Add example for Java build with Gradle (#658)

_examples/java/functions/with-gradle/.apexignore

@@ -0,0 +1,2 @@
+*
+!apex.jar

_examples/java/functions/with-gradle/build.gradle

@@ -0,0 +1,26 @@
+apply plugin: 'java'
+
+repositories {
+    mavenCentral()
+}
+
+sourceCompatibility = 1.8
+targetCompatibility = 1.8
+
+dependencies {
+    compile (
+        'com.amazonaws:aws-lambda-java-core:1.1.0',
+    )
+}
+
+task buildJar(type: Jar) {
+    archiveName = "apex.jar"
+    from compileJava
+    from processResources
+    into('lib') {
+        from configurations.runtime
+    }
+}
+
+build.dependsOn buildJar
+

_examples/java/functions/with-gradle/function.json

@@ -0,0 +1,9 @@
+{
+  "description": "Java example function with existing build.gradle",
+  "handler": "lambda.Example::handler",
+  "runtime": "java",
+  "hooks": {
+    "build": "gradle build",
+    "clean": "gradle clean"
+  }
+}

_examples/java/functions/with-gradle/src/main/java/lambda/Example.java

@@ -0,0 +1,48 @@
+package lambda;
+
+import com.amazonaws.services.lambda.runtime.Context;
+
+public class Example {
+
+    public static class ExampleRequest {
+        String hello;
+
+        public String getHello() {
+            return hello;
+        }
+
+        public void setHello(String hello) {
+            this.hello = hello;
+        }
+
+        public ExampleRequest(String hello) {
+            this.hello = hello;
+        }
+
+        public ExampleRequest() {
+        }
+    }
+
+    public static class ExampleResponse {
+        String hello;
+
+        public String getHello() {
+            return hello;
+        }
+
+        public void setHello(String hello) {
+            this.hello = hello;
+        }
+
+        public ExampleResponse(String hello) {
+            this.hello = hello;
+        }
+
+        public ExampleResponse() {
+        }
+    }
+
+    public ExampleResponse handler(ExampleRequest event, Context context) {
+        return new ExampleResponse(event.getHello());
+    }
+}