HttpURLConnection的使用（网络通信）

HttpURLConnection的使用（网络通信）

URLConnection类给应用程序和web资源之间架设起了通信的桥梁，

这些web资源通常是通过url来标记的,本文将讲述如何使用HttpURLConnection来访问web页面(发送数据流)和读取数据流。

案例：连个servlet的通信：

1、客户端的发送和接受数据：

HttpURLConnection +

URL+

OutputStream（写入数据）—-通过httpurlconnection获取+

InputStream（读取数据））—-通过httpurlconnection获取

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

@SuppressWarnings("serial")
public class IOServlet extends HttpServlet
{
/**
* 对于主动请求其它接口的参数流写入(POST方式)
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
System.out.println("begin send");  //=================================1
String inputParam = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><page><username>爱心天使</usernaem><age>26</age></page>";

URL url = null;
HttpURLConnection httpConn = null;
OutputStream output = null;
OutputStreamWriter outr = null;

url = new URL("http://127.0.0.1:8888/iotest/ReadServlet");
httpConn = (HttpURLConnection) url.openConnection();
HttpURLConnection.setFollowRedirects(true);
httpConn.setDoOutput(true);
httpConn.setRequestMethod("POST");
httpConn.setRequestProperty("Content-Type", "text/xml");
httpConn.connect();
output = httpConn.getOutputStream();
outr = new OutputStreamWriter(output);
// 写入请求参数
outr.write(inputParam.toString().toCharArray(), 0, inputParam
.toString().length());
outr.flush();
outr.close();
System.out.println("send ok");  //============================2
int code = httpConn.getResponseCode();
System.out.println("code " + code);   //==============================6  200
System.out.println(httpConn.getResponseMessage());   //==============7 OK

//读取响应内容
String sCurrentLine = "";
String sTotalString = "";
if (code == 200)
{
java.io.InputStream is = httpConn.getInputStream();
BufferedReader reader = new BufferedReader(
new InputStreamReader(is));
while ((sCurrentLine = reader.readLine()) != null)
if (sCurrentLine.length() > 0)
sTotalString = sTotalString + sCurrentLine.trim();
} else
{
sTotalString = "远程服务器连接失败,错误代码:" + code;

}
System.out.println("response:" + sTotalString);   //===============8  response:您已经请求成功，这是响应数据!

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
this.doGet(request, response);
}

}

2、服务器的接受和回应数据：

ServletInputStream（request中获取）–读取数据

PrintWriter（response中获取）—–相应数据

package com;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@SuppressWarnings("serial")
public class ReadServlet extends HttpServlet
{

public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException
{
System.out.println("begin read");             //==========================================3
ServletInputStream inStream = request.getInputStream(); // 取HTTP请求流
int size = request.getContentLength(); // 取HTTP请求流长度
byte[] buffer = new byte[size]; // 用于缓存每次读取的数据
byte[] in_b = new byte[size]; // 用于存放结果的数组
int count = 0;
int rbyte = 0;
// 循环读取
while (count < size)
{
rbyte = inStream.read(buffer); // 每次实际读取长度存于rbyte中 sflj
for (int i = 0; i < rbyte; i++)
{
in_b[count + i] = buffer[i];
}
count += rbyte;
}
System.out.println("result:" + new String(in_b,0,in_b.length));  //===============================4
//result:<?xml version="1.0" encoding="UTF-8"?><page><username>爱心天使</usernaem><age>26</age></page>

response.setContentType("text/html");
//注意响应中文数据时要设置
response.setCharacterEncoding("GBK");
PrintWriter out = response.getWriter();
//回与响应数据
out.write("您已经请求成功，这是响应数据!");  //================================5
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
this.doGet(request, response);
}

}