Maven checkstyle error during mvn eclipse:eclipse

Currently I just tried to download and build to make the Netty source code work. But when I tried to run the command mvn eclipse:eclipse in the source folder. I got an error said

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:2.10:check (check-style) on project netty-common: Failed during checkstyle execu
tion: There are 304 checkstyle errors. -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:2.10:check (check-style) on proj
ect netty-common: Failed during checkstyle execution
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.MojoExecutor.executeForkedExecutions(MojoExecutor.java:352)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:197)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:497)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoExecutionException: Failed during checkstyle execution
        at org.apache.maven.plugin.checkstyle.CheckstyleViolationCheckMojo.execute(CheckstyleViolationCheckMojo.java:374)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        ... 24 more
Caused by: org.apache.maven.plugin.checkstyle.CheckstyleExecutorException: There are 304 checkstyle errors.
        at org.apache.maven.plugin.checkstyle.DefaultCheckstyleExecutor.executeCheckstyle(DefaultCheckstyleExecutor.java:218)
        at org.apache.maven.plugin.checkstyle.CheckstyleViolationCheckMojo.execute(CheckstyleViolationCheckMojo.java:365)

It is error of the checkstyle plugin when validating the code netty-common project.

I am not familiar with this plugin . I want to know if I can just ignore it by removing the configuration from the pom.xml(in the ). like below.

          <plugin>
            <artifactId>maven-checkstyle-plugin</artifactId>
            <version>2.10</version>
            <executions>
              <execution>
                <id>check-style</id>
                <goals>
                  <goal>check</goal>
                </goals>
                <phase>validate</phase>
                <configuration>
                  <consoleOutput>true</consoleOutput>
                  <logViolationsToConsole>true</logViolationsToConsole>
                  <failsOnError>true</failsOnError>
                  <failOnViolation>true</failOnViolation>
                  <configLocation>io/netty/checkstyle.xml</configLocation>
                  <includeTestSourceDirectory>true</includeTestSourceDirectory>
                </configuration>
              </execution>
            </executions>
            <dependencies>
              <dependency>
                <groupId>${project.groupId}</groupId>
                <artifactId>netty-build</artifactId>
                <version>21</version>
              </dependency>
            </dependencies>
          </plugin>

Any idea ? Thanks.

CheckStyle is a module of maven that check the style of the code for things like tabs instead of spaces. Netty is using this to prevent basic formatting mistakes.

If you are planning to contribute to Netty, you should NOT remove the plugin as it probably means your patch will never applied.

If you are just using to play with, you are free to remove that plugin as its only purpose is to verify the installation, and not to change things from the installation.

If you choose to keep it, you should look in the output log to see what the mistakes are it detected, to quickly fix the mistakes, see this answer by Matthew Farwell.

1. Right click on the java file in Package Explorer or whatever, and select 'Apply Checkstyle Corrections'.
2. Click on the error in the problems view, and select 'Quick fix'. This corrects the problem.