java-http communication

The java project uses HTTP requests. There are two main ways:
① Use the HttpURLConnection method under the java.net package that comes with the JDK.

②Use apache's HttpClient method.

1. Use the HttpURLConnection method under the java.net package that comes with the JDK.

Method summary
`abstract void`	`disconnect()` Indicates that the server is unlikely to have other requests in the near future.
`InputStream`	`getErrorStream()` If the connection fails but the server still sent useful data, an error stream is returned.
`static boolean`	`getFollowRedirects()` Returns a `boolean`value .
`String`	`getHeaderField(int n)` Returns the value of the `n`^th header field.
`long`	`getHeaderFieldDate(String name, long Default)` Returns the value of the specified field parsed as a date.
`String`	`getHeaderFieldKey(int n)` Returns the key of the `n`^th header field.
`boolean`	`getInstanceFollowRedirects()` `HttpURLConnection`Returns `instanceFollowRedirects`the value of the field of this .
`Permission`	`getPermission()` Returns a permissions object representing the permissions required to establish the connection represented by this object.
`String`	`getRequestMethod()` Get request method.
`int`	`getResponseCode()` Get the status code from the HTTP response message.
`String`	`getResponseMessage()` Get the HTTP response message, if any, returned with the response code from the server.
`void`	`setChunkedStreamingMode(int chunklen)` This method is used to enable streaming of HTTP request bodies without internal buffering when the content length is not known in advance .
`void`	`setFixedLengthStreamingMode(int contentLength)` This method is used to enable streaming of HTTP request bodies without internal buffering when the content length is known in advance.
`static void`	`setFollowRedirects(boolean set)` Sets whether this class should automatically perform HTTP redirects (requests with response code 3xx).
`void`	`setInstanceFollowRedirects(boolean followRedirects)` Sets whether this `HttpURLConnection`instance should automatically perform HTTP redirects (requests with response code 3xx).
`void`	`setRequestMethod(String method)` Set the method for the URL request, GET POST HEAD OPTIONS PUT DELETE TRACE One of the above methods is legal, depending on the restrictions of the protocol.
`abstract boolean`	`usingProxy()` Indicates whether the connection goes through a proxy.

sender:

public void requestFunction(HttpServletRequest request, HttpServletResponse response){
        try {
            request.setCharacterEncoding( "utf-8"); // Set the encoding method of the request   
            response.setContentType("text/html;charset=utf-8"); // Set the encoding method when returning   
            String http = "" ;
            URL url = new URL(http); // Set the URL address of the HTTP connection 
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection(); // Generate the HttpURLConnection connection 
            httpURLConnection.setConnectTimeout(5000); // Set the connection timeout value 
            httpURLConnection.setRequestMethod ("post"); // Set the request method 
            httpURLConnection.setDoOutput( true ); // Allow output 
            httpURLConnection.setDoInput( true ); // Allow input 
            httpURLConnection.setUseCaches( false ); // Do not allow caching
            OutputStream outs = httpURLConnection.getOutputStream();
            OutputStreamWriter sWriter = new OutputStreamWriter(outs,"UTF-8"); // Set the output stream 
            sWriter.write(message); // Write the buffer stream 
            sWriter.flush(); // Flush the buffer stream 
            sWriter.close(); // Close the output stream 
            outs.close();
             int responseCode = httpURLConnection.getResponseCode(); // Get the returned request code
             // Indicates that the request is successful 
            if (responseCode == HttpURLConnection.HTTP_OK) {
                InputStream iStream = httpURLConnection.getInputStream(); // Get the output stream of the server, get the return data
                 // Read text from the character input stream, buffer each character, so as to achieve efficient reading of characters, arrays and lines. 
                BufferedReader bReader = new BufferedReader( new InputStreamReader(iStream));
                String len;
                String str = "";
                while ((len=bReader.readLine()) != null) {
                    str + = only;
                }
            }
        } catch (Exception e) {
        }
    }

Server:

private void responseFunction(HttpServletRequest request, HttpServletResponse response) {
        request.setCharacterEncoding("utf-8");  
        response.setContentType("text/html;charset=utf-8");  
        String str =request.getParameter("xxx"); // Get the parameters for sending HTTP request    
        response.getWriter().write("{\"message\":\"success\"}"); // Send to HTTP party returns response data   
    }

java-http communication

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