mirror of https://github.com/dapr/java-sdk.git
238 lines
9.9 KiB
Markdown
238 lines
9.9 KiB
Markdown
## Dapr SDK for Java
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[](https://github.com/dapr/java-sdk/actions?workflow=Build)
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[](https://discord.com/channels/778680217417809931/778749797242765342)
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[](https://codecov.io/gh/dapr/java-sdk)
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[](https://opensource.org/licenses/MIT)
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[](https://search.maven.org/search?q=g:%22io.dapr%22%20AND%20a:%22dapr-sdk%22)
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This is the Dapr SDK for Java, including the following features:
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* PubSub
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* Service Invocation
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* Binding
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* State Store
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* Actors
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### Getting Started
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#### Pre-Requisites
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* JDK 8 or above:
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* [Oracle's JDK 15](https://www.oracle.com/java/technologies/javase-jdk15-downloads.html)
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* [Oracle's JDK 11 - LTS](https://www.oracle.com/java/technologies/javase-jdk11-downloads.html)
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* [Oracle's JDK 8](https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html)
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* [OpenJDK](https://openjdk.java.net/)
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* Java IDE installed:
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* [IntelliJ](https://www.jetbrains.com/idea/download/)
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* [Eclipse](https://www.eclipse.org/downloads/)
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* [Apache NetBeans](https://netbeans.apache.org/download/index.html)
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* [Visual Studio Code](https://code.visualstudio.com/Download)
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* Any other IDE for Java that you prefer.
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* Install one of the following build tools for Java:
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* [Maven 3.x](https://maven.apache.org/install.html)
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* [Gradle 6.x](https://gradle.org/install/)
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* If needed, install the corresponding plugin for the build tool in your IDE, for example:
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* [Maven in IntelliJ](https://www.jetbrains.com/help/idea/maven.html)
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* [Gradle in IntelliJ](https://www.jetbrains.com/help/idea/gradle-settings.html)
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* [Maven in Eclipse with m2e](https://projects.eclipse.org/projects/technology.m2e)
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* [Gradle in Eclipse with Buildship](https://projects.eclipse.org/projects/tools.buildship)
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* An existing Java Maven or Gradle project. You may also start a new project via one of the options below:
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* [New Maven project in IntelliJ](https://www.jetbrains.com/help/idea/maven-support.html#create_new_maven_project)
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* [Maven in 5 minutes](https://maven.apache.org/guides/getting-started/maven-in-five-minutes.html)
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#### Importing Dapr's Java SDK
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For a Maven project, add the following to your `pom.xml` file:
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```xml
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<project>
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...
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<repositories>
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...
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<!-- BEGIN: Dapr's repositories -->
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<repository>
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<id>oss-snapshots</id>
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<url>https://oss.sonatype.org/content/repositories/snapshots</url>
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</repository>
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<repository>
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<id>oss-release</id>
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<url>https://oss.sonatype.org/content/repositories/releases/</url>
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</repository>
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<!-- END: Dapr's repositories -->
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...
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</repositories>
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...
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<dependencies>
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...
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<!-- Dapr's core SDK with all features, except Actors. -->
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<dependency>
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<groupId>io.dapr</groupId>
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<artifactId>dapr-sdk</artifactId>
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<version>1.1.0</version>
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</dependency>
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<!-- Dapr's SDK for Actors (optional). -->
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<dependency>
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<groupId>io.dapr</groupId>
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<artifactId>dapr-sdk-actors</artifactId>
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<version>1.1.0</version>
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</dependency>
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<!-- Dapr's SDK integration with SpringBoot (optional). -->
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<dependency>
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<groupId>io.dapr</groupId>
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<artifactId>dapr-sdk-springboot</artifactId>
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<version>1.1.0</version>
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</dependency>
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...
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</dependencies>
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...
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</project>
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```
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For a Gradle project, add the following to your `build.gradle` file:
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```
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repositories {
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...
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// Dapr repositories
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maven {
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url "https://oss.sonatype.org/content/repositories/snapshots"
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mavenContent {
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snapshotsOnly()
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}
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}
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maven {
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url "https://oss.sonatype.org/content/repositories/releases/"
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}
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}
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...
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dependencies {
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...
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// Dapr's core SDK with all features, except Actors.
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compile('io.dapr:dapr-sdk:1.1.0')
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// Dapr's SDK for Actors (optional).
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compile('io.dapr:dapr-sdk-actors:1.1.0')
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// Dapr's SDK integration with SpringBoot (optional).
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compile('io.dapr:dapr-sdk-springboot:1.1.0')
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}
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```
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#### Running the examples
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Clone this repository including the submodules:
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```sh
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git clone https://github.com/dapr/java-sdk.git
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```
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Then head over to build the [Maven](https://maven.apache.org/install.html) (Apache Maven version 3.x) project:
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```sh
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# make sure you are in the `java-sdk` directory.
