java利用java.net.URLConnection发送HTTP请求的方法详解

一、前言

如何通过Java发送HTTP请求，通俗点讲，如何通过Java（模拟浏览器）发送HTTP请求。

Java有原生的API可用于发送HTTP请求，即java.net.URL、java.net.URLConnection，这些API很好用、很常用，但不够简便；

所以，也流行有许多Java HTTP请求的framework，如，Apache的HttpClient。

目前项目主要用到Java原生的方式，所以，这里主要介绍此方式。

二、运用原生Java Api发送简单的Get请求、Post请求步骤

       1.通过统一资源 * （java.net.URL）获取连接器（java.net.URLConnection）

       2.设置请求的参数

       3.发送请求

       4.以输入流的形式获取返回内容

       5.关闭输入流

三、发送请求与接收响应流类 HttpRequestor

package me.http;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.Map;

public class HttpRequestor {

private String charset = "utf-8";
private Integer connectTimeout = null;
private Integer socketTimeout = null;
private String proxyHost = null;
private Integer proxyPort = null;

/**
 * Do GET request
 * @param url
 * @return
 * @throws Exception
 * @throws IOException
 */
public String doGet(String url) throws Exception {

URL localURL = new URL(url);

URLConnection connection = this.openConnection(localURL);
 HttpURLConnection httpURLConnection = (HttpURLConnection)connection;

httpURLConnection.setRequestProperty("Accept-Charset", charset);
 httpURLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

InputStream inputStream = null;
 InputStreamReader inputStreamReader = null;
 BufferedReader reader = null;
 StringBuffer resultBuffer = new StringBuffer();
 String tempLine = null;
 //响应失败
 if (httpURLConnection.getResponseCode() >= 300) {
  throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
 }

try {
  inputStream = httpURLConnection.getInputStream();
  inputStreamReader = new InputStreamReader(inputStream);
  reader = new BufferedReader(inputStreamReader);

while ((tempLine = reader.readLine()) != null) {
   resultBuffer.append(tempLine);
  }

} finally {

if (reader != null) {
   reader.close();
  }

if (inputStreamReader != null) {
   inputStreamReader.close();
  }

if (inputStream != null) {
   inputStream.close();
  }

}

return resultBuffer.toString();
}

/**
 * Do POST request
 * @param url
 * @param parameterMap
 * @return
 * @throws Exception
 */
public String doPost(String url, Map parameterMap) throws Exception {

/* Translate parameter map to parameter date string */
 StringBuffer parameterBuffer = new StringBuffer();
 if (parameterMap != null) {
  Iterator iterator = parameterMap.keySet().iterator();
  String key = null;
  String value = null;
  while (iterator.hasNext()) {
   key = (String)iterator.next();
   if (parameterMap.get(key) != null) {
    value = (String)parameterMap.get(key);
   } else {
    value = "";
   }

parameterBuffer.append(key).append("=").append(value);
   if (iterator.hasNext()) {
    parameterBuffer.append("&");
   }
  }
 }

System.out.println("POST parameter : " + parameterBuffer.toString());

URL localURL = new URL(url);

URLConnection connection = this.openConnection(localURL);
 HttpURLConnection httpURLConnection = (HttpURLConnection)connection;

httpURLConnection.setDoOutput(true);
 httpURLConnection.setRequestMethod("POST");
 httpURLConnection.setRequestProperty("Accept-Charset", charset);
 httpURLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
 httpURLConnection.setRequestProperty("Content-Length", String.valueOf(parameterBuffer.length()));

OutputStream outputStream = null;
 OutputStreamWriter outputStreamWriter = null;
 InputStream inputStream = null;
 InputStreamReader inputStreamReader = null;
 BufferedReader reader = null;
 StringBuffer resultBuffer = new StringBuffer();
 String tempLine = null;

try {
  outputStream = httpURLConnection.getOutputStream();
  outputStreamWriter = new OutputStreamWriter(outputStream);

outputStreamWriter.write(parameterBuffer.toString());
  outputStreamWriter.flush();
  //响应失败
  if (httpURLConnection.getResponseCode() >= 300) {
   throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
  }
  //接收响应流
  inputStream = httpURLConnection.getInputStream();
  inputStreamReader = new InputStreamReader(inputStream);
  reader = new BufferedReader(inputStreamReader);

while ((tempLine = reader.readLine()) != null) {
   resultBuffer.append(tempLine);
  }

