Director REST API 的使用

最近要使用IBM System Director的REST API，官方提供的例子上用的了HttpsURLConnection来发送GET、POST、DELETE、PUT请求。

REST架构风格是基于无状态web服务，通常使用HTTP协议访问。因此，简单的HTTP客户端是调用REST APIs最有效的工具，如poster。Java的javax.net.ssl 包提供了访问一组类（HttpsURLConnection）来访问IBM System Director的https连接。

Director的REST API的HTTP 请求方法

HTTP Method	Description
GET	请求资源 Return information concerning the resource in the body of the HTTP response.
PUT	更新资源，如果不存在此资源，则返回404  Update the resource if it already exists based on information passed in the body of the HTTP request. An HTTP response code of 404 will be returned if the resource doesn't exist.
POST	创建或新加资源 Create a new instance of a resource based on information passed in the body of the HTTP request.
DELETE	删除 Remove the resource.

HEAD	Used for POST Once Exactly

1、配置安全套接字 Secure Socket Layer

可以手动配置，官方的例子上也实现了动态生成的方法。

自动实现的方法：

   // create a temporary file that will be removed when the JVM exits (normally)
   // optionally, you can create a permanent file to hold the SSL certificate
   File keyStoreFile = File.createTempFile("tmpkeystore", ".jks"); 
   keyStoreFile.deleteOnExit();

   // retrieve the certificate and store it in the keystore file
   KeyStore ts = createKeyStore(serverName, port, keyStoreFile, certificateStorePassword);
   	  
   // set up the TrustManager and sslSocketFactory using keystore containing certificate 
   TrustManagerFactory tmf = TrustManagerFactory.getInstance("IBMX509");
   tmf.init(ts);
   TrustManager[] tm = tmf.getTrustManagers();

   SSLContext sslContext = SSLContext.getInstance("SSL");
   sslContext.init(null, tm, null);
   sslSocketFactory = sslContext.getSocketFactory();

   // disable hostname verification
   HostnameVerifier hv = new HostnameVerifier() {
        public boolean verify(String hostname, SSLSession session) {
            return true;
        }	  
    };

   // create authorization token string with the UserID and password
   String userInfo  = "DirectorServer_UserID" + ":" + new String("DirectorServer_Password");
   authToken = "Basic " + Base64.encode(userInfo.getBytes());
        
   URL myURL = new URL("https://mysystem.ibm.com:8422/ibm/director/rest/resources/OperatingSystem");
   HttpsURLConnection.setDefaultHostnameVerifier(hv);
   HttpsURLConnection conn = (HttpsURLConnection)myURL.openConnection();
   conn.setSSLSocketFactory(sslSocketFactory);
   conn.setRequestProperty("Authorization", authToken);
   conn.setRequestProperty("ISDAPIVersion", VERSION);
   conn.setRequestMethod("GET");

conn.setRequestProperty( "content-type", "application/json; charset=UTF-8" ); // 进行编码
        // if any keys are specified in requestHeaders that were already set (above), they are overridden here
	//设置参数
       
    if (requestHeaders != null) {
         Set<String> keys = requestHeaders.keySet();
         for (String key : keys) {
          conn.setRequestProperty(key, requestHeaders.get(key));
         }
    }
         
   //设置请求的body
   // 设置是否向connection输出，因为这个是post请求，参数要放在
     // http正文内，因此需要设为true
   if (requestBody != null) {
            secureConnection.setDoOutput(true);
            OutputStreamWriter out = new OutputStreamWriter(secureConnection.getOutputStream());  
            out.write(requestBody);
            out.close();
   }
   
   //连接
   conn.connect();

   //获得请求返回状态码
   responseCode    = conn.getResponseCode();

   //获得请求返回内容
    BufferedReader rd  = new BufferedReader(new InputStreamReader(conn.getInputStream(),"UTF-8")); //以utf-8的格式输出
        
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = rd.readLine()) != null) {
            if (line.trim().length() > 1) {
                sb.append(line);
            }
        }
        rd.close();
     String result = sb.toString();

这里面的conn.connect函数，实际上只是建立了一个与服务器的tcp连接，并没有实际发送http请求。无论是post还是get，http请求实际上直到conn.getInputStream()这个函数里面才正式发送出去。

http请求实际上由两部分组成，一个是http头，所有关于此次http请求的配置都在http头里面定义，一个是正文content，在connect()函数里面，会根据HttpURLConnection对象的配置值生成http头，因此在调用connect函数之前，就必须把所有的配置准备好。

紧接着http头的是http请求的正文，正文的内容通过outputStream写入，实际上outputStream不是一个网络流，充其量是个字符串流，往里面写入的东西不会立即发送到网络，而是在流关闭后，根据输入的内容生成http正文。

至此，http请求的东西已经准备就绪。在getInputStream()函数调用的时候，就会把准备好的http请求正式发送到服务器了，然后返回一个输入流，用于读取服务器对于此次http请求的返回信息。由于http请求在getInputStream的时候已经发送出去了（包括http头和正文），因此在getInputStream()函数之后对connection对象进行设置（对http头的信息进行修改）或者写入outputStream（对正文进行修改）都是没有意义的了，执行这些操作会导致异常的发生。

参考：Http学习之使用HttpURLConnection发送post和get请求 - pandazxx的专栏 - 博客频道 - youkuaiyun.com

http://book.51cto.com/art/201203/323928.htm   http和rest   深入理解http和rest的关系

http://www.cnblogs.com/springyangwc/archive/2012/01/18/2325784.html 介绍rest  深入理解rest的实现