lint Java in pre-commit

1. add spotless plugin to pom.xml

<plugin>
  <groupId>com.diffplug.spotless</groupId>
  <artifactId>spotless-maven-plugin</artifactId>
  <version>2.43.0</version>
  <executions>
     <execution>
      <goals>
       <goal>check</goal>
       <goal>apply</goal>
      </goals>
     </execution>
    </executions>
</plugin>

here, update <version>2.43.0</version> appropriately
google-java-format versions

2. add spotless configuratioin

<configuration>
    <java>
        <includes>
            <include>src/main/java/**/*.java</include>
            <include>src/test/java/**/*.java</include>
        </includes>
        <googleJavaFormat>
            <version>1.28.0</version>
            <style>AOSP</style>
        </googleJavaFormat>
        <importOrder />
        <removeUnusedImports />
    </java>
</configuration>

more spotless format configuration

3. add hooks/pre-commit

#!/usr/bin/env bash
mvn spotless:apply

4. configure maven plugin to install a pre-commit hook

<plugin>
   <groupId>com.rudikershaw.gitbuildhook</groupId>
   <artifactId>git-build-hook-maven-plugin</artifactId>
   <version>3.1.0</version>
   <configuration>
      <installHooks>
         <pre-commit>hooks/pre-commit</pre-commit>
      </installHooks>
   </configuration>
   <executions>
      <execution>
         <goals>
            <goal>install</goal>
         </goals>
      </execution>
   </executions>
</plugin>

you should be good to go

things learned

based on https://github.com/google/google-java-format, it looks like we add

<dependency>
  <groupId>com.google.googlejavaformat</groupId>
  <artifactId>google-java-format</artifactId>
  <version>${google-java-format.version}</version>
</dependency>

why do we add it under <plugin> tag?

✏️

• dependencies in pom.xml are for things application code needs at compile/run/test time
• plugins are for tools that run during the build (formatters, linters, code generators, packagers)
• google-java-format is a formatter engine, not something app code should ship with

all combined

<plugin>
    <groupId>com.diffplug.spotless</groupId>
    <artifactId>spotless-maven-plugin</artifactId>
    <version>2.43.0</version>
    <executions>
        <execution>
            <goals>
                <goal>check</goal>
                <goal>apply</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <java>
            <includes>
                <include>src/main/java/**/*.java</include>
                <include>src/test/java/**/*.java</include>
            </includes>
            <googleJavaFormat>
                <version>1.28.0</version>
                <style>AOSP</style>
            </googleJavaFormat>
            <importOrder />
            <removeUnusedImports />
        </java>
    </configuration>
</plugin>
<plugin>
    <groupId>com.rudikershaw.gitbuildhook</groupId>
    <artifactId>git-build-hook-maven-plugin</artifactId>
    <version>3.1.0</version>
    <configuration>
        <installHooks>
            <pre-commit>hooks/pre-commit</pre-commit>
        </installHooks>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>install</goal>
            </goals>
        </execution>
    </executions>
</plugin>