首先简单介绍下 Maven 的 profile 是什么。对于人来说，profile 是指人的肖像，轮廓，比如论坛里每个人注册了帐号后，可以设置自己的 profile，放上照片，介绍等等。对于 Maven 来说又是怎样呢？整个项目定义好了项目对象模型（POM），就像论坛为每个人提供了默认的行为功能，如果我想改变我机器上的 POM 呢？这时就可以使用 profile。下面举个例子：

  <profiles>
<profile>
<id>jdk16</id>
<activation>
<jdk>1.6</jdk>
</activation>
<modules>
<module>simple-script</module>
</modules>
</profile>
</profiles>

这个 profile 的意思是，当机器上的 JDK 为1.6的时候，构建 simple-script 这个子模块，如果是1.5或者1.4，那就不构建，这个 profile 是由环境自动激活的。

我们需要在合适的地方使用合适的 profile ，并且在合适的时候用合适的方式将其激活，你不能在构建服务器上激活非公共的 profile，你也不能要求开发人员写很复杂的命令来使用常规的 profile。因此这里介绍一下几种 profile 的激活方式。

1. 根据环境自动激活。

如前一个例子，当 JDK 为1.6的时候，Maven 就会自动构建 simple-script 模块。除了 JDK 之外，我们还可以根据操作系统参数和 Maven 属性等来自动激活 profile，如：

    <profile>
<id>dev</id>
<activation>
<activeByDefault>false</activeByDefault>
<jdk>1.5</jdk>
<os>
<name>Windows XP</name>
<family>Windows</family>
<arch>x86</arch>
<version>5.1.2600</version>
</os>
<property>
<name>mavenVersion</name>
<value>2.0.5</value>
</property>
<file>
<exists>file2.properties</exists>
<missing>file1.properties</missing>
</file>
</activation>
...
</profile>

2. 通过命令行参数激活。

这是最直接和最简单的方式，比如你定义了一个名为 myProfile 的 profile，你只需要在命令行输入 mvn clean install -Pmyprofile 就能将其激活，这种方式的好处很明显，但是有一个很大的弊端，当 profile 比较多的时候，在命令行输入这写 -P 参数会让人觉得厌烦，所以，如果你一直用这种方式，觉得厌烦了，可以考虑使用其它自动激活的方式。

3. 配置默认自动激活。

方法很简单，在配置 profile 的时候加上一条属性就可以了，如：

    <profile>
<id>dev</id>
<activation>
<activeByDefault>true</activeByDefault>
</activation>
...
</profile>

在一个特殊的环境下，配置默认自动激活的 profile 覆盖默认的 POM 配置，非常简单有效。

4. 配置 settings.xml 文件 profile 激活。

settings.xml 文件可以在 ~/.m2 目录下，为某个用户的自定义行为服务，也可以在 M2_HOME/conf 目录下，为整台机器的所有用户服务。而前者的配置会覆盖后者。同理，由 settings.xml 激活的 profile 意在为用户或者整个机器提供特定环境配置，比如，你可以在某台机器上配置一个指向本地数据库 URL 的 profile，然后使用该机器的 settings.xml 激活它。激活方式如下：

<settings>
...
<activeProfiles>
<activeProfile>local_db</activeProfile>
</activeProfiles>
</settings>

Maven 提供的 profile 功能非常强大和灵活，用得好的话，可以有效的隔离很多特殊的配置，使得整个项目能在不同环境中顺利的构建。但是，强大和灵活带来得问题是相对难掌握，希望本文能对 Maven 使用者有帮助。

# filter.properties

my.filter.value=hello!

将对它的引用添加到pom.xml中：

<build>

<filters>

<filter>${baseDir}/pom.properties</filter>

</filters>

</build>

不过这种方式要启动资源过滤，并设置好对应的文件夹才行，相对较麻烦。
2.使用插件：

maven-properties-plugin  使用方法可以看插件的官方地址：http://haroon.sis.utoronto.ca/zarar/properties-maven-plugin/index.html

Because I couldn't find a clear overview of which properties are availabe in maven2 I started this page. It is a collection of things found in the offcial maven documentation and postings to the maven user mailing list.

Note: In Maven 3.0, all pom.* properties are deprecated. Use project.* instead!

Build in properties

• ${basedir} represents the directory containing pom.xml
• ${version} equivalent to ${project.version} or ${pom.version}

Pom/Project properties

All elements in the pom.xml, can be referenced with the project. prefix or using pom. as prefix. This list is just an example of some commonly used elements.

• ${project.build.directory} results in the path to your "target" dir, this is the same as ${pom.project.build.directory}
• ${project.build.outputDirectory} results in the path to your "target/classes" dir
• ${project.name} or ${pom.name} refers to the name of the project.
• ${project.version} or ${pom.version} refers to the version of the project.
• ${project.build.finalName} refers to the final name of the file created when the built project is packaged

Local user settings

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.
• ${maven.repo.local} also works for backward compatibility with maven1 ??

Environment variables

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>

Java system properties

All Java System Properties defined by the JVM.

