Create java/patterns and add compensations pattern

This fixes #52.

.github/workflows/pre-release.yml

@@ -53,7 +53,7 @@ jobs:
       # When adding a new example make sure it's listed here
       - name: Find and replace restateVersion in build.gradle.kts for java templates
         if: github.event.inputs.sdkJavaVersion != ''
-        run: for jvmDir in hello-world-http hello-world-lambda food-ordering/app; do sed -i 's/val restateVersion = "[0-9A-Z.-]*"/val restateVersion = "${{ inputs.sdkJavaVersion }}"/' java/$jvmDir/build.gradle.kts; done
+        run: for jvmDir in hello-world-http hello-world-lambda food-ordering/app patterns; do sed -i 's/val restateVersion = "[0-9A-Z.-]*"/val restateVersion = "${{ inputs.sdkJavaVersion }}"/' java/$jvmDir/build.gradle.kts; done
       - name: Find and replace restateVersion in build.gradle.kts for kotlin templates
         if: github.event.inputs.sdkJavaVersion != ''
         run: for jvmDir in hello-world-http hello-world-lambda; do sed -i 's/val restateVersion = "[0-9A-Z.-]*"/val restateVersion = "${{ inputs.sdkJavaVersion }}"/' kotlin/$jvmDir/build.gradle.kts; done
@@ -80,6 +80,12 @@ jobs:
         with:
           arguments: check
           build-root-directory: java/food-ordering/app
+      - name: Test java/patterns
+        if: github.event.inputs.sdkJavaVersion != ''
+        uses: gradle/gradle-build-action@v2
+        with:
+          arguments: check
+          build-root-directory: java/patterns
       - name: Test kotlin/hello-world-http
         if: github.event.inputs.sdkJavaVersion != ''
         uses: gradle/gradle-build-action@v2

.github/workflows/test.yml

@@ -40,6 +40,11 @@ jobs:
         with:
           arguments: check
           build-root-directory: java/food-ordering/app
+      - name: Test java/patterns
+        uses: gradle/gradle-build-action@v2
+        with:
+          arguments: check
+          build-root-directory: java/patterns
       - name: Test kotlin/hello-world-http
         uses: gradle/gradle-build-action@v2
         with:

java/README.md

@@ -0,0 +1,15 @@
+# Java examples
+
+This directory contains Restate examples using the Java SDK.
+
+## Common patterns
+
+- A collection of [common patterns](patterns) you encounter when developing distributed applications.
+
+## Starter examples
+
+- [Hello World](hello-world-http): A simple example of a Restate service.
+- [Hello World - AWS Lambda](hello-world-lambda): A simple example of how you can run a Restate service on AWS Lambda.
+
+## Applications
+- [Food ordering](food-ordering): See how to integrate Restate with external services using Awakeables and side effects.

java/patterns/.gitignore

@@ -0,0 +1,35 @@
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build
+
+.idea
+*.iml
+
+# Unignore the gradle wrapper
+!gradle/wrapper/gradle-wrapper.jar

java/patterns/README.md

@@ -0,0 +1,11 @@
+# Restate Sample Patterns
+
+A collections of useful patterns in distributed applications, and how to
+implement them with [Restate](https://github.com/restatedev/restate).
+This is a continuously evolving list.
+
+All patterns are described in one file and have a comment block at the top that explains them.
+
+### List of Patterns
+
+- [**Compensations**](src/main/java/dev/restate/patterns/Compensations.java)

java/patterns/build.gradle.kts

@@ -0,0 +1,71 @@
+import com.google.protobuf.gradle.id
+
+plugins {
+  java
+  application
+
+  id("com.google.protobuf") version "0.9.1"
+  id("com.diffplug.spotless") version "6.24.0"
+}
+
+repositories {
+  mavenCentral()
+}
+
+val restateVersion = "0.7.0"
+
+dependencies {
+  // Restate SDK
+  implementation("dev.restate:sdk-api:$restateVersion")
+  implementation("dev.restate:sdk-http-vertx:$restateVersion")
+  // To use Jackson to read/write state entries (optional)
+  implementation("dev.restate:sdk-serde-jackson:$restateVersion")
+
+  // Protobuf and grpc dependencies
+  implementation("com.google.protobuf:protobuf-java:3.24.3")
+  implementation("io.grpc:grpc-stub:1.58.0")
+  implementation("io.grpc:grpc-protobuf:1.58.0")
+  // This is needed to compile the @Generated annotation forced by the grpc compiler
+  // See https://github.com/grpc/grpc-java/issues/9153
+  compileOnly("org.apache.tomcat:annotations-api:6.0.53")
+
+  // Logging (optional)
+  implementation("org.apache.logging.log4j:log4j-core:2.20.0")
+
+  // Testing (optional)
+  testImplementation("org.junit.jupiter:junit-jupiter:5.9.1")
+  testImplementation("dev.restate:sdk-testing:$restateVersion")
+}
+
+configure<com.diffplug.gradle.spotless.SpotlessExtension> {
+  java {
+    targetExclude("build/generated/**/*.java")
+
+    googleJavaFormat()
+  }
+}
+
+// Configure protoc plugin
+protobuf {
+  protoc { artifact = "com.google.protobuf:protoc:3.24.3" }
+
+  // We need both grpc and restate codegen(s) because the restate codegen depends on the grpc one
+  plugins {
+    id("grpc") { artifact = "io.grpc:protoc-gen-grpc-java:1.58.0" }
+    id("restate") { artifact = "dev.restate:protoc-gen-restate:$restateVersion:all@jar" }
+  }
+
+  generateProtoTasks {
+    all().forEach {
+      it.plugins {
+        id("grpc")
+        id("restate")
+      }
+    }
+  }
+}
+
+// Configure test platform
+tasks.withType<Test> {
+  useJUnitPlatform()
+}

java/patterns/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.2-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists