Servlet

Servlet 是运行在Web服务器中的小型Java程序。Servlet 通过HTTP(超文本传输协议)接收和响应来自Web客户端的请求。

一、实现Servlet接口

实现接口，此接口定义了初始化Servlet的方法、为请求提供服务的方法和从服务器移除Servlet的方法。

1. 生命周期方法

• 构造Servlet，然后使用init方法将其初始化

public void init(ServletConfig servletConfig) throws ServletException { }

• 处理来自客户端对service方法的所有调用

public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("hello servlet");
 }

• 从服务中取出Servlet，然后使用destroy方法销毁它，最后进行垃圾回收并终止它

public void destroy() { }

二、具体实现如下

1. 实现Servlet接口

package com.text.servletTest;
import javax.servlet.*;
import java.io.IOException;
// 实现相应的接口
public class ServletDemo1 implements Servlet {
    @Override
    public void init(ServletConfig servletConfig) throws ServletException {

    }
    @Override
    public ServletConfig getServletConfig() {
        return null;
    }
    // 由Servlet容器调用，以允许Servlet响应某个请求
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("hello servlet");
    }
    @Override
    public String getServletInfo() {
        return null;
    }
    @Override
    public void destroy() {

    }
}

2. Web.xml配置

 <!--创建一个Servlet实例-->
    <servlet>
        <servlet-name>servletDemo1</servlet-name>
        <servlet-class>com.text.servletTest.ServletDemo1</servlet-class>
        <load-on-startup>2</load-on-startup>

    </servlet>
    <!--给Servlet提供（映射）一个可供客户端访问的URI-->
    <servlet-mapping>
        <servlet-name>servletDemo1</servlet-name>
        <!--
        http://localhost:8080/myApp/
        -->
        <url-pattern>/demo1</url-pattern>
    </servlet-mapping>

三、Servlet通过继承GenericServlet实现抽象方法

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;

public class ServletDemoTwo extends GenericServlet {

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {

    }
}

四、通过继承HttpServlet方法进行相应处理

public class ServletHttpDemoTwo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
        System.out.println("servlet isDo Get");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
        System.out.println("servlet isDo Post");
    }
}