HttpURLConnection 通过对象流实现客户端和服务器端的数据交互

需求：客户端向服务器端发送请求，服务器端接收到请求后进行流程处理，生成list对象，返回到客户端。

1.传递的包装类（必须序列化）

  package com;
  import java.io.Serializable;
    /*
     * 使用对象流序列化和反序列化对象
     * 1.创建一个对象，这个对象将被序列化，并写入文件中，前提是：当前类实现了Serializable接口
     * 2.实例化ObjectOutputStream的对象
     * 3.调用ObjectOutputStream类的writeObject()方法，将对象写入流中
     * 4.实例化ObjectInputStream类的对象
     * 5.调用ObjectInputStream类的readObject()方法，获取对象的时候要进行强制类型转化
     *
     * transient关键字
     * 可以保护对象中的敏感信息不被写入到对象流中
     */
    public class Student implements Serializable{
        private String name;
        private int age;
        public Student(String name,int age){
            this.name=name;
            this.age=age;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
    }

2.数据流写的方法

package com;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.servlet.ServletException;

public class TaskSendMsg {
    
    public TaskSendMsg() {}
    
    public void sendM(String url)throws ServletException, IOException{
        List<Student> a = new ArrayList<Student>();
        a.add(new Student("1",2));
        a.add(new Student("2",2));
        a.add(new Student("3",2));
        
        URL objUrl = new URL(url);
        HttpURLConnection httpConn = null;
        OutputStream output = null;
        
        httpConn = (HttpURLConnection) objUrl.openConnection();
        HttpURLConnection.setFollowRedirects(true);
        httpConn.setDoOutput(true);
        httpConn.setRequestMethod("POST");//请求方法的动作
        httpConn.setRequestProperty("Content-Type", "text/xml");
        httpConn.connect();
        output = httpConn.getOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(output);
       // 写入请求参数
        oos.writeObject(a);
         oos.flush();
        oos.close();
        System.out.println("send ok");
        int code = httpConn.getResponseCode();
        System.out.println("code " + code);
        System.out.println(httpConn.getResponseMessage());
}

3.Servlet中调用数据流写入方法，向特定的url返回封装后的list

package com;


import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;


public class TaskServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static String encoding = "UTF-8";
    private Log log = LogFactory.getLog(TaskServlet.class);
    protected void service(HttpServletRequest req, HttpServletResponse resp) {
       
       //获取请求的IP地址，用来处理响应的值，与接收端协商定义
        String respUrl = "http://" + req.getServerName() //服务器地址  
        + ":" + req.getServerPort()           //端口号  
        + "/task"  ;    //请求页面或其他地址  
    
        //通过字节流写返回值，传回给请求的URL
        TaskSendMsg ts = new TaskSendMsg();
        try {
            ts.sendM(respUrl);
        } catch (Exception e) {
            e.printStackTrace();
        } 
     }
}

4.接收端获取数据流

package com;

import java.io.ObjectInputStream;
import java.util.List;

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.Student;



public class TestServlet extends HttpServlet {
        private static final long serialVersionUID = 1L;
        protected void service(HttpServletRequest req, HttpServletResponse resp) {
        try {
            System.out.println("begin read");
            
            List<Student> students =null;
           
            ServletInputStream inStream = req.getInputStream(); // 取HTTP请求流
            ObjectInputStream ois = new ObjectInputStream(inStream);
            
          //依次从对象流中取出list
            while(inStream.available()>0){
                students=(List<Student>)ois.readObject();
                for(Student s:students){
                   System.out.println("获取的Student的名字有："+s.getName());
                }
            }
           inStream.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
      }
	
}

在浏览器输入http://服务器IP：端口/服务器servlet对应的方法
会在TestServlet中获取传递的Student信息。


servlet配置：
servlet直接实现service方法即可，在web.xml中配置路径
 

  <servlet>
    <servlet-name>test_servlet</servlet-name>
	  <servlet-class>com.TestServlet</servlet-class>   
	  <load-on-startup>1</load-on-startup>
    </servlet>
  
  <servlet-mapping>
	<servlet-name>test_servlet</servlet-name>
	<url-pattern>/ajax/test</url-pattern>
  </servlet-mapping> 

在浏览器上 输入http：//localhost:8080/ajax/test
执行servlet中的service程序。