1.說明
工作中使用到很多的Maven插件，
從網上拷貝別人的配置用起來很簡單，
但是想改幾個參數就感覺無處下手了，
當然可以從插件的官方網站查看幫助手冊，
也可以通過Maven的help命令查看插件幫助，
包括插件的簡略和詳細的描述信息，
也可以查看插件所有的目標goal，
以及插件的配置參數等。
2.幫助命令
在命令行下面，
使用Maven的help:describe目標查看插件信息：
mvn help:describe -Dplugin=插件標識
通過plugin參數指定要查看的插件，
插件標識可以是groupId:artifactId[:version]形式的，
其中version是可選的，
也可以是插件前綴，
它是插件的簡稱，
插件前綴和插件是一一對應的，
這種對應關係存儲在Maven倉庫元數據中：
https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-metadata.xml
比如插件前綴help和插件maven-help-plugin是對應的：
<plugin>
<name>Apache Maven Help Plugin</name>
<prefix>help</prefix>
<artifactId>maven-help-plugin</artifactId>
</plugin>
3.使用舉例
下面查看maven-help-plugin插件的信息，
即查看幫助命令自己的信息，
下面兩條命令是等價的：
mvn help:describe -Dplugin=org.apache.maven.plugins:maven-help-plugin
mvn help:describe -Dplugin=help
輸出查詢結果如下：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ standalone-pom ---
[INFO] org.apache.maven.plugins:maven-help-plugin:3.2.0
Name: Apache Maven Help Plugin
Description: The Maven Help plugin provides goals aimed at helping to make
sense out of the build environment. It includes the ability to view the
effective POM and settings files, after inheritance and active profiles have
been applied, as well as a describe a particular plugin goal to give usage
information.
Group Id: org.apache.maven.plugins
Artifact Id: maven-help-plugin
Version: 3.2.0
Goal Prefix: help
This plugin has 8 goals:
help:active-profiles
Description: Displays a list of the profiles which are currently active for
this build.
help:all-profiles
Description: Displays a list of available profiles under the current
project.
Note: it will list all profiles for a project. If a profile comes up with a
status inactive then there might be a need to set profile activation
switches/property.
help:describe
Description: Displays a list of the attributes for a Maven Plugin and/or
goals (aka Mojo - Maven plain Old Java Object).
help:effective-pom
Description: Displays the effective POM as an XML for this build, with the
active profiles factored in, or a specified artifact. If verbose, a comment
is added to each XML element describing the origin of the line.
help:effective-settings
Description: Displays the calculated settings as XML for this project,
given any profile enhancement and the inheritance of the global settings
into the user-level settings.
help:evaluate
Description: Evaluates Maven expressions given by the user in an
interactive mode.
help:help
Description: Display help information on maven-help-plugin.
Call mvn help:help -Ddetail=true -Dgoal=<goal-name> to display parameter
details.
help:system
Description: Displays a list of the platform details like system properties
and environment variables.
For more information, run 'mvn help:describe [...] -Ddetail'
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.613 s
[INFO] Finished at: 2021-10-12T15:38:22+08:00
[INFO] ------------------------------------------------------------------------
可以看到maven-help-plugin對應的插件前綴是help：
Group Id: org.apache.maven.plugins
Artifact Id: maven-help-plugin
Version: 3.2.0
Goal Prefix: help
可以看到help:describe用來查看插件的屬性和目標:
help:describe
Description: Displays a list of the attributes for a Maven Plugin and/or
goals (aka Mojo - Maven plain Old Java Object).
可以看到help命令自帶的幫助：
mvn help:help
輸出的結果基本和上面的相同，
這裏更推薦使用help:describe命令。
4.查看詳細信息
通過在命令後追加-Ddetail參數，
可以查看插件的詳細信息：
簡略信息：
mvn help:describe -Dplugin=help
詳細信息：
mvn help:describe -Dplugin=help -Ddetail
詳細信息輸出如下,
這是可以看到每個goal的配置參數說明：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ standalone-pom ---
[INFO] org.apache.maven.plugins:maven-help-plugin:3.2.0
Name: Apache Maven Help Plugin
Description: The Maven Help plugin provides goals aimed at helping to make
sense out of the build environment. It includes the ability to view the
effective POM and settings files, after inheritance and active profiles have
been applied, as well as a describe a particular plugin goal to give usage
information.
