j2me和Sevlet通信

 

按过程来描述：

j2me提交请求给sevlet-->sevlet处理POST请求doPost()-->j2me处理回应

只有Post才能提交给sevlet.

1） J2ME提交请求：

String [] endpoints = ChooseCourse.getCourseEndpointURL ();

//准备URL[http://localhost:8080/WebModule1/server]

      String url = endpoints[ChooseCourse.getIndex ()];//取得长度赋予字符串

      conn = (HttpConnection) Connector.open( url );//设置CONN连接的URL

      conn.setRequestMethod(HttpConnection.POST);//设置CONN连接的POST类型

      dout = conn.openDataOutputStream();//设置CONN连接的发出请求

      dout.writeInt(0); // 设置 opcode=0，表示取得服务上答案的记录

      dout.writeUTF( UpdateToken.getToken () );//得到代号

      dout.flush();//提交发出请求

 

      din = conn.openDataInputStream();//设置CONN连接的接受请求

      boolean succ = din.readBoolean();

      if ( succ ) {//循环读入接受的请求

        ShowQuestion.setQid ( din.readInt() );//得到ID

       ShowQuestion.setQuestion ( din.readUTF() );//得到问题

        int numchoices = din.readInt();//得到答案的个数

        String [] choices = new String [numchoices];

        for (int i=0; i < numchoices; i++) {

          choices[i] = din.readUTF();//取得选择的答案列表

        }

        //将请求显示出来，利用ShowQuestion类

        ShowQuestion.setChoices(choices);

        ShowQuestion.setComment("");

 

2）sevlet处理POST请求doPost()

public void doPost(HttpServletRequest request,HttpServletResponse response)

      throws ServletException, IOException {

 

    response.setContentType("application/binary");

try {

//准备输入输出流

      InputStream in =

           (InputStream) request.getInputStream();

      OutputStream out =

           (OutputStream) response.getOutputStream();

      DataInputStream din = new DataInputStream(in);

      DataOutputStream dout =

                          new DataOutputStream(out);

//按请求发出的顺序读入

      int opcode = din.readInt();//读入opcode

      String securityToken = din.readUTF();//读入安全代号

    

      //通过验证

      userid = securityToken.substring(0, securityToken.indexOf(":"));

      if ( opcode == 0 ) {//当处理代码为0时，只是查询有什么问题

        getQuestion(din, dout);

      } else if ( opcode == 1 ) {//插入回答的问题

        submitAnswer(din, dout);

      }

 

    } catch (Exception e) {

      e.printStackTrace();

    }

 }