlet地址，可以把request作用域里面的值传过去</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">request.getRequestDispatcher("MessageServlet?method=findAll").forward(request, response);</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//地址栏是最终地址栏，request作用域里的值传不过去，还可以跳站外资源（例如百度）</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">response.sendRedirect("MessageServlet?method=findAll");</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//第二种跳转链接可以传值，第二个页面可以拿到。</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//跳servlet时，不一定调用dopost，还是doget,看根源处走的是什么</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"></pre>

</pre>

隐式对象

输入输出：request ，response,out

作用域通信:session,application,PageContext

Servlet对象：page（Object类型对象）config（配置文件信息）

错误对象：exception

application:作用于整个应用服务器的全局作用域

request：出了这个请求响应就不能用

session：不是一个ID就不能用

pageContext:当前页面作用域

错误

04(路径错误)

500（代码错误）

401（验证错误）

405（doPost/doGet方法不全）

编写显示错误的页面

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n241" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//在web.xml文件中配置，写jsp错误页面，location里面是jsp文件路径</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><error-page></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> <error-code>404</error-code></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> <location>/error404.jsp</location></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> </error-page></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> <error-page></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> <error-code>500</error-code></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> <location>/error500.jsp</location></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"> </error-page></pre>

</pre>

Jsp El

1.减少JSP页面中Java代码

2.方便JSP中代码的修改，也方便美工修改页面外观

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n250" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>10+10=<%=10+10 %></h3></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>10+10=${10+10 }</h3></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">效果差不多</pre>

</pre>

<pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n251" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">

<textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="box-sizing: border-box; overflow: auto; color: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; margin: 0px; position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>name=<%=x %></h3> //x是get取到的</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>name2=${name }</h3>//前面的set方法第一个参数叫name</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;">//u是set的第一个参数，第二个参数是u这个对象，el表达式可以支架用第一个参数点出对象中的属性</pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>username:${u.username }</h3></pre>

<pre class=" CodeMirror-line " role="presentation" style="box-sizing: border-box; overflow: visible; font-family: inherit; font-size: inherit; white-space: pre-wrap; line-height: 1.71429em; break-inside: avoid; padding: 0px 4px; border-radius: 0px; border-top-width: 0px; border-right: none; border-bottom-width: 0px; border-left-width: 0px; background: 0px 0px; margin: 0px; word-wrap: break-word; color: inherit; z-index: 2; position: relative; word-break: normal; width: inherit;"><h3>pwd:${u.pwd }</h3></pre>

</pre>

[图片上传失败...(image-a1653d-1576216451512)]

JSP EL的内置对象

requestScope

sessionScope

applicationScope

param

paramValues

el表达式读取顺序

page-request-session-application

当四个域的set方法存的第一个参数一样时，有固定的读取顺序

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n271" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">//内置对象的用法，固定读取
<h3>name: ${requestScope.name};</h3> <h3>name:$ {sessionScope.name};</h3>
<h3>name:${applicationScope.name};</h3>
</pre>

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n272" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 0px; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">//同request.getParmeter("name")
<h3>name4:${param.name};</h3>
</pre>

MVC

是一种编程的思想，包括M V C ,m:数据模型。V：显示层 C：控制层，能使各层都分开，便于我们日常的分工合作，但能增加一点代码的复杂度

定制标记库

增加表现层的处理能力

减少JSP文件中的Java代码

定制标记的作用类似

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n285" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">//导入标记库
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
</pre>

1.set标签，可以向不同的作用域里传值

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n290" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><c:set var="name2" scope="session" value="session里面的值"></c:set>
</pre>

2.放在catch标签里，即使错误，程序也能继续运行

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n293" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><c:catch var="e">
<%
int p=Integer.parseInt(request.getParameter("page")) ;

%>
<h3>page=<%=p %></h3>

</c:catch>
//错误信息
<h3>e=${e}</h3>
</pre>

3.if标签，跟if语句一样,没有else

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n296" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><c:if test=" ${empty name3 }"> <h3>name3里面为空</h3> </c:if> <c:if test="$ { not empty name3 }">
<h3>name3里面不为空name3=${name3}</h3>