Group Id: org.apache.maven.plugins
Artifact Id: maven-help-plugin
Version: 3.2.0
Goal Prefix: help
This plugin has 8 goals:
help:active-profiles
Description: Displays a list of the profiles which are currently active for
this build.
Implementation: org.apache.maven.plugins.help.ActiveProfilesMojo
Language: java
Available parameters:
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
help:all-profiles
Description: Displays a list of available profiles under the current
project.
Note: it will list all profiles for a project. If a profile comes up with a
status inactive then there might be a need to set profile activation
switches/property.
Implementation: org.apache.maven.plugins.help.AllProfilesMojo
Language: java
Available parameters:
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
help:describe
Description: Displays a list of the attributes for a Maven Plugin and/or
goals (aka Mojo - Maven plain Old Java Object).
Implementation: org.apache.maven.plugins.help.DescribeMojo
Language: java
Available parameters:
artifactId
User property: artifactId
The Maven Plugin artifactId to describe.
Note: Should be used with groupId parameter.
cmd
User property: cmd
A Maven command like a single goal or a single phase following the Maven
command line:
mvn [options] [<goal(s)>] [<phase(s)>]
detail (Default: false)
User property: detail
This flag specifies that a detailed (verbose) list of goal (Mojo)
information should be given.
goal
User property: goal
The goal name of a Mojo to describe within the specified Maven Plugin. If
this parameter is specified, only the corresponding goal (Mojo) will be
described, rather than the whole Plugin.
groupId
User property: groupId
The Maven Plugin groupId to describe.
Note: Should be used with artifactId parameter.
minimal (Default: false)
User property: minimal
This flag specifies that a minimal list of goal (Mojo) information should
be given.
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
plugin
Alias: prefix
User property: plugin
The Maven Plugin to describe. This must be specified in one of three
ways:
1. plugin-prefix, i.e. 'help'
2. groupId:artifactId, i.e. 'org.apache.maven.plugins:maven-help-plugin'
3. groupId:artifactId:version, i.e.
'org.apache.maven.plugins:maven-help-plugin:2.0'
version
User property: version
The Maven Plugin version to describe.
Note: Should be used with groupId/artifactId parameters.
help:effective-pom
Description: Displays the effective POM as an XML for this build, with the
active profiles factored in, or a specified artifact. If verbose, a comment
is added to each XML element describing the origin of the line.
Implementation: org.apache.maven.plugins.help.EffectivePomMojo
Language: java
Available parameters:
artifact
User property: artifact
The artifact for which to display the effective POM.
Note: Should respect the Maven format, i.e. groupId:artifactId[:version].
The latest version of the artifact will be used when no version is
specified.
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
verbose (Default: false)
User property: verbose
Output POM input location as comments.
help:effective-settings
Description: Displays the calculated settings as XML for this project,
given any profile enhancement and the inheritance of the global settings
into the user-level settings.
Implementation: org.apache.maven.plugins.help.EffectiveSettingsMojo
Language: java
Available parameters:
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
showPasswords (Default: false)
User property: showPasswords
For security reasons, all passwords are hidden by default. Set this to
true to show all passwords.
help:evaluate
Description: Evaluates Maven expressions given by the user in an
interactive mode.
Implementation: org.apache.maven.plugins.help.EvaluateMojo
Language: java
Available parameters:
artifact
User property: artifact
An artifact for evaluating Maven expressions.
Note: Should respect the Maven format, i.e. groupId:artifactId[:version].
The latest version of the artifact will be used when no version is
specified.
expression
User property: expression
An expression to evaluate instead of prompting. Note that this must not
include the surrounding ${...}.
forceStdout (Default: false)
User property: forceStdout
This options gives the option to output information in cases where the
output has been suppressed by using -q (quiet option) in Maven. This is
useful if you like to use maven-help-plugin:evaluate in a script call
(for example in bash) like this:
RESULT=$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)
echo $RESULT
This will only printout the information which has been requested by
expression to stdout.
