Java发送HTTP POST请求示例

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概述：

http请求在所有的编程语言中几乎都是支持的，我们常用的两种为：GET，POST请求。一般情况下，发送一个GET请求都很简单，因为参数直接放在请求的URL上，所以，对于PHP这种语言，甚至只需要一行：file_get_content(url);就能完成数据的获取，但对于POST请求，由于其数据是在消息体中发送出去的，所以相对来说要麻烦一点，再涉及到需要发送文件等二进制的数据类型，就更需要更多的处理，下面我们用Java语言来实现POST请求发送数据，其他语言类似。

public class MainUI {

    private static final String REQUEST_PATH = "http://localhost/server_url.php";

    private static final String BOUNDARY = "20140501";

    /**

     * @param args

     * @throws Exception

     */

    public static void main(String[] args) throws Exception {

        // TODO Auto-generated method stub

        URL url = new URL(REQUEST_PATH);

        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();

        httpConn.setConnectTimeout(3000); // 设置发起连接的等待时间，3s

        httpConn.setReadTimeout(30000); // 设置数据读取超时的时间，30s

        httpConn.setUseCaches(false); // 设置不使用缓存

        httpConn.setDoOutput(true);

        httpConn.setRequestMethod("POST");

        httpConn.setRequestProperty("Connection", "Keep-Alive");

        httpConn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.6)");

        httpConn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);

        OutputStream os = httpConn.getOutputStream();

        BufferedOutputStream bos = new BufferedOutputStream(os);

        String content = "--" + BOUNDARY + "\r\n";

        content       += "Content-Disposition: form-data; name=\"title\"" + "\r\n\r\n";

        content       += "我是post数据的值";

        content       += "\r\n--" + BOUNDARY + "\r\n";

        content       += "Content-Disposition: form-data; name=\"cover_img\"; filename=\"avatar.jpg\"\r\n";

        content       += "Content-Type: image/jpeg\r\n\r\n";

        bos.write(content.getBytes());

        // 开始写出文件的二进制数据

        FileInputStream fin = new FileInputStream(new File("avatar.jpg"));

        BufferedInputStream bfi = new BufferedInputStream(fin);

        byte[] buffer = new byte[4096];

        int bytes = bfi.read(buffer, 0, buffer.length);

        while (bytes != -1) {

            bos.write(buffer, 0, bytes);

            bytes = bfi.read(buffer, 0, buffer.length);

        }

        bfi.close();

        fin.close();

        bos.write(("\r\n--" + BOUNDARY).getBytes());

        bos.flush();

        bos.close();

        os.close();

         // 读取返回数据

        StringBuffer strBuf = new StringBuffer();

        BufferedReader reader = new BufferedReader(new InputStreamReader(

                httpConn.getInputStream()));

        String line = null;

        while ((line = reader.readLine()) != null) {

            strBuf.append(line).append("\n");

        }

        String res = strBuf.toString();

        System.out.println(res);

        reader.close();

        httpConn.disconnect();

    }

}