</c:if>
</pre>

4.choose标签，和when标签一起使用，相当于else if,otherwide标签相当于else

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n299" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><c:choose>
<c:when test=" ${param.p<10 }"> <h3>p小于10</h3> </c:when> <c:when test="$ {param.p<50 }">
<h3>p小于50</h3>
</c:when>
<c:otherwise>

<h3>p不小于50</h3>
</c:otherwise>
</c:choose>
</pre>

5循环.标签，从1开始，没回走2，走到10

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n302" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><c:forEach begin="1" end="10" var="i" step="2" varStatus="s">
i= ${i }==>$ {s.count }

</c:forEach>
</pre>

6.forTokens标签,以逗号分割

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n305" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 0px; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><%
request.setAttribute("aihao", "吃,喝,玩,乐");
%>
<c:forTokens items=" ${aihao }" delims="," var="a" varStatus="s">$ {s.index}==>${a }

</c:forTokens>
</pre>

Servlet监听器

在Web应用中响应特定对象的特定事件

1.更加方便的控制application、session 和request 对象的发生的特定事件。

2.可以集中处理特定的事件。

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n314" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"> session.invalidate();
//关闭session
</pre>

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n315" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">//当前页面有session，就用当前session，没有也不创建session
<%@page session="false" %>
</pre>

servlet监听器创建过程

需要配置web.xml文件

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n320" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><listener>
<listener-class>com.neusoft.listener.CountListener</listener-class>
</listener>
</pre>

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n321" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">package com.neusoft.listener;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class CountListener implements HttpSessionListener {
public static int count=0;

@Override
public void sessionCreated(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
  count++;
  System.out.println("创建 count="+count);
}

@Override
public void sessionDestroyed(HttpSessionEvent arg0) {
// TODO Auto-generated method stu
count--;
System.out.println("销毁 count="+count);

}

}

</pre>

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n322" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">package com.neusoft.listener;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class MyListener implements HttpSessionAttributeListener {

@Override
public void attributeAdded(HttpSessionBindingEvent arg0) {
System.out.println("添加");

}

@Override
public void attributeRemoved(HttpSessionBindingEvent arg0) {
System.out.println("移除");

}

@Override
public void attributeReplaced(HttpSessionBindingEvent arg0) {
System.out.println("替换");

}

}

</pre>

Servlet过滤器

Filter接口，需要实现这个接口，有初始化，执行，销毁3个方法

初始化：在启动服务时调用

执行：在进入另一个窗口时调用

销毁：在关闭服务式调用

需要配置web.xml文件

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n337" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;"><filter>
<filter-name>正常写文件名</filter-name>
<filter-class>cm.neusoft.filter.MyFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>正常写文件名</filter-name>
<url-pattern>/</url-pattern>
// /代表所有都过滤,即使地址写错了，或者没有这个地址，也都会过滤
</filter-mapping>
</pre>

<pre class="md-fences mock-cm md-end-block" lang="" contenteditable="false" cid="n338" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9rem; white-space: pre-wrap; line-height: 1.71429em; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; padding-left: 1ch; padding-right: 1ch; margin-left: 2em; width: inherit;">package cm.neusoft.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class MyFilter implements Filter{

@Override
public void destroy() {
System.out.println("销毁");

}

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
System.out.println("执行");
/*

如果有下一个filter,执行下一个filter

如果没有下一个filter,执行原请求
*/
chain.doFilter(request, response);
}

@Override
public void init(FilterConfig arg0) throws ServletException {
System.out.println("初始化");

}

}

</pre>

由一个jsp跳到一个servlet，然后这个servlet以.forward跳到另一个jsp或者servlet里面，下一个jsp或者servlet不会被拦截(不会被过滤)。

当跳转的时候，以sendRedirect进行跳转的时候，无脑被过滤，以.forward跳转的时候，跳转的界面不会被过滤

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2019-12-13

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