java如何利用java.net.URLConnection发送HTTP请求
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) { 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()); } }