Java Http Client

为了准备LilyBookStore下一步的功能，访问豆瓣的API，今天熟悉了一下JDK和Commons HttpClient中和http相关的接口。Commons中的HttpClient现在已经从Commons中独立出来了，不过新的4.0版还没有stable的release，现在用的3.1还是打着Commons标记的。

JDK实例：

   public void exe(String urlAsString) throws IOException{ 
        URL url = new URL(urlAsString); 
        HttpURLConnection conn = (HttpURLConnection)url.openConnection(); 
        int size = conn.getHeaderFields().size(); 
        for(int i=0; i< size; i++){ 
            System.out.print(conn.getHeaderFieldKey(i)+"\t"); 
            System.out.println(conn.getHeaderField(i)); 
        } 
        System.out.println("Request Method: "+conn.getRequestMethod()); 
        System.out.println("Response Code: "+conn.getResponseCode()); 
        System.out.println("Response Message: " +conn.getResponseMessage()); 
        System.out.println("Last Modified: " +conn.getLastModified()); 
        System.out.println("ContentHandler: " +conn.getContent().getClass().getName()); 
        InputStream in = (InputStream)conn.getContent(); 
        FileOutputStream out = new FileOutputStream(new File("index.html")); 
        copyStream(in, out); 
         
    } 

java.net.HttpURLConnection里主要注意的就是getContent方法，对于不同的请求返回不同的对象。普通网页返回的是sun.net.www.protocol.http.HttpURLConnection$HttpInputStream，而图片、音频文件返回的则是各自的handler。

Commons的HttpClient实例：

    public void exe(String urlAsString) throws IOException{ 
        HttpClient client = new HttpClient(); 
        HttpMethod http = new GetMethod(urlAsString); 
        http.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, 
                new DefaultHttpMethodRetryHandler(1, false)); 
        client.executeMethod(http); 
        System.out.println(http.getStatusCode()); 
        System.out.println(http.getStatusText()); 
        InputStream in = http.getResponseBodyAsStream(); 
        FileOutputStream out = new FileOutputStream(new File("index2.html")); 
        copyStream(in, out); 
        http.releaseConnection(); 
    } 

Commons中除了getResponseBodyAsStream，还有getResponseBodyAsString，使用起来相对方便一些。

等开学以后到学校复杂的网络环境里试一下，再决定最后选择哪个。