Maven Tips

Reference

Maven: The Complete Reference

Maven的生命周期

Maven 构建生命周期

Maven有以下三种标准的生命周期：clean、default(或 build)、site
这是 Maven 主要的生命周期，用于构建应用程序。它有以下 23 个阶段。
validate    验证项目是否正确，并且所有必要的信息可用于完成构建过程
initialize    建立初始化状态，例如设置属性
generate-sources    产生任何的源代码包含在编译阶段
process-sources    处理源代码，例如，过滤器值
generate-resources    包含在包中产生的资源
process-resources    复制和处理资源到目标目录，准备打包阶段
compile    编译该项目的源代码
process-classes    从编译生成的文件提交处理，例如：Java类的字节码增强/优化
generate-test-sources    生成任何测试的源代码包含在编译阶段
process-test-sources    处理测试源代码，例如，过滤器任何值
test-compile    编译测试源代码到测试目标目录
process-test-classes    处理测试代码文件编译生成的文件
test    运行测试使用合适的单元测试框架（JUnit）
prepare-package    执行必要的任何操作的实际打包之前准备一个包
package    提取编译后的代码，并在其分发格式打包，如JAR，WAR或EAR文件
pre-integration-test    完成执行集成测试之前所需操作。例如，设置所需的环境
integration-test    处理并在必要时部署软件包到集成测试可以运行的环境
pre-integration-test    完成集成测试已全部执行后所需操作。例如，清理环境
verify    运行任何检查，验证包是有效的，符合质量审核规定
install    将包安装到本地存储库，它可以用作当地其他项目的依赖
7
deploy    复制最终的包到远程仓库与其他开发者和项目共享    

Maven的预定义变量

List of predefined Maven properties

${basedir} represents the directory containing pom.xml
${version} equivalent to ${project.version} (deprecated: ${pom.version})
All elements in the pom.xml, can be referenced with the project. prefix. This list is just an example of some commonly used elements. (deprecated: ${pom.} prefix)
${project.build.directory} results in the path to your "target" directory, this is the same as ${pom.project.build.directory}
${project.build.outputDirectory} results in the path to your "target/classes" directory
${project.name} refers to the name of the project (deprecated: ${pom.name} ).
${project.version} refers to the version of the project (deprecated: ${pom.version}).
${project.build.finalName} refers to the final name of the file created when the built project is packaged

Similarly, values in the user's settings.xml can be referenced using property names with settings. prefix. ${settings.localRepository} refers to the path of the user's local repository

Environment variables can be referenced using the env prefix
${env.M2_HOME} returns the Maven2 installation path.
${java.home} specifies the path to the current JRE_HOME environment use with relative paths to get for example: <jvm>${java.home}../bin/java.exe</jvm>

All Java System Properties defined by the JVM: ${file.separator}
${java.class.path}
${java.home}
${java.vendor}
${java.vendor.url}
${java.version}
${line.separator}
${os.arch}
${os.name}
${os.version}
${path.separator}
${user.dir}
${user.home}
${user.name}

User defined properties in the pom.xml.
<project>
...
  <properties>
     <my.filter.value>hello</my.filter.value>
  </properties>
...
</project>
${my.filter.value} will result in hello if you inserted the above XML fragment in your pom.xml

插件机制

Maven 插件机制

Maven的pom.xml文件详解------Build Settings

如果你的POM有一个parent，它可以从parent的build/plugins或者pluginManagement集成plugin配置。这样孩子POM和parent POM中都存在groupId为my.group的plugin，Maven默认的行为将是根据属性名称将两个plugin的configuration的内容进行合并。如果孩子POM中有一个属性，则该属性是有效的，如果孩子POM中没有一个属性，但parent POM中存在，则parent中的属性是有效的。通过在configuration元素中增加combine.children和combine.self属性，孩子POM可以控制Maven怎么合并plugin的configuration。combine.children="append"表示父POM和子POM的属性合并起来；combine.self="override"表示子POM的属性完全覆盖父POM的。

Plugin

Maven Failsafe Plugin

Groovy Eclipse Maven plugin

The simplest way to set up your source folders is to do nothing at all: add all of your Groovy files to src/main/java and src/test/java. This requires absolutely no extra configuration and is easy to implement. However, this is not a standard maven approach to setting up your project. If you require a more standard maven approach, then it is possible to put your Groovy files in src/main/groovy and src/test/groovy and you Java files in src/main/java and src/test/java. There are several ways of doing this.

