# Generate server and client code in Java

After creating the .proto, we can generate the server and client Java code by using **protobuf compiler (protoc)** or **Maven's gRPC Java plugin for protobuf compiler.**

Maven is a build automation tool used primarily for Java projects. In this lab, we will use Maven for:

1. Managing the dependency of gRPC
2. Generate the gRPC server and client code
3. Compile all the source code

**pom.xml** is needed (just like **Makefile**) to define the details of our project.

Create the **pom.xml** in the root of your workspace:

```
cd ~/grpclab
nano pom.xml
```

{% code title="pom.xml" %}
```markup
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cslab</groupId>
    <artifactId>grpclab</artifactId>

    <packaging>jar</packaging>
    <!-- Feel free to delete the comment at the end of these lines. It is just
         for safely updating the version in our release process. -->
    <version>1</version><!-- CURRENT_GRPC_VERSION -->
    <name>examples</name>
    <url>https://github.com/grpc/grpc-java</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <grpc.version>1.24.0</grpc.version><!-- CURRENT_GRPC_VERSION -->
        <protobuf.version>3.10.0</protobuf.version>
        <protoc.version>3.10.0</protoc.version>
        <!-- required for jdk9 -->
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty-shaded</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>${grpc.version}</version>
        </dependency>
    </dependencies>

    <build>
        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>1.6.2</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:${protoc.version}:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}</pluginArtifact>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-enforcer-plugin</artifactId>
                <version>1.4.1</version>
                <executions>
                    <execution>
                        <id>enforce</id>
                        <goals>
                            <goal>enforce</goal>
                        </goals>
                        <configuration>
                            <rules>
                                <requireUpperBoundDeps/>
                            </rules>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>
```
{% endcode %}

Next, execute the following command in your workspace. The "-o" flag is specified to use local dependencies.

```bash
mvn -o generate-sources
```

Two Java files are generated:

`~/grpclab/target/generated-sources/protobuf/grpc-java/cslab/grpclab/CalculatorGrpc.java`&#x20;

`~/grpclab/target/generated-sources/protobuf/java/cslab/grpclab/CalculatorOuterClass.java`

In `CalculatorGrpc.java` , it contains the Java classes which represents **CalculatorServices** and the rpc defined in .proto.

In `CalculatorOuterClass.java`, it contains the Java classes which represents **CalculationRequest** and **CalculationResponse** defined in .proto.

We won't edit these 2 files. We will use or extend them in the following sections.

