BAEL-7444 create custom url connection (#15717)

core-java-modules/core-java-networking-4/src/main/java/com/baeldung/customurlconnection/CustomURLConnection.java

@@ -0,0 +1,55 @@
+package com.baeldung.customurlconnection;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URL;
+import java.net.URLConnection;
+
+public class CustomURLConnection extends URLConnection {
+    private final String simulatedData = "This is the simulated data from the resource.";
+    private URL url;
+    private boolean connected = false;
+    private String headerValue = "SimulatedHeaderValue";
+
+    protected CustomURLConnection(URL url) {
+        super(url);
+        this.url = url;
+    }
+
+    @Override
+    public void connect() throws IOException {
+        connected = true;
+        System.out.println("Connection established to: " + url);
+    }
+
+    @Override
+    public InputStream getInputStream() throws IOException {
+        if (!connected) {
+            connect();
+        }
+        return new ByteArrayInputStream(simulatedData.getBytes());
+    }
+
+    @Override
+    public OutputStream getOutputStream() throws IOException {
+        ByteArrayOutputStream simulatedOutput = new ByteArrayOutputStream();
+        return simulatedOutput;
+    }
+
+    @Override
+    public int getContentLength() {
+        return simulatedData.length();
+    }
+
+    @Override
+    public String getHeaderField(String name) {
+        if ("SimulatedHeader".equalsIgnoreCase(name)) { // Example header name
+            return headerValue;
+        } else {
+            return null; // Header not found
+        }
+    }
+}

core-java-modules/core-java-networking-4/src/main/java/com/baeldung/customurlconnection/CustomURLStreamHandler.java

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+package com.baeldung.customurlconnection;
+
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+
+public class CustomURLStreamHandler extends URLStreamHandler {
+
+    @Override
+    protected URLConnection openConnection(URL u) throws IOException {
+        // Create and return an instance of CustomURLConnection
+        return new CustomURLConnection(u);
+    }
+}

core-java-modules/core-java-networking-4/src/main/java/com/baeldung/customurlconnection/CustomURLStreamHandlerFactory.java

@@ -0,0 +1,16 @@
+package com.baeldung.customurlconnection;
+
+import java.net.URLStreamHandler;
+import java.net.URLStreamHandlerFactory;
+
+public class CustomURLStreamHandlerFactory implements URLStreamHandlerFactory {
+
+    @Override
+    public URLStreamHandler createURLStreamHandler(String protocol) {
+        // Check if the requested protocol is our custom protocol
+        if ("myprotocol".equals(protocol)) {
+            return new CustomURLStreamHandler();
+        }
+        return null; // Let the default handler deal with other protocols
+    }
+}

core-java-modules/core-java-networking-4/src/main/java/com/baeldung/customurlconnection/Main.java

@@ -0,0 +1,34 @@
+package com.baeldung.customurlconnection;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.Scanner;
+
+public class Main {
+
+    public static void main(String[] args) {
+        URL.setURLStreamHandlerFactory(new CustomURLStreamHandlerFactory());
+
+        try {
+            URL url = new URL("myprotocol://example.com/resource");
+
+            CustomURLConnection customConnection = (CustomURLConnection) url.openConnection();
+            customConnection.connect();
+
+            InputStream inputStream = customConnection.getInputStream();
+
+            String content = new Scanner(inputStream).useDelimiter("\\A").next();
+            System.out.println(content);
+
+            int contentLength = customConnection.getContentLength();
+            System.out.println("Content Length: " + contentLength);
+
+            String headerValue = customConnection.getHeaderField("SimulatedHeader");
+            System.out.println("Header Value: " + headerValue);
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}