Maven Tips and Tricks: Describing Maven Plugins with help:describe


September 29, 2009 By Tim O'Brien

If you do any non-trivial customization of a Maven build, you’ll understand that you need to have a good understanding of Maven Plugin configuration. What configuration parameters are available for a particular plugin goal? Most users tend to Google for the particular Maven plugin and rely on the fact that most Maven-generate plugin sites contain a standard list of goals and configuration parameters. While this works, there is a better way: use the Maven Help plugin’s describe goal to list the available configuration parameters for a Maven plugin.

Describing Plugin Configuration Parameters with a Command


$ mvn help:describe -Dcmd=compiler:compile
[INFO] [help:describe {execution: default-cli}]
[INFO] 'compiler:compile' is a plugin goal (aka mojo).
Mojo: 'compiler:compile'
compiler:compile
  Description: Compiles application sources
  Deprecated. No reason given

Sure, the compile goal in the compiler plugin will compile application sources. That’s not exactly what you were looking for, what you usually need is a detailed list of plugin configuration parameters. You can get this by passing in a -Ddetail argument.

$mvn help:describe -Dcmd=compiler:compile -Ddetail
[INFO] [help:describe {execution: default-cli}]
[INFO] 'compiler:compile' is a plugin goal (aka mojo).
Mojo: 'compiler:compile'
compiler:compile
  Description: Compiles application sources
  Deprecated. No reason given
  Implementation: org.apache.maven.plugin.CompilerMojo
  Language: java
  Bound to phase: compile

  Available parameters:

    compilerArgument
      Sets the unformatted argument string to be passed to the compiler if fork
      is set to true.

      This is because the list of valid arguments passed to a Java compiler
      varies based on the compiler version.
      Deprecated. No reason given

    compilerArguments
      Sets the arguments to be passed to the compiler (prepending a dash) if
      fork is set to true.

      This is because the list of valid arguments passed to a Java compiler
      varies based on the compiler version.
      Deprecated. No reason given

    compilerId (Default: javac)
      The compiler id of the compiler to use. See this guide for more
      information.
      Deprecated. No reason given

    compilerVersion
      Version of the compiler to use, ex. '1.3', '1.5', if fork is set to true.
      Deprecated. No reason given

    debug (Default: true)
      Set to true to include debugging information in the compiled class files.
      Deprecated. No reason given

    encoding
      The -encoding argument for the Java compiler.
      Deprecated. No reason given

    excludes
      A list of exclusion filters for the compiler.
      Deprecated. No reason given

    executable
      Sets the executable of the compiler to use when fork is true.
      Deprecated. No reason given

    failOnError (Default: true)
      Indicates whether the build will continue even if there are compilation
      errors; defaults to true.
      Deprecated. No reason given

    fork (Default: false)
      Allows running the compiler in a separate process. If 'false' it uses the
      built in compiler, while if 'true' it will use an executable.
      Deprecated. No reason given

    includes
      A list of inclusion filters for the compiler.
      Deprecated. No reason given

    maxmem
      Sets the maximum size, in megabytes, of the memory allocation pool, ex.
      '128', '128m' if fork is set to true.
      Deprecated. No reason given

    meminitial
      Initial size, in megabytes, of the memory allocation pool, ex. '64',
      '64m' if fork is set to true.
      Deprecated. No reason given

    optimize (Default: false)
      Set to true to optimize the compiled code using the compiler's
      optimization methods.
      Deprecated. No reason given

    outputFileName
      Sets the name of the output file when compiling a set of sources to a
      single file.
      Deprecated. No reason given

    showDeprecation (Default: false)
      Sets whether to show source locations where deprecated APIs are used.
      Deprecated. No reason given

    showWarnings (Default: false)
      Set to true to show compilation warnings.
      Deprecated. No reason given

    source
      The -source argument for the Java compiler.
      Deprecated. No reason given

    staleMillis (Default: 0)
      Sets the granularity in milliseconds of the last modification date for
      testing whether a source needs recompilation.
      Deprecated. No reason given

    target
      The -target argument for the Java compiler.
      Deprecated. No reason given

    verbose (Default: false)
      Set to true to show messages about what the compiler is doing.
      Deprecated. No reason given

That’s more like it. If you ever find yourself wondering what a particular plugin configuration parameter’s name is, or what a default value for a parameter is. You now know how to find it. For more information see the Configuring Maven chapter in Maven: The Definitive Guide.