通过java.net.URLConnection发送HTTP请求的方法

爱被打了一巴掌 2022-06-16 09:57 225阅读 0赞

阅读目录

*  运用原生Java Api发送简单的Get请求、Post请求
 *  简单封装
 *  简单测试

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。（详细的请见：[Hypertext Transfer Protocol -- HTTP/1.1 - Method Definitions][Hypertext Transfer Protocol -- HTTP_1.1 - Method Definitions]）

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.nicchagil.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.nicchagil.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，

*  可以大大减少代码量（不需每次都写一大段原生的请求Source code）
 *  也可以使配置更灵活、方便（全局设置一些项目特有的配置，比如已商榷的time out时间、已确定的Proxy Server，避免以后改动繁琐）

以下简单封装成HttpRequestor，以便使用：

package com.nicchagil.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.nicchagil.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>

感觉自己萌萌哒!~~

作者：Nick Huang 博客：http://www.cnblogs.com/nick-huang/ 本博客为学习、笔记之用，以笔记形式记录学习的知识与感悟。学习过程中可能参考各种资料，如觉文中表述过分引用，请务必告知，以便迅速处理。如有错漏，不吝赐教。

[Hypertext Transfer Protocol -- HTTP_1.1 - Method Definitions]: https://tools.ietf.org/html/rfc2616#section-9