java net.URLConnection http请求

通过java.net.URLConnection发送HTTP请求的方法

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）

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();
    }
    
}

HttpGetRequest

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());//添加请求参数
            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();
    }

}

HttpPostRequest