} finally {

if (outputStreamWriter != null) {
   outputStreamWriter.close();
  }

if (outputStream != null) {
   outputStream.close();
  }

if (reader != null) {
   reader.close();
  }

if (inputStreamReader != null) {
   inputStreamReader.close();
  }

if (inputStream != null) {
   inputStream.close();
  }

}

return resultBuffer.toString();
}

private URLConnection openConnection(URL localURL) throws IOException {
 URLConnection connection;
 if (proxyHost != null && proxyPort != null) {
  Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(proxyHost, proxyPort));
  connection = localURL.openConnection(proxy);
 } else {
  connection = localURL.openConnection();
 }
 return connection;
}

/**
 * Render request according setting
 * @param request
 */
private void renderRequest(URLConnection connection) {

if (connectTimeout != null) {
  connection.setConnectTimeout(connectTimeout);
 }

if (socketTimeout != null) {
  connection.setReadTimeout(socketTimeout);
 }

}

/*
 * Getter & Setter
 */
public Integer getConnectTimeout() {
 return connectTimeout;
}

public void setConnectTimeout(Integer connectTimeout) {
 this.connectTimeout = connectTimeout;
}

public Integer getSocketTimeout() {
 return socketTimeout;
}

public void setSocketTimeout(Integer socketTimeout) {
 this.socketTimeout = socketTimeout;
}

public String getProxyHost() {
 return proxyHost;
}

public void setProxyHost(String proxyHost) {
 this.proxyHost = proxyHost;
}

public Integer getProxyPort() {
 return proxyPort;
}

public void setProxyPort(Integer proxyPort) {
 this.proxyPort = proxyPort;
}

public String getCharset() {
 return charset;
}

public void setCharset(String charset) {
 this.charset = charset;
}

}

四、为测试方便,新建一个项目,并新建一个Servlet,接收post请求并对HttpRequestor请求响应,发出响应流

LoginServlet.java代码:此处使用了

注解: @WebServlet("/LoginServlet") ,也可以在web.xml配置Servlet

package me.loginServlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public LoginServlet() {
 super();
 // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 System.out.println("111");
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
  String username = request.getParameter("username");
  String blog = request.getParameter("blog");

System.out.println(username);
  System.out.println(blog);

response.setContentType("text/plain; charset=UTF-8");
  response.setCharacterEncoding("UTF-8");
//响应流
  response.getWriter().write("It is ok!");

}

}

五.测试类Test.java

package me.http;

import java.util.HashMap;
import java.util.Map;

public class Test {
public static void main(String[] args) {
 /* Post Request */
Map dataMap = new HashMap();
dataMap.put("username", "Nick Huang");
dataMap.put("blog", "IT");
try {
 System.out.println(new HttpRequestor().doPost("http://localhost:8081/TestProgect2/LoginServlet", dataMap));
 //System.out.println(new HttpRequestor().doGet("http://localhost:8081/TestProgect2/LoginServlet"));
} catch (Exception e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
}

/* Get Request */

}
}

1.接收post请求类LoginServlet,控制台测试结果

2.HttpRequestor接收LoginServlet返回的流

OK,完成

六.对于接收TestProgect2项目中LoginServlet.java类返回的流,在真实环境中可能是异步接收返回的流的,当一台机器A向另外一台机器B发送请求,B接收到A的信息,将信息处理后,需要将处理结果返回即响应返回给A,A会接收到B返回的信息

可以另外建一个Servlet类HttpListenerServlet.java来专门异步接收返回的信息

package me.http;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class HttpListenerServlet
*/
@WebServlet("/HttpListenerServlet")
public class HttpListenerServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public HttpListenerServlet() {
 super();
 // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
  InputStream inputStream = null;
  inputStream = request.getInputStream();
  InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
  BufferedReader reader = new BufferedReader(inputStreamReader);
  String tempLine = null;
  StringBuffer resultBuffer=new StringBuffer();
  while ((tempLine = reader.readLine()) != null) {
   resultBuffer.append(tempLine);
  }

System.out.println(resultBuffer.toString());
}

}

来源：http://www.cnblogs.com/cl1255674805/p/5708735.html