目录
1.Servlet引入
2.简单的Servlet程序
1.Servlet引入
百度百科：Servlet简介
主要功能在于交互式地浏览和生成数据，生成动态Web内容；
从原理上讲，Servlet可以响应任何类型的请求，但绝大多数情况下Servlet只用来扩展基于HTTP协议的Web服务器。
2.简单的Servlet程序
先建立一个HelloWorldServlet类：
这个类继承HttpServelt，且alt+shift+s里面的重写方法选中doGet()和doPost()；
package com.java.web;
import java.io.IOException;
import javax.net.ssl.HttpsURLConnection;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloWorldServlet extends HttpServlet{
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//用户请求doGet时交给doPost去处理
this.doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
这里还要将配置文件web.xml里面修改一下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>HelloWorldServlet</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>HelloWorldServlet</servlet-name>
<servlet-class>com.java.web.HelloWorldServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorldServlet</servlet-name>
<url-pattern>HelloWorld</url-pattern>
</servlet-mapping>
</web-app>这时再编辑原先类里面的代码：
package com.java.web;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloWorldServlet extends HttpServlet{
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//用户请求doGet时交给doPost去处理
this.doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置默认编码为gbk
response.setCharacterEncoding("gbk");
PrintWriter out=response.getWriter();
out.println("<html>");
out.println("<head><title>简单的Servlet程序</title></head>");
out.println("HelloWorld!你好！");
out.println("</html>");
out.close();
}
}
我们在浏览器运行时其实是运行HelloWorld:
http://localhost:8080/HelloWorldServlet/HelloWorld
运行结果：
原理：首先浏览器请求HelloWorld，然后找到匹配的name（即HelloWorldServlet）；然后name去找Servlet里面相匹配的name，请求其中的class，然后根据返回的get请求，找到doPost()方法，运行其中的代码就完成了！
3.Servlet生命周期
Servlet 的生命周期，简单的概括这就分为四步：servlet 类加载--->实例化--->服务--->销毁。
我们建一个测试类LifeServlet:
package com.java.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LifeServlet extends HttpServlet{
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("service");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("service");
}
@Override
public void destroy() {
System.out.println("Servlet销毁");
}
@Override
public void init() throws ServletException {
System.out.println("Servlet初始化");
}
}
当然在web.xml里面也要添加配置：
运行http://localhost:8080/HelloWorldServlet/Life
可以看到Servlet的生命周期分为四步：
1.调用LifeServlet时会进行类加载；
2.Servlet初始化时会进行实例化，并调用init()方法；
3.请求要求时会有服务service；
4.长时间不用或者关闭LifeServlet就会销毁Servlet！并调用destroy()方法；