grpc-java/examples

gRPC Examples

The examples require grpc-java to already be built. You are strongly encouraged to check out a git release tag, since there will already be a build of gRPC available. Otherwise you must follow COMPILING.

You may want to read through the Quick Start before trying out the examples.

Basic examples

• Hello world

• Route guide

• Metadata

• Error handling

• Compression

• Flow control

• Wait For Ready

• Json serialization

• Hedging example

• Retrying example

• Health Service example

• Keep Alive

• Cancellation

• Custom Load Balance

• Deadline

• Error Details

• GRPC Proxy

• Load Balance

• Multiplex

• Name Resolve

• Pre-Serialized Messages

To build the examples

1. Install gRPC Java library SNAPSHOT locally, including code generation plugin (Only need this step for non-released versions, e.g. master HEAD).

2. From grpc-java/examples directory:

$ ./gradlew installDist

This creates the scripts hello-world-server, hello-world-client, route-guide-server, route-guide-client, etc. in the build/install/examples/bin/ directory that run the examples. Each example requires the server to be running before starting the client.

For example, to try the hello world example first run:

$ ./build/install/examples/bin/hello-world-server

And in a different terminal window run:

$ ./build/install/examples/bin/hello-world-client

That's it!

For more information, refer to gRPC Java's README and tutorial.

Maven

If you prefer to use Maven:

1. Install gRPC Java library SNAPSHOT locally, including code generation plugin (Only need this step for non-released versions, e.g. master HEAD).

2. Run in this directory:

$ mvn verify
$ # Run the server
$ mvn exec:java -Dexec.mainClass=io.grpc.examples.helloworld.HelloWorldServer
$ # In another terminal run the client
$ mvn exec:java -Dexec.mainClass=io.grpc.examples.helloworld.HelloWorldClient

Bazel

If you prefer to use Bazel:

$ bazel build :hello-world-server :hello-world-client
$ # Run the server
$ bazel-bin/hello-world-server
$ # In another terminal run the client
$ bazel-bin/hello-world-client

Other examples

• Android examples

• Secure channel examples

  • TLS examples

  • ALTS examples

• Google Authentication

• JWT-based Authentication

• OAuth2-based Authentication

• Pre-serialized messages

Unit test examples

Examples for unit testing gRPC clients and servers are located in examples/src/test.

In general, we DO NOT allow overriding the client stub and we DO NOT support mocking final methods in gRPC-Java library. Users should be cautious that using tools like PowerMock or mockito-inline can easily break this rule of thumb. We encourage users to leverage InProcessTransport as demonstrated in the examples to write unit tests. InProcessTransport is light-weight and runs the server and client in the same process without any socket/TCP connection.

Mocking the client stub provides a false sense of security when writing tests. Mocking stubs and responses allows for tests that don't map to reality, causing the tests to pass, but the system-under-test to fail. The gRPC client library is complicated, and accurately reproducing that complexity with mocks is very hard. You will be better off and write less code by using InProcessTransport instead.

Example bugs not caught by mocked stub tests include:

• Calling the stub with a null message
• Not calling close()
• Sending invalid headers
• Ignoring deadlines
• Ignoring cancellation

For testing a gRPC client, create the client with a real stub using an InProcessChannel, and test it against an InProcessServer with a mock/fake service implementation.

For testing a gRPC server, create the server as an InProcessServer, and test it against a real client stub with an InProcessChannel.

The gRPC-java library also provides a JUnit rule, GrpcCleanupRule, to do the graceful shutdown boilerplate for you.

Even more examples

A wide variety of third-party examples can be found here.