自定义标签步骤
- 定义处理类
- 编写tld文件
- 页面引用
自定义标签常量
| skip body | 跳到doEndTag |
| eval body include | 执行标签体 |
| eval body again | 重复执行doAfterTag |
| skip page | doEndTag release - 停止 |
| eval page | doEndTag release - 继续执行 |
示例
TagSupport：输出内容到页面
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
public class WriterTag extends TagSupport {
private static final long serialVersionUID = 1L;
@Override
public int doStartTag() throws JspException {
try {
JspWriter jspOut = pageContext.getOut();
jspOut.print("JSP页面内置的out就是JspWriter JspWriter缓冲了再输出 print参数各种类型<br/>");
jspOut.write("JSP页面内置的out就是JspWriter JspWriter缓冲了再输出 write参数String/char/int<br/><br/>");
// jspOut.flush();//刷新缓冲区保证先输出
PrintWriter servletOut = pageContext.getResponse().getWriter();
servletOut.print("Servlet里常用的out PrintWriter没有使用缓冲区所以先输出 print参数各种类型<br/>");
servletOut.write("Servlet里常用的out PrintWriter没有使用缓冲区所以先输出 write参数String/char/int<br/><br/>");
} catch (IOException e) {
e.printStackTrace();
}
return SKIP_BODY;
}
}
TagSupport：转换日期
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;
public class DateFormat extends TagSupport {
private static final long serialVersionUID = 1L;
private String pattern;
private String var;
private Date date; //可选 默认当前时间
private String scope; //可选 默认page作用域
@Override
public int doStartTag() throws JspException {
if (date == null) {date = new Date();}
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
if (scope == null || "".equals(scope) || "page".equals(scope)) {
pageContext.setAttribute(var, sdf.format(date),PageContext.PAGE_SCOPE);
}else if ("request".equals(scope)) {
pageContext.setAttribute(var, sdf.format(date),PageContext.REQUEST_SCOPE);
}else if ("session".equals(scope)) {
pageContext.setAttribute(var, sdf.format(date),PageContext.SESSION_SCOPE);
}else if ("application".equals(scope)) {
pageContext.setAttribute(var, sdf.format(date),PageContext.APPLICATION_SCOPE);
}
return SKIP_BODY;
}
//属性名随意 但是方法名必须与标签属性的名字有关系 保证能找到对应的方法
public String getScope() {
return scope;
}
public void setScope(String scope) {
this.scope = scope;
}
public String getVar() {
return var;
}
public void setVar(String var) {
this.var = var;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getPattern() {
return pattern;
}
public void setPattern(String pattern) {
this.pattern = pattern;
}
}
SimpleTagSupport
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class SimpleTagIterator extends SimpleTagSupport {
private List<?> items;
private String var;
private Iterator<?> iterator;
@Override
public void doTag() throws JspException, IOException {
iterator = items.iterator();
while (iterator.hasNext()) {
getJspContext().setAttribute(var, iterator.next());
getJspBody().invoke(null);
}
}
public List<?> getItems() {
return items;
}
public void setItems(List<?> items) {
this.items = items;
}
public String getVar() {
return var;
}
public void setVar(String var) {
this.var = var;
}
}
编写mytags.tld
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>baozi</short-name>
<tag>
<name>writer</name>
<tag-class>org.baozi.tag.WriterTag</tag-class>
<body-content>empty</body-content>
</tag>
<tag>
<name>format</name>
<tag-class>org.baozi.tag.DateFormat</tag-class>
<body-content>empty</body-content>
<attribute>
<name>pattern</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>date</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>scope</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>iter</name>
<tag-class>org.baozi.tag.IteratorTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>simpleiter</name>
<tag-class>org.baozi.tag.SimpleTagIterator</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<!--
可以使用这种配置 将tag的tld配置文件映射到一个uri中
jsp页面:uri="mytags"
<jsp-config>
<taglib>
<taglib-uri>mytags</taglib-uri>
<taglib-location>/WEB-INF/mytags.tld</taglib-location>
</taglib>
</jsp-config>
-->
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
页面中引用
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="baozi" uri="/WEB-INF/mytags.tld" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<%
List<String> list = new ArrayList<String>();
list.add("AA");
list.add("BB");
list.add("CC");
pageContext.setAttribute("list", list);
%>
<baozi:simpleiter items="${list}" var="test">
${test}-
</baozi:simpleiter>
</body>
</html>
