build-helper-maven-plugin 插件主要的作用就是用来指定额外的源码路径和资源路径。它总共有15个goal：
- build-helper:add-source Add more source directories to the POM.
- build-helper:add-test-source Add test source directories to the POM.
- build-helper:add-resource Add more resource directories to the POM.
- build-helper:add-test-resource Add test resource directories to the POM.
- build-helper:attach-artifact Attach additional artifacts to be installed and deployed.
- build-helper:maven-version Set a property containing the current version of maven.
- build-helper:parse-version Set properties containing the parsed components of a version string.
- build-helper:regex-property Sets a property by applying a regex replacement rule to a supplied value.
- build-helper:regex-properties Sets a property by applying a regex replacement rule to a supplied value.
- build-helper:released-version Resolve the latest released version of this project.
- build-helper:remove-project-artifact Remove project's artifacts from local repository.
- build-helper:reserve-network-port Reserve a list of random and unused network ports.
- build-helper:local-ip Retrieve current host IP address.
- build-helper:cpu-count Retrieve number of available CPU.
- build-helper:timestamp-property Sets a property based on the current date and time.
这里重点介绍一下attach-artifact这个goal，它的作用就是在安装或部署artifact的时候，附加的安装或部署一些其他资源或文件。
要使用 build-helper-maven-plugin，首先添加插件声明：
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.9</version>
</plugin>
</plugins>
</build>
然后和其他插件一样，定义它的phase和goal。
attach-artifact默认的phase是package：
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.8</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>attach-artifact</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
剩下的就是configuratino配置了。
attach-artifact可用的配置如下：
必选
| Name | Type | Since | Description |
|---|
| artifacts | Artifact[] | 1.0 | Attach an array of artifacts to the project. |
可选
| Name | Type | Since | Description |
|---|
| basedir | String | 1.5 | This project's base directory.
Default value is: ${basedir}. |
| runOnlyAtExecutionRoot | boolean | 1.5 | This will cause the execution to be run only at the top of a given module tree. That is, run in the project contained in the same folder where the mvn execution was launched.
Default value is: false.
User property is: buildhelper.runOnlyAtExecutionRoot. |
| skipAttach | boolean | 1.6 | This allows to skip the attach execution in case it is known that the corresponding file does not exists. For exemple, when the previous ant-run task is skipped with a unless.
Default value is: false.
User property is: buildhelper.skipAttach. |
这里只有artifacts是必选的；artifacts的说明如下：
artifacts:
Attach an array of artifacts to the project.
- Type: org.codehaus.mojo.buildhelper.Artifact[]
- Since: 1.0
- Required: Yes
其中的每个artifact是类型org.codehaus.mojo.buildhelper.Artifact。根据Artifact Doc说明，它只有三个可配置项：
- file：指定欲附加的文件
- type：指定文件类型
- classifier：指定文件的附属信息
最后生成的文件名会是：
${artifactId}-${version}-${classifier}.${type}
例如，想在安装或部署的时候附加 etc/a.properties 文件，则配置如下：
<configuration>
<artifacts>
<artifact>
<file>etc/a.properties</file>
<type>properties</type>
<classifier>org.liugang.settings</classifier>
</artifact>
</artifacts>
</configuration>
假设当前pom的groupId/artifactId/version为： org.liugang.maven.resources/BuilderHelperTester/0.0.1-SNAPSHOT
则运行完 mvn clean install 之后，到本地Maven库的目录：
${M2Repository}\org\liugang\maven\resources\BuilderHelperTester\0.0.1-SNAPSHOT
下就可以看到除了生成对应的jar文件，还会生成一个文件：
BuilderHelperTester-0.0.1-SNAPSHOT-org.liugang.settings.properties
这个文件的内容即 etc/a.properties 里的内容。
然后如果要引用这个properties文件，需要指定具体的type和classifier，例如：
<groupId>org.liugang.maven.resources</groupId>
<artifactId>BuilderHelperTester</artifactId>
<version>0.0.1-SNAPSHOT</version>
<type>properties</type>
<classifier>org.liugang.settings</classifier>
像在karaf里就可以通过这种方式读取一些bundle的额外设置：
<configfile finalname="/etc/org.liugang.settings.cfg">mvn:org.liugang.maven.resources/BuilderHelperTester/0.0.1-SNAPSHOT/properties/org.liugang.settings</configfile>
其中路径的格式为：
mvn:${groupId}/${artifactId}/${version}/${type}/${classifier}