Maven插件之build-helper-maven-plugin

把原有项目添加到Maven管理时，总会出现很多莫名奇妙的问题，其中之一便是Maven默认的项目结构和自己的项目结构不一致，导致无法编译源代码，更不用说部署、运行项目了。Java程序开发，一般使用Eclipse、MyEclipse等工具，其源码目录为src，这与Maven默认的src/main/java不同。因此，在没有额外配置的情况下，使用Maven命令无法完成代码的编译。针对这种情况，codehaus提供了build-helper-maven-plugin插件来支持自定义的项目目录结构(相对于Maven默认目录结构来说)。

Maven Help插件的使用

help:describe
 描述插件的属性。它不需要在项目目录下运行。但是你必须提供你想要描述插件的前缀或者 groupId 和 artifactId。
通过 plugin 参数你可以指定你想要了解哪个插件，你可以传入插件的前缀（如 maven-war-plugin 插件的前缀就是war），或者可以是 groupId:artifact[:version] ，这里 version 是可选的
 举例说明如下（以maven-war-plugin 为例 ）
 mvn help:describe -Dplugin=war
 或者
 mvn help:describe -Dplugin=org.apache.maven.plugins:maven-war-plugin
 或者
 mvn help:describe -DgroupId=org.apache.maven.plugins -DartifactId=maven-war-plugin

 如果想了解详细信息，可以在其后加上-Ddetail 或者 -Dfull
 如：mvn help:describe -Dplugin=org.apache.maven.plugins:maven-war-plugin -Ddetail

Maven忽略测试失败

通常，你会开发一个带有很多失败单元测试的系统。 如果你正在实践测试驱动开发(TDD)，你可能会使用测试失败来衡量你离项目完成有多远。 如果你有失败的单元测试，但你仍然希望产生构建输出，你就必须告诉 Maven 让它忽略测试失败。 当Maven 遇到一个测试失败，它默认的行为是停止当前的构建。 如果你希望继续构建项目，即使 Surefire 插件遇到了失败的单元测试，你就需要设置 Surefire 的testFailureIgnore 这个配置属性为 true。
mvn test -Dmaven.test.failure.ignore=true

Tips

Maven Dependency Scope

Transitive dependencies which are compile and runtime scoped usually affect a project regardless of the scope of a direct dependency. Transitive dependencies which are compile scoped will have the same scope regardless of the scope of the direct dependency. Transitive dependencies which are runtime scoped will generally have the same scope of the direct dependency except when the direct dependency has a scope of compile. When a transitive dependency is runtime scoped and a direct is compile scoped the direct dependency the transitive dependency will have an effective scope of runtime.

Maven Test

Can I run a specific testng test group via maven?

Try mvn test -Dgroups=group3,group2

Separating Integration Tests from Unit Tests Using Maven Failsafe & JUnit @Category

There's more than one way to separate integration tests. By default, Failsafe picks up any class with a suffix "IT" or "ITCase", or prefixed with "IT"    

How do I find out which settings.xml file maven is using

Use the Maven debug option, ie mvn -X     

[Introduction to Plugin Prefix Resolution] (http://maven.apache.org/guides/introduction/introduction-to-plugin-prefix-mapping.html)

In order to give users a convenient prefix with which to reference your plugin a prefix must be associated with your plugin when it is built. By default, Maven will make a guess at the plugin-prefix to be used, by removing any instances of "maven" or "plugin" surrounded by hyphens in the plugin's artifact ID. The conventional artifact ID formats to use are:

maven-${prefix}-plugin - for official plugins maintained by the Apache Maven team itself (you must not use this naming pattern for your plugin, see this note for more informations)
${prefix}-maven-plugin - for plugins from other sources
If your plugin's artifactId fits this pattern, Maven will automatically map your plugin to the correct prefix in the metadata stored within your plugin's groupId path on the repository. However, if you want to customize the prefix used to reference your plugin, you can specify the prefix directly through a configuration parameter on the maven-plugin-plugin in your plugin's POM:

<project>
  ...
  <build>
    ...
<plugins>
  ...
  <plugin>
    <artifactId>maven-plugin-plugin</artifactId>
    <version>2.3</version>
    <configuration>
      ...
      <goalPrefix>somePrefix</goalPrefix>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

mvn somePrefix:goal

Why Maven command MVN sonar:sonar works without any plugin configuration in my POM.xml

参考：Introduction to Plugin Prefix Resolution

The reason is that the Sonar Maven Plugin is hosted at the Codehaus Mojo project and benefits from the groupId "org.codehaus.mojo". This allows to use the shortcut "sonar:sonar" instead of "org.codehaus.mojo:sonar-maven-plugin::sonar" (see the section "Configuring Maven to Search for Plugins" of the Maven documentation)

如何显示maven的生命周期

mvn help:describe -Dcmd=compile (or any other valid phase)

子模块如何设置父工程的版本

Warning on using project.parent.version as the version of a module in Maven 3

maven project version inheritance - do I have to specify the parent version

如果子工程的版本想动态的依赖父工程的版本，用变量的话会收到warning报警。[WARNING] 'version' contains an expression but should be a constant. maven要求必输设置父工程的版本号。只能通过后期的不久措施来设置mvn versions:set -DgenerateBackupPoms=false

如果子工程的自己的版本想要跟着父工程的变化而变化，只有删除子工程的version就还了，子工程会从父工程继承version定义