java網絡URL請求編程入門

對於使用URL類請求網絡服務器並接受請求進行簡單處理的示例，記錄下學習過程。

 

 

 

• GET請求

1. 代碼示例如下

   package testHttpGet;
   
   import java.io.BufferedReader;
   import java.io.IOException;
   import java.io.InputStream;
   import java.io.InputStreamReader;
   import java.io.OutputStream;
   import java.io.OutputStreamWriter;
   import java.net.MalformedURLException;
   import java.net.URL;
   import java.net.URLConnection;
   
   public class TestGet {
       public static void main(String[] args) {
           new ReadByGet().start();
       }
       
       static class ReadByGet extends Thread{
           @Override
           public void run() {
               try {
                   //根據URL地址創建一個URL對象
                   URL url = new URL("https://easy-mock.com/mock/5c2f632779696b7e93ba23d6/example/testhttpget");
                   
                   //獲取URL連接，open方法返回一個URLConnection類的對象
                   URLConnection conn = url.openConnection();
                   
                   //從連接獲取輸入流，請求的輸入也就是對請求的輸入，即是相應，
                   InputStream in = conn.getInputStream();
                   InputStreamReader is = new InputStreamReader(in);
                   
                   //將字節流轉換成字符流，方便操作
                   BufferedReader br = new BufferedReader(is);
                   String line = null;
                   while((line = br.readLine())!=null) {
                       //打印相應的內容
                       System.out.println(line);
                   }
               } catch (MalformedURLException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
               } catch (IOException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
               }
           }
       }
   }
   
   結果：返回一個html頁面

    

    

2. 內部類如果在靜態方法里面創建對象必須是靜態內部類，或者將其聲明在外部。

 

 

• POST請求

1. 代碼示例如下：

   package testHttpGet;
   
   import java.io.BufferedReader;
   import java.io.BufferedWriter;
   import java.io.IOException;
   import java.io.InputStream;
   import java.io.InputStreamReader;
   import java.io.OutputStream;
   import java.io.OutputStreamWriter;
   import java.net.HttpURLConnection;
   import java.net.MalformedURLException;
   import java.net.URL;
   
   public class TestHttpPost {
       public static void main(String[] args) {
           new ReadByPost().start();
       }
       
       static class ReadByPost extends Thread{
           @Override
           public void run() {
               try {
                   URL url = new URL("https://easy-mock.com/mock/5c2f632779696b7e93ba23d6/example/testhttpget");
                   
                   //返回一個HttpURLConnection對象，他繼承自URLConnection，
                   HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                   
                   //設置請求頭
                   conn.addRequestProperty("encoding", "utf-8");
                   
                   //設置允許對請求輸入和輸出參數，也就是對請求加上參數
                   conn.setDoInput(true);
                   conn.setDoOutput(true);
                   
                   //設置請求方式為POST
                   conn.setRequestMethod("POST");
                   
                   OutputStream out = conn.getOutputStream();
                   OutputStreamWriter owt = new OutputStreamWriter(out);
                   BufferedWriter bw = new BufferedWriter(owt);
                   //對請求設置參數
                   bw.write("name=Tom&age=18");
                   
                   //獲取請求的響應，輸入流
                   InputStream in = conn.getInputStream();
                   InputStreamReader is = new InputStreamReader(in);
                   BufferedReader br = new BufferedReader(is);
                   String line = null;
                   while((line = br.readLine()) != null) {
                       System.out.println(line);
                   }
               } catch (MalformedURLException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
               } catch (IOException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
               }
           }
       }
   }
   
   注意點：設置請求參數之前必須先設置請求方式為POST，否則會拋出異常，輸入流和輸出流的先后順序也不能顛倒，因為是先請求再得到響應，所以是輸出流在前，為請求設置請求參數，
   輸入流在后，就是得到的響應的具體內容！