Add example of a Jib-Maven multi-module project

examples/jib-multimodule/.gitignore

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+target
+.classpath
+.project
+.settings
+.vscode

examples/jib-multimodule/.mvn/wrapper/MavenWrapperDownloader.java

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+/*
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+*/
+
+import java.net.*;
+import java.io.*;
+import java.nio.channels.*;
+import java.util.Properties;
+
+public class MavenWrapperDownloader {
+
+    /**
+     * Default URL to download the maven-wrapper.jar from, if no 'downloadUrl' is provided.
+     */
+    private static final String DEFAULT_DOWNLOAD_URL =
+            "https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.4.2/maven-wrapper-0.4.2.jar";
+
+    /**
+     * Path to the maven-wrapper.properties file, which might contain a downloadUrl property to
+     * use instead of the default one.
+     */
+    private static final String MAVEN_WRAPPER_PROPERTIES_PATH =
+            ".mvn/wrapper/maven-wrapper.properties";
+
+    /**
+     * Path where the maven-wrapper.jar will be saved to.
+     */
+    private static final String MAVEN_WRAPPER_JAR_PATH =
+            ".mvn/wrapper/maven-wrapper.jar";
+
+    /**
+     * Name of the property which should be used to override the default download url for the wrapper.
+     */
+    private static final String PROPERTY_NAME_WRAPPER_URL = "wrapperUrl";
+
+    public static void main(String args[]) {
+        System.out.println("- Downloader started");
+        File baseDirectory = new File(args[0]);
+        System.out.println("- Using base directory: " + baseDirectory.getAbsolutePath());
+
+        // If the maven-wrapper.properties exists, read it and check if it contains a custom
+        // wrapperUrl parameter.
+        File mavenWrapperPropertyFile = new File(baseDirectory, MAVEN_WRAPPER_PROPERTIES_PATH);
+        String url = DEFAULT_DOWNLOAD_URL;
+        if(mavenWrapperPropertyFile.exists()) {
+            FileInputStream mavenWrapperPropertyFileInputStream = null;
+            try {
+                mavenWrapperPropertyFileInputStream = new FileInputStream(mavenWrapperPropertyFile);
+                Properties mavenWrapperProperties = new Properties();
+                mavenWrapperProperties.load(mavenWrapperPropertyFileInputStream);
+                url = mavenWrapperProperties.getProperty(PROPERTY_NAME_WRAPPER_URL, url);
+            } catch (IOException e) {
+                System.out.println("- ERROR loading '" + MAVEN_WRAPPER_PROPERTIES_PATH + "'");
+            } finally {
+                try {
+                    if(mavenWrapperPropertyFileInputStream != null) {
+                        mavenWrapperPropertyFileInputStream.close();
+                    }
+                } catch (IOException e) {
+                    // Ignore ...
+                }
+            }
+        }
+        System.out.println("- Downloading from: : " + url);
+
+        File outputFile = new File(baseDirectory.getAbsolutePath(), MAVEN_WRAPPER_JAR_PATH);
+        if(!outputFile.getParentFile().exists()) {
+            if(!outputFile.getParentFile().mkdirs()) {
+                System.out.println(
+                        "- ERROR creating output direcrory '" + outputFile.getParentFile().getAbsolutePath() + "'");
+            }
+        }
+        System.out.println("- Downloading to: " + outputFile.getAbsolutePath());
+        try {
+            downloadFileFromURL(url, outputFile);
+            System.out.println("Done");
+            System.exit(0);
+        } catch (Throwable e) {
+            System.out.println("- Error downloading");
+            e.printStackTrace();
+            System.exit(1);
+        }
+    }
+
+    private static void downloadFileFromURL(String urlString, File destination) throws Exception {
+        URL website = new URL(urlString);
+        ReadableByteChannel rbc;
+        rbc = Channels.newChannel(website.openStream());
+        FileOutputStream fos = new FileOutputStream(destination);
+        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
+        fos.close();
+        rbc.close();
+    }
+
+}

examples/jib-multimodule/.mvn/wrapper/maven-wrapper.properties

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+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.0/apache-maven-3.6.0-bin.zip

examples/jib-multimodule/README.adoc

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+=== Example: Jib Multi-Module
+:icons: font
+
+Jib is one of the supported builders in Skaffold.
+[Jib](https://github.com/GoogleContainerTools/jib) builds Docker and OCI images
+for your Java applications and is available as plugins for Maven and Gradle.
+
+Sometimes a project is configured to have multiple modules to create several
+container images.  Skaffold can work with Jib to build these containers as
+required.
+
+The way you configure it in `skaffold.yaml` is the following build stanza:
+
+[source,yaml]
+----
+build:
+     artifacts:
+     - image: gcr.io/k8s-skaffold/skaffold-jib-1
+       # context is the root of the multi-module project
+       context: .
+       jibMaven:
+          # module is either the relative location within the project (i.e.,
+          # relative to `context`) or :artifactId or groupId:artifactId
+          module: moduleLocation
+     - image: gcr.io/k8s-skaffold/skaffold-jib-2
+       context: .
+       jibMaven:
+          module: :artifactId
+----
+
+There are a few caveats:
+
+  - The `jib-maven-plugin` must be either be configured referenced in the
+    root module of the project.  This is easily done through a `pluginManagement`
+    block.
+
+  - The artifact modules must have a `jib:xxx` goal bound to the `package` phase.
+
+ifndef::env-github[]
+==== link:{github-repo-tree}/examples/jib[Example files icon:github[]]
+
+[source,yaml, indent=3, title=skaffold.yaml]
+----
+include::skaffold.yaml[]
+----
+
+[source,xml, indent=3, title=pom.xml, syntax=xml]
+----
+include::pom.xml[]
+----
+endif::[]

examples/jib-multimodule/k8s/web.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: web1
+spec:
+  selector:
+    matchLabels:
+      app: web1
+  template:
+    metadata:
+      labels:
+        app: web1
+    spec:
+      containers:
+      - name: web1
+        image: gcr.io/k8s-skaffold/skaffold-jib-1
+        ports:
+          - containerPort: 8080
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: web2
+spec:
+  selector:
+    matchLabels:
+      app: web2
+  template:
+    metadata:
+      labels:
+        app: web2
+    spec:
+      containers:
+      - name: web2
+        image: gcr.io/k8s-skaffold/skaffold-jib-2
+        ports:
+          - containerPort: 8080