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console. This parameter will be ignored if no
expression is specified.
Note: Could be a relative path.
help:help
Description: Display help information on maven-help-plugin.
Call mvn help:help -Ddetail=true -Dgoal=<goal-name> to display parameter
details.
Implementation: org.apache.maven.plugins.help.HelpMojo
Language: java
Available parameters:
detail (Default: false)
User property: detail
If true, display all settable properties for each goal.
goal
User property: goal
The name of the goal for which to show help. If unspecified, all goals
will be displayed.
indentSize (Default: 2)
User property: indentSize
The number of spaces per indentation level, should be positive.
lineLength (Default: 80)
User property: lineLength
The maximum length of a display line, should be positive.
help:system
Description: Displays a list of the platform details like system properties
and environment variables.
Implementation: org.apache.maven.plugins.help.SystemMojo
Language: java
Available parameters:
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.904 s
[INFO] Finished at: 2021-10-12T15:53:53+08:00
[INFO] ------------------------------------------------------------------------
5.查看指定目標
可以通過-Dgoal參數，
查看指定目標的詳細信息：
簡略信息：
mvn help:describe -Dplugin=help -Dgoal=describe
詳細信息：
mvn help:describe -Dplugin=help -Dgoal=describe -Ddetail
簡略信息輸出如下：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ standalone-pom ---
[INFO] Mojo: 'help:describe'
help:describe
Description: Displays a list of the attributes for a Maven Plugin and/or
goals (aka Mojo - Maven plain Old Java Object).
For more information, run 'mvn help:describe [...] -Ddetail'
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.031 s
[INFO] Finished at: 2021-10-12T15:56:50+08:00
[INFO] ------------------------------------------------------------------------
詳細信息輸出如下：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ standalone-pom ---
[INFO] Mojo: 'help:describe'
help:describe
Description: Displays a list of the attributes for a Maven Plugin and/or
goals (aka Mojo - Maven plain Old Java Object).
Implementation: org.apache.maven.plugins.help.DescribeMojo
Language: java
Available parameters:
artifactId
User property: artifactId
The Maven Plugin artifactId to describe.
Note: Should be used with groupId parameter.
cmd
User property: cmd
A Maven command like a single goal or a single phase following the Maven
command line:
mvn [options] [<goal(s)>] [<phase(s)>]
detail (Default: false)
User property: detail
This flag specifies that a detailed (verbose) list of goal (Mojo)
information should be given.
goal
User property: goal
The goal name of a Mojo to describe within the specified Maven Plugin. If
this parameter is specified, only the corresponding goal (Mojo) will be
described, rather than the whole Plugin.
groupId
User property: groupId
The Maven Plugin groupId to describe.
Note: Should be used with artifactId parameter.
minimal (Default: false)
User property: minimal
This flag specifies that a minimal list of goal (Mojo) information should
be given.
output
User property: output
Optional parameter to write the output of this help in a given file,
instead of writing to the console.
Note: Could be a relative path.
plugin
Alias: prefix
User property: plugin
The Maven Plugin to describe. This must be specified in one of three
ways:
1. plugin-prefix, i.e. 'help'
2. groupId:artifactId, i.e. 'org.apache.maven.plugins:maven-help-plugin'
3. groupId:artifactId:version, i.e.
'org.apache.maven.plugins:maven-help-plugin:2.0'
version
User property: version
The Maven Plugin version to describe.
Note: Should be used with groupId/artifactId parameters.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.162 s
[INFO] Finished at: 2021-10-12T15:57:13+08:00
[INFO] ------------------------------------------------------------------------
6.其他命令
該幫助插件還有很多有用的goal，
下面僅列出幾個常用的，
更多的請自行嘗試。
查看當前pom.xml具體生效的結果，
並且輸出到文件：
mvn help:effective-pom -Doutput=EffectivePom.xml
查看pom中生效的profile：
mvn help:active-profiles -N
查看系統所有環境變量：
mvn help:system