Getting started with protobuf.

message.proto

syntax = "proto2";

// This is the package where the java source code will be placed. 
option java_package = "le.arn";

// This is the name of the class. 
// If not provided, it will be created as <message name>OuterClass. 
option java_outer_classname = "GreetingProtos";

message Greeting {
  required string greeting = 1;
  
} 

protobuf-java.xml

<!-- protobuf. (de)serialize proto buffers using java api. -->
<dependency>
  <groupId>com.google.protobuf</groupId>
  <artifactId>protobuf-java</artifactId>
  <version>3.2.0</version>
</dependency>

protoc-jar-maven-plugin.xml

<!-- compile proto file into java files. -->
<plugin>
  <groupId>com.github.os72</groupId>
  <artifactId>protoc-jar-maven-plugin</artifactId>
  <version>3.2.0.1</version>
  <executions>
    <execution>
      <phase>generate-sources</phase>
      <goals>
        <goal>run</goal>
      </goals>
      <configuration>
        <!-- <includeDirectories> <include>src/main/protobuf</include> </includeDirectories> -->
        <inputDirectories>
          <include>src/main/protobuf</include>
        </inputDirectories>
        <!-- Create java files. And put them in the src/main/java directory. -->
        <outputTargets>
          <outputTarget>
            <type>java</type>
            <outputDirectory>src/main/java</outputDirectory>
          </outputTarget>
        </outputTargets>
      </configuration>
    </execution>
  </executions>
</plugin>

UnitTest.java

// 1 : Create a Greeting object using the Protobuf builder.
Builder greetingBuilder = GreetingProtos.Greeting.newBuilder();
greetingBuilder.setGreeting(HELLO_WORLD);
Greeting greeting = greetingBuilder.build();
try {
  // 2 : Write the message into a file. Serialize the object.
  FileOutputStream output = new FileOutputStream(SER_FILE);
  greeting.writeTo(output);
  output.close();
  // 3 : Deserialize the object from the file.
  Greeting greetingFromFile = Greeting.parseFrom(new FileInputStream(
      SER_FILE));
  logger.debug("We read this from the file {}", greetingFromFile);
  // 4 : All is well?
  assertEquals(HELLO_WORLD, greetingFromFile.getGreeting());
} catch (IOException e) {
  e.printStackTrace();
}