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。
运用原生Java Api发送简单的Get请求、Post请求
HTTP请求粗分为两种,一种是GET请求,一种是POST请求。使用Java发送这两种请求的代码大同小异,只是一些参数设置的不同。步骤如下:
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
简单的Get请求示例如下:
package com.bjpowernode.httprequestdemo; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLConnection; public class HttpGetRequest { /** * Main * @param args * @throws Exception */ public static void main(String[] args) throws Exception { System.out.println(doGet()); } /** * Get Request * @return * @throws Exception */ public static String doGet() throws Exception { URL localURL = new URL("http://localhost:8080/OneHttpServer/"); URLConnection connection = localURL.openConnection(); HttpURLConnection httpURLConnection = (HttpURLConnection)connection; httpURLConnection.setRequestProperty("Accept-Charset", "utf-8"); 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; 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(); } }
简单的Post请求示例如下:
package com.bjpowernode.httprequestdemo; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLConnection; public class HttpPostRequest { /** * Main * @param args * @throws Exception */ public static void main(String[] args) throws Exception { System.out.println(doPost()); } /** * Post Request * @return * @throws Exception */ public static String doPost() throws Exception { String parameterData = "username=nickhuang&blog=http://www.cnblogs.com/nick-huang/"; URL localURL = new URL("http://localhost:8080/OneHttpServer/"); URLConnection connection = localURL.openConnection(); HttpURLConnection httpURLConnection = (HttpURLConnection)connection; httpURLConnection.setDoOutput(true); httpURLConnection.setRequestMethod("POST"); httpURLConnection.setRequestProperty("Accept-Charset", "utf-8"); httpURLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); httpURLConnection.setRequestProperty("Content-Length", String.valueOf(parameterData.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(parameterData.toString()); outputStreamWriter.flush(); if (httpURLConnection.getResponseCode() >= 300) { throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode()); } 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(); } }
简单封装
如果项目中有多处地方使用HTTP请求,我们适当对其进行封装,
以下简单封装成HttpRequestor,以便使用:
package com.bjpowernode.util.httprequestor; 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 = 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; 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 = 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(); if (httpURLConnection.getResponseCode() >= 300) { throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode()); } 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; } }
写一个调用的测试类:
package com.bjpowernode.util.httprequestor; import java.util.HashMap; import java.util.Map; public class Call { public static void main(String[] args) throws Exception { /* Post Request */ Map dataMap = new HashMap(); dataMap.put("username", "Nick Huang"); dataMap.put("blog", "IT"); System.out.println(new HttpRequestor().doPost("http://localhost:8080/OneHttpServer/", dataMap)); /* Get Request */ System.out.println(new HttpRequestor().doGet("http://localhost:8080/OneHttpServer/")); } }
OK,完成!!
简单测试
以上的请求地址都是http://localhost:8080/OneHttpServer/
这是自己的一个用于测试的Web Application,就一个简单的Servlet和web.xml。毕竟需要测试请求参数是否能正常接收,处理超时的情况。
LoginServlet
import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L; public LoginServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 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"); response.getWriter().write("It is ok!"); } }
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>OneHttpServer</display-name> <welcome-file-list> <welcome-file>LoginServlet</welcome-file> </welcome-file-list> <servlet> <description></description> <display-name>LoginServlet</display-name> <servlet-name>LoginServlet</servlet-name> <servlet-class>LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping> </web-app>
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