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

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.通过统一资源定位器（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) {

http:// 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(HttpServletRequesthttp:// 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());

}

}

总结

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