okhttp用法

1. Get操作（get操作参数是拼接在url后面的）

    1 public void doGet(View view) {
    2         //1.拿到okHttpClient对象
    3   //      OkHttpClient okHttpClient = new OkHttpClient();
    4         //2、构造Request
    5         Request.Builder builder = new Request.Builder();
    6         Request request = builder
    7                 .get()
    8                 .url(mBaseUrl+"login?username=cyd&password=1234")
    9                 .build();
   10         //3、4
   11         executeRequest(request);
   12     }

2. GAT、POST抽取出来的公共方法

    1 public void executeRequest(Request request ){
    2         //3、将Request封装为Call
    3         Call call = okHttpClient.newCall(request);
    4         //4、执行Call（回调的返回值是response,不在UI线程之内）
    5         call.enqueue(new Callback() {
    6             @Override
    7             public void onFailure(Request request, IOException e) {
    8                 L.e("onFailure"+e.getMessage());
    9             }
   10             @Override
   11             public void onResponse(Response response) throws IOException {
   12                 L.e("onResponse：");
   13                 final String str = response.body().string();
   14                 //             textView.setText(str);不能在子线程操作UI
   15                 //正确方法：
   16                 runOnUiThread(new Runnable() {
   17                     @Override
   18                     public void run() {
   19                         textView.setText(str);
   20                     }
   21                 });
   22             }
   23         });
   24 
   25     }
3. Post(post参数是构造一个请求体responseBody)

    1 public void doPost(View view) {
    2         //1.拿到okHttpClient对象
    3         //2、构造Request
    4         //2.1、构造requestBody
    5         //FormEncodingBuilder是传递post的参数的builder
    6         FormEncodingBuilder requestBodyBuilder = new FormEncodingBuilder();
    7         RequestBody requestBody = requestBodyBuilder
    8                 .add("username","cyd")
    9                 .add("password","123456789").build();
   10 
   11         Request.Builder builder = new Request.Builder();
   12         Request request = builder.url(mBaseUrl + "login").post(requestBody).build();
   13         //3、4
   14         executeRequest(request);
   15     }

4. POST一个JSON字符串

    1 public void doPostString(View view) {
    2         //将String作为requestBody发送出去，与上面不同的只有requestBody的构造方法
    3         //仅仅post字符串不需要使用FormEncodingBuilder的构造者模式
    4 
    5         //第一个参数包含类型和字符编码，第二个是字符串
    6         RequestBody requestBody = RequestBody.create(MediaType.parse("text/plain;chaset=utf-8"), "{username:cyd,password:09876}");
    7         Request.Builder builder = new Request.Builder();
    8         Request request = builder.url(mBaseUrl + "postString").post(requestBody).build();
    9         //3、4
   10         executeRequest(request);
   11     }

   服务端打印出字符串结果：

5. 服务端代码：

    1 public String login() {
    2         System.out.println(username+","+password);
    3         HttpServletResponse response = ServletActionContext.getResponse();
    4         try {
    5             PrintWriter writer = response.getWriter();
    6             writer.write("login success!");
    7             writer.flush();
    8         } catch (IOException e) {
    9             // TODO Auto-generated catch block
   10             e.printStackTrace();
   11         }        
   12         return null;        
   13     }
   14     public String postString() {
   15         HttpServletRequest request = ServletActionContext.getRequest();
   16         try {
   17             ServletInputStream iServletInputStream = request.getInputStream();
   18             
   19             StringBuilder sb = new StringBuilder();
   20             int len =0;
   21             byte[] buf = new byte[1024];
   22             while((len = iServletInputStream.read(buf))!= -1) {
   23                 sb.append(new String (buf,0 ,len));
   24             }
   25             System.out.println(sb.toString());
   26             
   27         } catch (IOException e) {
   28             // TODO Auto-generated catch block
   29             e.printStackTrace();
   30         }
   31         
   32         return null;
   33     }

6. 服务端接收参数是通过成员变量获取，客户端接收到服务端的数据一般是通过回调里面的response拿到inputStream，服务端获取客户端的数据流是通过request拿到的
7. session保持问题：用户登录后服务端会产生一个sessionID，sessionID会以cookie的形式返回给客户端，客户端拿到sessionID后若服务端sessionID还在生命周期中则可以不用重复登录，可以作为判断用户是否登录。可以获取sessionID
8. 笔记来源于：https://www.imooc.com/learn/764