py4j

import os from py4j.java_gateway import JavaGateway, GatewayParameters import subprocess import time # --- Java Gateway Server Setup (for demonstration) --- # In a real application, the Java Gateway Server would be started separately. # For this example, we'll try to start a minimal one programmatically. # This assumes 'py4j<version>.jar' is in the classpath. For simplicity, # we'll use a placeholder for py4j.jar path. Users need to replace it. # Usually, py4j.jar is found in your Python environment's site-packages/py4j/ directory. # NOTE: Replace '/path/to/py4j<version>.jar' with the actual path to your Py4J JAR file. # You can find it by running: `python -c "import py4j; import os; print(os.path.join(os.path.dirname(py4j.__file__), 'py4j0.10.9.9.jar'))"` PY4J_JAR_PATH = os.environ.get('PY4J_JAR_PATH', '/path/to/py4j0.10.9.9.jar') # Update this path! java_code = """ import py4j.GatewayServer; public class AdditionApplication { public int addition(int first, int second) { return first + second; } public static void main(String[] args) { AdditionApplication app = new AdditionApplication(); GatewayServer server = new GatewayServer(app, 25333); server.start(); System.out.println("Gateway Server Started on port 25333"); } } """ # Attempt to compile and run the Java code for quickstart demo # This is a simplification and might require manual setup for complex environments. # In a production setting, the Java server would be a separate, long-running process. # Create temporary files for Java code and compiled class java_file_name = "AdditionApplication.java" class_file_name = "AdditionApplication.class" with open(java_file_name, "w") as f: f.write(java_code) try: # Compile Java code (requires javac in PATH) compile_process = subprocess.run( ["javac", "-cp", PY4J_JAR_PATH, java_file_name], capture_output=True, text=True ) if compile_process.returncode != 0: print("Java compilation failed:", compile_process.stderr) print("Please ensure javac is in your PATH and PY4J_JAR_PATH is correct.") # Fallback for systems without javac or if compilation fails: manual start instruction print("Alternatively, you can manually compile and run the Java server:") print(f"1. Save the Java code above as {java_file_name}") print(f"2. Compile: javac -cp {PY4J_JAR_PATH} {java_file_name}") print(f"3. Run: java -cp {PY4J_JAR_PATH}:. AdditionApplication") # If on Windows, use ';' instead of ':' for classpath separator in commands raise RuntimeError("Java compilation failed, cannot run quickstart.") # Run Java Gateway Server in a separate process # Using 'nohup' and '&' for background on *NIX, or 'start' on Windows if os.name == 'nt': # Windows java_server_command = ["java", "-cp", f".;{PY4J_JAR_PATH}", "AdditionApplication"] java_process = subprocess.Popen(java_server_command, creationflags=subprocess.CREATE_NEW_PROCESS_GROUP) else: # Unix-like java_server_command = ["java", "-cp", f":{PY4J_JAR_PATH}", "AdditionApplication"] java_process = subprocess.Popen(java_server_command, preexec_fn=os.setsid) print("Starting Java Gateway Server...") time.sleep(5) # Give Java server time to start # --- Python Client --- gateway = JavaGateway(gateway_parameters=GatewayParameters(port=25333)) # Access the Java entry point (AdditionApplication instance) addition_app = gateway.entry_point # Call a Java method number1 = 5 number2 = 3 result = addition_app.addition(number1, number2) print(f"Python calling Java: {number1} + {number2} = {result}") # Access JVM directly for standard Java objects java_list = gateway.jvm.java.util.ArrayList() java_list.add("Hello from Python!") print(f"Java list created and modified from Python: {java_list}") except Exception as e: print(f"An error occurred during quickstart: {e}") finally: # Clean up Java process if it was started if 'java_process' in locals() and java_process.poll() is None: print("Shutting down Java Gateway Server...") if os.name == 'nt': subprocess.run(["taskkill", "/F", "/T", "/PID", str(java_process.pid)], capture_output=True) else: os.killpg(os.getpgid(java_process.pid), 15) # Send SIGTERM java_process.wait(timeout=5) # Clean up temporary files os.remove(java_file_name) if os.path.exists(java_file_name) else None os.remove(class_file_name) if os.path.exists(class_file_name) else None # Also remove AdditionApplication$*.class files if they exist for f in os.listdir('.'): if f.startswith('AdditionApplication$') and f.endswith('.class'): os.remove(f)