Request-Response Flow

Connection Configuration Methods

• setAllowUserInteraction
• setDoInput
• setDoOutput
• setIfModifiedSince
• setUseCaches
• setDefaultAllowUserInteraction
• setDefaultUseCaches

Header Management

• setRequestProperty(key,value)
• addRequestProperty(key,value)

setRequestProperty replaces all existing values for a given key, effectively clearing and reassigning. addRequestProperty appends additional values to an existing key.

Sending URL Requests

After establishing a connection, send requests by transmitting parameters to the server using output streams:

• getOutputStream

Reading Responses

• getContent
• getHeaderField
• getInputStream

HttpURLConnection Architecture

Network connections require sockets, but HttpURLConnection operates at a higher abstraction level without direct socket configuration. This abstraction explains why HttpURLConnection is a abstract clas instantiated only through URL.openConnection().

While underlying network connections can be shared across multiple HttpURLConnection instances, each instance handles only one request. After request completion, close the InputStream or OutputStream to release network resources. For persistent connections, use disconnect() to close the underlying socket.

Configuration Examples

Serialized Objects

// Configure content type for serialized Java objects
// Without this setting, serialization may throw java.io.EOFException
httpConnection.setRequestProperty("Content-type", "application/x-java-serialized-object");

// URLConnection establishes connection
// getOutputStream implicitly calls connect()
OutputStream output = httpConnection.getOutputStream();

// Send serialized data
ObjectOutputStream objStream = new ObjectOutputStream(output);
objStream.writeObject(new String("Test payload"));

String Data

connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");

Implementation Example

BufferedReader inputReader = null;
OutputStreamWriter outputWriter = null;
HttpURLConnection httpConn = null;
String responseData = "";

try {
    URL targetUrl = new URL(apiEndpoint);
    httpConn = (HttpURLConnection) targetUrl.openConnection();
    
    // Configure input/output streams
    httpConn.setDoOutput(true);
    httpConn.setDoInput(true);
    
    // Timeout settings
    httpConn.setConnectTimeout(10000);
    httpConn.setReadTimeout(10000);
    
    // Disable caching for POST
    httpConn.setUseCaches(false);
    httpConn.setInstanceFollowRedirects(true);
    
    // Request configuration
    httpConn.setRequestMethod("POST");
    httpConn.setRequestProperty("Content-Type", "application/json;charset=utf-8");
    httpConn.setRequestProperty("Accept", "application/json");
    httpConn.setRequestProperty("access_key", apiKey);
    
    // Send JSON payload
    outputWriter = new OutputStreamWriter(httpConn.getOutputStream(), "UTF-8");
    outputWriter.write(jsonPayload);
    outputWriter.flush();
    
    // Process response
    inputReader = new BufferedReader(new InputStreamReader(httpConn.getInputStream(), "UTF-8"));
    String currentLine;
    while ((currentLine = inputReader.readLine()) != null) {
        responseData += currentLine;
    }
    
    // Release connection
    httpConn.disconnect();
    
    JSONObject result = JSON.parseObject(responseData);
} catch (Exception ex) {
    ex.printStackTrace();
} finally {
    try {
        if (outputWriter != null) outputWriter.close();
        if (inputReader != null) inputReader.close();
    } catch (IOException ioEx) {
        ioEx.printStackTrace();
    }
}