HelloServlet类继承HttpServlet利用HttpServletResponse对象

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HelloServlet类的doGet()方法先得到username请求参数，对其进行中文字符编码转换，然后判断username是否为空，如果为空就返回403响应状态代码，否则就通过HttpServletResponse对象的getWriter()方法得到一个PrinterWriter对象，然后通过PrintWriter对象来输出HTML文档

HelloServlet.java

package com.demo.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
/* Created by 谭雪娇 on 2017/4/5.
*/
public class HelloServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException,IOException{
        //获得sername的请求参数
        String username=request.getParameter("username");
        /*字符编码转换
        * HTTP请求的默认字符编码为ISO-8859-1，如果请求中包含中文需要把它转换为GB2312中文编码。*/
        if(username!=null){
            username=new String(username.getBytes("ISO-8859-1"),"UTF-8");
            if(username==null){
                response.sendError(response.SC_FORBIDDEN);
                return;
            }
            //设置HTTP响应的正文的MIME类型及字符编码
            response.setContentType("text/html;charset=UTF-8");
            /*输出HTML文档*/
            PrintWriter out=response.getWriter();
            out.println("<html><head><title>HelloServlet</title><head>");
            out.println("<body>");
            out.println("你好："+username);
            out.println("</body></html>");
            System.out.println("before close():"+response.isCommitted());
            out.close();
            System.out.println("before close():"+response.isCommitted());
        }
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
        <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>com.demo.servlet.RequestInfoServlet</servlet-class>

</servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/info</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>dispatcher1</servlet-name>
        <servlet-class>com.demo.servlet.HelloServlet</servlet-class>
    </servlet>
   <servlet-mapping>
       <servlet-name>dispatcher1</servlet-name>
       <url-pattern>/hello</url-pattern>
   </servlet-mapping>
</web-app>