本文主要說明如何使用maven的help插件查看其他maven插件提供的goal信息。
maven項目的構建生命周期（build lifecycle）由很多階段組成：從validate到deploy。
maven插件中包含goal。這些goal可以被綁定到不同的maven的構建階段上。goal表示一個特定的任務，是一個比構建階段更細粒度的構建步驟，用於構建和管理當前項目。
要使用maven插件提供的goal，首先得知道這些插件提供了哪些goal以及他們的用法。
maven的核心插件之一 --- help插件（Maven Help Plugin）可以用於查看插件提供了哪些goal。
以下是maven help插件的概述信息：
The Maven Help Plugin is used to get relative information about a project or the system. It can be used to get a description of a particular plugin, including the plugin's mojos with their parameters and component requirements, the effective POM and effective settings of the current build, and the profiles applied to the current project being built.
關於maven help插件的詳細信息請參考Maven Help Plugin頁面。此處，僅舉例說明如何使用help插件查看plugin goal的信息。
以maven-eclipse-plugin為例，舉例說明。
1，首先在pom.xml文件中配置插件。
<project> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-eclipse-plugin</artifactId> <version>2.10</version> <configuration> <downloadSources>true</downloadSources> <downloadJavadocs>true</downloadJavadocs> <wtpversion>2.0</wtpversion> <wtpContextName>spring3</wtpContextName> </configuration> </plugin> </plugins> </build> </project>
2，從命令行進入項目所在路徑（pom.xml所在的路徑）。
3，按如下格式執行命令：
mvn help:describe -Dplugin=groupId:artifactId:version
如：
mvn help:describe -Dplugin=org.apache.maven.plugins:maven-eclipse-plugin:2.10
然后回車，則輸出如下信息：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building development 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-help-plugin:2.2:describe (default-cli) @ development ---
[INFO] org.apache.maven.plugins:maven-eclipse-plugin:2.10
Name: Apache Maven Eclipse Plugin
Description: The Eclipse Plugin is used to generate Eclipse IDE files
(.project, .classpath and the .settings folder) from a POM.
Group Id: org.apache.maven.plugins
Artifact Id: maven-eclipse-plugin
Version: 2.10
Goal Prefix: eclipse
This plugin has 12 goals:
eclipse:clean
Description: Deletes the .project, .classpath, .wtpmodules files and
.settings folder used by Eclipse.
eclipse:configure-workspace
Description: Configures The following Eclipse Workspace features:
- Adds the classpath variable MAVEN_REPO to Eclipse.
- Optionally load Eclipse code style file via a URL.
eclipse:eclipse
Description: Generates the following eclipse configuration files:
- .project and .classpath files
- .setting/org.eclipse.jdt.core.prefs with project specific compiler
settings
- various configuration files for WTP (Web Tools Project), if the parameter
wtpversion is set to a valid version (WTP configuration is not generated
by default)
If this goal is run on a multiproject root, dependencies between modules
will be configured as direct project dependencies in Eclipse (unless
useProjectReferences is set to false).
eclipse:help
Description: Display help information on maven-eclipse-plugin.
Call mvn eclipse:help -Ddetail=true -Dgoal=<goal-name> to display parameter
details.
eclipse:install-plugins
Description: Install plugins resolved from the Maven repository system into
an Eclipse instance.
eclipse:myeclipse
Description: Generates MyEclipse configuration files
eclipse:myeclipse-clean
Description: Deletes configuration files used by MyEclipse
eclipse:rad
Description: Generates the rad-6 configuration files.
eclipse:rad-clean
Description: Deletes the config files used by Rad-6. the files .j2ee and
the file .websettings
eclipse:remove-cache
Description: Removes the not-available marker files from the repository.
eclipse:resolve-workspace-dependencies
Description: For all projects currently part of the workspace, all
references to the M2_REPO classpath variable are resolved.
Note: not the projects of the reactor are inspected for unresolved
artifacts, but the projects that are part of the workspace.
eclipse:to-maven
Description: Add eclipse artifacts from an eclipse installation to the
local repo. This mojo automatically analize the eclipse directory, copy
plugins jars to the local maven repo, and generates appropriate poms. This
is the official central repository builder for Eclipse plugins, so it has
the necessary default values. For customized repositories see
MakeArtifactsMojo Typical usage: mvn eclipse:to-maven
-DdeployTo=maven.org::default::scpexe://repo1.maven.org/home/maven/repository-staging/to-ibiblio/eclipse-staging
-DeclipseDir=.
For more information, run 'mvn help:describe [...] -Ddetail'
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.887 s
[INFO] Finished at: 2017-09-22T11:10:52+08:00
[INFO] Final Memory: 11M/150M
[INFO] ------------------------------------------------------------------------