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mvn clean install
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```
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Try the following examples to learn more about Dapr's Java SDK:
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* [Invoking a Http service](./examples/src/main/java/io/dapr/examples/invoke/http)
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* [Invoking a Grpc service](./examples/src/main/java/io/dapr/examples/invoke/grpc)
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* [State management](./examples/src/main/java/io/dapr/examples/state)
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* [PubSub with subscriber over Http](./examples/src/main/java/io/dapr/examples/pubsub/http)
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* [Binding with input over Http](./examples/src/main/java/io/dapr/examples/bindings/http)
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* [Actors](./examples/src/main/java/io/dapr/examples/actors/)
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* [Secrets management](./examples/src/main/java/io/dapr/examples/secrets)
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* [Distributed tracing with OpenTelemetry SDK](./examples/src/main/java/io/dapr/examples/tracing)
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* [Exception handling](./examples/src/main/java/io/dapr/examples/exception)
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* [Unit testing](./examples/src/main/java/io/dapr/examples/unittesting)
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#### API Documentation
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Please, refer to our [Javadoc](https://dapr.github.io/java-sdk/) website.
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#### Reactor API
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The Java SDK for Dapr is built using [Project Reactor](https://projectreactor.io/). It provides an asynchronous API for Java. When consuming a result is consumed synchronously, as in the examples referenced above, the `block()` method is used.
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The code below does not make any API call, it simply returns the [Mono](https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html) publisher object. Nothing happens until the application subscribes or blocks on the result:
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```java
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Mono<Void> result = daprClient.publishEvent("mytopic", "my message");
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```
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To start execution and receive the result object synchronously(`void` or `Void` becomes an empty result), use `block()`. The code below shows how to execute the call and consume an empty response:
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```java
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Mono<Void> result = daprClient.publishEvent("mytopic", "my message");
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result.block();
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```
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#### How to use a custom serializer
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This SDK provides a basic serialization for request/response objects but also for state objects. Applications should provide their own serialization for production scenarios.
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1. Implement the [DaprObjectSerializer](https://dapr.github.io/java-sdk/io/dapr/serializer/DaprObjectSerializer.html) interface. See [this class](sdk-actors/src/test/java/io/dapr/actors/runtime/JavaSerializer.java) as example.
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2. Use your serializer class in the following scenarios:
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* When building a new instance of [DaprClient](https://dapr.github.io/java-sdk/io/dapr/client/DaprClient.html):
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```java
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DaprClient client = (new DaprClientBuilder())
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.withObjectSerializer(new MyObjectSerializer()) // for request/response objects.
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.withStateSerializer(new MyStateSerializer()) // for state objects.
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.build();
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```
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* When registering an Actor Type:
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```java
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ActorRuntime.getInstance().registerActor(
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DemoActorImpl.class,
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new MyObjectSerializer(), // for request/response objects.
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new MyStateSerializer()); // for state objects.
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```
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* When building a new instance of [ActorProxy](https://dapr.github.io/java-sdk/io/dapr/actors/client/ActorProxy.html) to invoke an Actor instance, use the same serializer as when registering the Actor Type:
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```java
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try (ActorClient actorClient = new ActorClient()) {
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DemoActor actor = (new ActorProxyBuilder(DemoActor.class, actorClient))
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.withObjectSerializer(new MyObjectSerializer()) // for request/response objects.
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.build(new ActorId("100"));
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}
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```
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#### Debug Java application or Dapr's Java SDK
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**In IntelliJ Community Edition, consider [debugging in IntelliJ](https://docs.dapr.io/developing-applications/ides/intellij/).**
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**In Visual Studio Code, consider [debugging in Visual Studio Code](https://docs.dapr.io/developing-applications/ides/vscode-debugging/).**
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If you need to debug your Application, run Dapr sidecar separately and then start the application from your IDE (IntelliJ, for example).
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For Linux and MacOS:
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```sh
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dapr run --app-id testapp --app-port 3000 --dapr-http-port 3500 --dapr-grpc-port 5001
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```
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> Note: confirm the correct port that the app will listen to and that the Dapr ports above are free, changing the ports if necessary.
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When running your Java application from IDE, make sure the following environment variables are set, so the Java SDK knows how to connect to Dapr's sidecar:
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```
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DAPR_HTTP_PORT=3500
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DAPR_GRPC_PORT=5001
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```
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Now you can go to your IDE (like Eclipse, for example) and debug your Java application, using port `3500` to call Dapr while also listening to port `3000` to expose Dapr's callback endpoint.
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#### Exception handling
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Most exceptions thrown from the SDK are instances of `DaprException`. `DaprException` extends from `RuntimeException`, making it compatible with Project Reactor. See [example](./examples/src/main/java/io/dapr/examples/exception) for more details.
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### Development
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#### Update proto files
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Change the properties below in [pom.xml](./pom.xml) to point to the desired reference URL in Git. Avoid pointing to `master` branch since it can change over time and create unpredictable behavior in the build.
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```xml
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<project>
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...
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<properties>
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...
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<dapr.proto.url>https://raw.githubusercontent.com/dapr/dapr/v1.0.0/pkg/proto/dapr/dapr.proto</dapr.proto.url>
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<dapr.client.proto.url>https://raw.githubusercontent.com/dapr/dapr/v1.0.0/pkg/proto/daprclient/daprclient.proto</dapr.client.proto.url>
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...
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</properties>
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...
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</project>
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```
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