Java

• 8+=

• 8- -> use specific branch

  • Check gRFC P5 JDK Version Support Policy

  Java version	gRPC Branch
  7	1.41.x

Android

• minSdkVersion 21+= (Lollipop)
  • +21 -- supported with -- Java 8 language desugaring.
• if you want TLS -> use Play Services Dynamic Security Provider -- Check Security Readme --

• guided tour

• more explanatory

• examples
• Android example

• grpc-okhttp -- instead of -- grpc-netty-shaded and
• grpc-protobuf-lite -- instead of -- grpc-protobuf

  implementation 'io.grpc:grpc-okhttp:1.63.0'
  implementation 'io.grpc:grpc-protobuf-lite:1.63.0'
  implementation 'io.grpc:grpc-stub:1.63.0'
  compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+

• Maven -- (with the GAVs from above) --OR
• @io_grpc_grpc_java//api et al (see below)

• Sonatypes's snapshot repository

• -> put your proto files in
  • src/main/proto &
  • src/test/proto

• -> use protobuf-maven-plugin
  • if Eclipse and NetBeans users - > check os-maven-plugin's IDE documentation)

  <build>
    <extensions>
      <extension>
        <groupId>kr.motd.maven</groupId>
        <artifactId>os-maven-plugin</artifactId>
        <version>1.7.1</version>
      </extension>
    </extensions>
    <plugins>
      <plugin>
        <groupId>org.xolstice.maven.plugins</groupId>
        <artifactId>protobuf-maven-plugin</artifactId>
        <version>0.6.1</version>
        <configuration>
          <protocArtifact>com.google.protobuf:protoc:3.25.1:exe:${os.detected.classifier}</protocArtifact>
          <pluginId>grpc-java</pluginId>
          <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.63.0:exe:${os.detected.classifier}</pluginArtifact>
        </configuration>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>compile-custom</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

• -> use protobuf-gradle-plugin:

  plugins {
      id 'com.google.protobuf' version '0.9.4'
  }
  
  protobuf {
    protoc {
      artifact = "com.google.protobuf:protoc:3.25.1"
    }
    plugins {
      grpc {
        artifact = 'io.grpc:protoc-gen-grpc-java:1.63.0'
      }
    }
    generateProtoTasks {
      all()*.plugins {
        grpc {}
      }
    }
  }

  • prebuilt protoc-gen-grpc-java binary uses glibc on Linux
    • if you are compiling on Alpine Linux -> use Alpine grpc-java package -- which uses musl instead --

• -> use protobuf-gradle-plugin / specify the 'lite' options

  plugins {
      id 'com.google.protobuf' version '0.9.4'
  }
  
  protobuf {
    protoc {
      artifact = "com.google.protobuf:protoc:3.25.1"
    }
    plugins {
      grpc {
        artifact = 'io.grpc:protoc-gen-grpc-java:1.63.0'
      }
    }
    generateProtoTasks {
      all().each { task ->
        task.builtins {
          java { option 'lite' }
        }
        task.plugins {
          grpc { option 'lite' }
        }
      }
    }
  }

• -> use
  • proto_library &
  • java_proto_library
    • no load() required
  • load("@io_grpc_grpc_java//:java_grpc_library.bzl", "java_grpc_library")
    • Example: BUILD.bazel

• @Internal
  • uses
    • internal use by the gRPC library
    • NOT by gRPC users
• @ExperimentalApi
  • == subject to change in future releases
    • -> NOT depend on them

• := Error Prone plugin /
  • allows
    • checking usages in any library code / depends on gRPC of
      • @ExperimentalApi
      • @Internal
    • checking consumption in non-library code of
      • @ExperimentalApi
      • @Internal

• Stub
• Channel
• Transport

• exposed to most developers
• provides
  • type-safe bindings -- to -- whatever datamodel/IDL/interface you are adapting
    • built-in plugin to the protocol-buffers compiler
      • based on .proto files -- generates -- Stub interfaces
    • to other datamodel/IDL are easy and encouraged (❓to build)

• abstraction over Transport handling
• vs Stub
  • exposes more behavior to the application
• uses
  • interception/decoration
  • application frameworks for cross-cutting concerns -- Example: logging, monitoring, auth, etc. --

• characteristics
  • their interfaces are abstract just enough -- to allow -- plugging in of different implementations
    • built-in implementations
      • Netty-based HTTP/2 transport
        • based on Netty
        • 👁️ NOT 👁️ officially supported on Android
        • 👁 exist a "grpc-netty-shaded" version 👁
          • 👁 generally preferred 👁
            • Reasons: 🧠less dependency management & easier to upgrade 🧠
      • OkHttp-based HTTP/2 transport
        • := lightweight transport based on
          • Okio &
          • low-level parts of OkHttp
        • uses
          • Android
      • in-process transport
        • uses
          • process with the server == process with the client
          • testing
      • Binder transport
        • uses
          • Android cross-process communication | single device
  • internal to gRPC
  • vs core API under package io.grpc
    • weaker API guarantees
• in charge of
  • put and take bytes off the wire