Added working example-java. Functionally the same as example-go.

Author: yualexan

sample-apps/example-java/function/build.gradle

@@ -0,0 +1,28 @@
+plugins {
+    id 'java'
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation 'com.amazonaws:aws-lambda-java-core:1.2.3'
+    implementation 'software.amazon.awssdk:s3:2.28.29'
+    implementation 'org.slf4j:slf4j-nop:2.0.16'
+}
+
+task buildZip(type: Zip) {
+    from compileJava
+    from processResources
+    into('lib') {
+        from configurations.runtimeClasspath
+    }
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_21
+    targetCompatibility = JavaVersion.VERSION_21
+}
+
+build.dependsOn buildZip

sample-apps/example-java/function/event.json

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+{
+  "orderId": "1200Gradle",
+  "amount": 359.99,
+  "item": "Aviation Headset"
+}

sample-apps/example-java/function/output.txt

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+"Success"

sample-apps/example-java/function/pom.xml

@@ -0,0 +1,73 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.example</groupId>
+  <artifactId>example-java</artifactId>
+  <packaging>jar</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <name>example-java-function</name>
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>21</maven.compiler.source>
+    <maven.compiler.target>21</maven.compiler.target>
+  </properties>
+  <dependencies>
+    <dependency>
+        <groupId>com.amazonaws</groupId>
+        <artifactId>aws-lambda-java-core</artifactId>
+        <version>1.2.3</version>
+    </dependency>
+    <dependency>
+        <groupId>software.amazon.awssdk</groupId>
+        <artifactId>s3</artifactId>
+        <version>2.28.29</version>
+    </dependency>
+    <dependency>
+        <groupId>org.slf4j</groupId>
+        <artifactId>slf4j-nop</artifactId>
+        <version>2.0.16</version>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>3.5.2</version>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-shade-plugin</artifactId>
+        <version>3.4.1</version>
+        <configuration>
+          <createDependencyReducedPom>false</createDependencyReducedPom>
+          <filters>
+            <filter>
+                <artifact>*:*</artifact>
+                <excludes>
+                    <exclude>META-INF/*</exclude>
+                    <exclude>META-INF/versions/**</exclude>
+                </excludes>
+            </filter>
+          </filters>
+        </configuration>
+        <executions>
+          <execution>
+            <phase>package</phase>
+            <goals>
+              <goal>shade</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.13.0</version>
+        <configuration>
+           <release>21</release>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>

sample-apps/example-java/function/src/main/java/example/OrderHandler.java

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+package example;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+import software.amazon.awssdk.core.sync.RequestBody;
+import software.amazon.awssdk.services.s3.S3Client;
+import software.amazon.awssdk.services.s3.model.PutObjectRequest;
+import software.amazon.awssdk.services.s3.model.S3Exception;
+
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Lambda handler for processing orders and storing receipts in S3.
+ */
+public class OrderHandler implements RequestHandler<OrderHandler.Order, String> {
+
+    private static final S3Client S3_CLIENT = S3Client.builder().build();
+
+    /**
+     * Record to model the input event.
+     */
+    public record Order(String orderId, double amount, String item) {}
+
+    @Override
+    public String handleRequest(Order event, Context context) {
+        try {
+            // Access environment variables
+            String bucketName = System.getenv("RECEIPT_BUCKET");
+            if (bucketName == null || bucketName.isEmpty()) {
+                throw new IllegalArgumentException("RECEIPT_BUCKET environment variable is not set");
+            }
+
+            // Create the receipt content and key destination
+            String receiptContent = String.format("OrderID: %s\nAmount: $%.2f\nItem: %s",
+                    event.orderId(), event.amount(), event.item());
+            String key = "receipts/" + event.orderId() + ".txt";
+
+            // Upload the receipt to S3
+            uploadReceiptToS3(bucketName, key, receiptContent);
+
+            context.getLogger().log("Successfully processed order " + event.orderId() +
+                    " and stored receipt in S3 bucket " + bucketName);
+            return "Success";
+
+        } catch (Exception e) {
+            context.getLogger().log("Failed to process order: " + e.getMessage());
+            throw new RuntimeException(e);
+        }
+    }
+
+    private void uploadReceiptToS3(String bucketName, String key, String receiptContent) {
+        try {
+            PutObjectRequest putObjectRequest = PutObjectRequest.builder()
+                    .bucket(bucketName)
+                    .key(key)
+                    .build();
+
+            // Convert the receipt content to bytes and upload to S3
+            S3_CLIENT.putObject(putObjectRequest, RequestBody.fromBytes(receiptContent.getBytes(StandardCharsets.UTF_8)));
+        } catch (S3Exception e) {
+            throw new RuntimeException("Failed to upload receipt to S3: " + e.awsErrorDetails().errorMessage(), e);
+        }
+    }
+}