Merge pull request #2 from surajkumar/add-logger

Added logger and throw errors where needed

Author: surajkumar

build.gradle

@@ -22,5 +22,8 @@ subprojects {
         implementation 'com.amazonaws:aws-lambda-java-core:1.2.3'
         implementation 'com.amazonaws:aws-lambda-java-events:3.13.0'
         implementation 'com.amazonaws:aws-lambda-java-runtime-interface-client:2.6.0'
+
+        implementation 'org.slf4j:log4j-over-slf4j:2.0.16'
+        implementation 'ch.qos.logback:logback-classic:1.5.7'
     }
 }

lib/src/main/java/org/example/aws/CustomLogger.java

@@ -1,12 +1,16 @@
 package org.example.aws;
 
+import com.amazonaws.services.lambda.runtime.Context;
 import com.amazonaws.services.lambda.runtime.LambdaLogger;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
 
 public class CustomLogger implements LambdaLogger {
+    private static final Logger LOGGER = LogManager.getLogger(Context.class);
 
     @Override
     public void log(String s) {
-        System.out.println(s);
+        LOGGER.info(s);
     }
 
     @Override

lib/src/main/java/org/example/aws/LambdaRuntimeLoop.java

@@ -6,11 +6,15 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
 
 import java.io.IOException;
 import java.net.http.HttpResponse;
 
 public class LambdaRuntimeLoop {
+    private static final Logger LOGGER = LogManager.getLogger(LambdaRuntimeLoop.class);
+
     private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
             .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
 
@@ -33,15 +37,13 @@ public void run() throws IOException, InterruptedException {
             HttpResponse<String> event = lambdaRuntimeHttpClient.nextInvocation();
             String requestId = event.headers().firstValue(AWS_LAMBDA_REQUEST_ID).orElseThrow();
             String functionArn = event.headers().firstValue(AWS_LAMBDA_INVOKED_FUNCTION_ARN).orElseThrow();
-
-
             try {
                 APIGatewayProxyRequestEvent request = OBJECT_MAPPER.readValue(event.body(), APIGatewayProxyRequestEvent.class);
                 APIGatewayProxyResponseEvent output
                         = handler.handleRequest(request, new CustomContext(requestId, functionArn, 0));
                 lambdaRuntimeHttpClient.invocationResponse(requestId, writeValue(output));
             } catch (Exception e) {
-                System.err.println(e.getMessage());
+                LOGGER.error(e.getMessage());
                 try {
                     lambdaRuntimeHttpClient.invocationError(requestId);
                 } catch (IOException | InterruptedException ex) {

lib/src/main/java/org/example/aws/Main.java

@@ -3,46 +3,40 @@
 import com.amazonaws.services.lambda.runtime.RequestHandler;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
 
 import java.lang.reflect.Constructor;
 
 public class Main {
+    private static final Logger LOGGER = LogManager.getLogger(Main.class);
+
     public static void main(String[] args) throws Exception {
         LambdaRuntimeHttpClient lambdaRuntimeHttpClient = new LambdaRuntimeHttpClient();
 
         String handlerName = System.getenv("_HANDLER");
-        System.out.println("Invoking handler " + handlerName);
+        LOGGER.info("Invoking handler " + handlerName);
 
         RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> handler = getHandlerInstance(handlerName);
-        if (handler == null) {
-            System.out.println("Handler is null");
-            return;
-        }
-
         LambdaRuntimeLoop lambdaRuntimeLoop = new LambdaRuntimeLoop(lambdaRuntimeHttpClient, handler);
         lambdaRuntimeLoop.run();
     }
 
     private static RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> getHandlerInstance(String handlerName) {
         Class<?> handlerClass = loadHandlerClass(handlerName);
-        if (handlerClass == null) {
-            return null;
-        }
         Constructor<?> constructor = findZeroArgConstructor(handlerClass);
         if (constructor == null) {
-            System.out.println("No zero-arg constructor found for " + handlerName);
-            return null;
+            throw new RuntimeException("No zero-arg constructor");
         }
-
         return instantiateHandler(constructor);
     }
 
     private static Class<?> loadHandlerClass(String handlerName) {
         try {
             return Class.forName(handlerName);
         } catch (ClassNotFoundException e) {
-            System.out.println("Handler not found: " + e.getMessage());
-            return null;
+            LOGGER.error("Handler not found on classpath: " + handlerName);
+            throw new RuntimeException(e);
         }
     }
 
@@ -52,6 +46,7 @@ private static Constructor<?> findZeroArgConstructor(Class<?> clazz) {
                 return constructor;
             }
         }
+        LOGGER.warn("No zero-arg constructor found for " + clazz.getName());
         return null;
     }
 
@@ -60,8 +55,8 @@ private static RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyRespon
         try {
             return (RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent>) constructor.newInstance();
         } catch (Exception e) {
-            System.out.println("Failed to construct handler: " + e.getMessage());
-            return null;
+            LOGGER.error("Failed to construct instance of handler: ", e);
+            throw new RuntimeException(e);
         }
     }
 }