Java通过HTTP POST请求上传文件示例

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();
    }

}

下面,对上述的代码做一些必要的说明:

http发送的post数据是通过boundary和换行符来分割的,boundary是一个随机的字符串即可,但不要与你传递的参数名或参数值相同。

换行符要求也是比较严格的,数据的声明和数据的值之间需要两个换行符,两个数据之间要用boundary来划分。对于二进制的数据来说,只是参数的类型声明和普通的数据有点区别,比如上述的代码增加了filename和content-type,二进制的数据以字符流写出去就行了。

posted @ 2016-10-24 10:52  迷茫小左  阅读(40287)  评论(0编辑  收藏  举报