HttpClient 的使用

应用场合，项目在做数据通信时，开始使用的是socket 做数据通信，最后搞了半天又说socket 通信对外不能提供服务，

需要做一个代理，然后就用到了HttpClient 。

 1.把请求数据使用httpClient 发送到某一个servlet.

 2.然后在servlet 使用socket 进行转发。达到目的。

代码如下： 最后一个参数是http client 请求url 报错时， 三次请求url

	/** 把报文结构发送到服务器端 post */
	public HttpMethod getPostMethod(String ip, String port, String result) {
		String url = "http://" + HttpClientUtil.localIP() + ":"
				+ HttpClientUtil.localPort() + "/httpclienttest/client";
		PostMethod postMethod = new PostMethod(url);
		postMethod.addParameter("ip", ip);
		postMethod.addParameter("port", port);
		postMethod.addParameter("result", result);
		postMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
				new DefaultHttpMethodRetryHandler(RETRY_COUNT, SENT_RETRY));
		return postMethod;
	}

  HttpClient client=null; HttpMethod method = null; System.out.println("客户端正在连接..."); client = new HttpClient(); method = getPostMethod(HttpClientUtil.gxIP(),HttpClientUtil.gxPort(),resultAnt());// 使用POST方式提交数据 int state= client.executeMethod(method); System.out.println("state:"+state); String res = new String(method.getResponseBodyAsString().getBytes("GB2312"));//读取服务器端返回xml method.releaseConnection(); 

以下是服务器端 servlet 转发代码

@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {String ip = req.getParameter("ip");String port = req.getParameter("port");String result = req.getParameter("result");System.out.println("IP:"+ip+"/tport:"+port+"/tresult:"+result);Socket socket = SocketUtil.getSocket(ip,Integer.valueOf(port));SocketUtil.send(socket,result);String respResult= SocketUtil.incept(socket);resp.getOutputStream().write(respResult.getBytes());socket.close();super.doPost(req, resp);} 

web.xml配置

<servlet> <servlet-name>client</servlet-name> <servlet-class>test.servlet.MyServlet</servlet-class></servlet><servlet-mapping> <servlet-name>client</servlet-name> <url-pattern>/client</url-pattern></servlet-mapping> 

SocketUtil.java

public class SocketUtil {private static Socket socket = null; /**获取一个socket 连接*/public static Socket getSocket(String ip,int port) {try {socket = new Socket(ip,port);} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}return socket;}/** * 发送请求报文 * 注:不可以关闭流 否则会关闭对应的socket */public static void send(Socket socket, String msg) { PrintWriter out=null;try {out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()),true);} catch (IOException e) {e.printStackTrace();} out.println(msg);}/** * 接收服务器返回的报文 * 注:不可以关闭流 否则会关闭对应的socket */public static String incept(Socket socket) {String result = null;try {BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));result = br.readLine();} catch (IOException e) {e.printStackTrace();} return result;}} 

SocketUtil.java 最终改成以下方式 在服务器发送过一的数据时，有固定的报文长度。

public class SocketUtil {
	private static Socket socket = null;
    /**获取一个socket 连接*/
	public static Socket getSocket(String ip,int port) {
		try {
			socket = new Socket(ip,port);
		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return socket;
	}

	/**
	 *  发送请求报文 
	 *  注:不可以关闭流 否则会关闭对应的socket
	 */
	public static void send(Socket socket, byte[] msg) {
	   DataOutputStream out=null;
		try {
			out = new DataOutputStream((socket.getOutputStream()));
			out.write(msg);
			out.flush();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 *  接收服务器返回的报文
	 *  注:不可以关闭流 否则会关闭对应的socket 
	 */
	public static byte [] incept(Socket socket) {
		byte [] head = new byte[4];
		byte [] body=null;
		try {
			BufferedInputStream bufIn = new BufferedInputStream(socket.getInputStream());
			bufIn.read(head);
			int len1 = Integer.parseInt(new String(head));
			body = new byte[len1];
			bufIn.read(body);
		} catch (IOException e) {
			e.printStackTrace();
		}
		  return body;
	}
	
}

httpClient 使用的jar包如下