feat: custom resource example for Java

java/custom-resource/.gitignore

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+.classpath.txt
+target
+.classpath
+.project
+.idea
+.settings
+.vscode
+*.iml
+
+# CDK asset staging directory
+.cdk.staging
+cdk.out
+

java/custom-resource/README.md

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+# Custom Resource
+<!--BEGIN STABILITY BANNER-->
+---
+
+![Stability: Stable](https://img.shields.io/badge/stability-Stable-success.svg?style=for-the-badge)
+
+> **This is a stable example. It should successfully build out of the box**
+>
+> This examples only on the core CDK library, and does not have any infrastructure prerequisites to build.
+
+---
+<!--END STABILITY BANNER-->
+
+This example shows adding a custom resource to a CDK app in Java. This custom resource is useful when considering design of constructs, or separating your architecture into components.
+
+
+## Building
+
+To build this app, run `mvn compile`. This will download the required
+dependencies to compile the Java code.
+
+You can use your IDE to write code and unit tests, but you will need to use the
+CDK toolkit if you wish to synthesize/deploy stacks.
+
+## CDK Toolkit
+
+The [`cdk.json`](./cdk.json) file in the root of this repository includes
+instructions for the CDK toolkit on how to execute this program.
+
+Specifically, it will tell the toolkit to use the `mvn exec:java` command as the
+entry point of your application. After changing your Java code, you will be able
+to run the CDK toolkit commands as usual (Maven will recompile as needed):
+
+    $ cdk ls
+    <list all stacks in this program>
+
+    $ cdk synth
+    <cloudformation template>
+
+    $ cdk deploy
+    <deploy stack to your account>
+
+    $ cdk diff
+    <diff against deployed stack>

java/custom-resource/cdk.json

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+{
+  "app": "mvn exec:java -Dexec.mainClass=software.amazon.awscdk.examples.CustomResourceApp"
+
+}

java/custom-resource/lambda/custom-resource-handler.py

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+def handler(event, context):
+    import logging as log
+    import cfnresponse
+    log.getLogger().setLevel(log.INFO)
+
+    # This needs to change if there are to be multiple resources in the same stack
+    physical_id = 'TheOnlyCustomResource'
+
+    try:
+        log.info('Input event: %s', event)
+
+        # Check if this is a Create and we're failing Creates
+        if event['RequestType'] == 'Create' and event['ResourceProperties'].get('FailCreate', False):
+            raise RuntimeError('Create failure requested')
+
+        # Do the thing
+        message = event['ResourceProperties']['Message']
+        attributes = {
+            'Response': 'Hello "%s"' % message
+        }
+
+        cfnresponse.send(event, context, cfnresponse.SUCCESS, attributes, physical_id)
+    except Exception as e:
+        log.exception(e)
+        # cfnresponse's error message is always "see CloudWatch"
+        cfnresponse.send(event, context, cfnresponse.FAILED, {}, physical_id)

java/custom-resource/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.amazonaws.cdk</groupId>
+    <artifactId>custom-resource</artifactId>
+    <version>1.0.0</version>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.7.0</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+
+             <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <version>3.1.0</version>
+                <configuration>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <archive>
+                        <manifest>
+                            <mainClass>com.amazonaws.cdk.examples.CustomResourceApp</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>make-assembly</id> <!-- this is used for inheritance merges -->
+                        <phase>package</phase> <!-- bind to the packaging phase -->
+                            <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+              </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>
+        <!-- AWS Cloud Development Kit -->
+        <dependency>
+            <groupId>software.amazon.awscdk</groupId>
+            <artifactId>core</artifactId>
+            <version>1.18.0</version>
+        </dependency>
+
+        <!-- Respective AWS Construct Libraries -->
+        <dependency>
+            <groupId>software.amazon.awscdk</groupId>
+            <artifactId>cloudformation</artifactId>
+            <version>1.18.0</version>
+        </dependency>
+        <dependency>
+            <groupId>software.amazon.awscdk</groupId>
+            <artifactId>lambda</artifactId>
+            <version>1.18.0</version>
+        </dependency>
+
+        <!-- https://mvnrepository.com/artifact/junit/junit -->
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

java/custom-resource/src/main/java/software/amazon/awscdk/examples/CustomResourceApp.java

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+package software.amazon.awscdk.examples;
+
+import software.amazon.awscdk.core.App;
+
+public class CustomResourceApp {
+    public static void main(final String args[]) {
+        App app = new App();
+
+        new CustomResourceStack(app, "cdk-custom-resource-example2");
+
+        app.synth();
+    }
+}

java/custom-resource/src/main/java/software/amazon/awscdk/examples/CustomResourceStack.java

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+package software.amazon.awscdk.examples;
+
+import software.amazon.awscdk.core.CfnOutput;
+import software.amazon.awscdk.core.Construct;
+import software.amazon.awscdk.core.Duration;
+import software.amazon.awscdk.core.Stack;
+import software.amazon.awscdk.services.cloudformation.*;
+import software.amazon.awscdk.services.lambda.*;
+import software.amazon.awscdk.services.lambda.Runtime;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.nio.file.*;
+
+public class CustomResourceStack extends Stack {
+
+    public CustomResourceStack(final Construct scope, final String id) {
+        super(scope, id);
+
+        try {
+
+            // Get the lambda function code
+            String LambdaContent = readFileAsString("./lambda/custom-resource-handler.py");
+
+            // Sample Lambda Function Resource
+            final SingletonFunction lambdaFunction = SingletonFunction.Builder.create(this, "cdk-lambda-customresource")
+                                                            .description("My Custom Resource Lambda")
+                                                            .code(Code.fromInline(LambdaContent))
+                                                            .handler("index.handler")
+                                                            .timeout(Duration.seconds(300))
+                                                            .runtime(Runtime.PYTHON_2_7)
+                                                            .uuid(UUID.randomUUID().toString())
+                                                            .build();
+
+            // Sample Property to send to Lambda Function
+            Map<String, Object> map = new HashMap<String, Object>();
+            map.put("Message", "AWS CDK");
+
+            final CustomResource myCustomResource = CustomResource.Builder.create(this, "MyCustomResource")
+                                                    .provider(CustomResourceProvider.fromLambda(lambdaFunction))
+                                                    .properties(map).build();
+
+
+            // Publish the custom resource output
+            CfnOutput cfnoutput = CfnOutput.Builder.create(this, "MyCustomResourceOutput")
+                                    .description("The message that came back from the Custom Resource")
+                                    .value(myCustomResource.getAtt("Response").toString()).build();
+
+
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+    }
+    // function to read the file content
+    public static String readFileAsString(String fileName) throws Exception 
+    {   
+        String data = ""; 
+        try
+        {
+            data = new String(Files.readAllBytes(Paths.get(fileName)),"UTF-8"); 
+        } 
+        catch (Exception e) 
+        {
+            e.printStackTrace();
+        }
+        return data; 
+    } 
+}