[JAVA] CheckStyle support

Java development environment memo I am building a development environment with CheckStyle, but since a lot of alerts are issued with CheckStyle, I will investigate and describe how to deal with it.

1.CheckStyle

1-1. Pom setting

pom.xml

			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-checkstyle-plugin</artifactId>
				<version>3.1.1</version>
				<dependencies>
					<dependency>
						<groupId>com.puppycrawl.tools</groupId>
						<artifactId>checkstyle</artifactId>
						<version>8.37</version>
					</dependency>
				</dependencies>
				<configuration>
					<configLocation>google_checks.xml</configLocation>
					<failsOnError>true</failsOnError>
					<failOnViolation>true</failOnViolation>
					<violationSeverity>error</violationSeverity>
					<consoleOutput>true</consoleOutput>
				</configuration>
				<executions>
					<execution>
						<id>checkstyle</id>
						<phase>verify</phase>
						<goals>
							<goal>check</goal>
						</goals>
					</execution>
				</executions>
			</plugin>

1-2. Downloading the configuration file

Download from below?

https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml

The pom.xml file has the following sites set for selection. https://maven.apache.org/plugins/maven-checkstyle-plugin/examples/custom-checker-config.html

What if I get an error?

https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml

There may be a difference between the rule file and library versions.

2-1. The import statement is not in lexicographic order.

2-1-1. Cause

If the package of your own class is at the beginning of the alphabet than org (jp etc.), you will be warned.

1-2. Solution by Eclipse

1. [Window]-[Settings]
2. [Java]-[Code Style]-[Organize Import]
3. Create your own package (jp) with the "New" button and move it to org.

2.Package name'must match pattern' ^ [a-z] + (. [A-z] [a-z0-9] *) * $'.

Cause The package name contains symbols such as "_".

2-1. CheckStyle solution

Before correction

    <module name="PackageName">
      <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
      <message key="name.invalidPattern"
             value="Package name ''{0}'' must match pattern ''{1}''."/>
    </module>

Change the above rule to INFO instead of warning. You can specify either ignore, info, warning, or error.

Revised

    <module name="PackageName">
      <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
      <message key="name.invalidPattern"
             value="Package name ''{0}'' must match pattern ''{1}''."/>
             <property name="severity" value="info" />
    </module>

Reference URL

Share rules such as CheckStyle with multiple modules https://ssogabe.hatenadiary.org/entry/20091219/1261196056

Cause

Eclipse solution

CheckStyle solution