java

Java example

A minimal Java client for PushService.StreamPush, built with Gradle 9.x and the protobuf-gradle-plugin.

Layout

java/
  gradlew, gradlew.bat            # Gradle wrapper (use these, not system `gradle`)
  gradle/wrapper/                 # pinned to Gradle 9.5.0
  build.gradle
  settings.gradle                 # applies the Foojay JDK-resolver plugin
  src/main/proto/push.proto       # symlink → ../../../../push.proto
  src/main/java/com/example/pushclient/PushClient.java

src/main/proto/push.proto is a relative symlink back to the repo-root proto, so there's exactly one source of truth. The protobuf-gradle-plugin picks it up via its default source set; no srcDir override needed.

(The symlink keeps srcDir to a dedicated directory. Pointing it at the repo root causes the plugin to conflict with its own build/extracted-include-protos/ cache.)

Prerequisites

• A JDK on PATH capable of launching Gradle 9 (Gradle 9 itself requires JDK 17+ to start). Any of Homebrew openjdk, openjdk@17, openjdk@21 will work; the wrapper picks whatever JAVA_HOME (or java on PATH) points at to bootstrap.
• That's the only prereq — the actual build target is JDK 17, which the Foojay toolchain resolver (configured in settings.gradle) will auto-download from Adoptium on first use and cache under ~/.gradle/jdks/.

You do not need to install Gradle separately; the checked-in wrapper handles it.

Run

export PUSH_API_KEY=...
export PUSH_API_SECRET=...
export PUSH_APP_ID=...

./gradlew run

First run downloads Gradle (~150 MB) and JDK 17 (~180 MB) into the per-user Gradle cache. Subsequent runs are fast.

Notes on the generated code

push.proto declares package push; and does not set option java_package, option java_outer_classname, or option java_multiple_files. That means:

• Generated message classes are nested inside a single outer class: push.Push.Alert, push.Push.PushRequest, etc.
• The gRPC service stub is generated separately at push.PushServiceGrpc.

PushClient.java imports both.