Custom properties in the POM

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

Parent Project variables

How can parent project variables be accessed?

You can use the prefix: ${project.parent}.

A good way to determine possible variables is to have a look directly at the API. I'm currently using Maven 2.2.1, and to access the Parent you can use ${project.parent}. This will return an org.apache.maven.project.MavenProject instance.

To access the parent version: ${parent.version}.

Reflection Properties

The pattern ${someX.someY.someZ} can simply sometimes mean getSomeX().getSomeY().getSomeZ(). Thus, properties such as ${project.build.directory} is translated to getProject().getBuild().getDirectory().

One of the coolest features of these containers is the hot-deployment.

However, every second time a hot deployment is executed, it crashes due to a PermGen space Exception or a similar OutOfMemoryException.

The cause for this behaviour is a memory leak with the classloaded of these containers. If you are interested in the details, you may read this article on the Classloader Memory Leaks.

Actually, you can’t fix this bug. But there is a way to prevent it from beeing so painful. And it’s pretty easy: simply assign more memory to your JVM!

In order to do so, create a new environment variable named MAVEN_OPTS. Maybe you already defined this variable. What you have to do now is to adjust the MaxPermSize (and the other parameters, too) to a proper value according to your machine’s memory.
For instance, set the MAVEN_OPTS like this:

-Xms512m -Xmx1024m -XX:PermSize=256m -XX:MaxPermSize=512m

Having 2 GB of RAM, these values are a good start.

Now you should be rid of the nasty PermGen space exceptions.

解决的方法是调整java的堆大小的值。

Windows环境中

找到文件%M2_HOME%"bin"mvn.bat ，这就是启动Maven的脚本文件，在该文件中你能看到有一行注释为：

  @REM set MAVEN_OPTS=-Xdebug -Xnoagent -Djava.compiler=NONE...

它的意思是你可以设置一些Maven参数，我们就在注释下面加入一行：

之后，当你运行Maven命令如 mvn -version 的时候，你会看到如下的输出：

我们看到，配置的Maven选项生效了，OutOfMemoryError也能得以相应的解决。

Linux环境中

也可以通过设置环境变量解决该问题， 如，编辑文件 /etc/profile 如下

如果你使用Hudson

用 Hudson + Maven做持续集成，并不幸也遇到了类似的错误，那么上述两种方式都将不再起作用了，因为Hudson使用自己的maven-agent来启动Maven，不会去调用Maven的脚本，自然相应的配置也就无效了。

好在Hudson也给为我们提供了配置点，在Hudson的项目配置页面中，有一块Build区域，这里我们已经 设置了Root Pom和Goals。注意该区域的右下角有一个"Advanced..."按钮，点击会看到MAVEN_OPTS输入框，这里输入"-Xmx512m"就 OK了。

m2eclipse中

类似以上的方法都会失效，所幸m2eclipse提供了配置点。步骤如下：

项目上右击 -> Run As -> Run Configurations -> Maven Build 上右击 -> New

这时会看到一个maven运行配置对话框，这里面其它的配置我不多解释了，为了解决内存溢出的问题，我们可以选择第二个TAB: JRE，然后在VM arguments中输入配置如：-Xms128m -Xmx512m。

还有一种说法：

编辑maven"bin中的mvn文件：

• 在exec "$JAVACMD" "之后加上 -Xmx256m "即可。
• 形式如：
  

    exec "$JAVACMD" "
  
  -Xmx256m "

The configuration free classic way to start Eclipse with desired VM.

$>eclipse -vm "C:\Program Files\Java\jdk1.6.0_01\bin"



这个问题一般是由于使用了struts2引起的：

用了m2eclipse 插件后，使用struts2时，需要依赖 com.sun 的 default-tools.jar，见pom.xml











<?xml version="1.0" encoding="UTF-8"?>



<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">



  <modelVersion>4.0.0</modelVersion>



  <groupId>cn.tianxing.gehouse.admin</groupId>



  <artifactId>admin.gehouse.cn</artifactId>



  <name>admin.gehouse.cn</name>



  <version>0.0.1</version>



  <description>admin.gehouse.cn</description>



  <url>http://admin.gehouse.cn</url>



  <issueManagement>



    <system>jira</system>



    <url>http://jira.gehouse.cn:8080/BrowseProject.jspa?id=10000</url>



  </issueManagement>



  <ciManagement>



    <system>continuum</system>



    <url>http://ci.gehouse.cn:8090/continuum</url>



    <notifiers>



      <notifier>



        <type>msn</type>



        <sendOnSuccess>false</sendOnSuccess>



        <sendOnWarning>false</sendOnWarning>



        <configuration>



          <address>kylindai@hotmail.com</address>



        </configuration>



      </notifier>



      <notifier>



        <type>msn</type>



        <sendOnSuccess>false</sendOnSuccess>



        <sendOnWarning>false</sendOnWarning>



        <configuration>



          <address>larrin2002@msn.com</address>



        </configuration>



      </notifier>



      <notifier>



        <type>msn</type>



        <sendOnSuccess>false</sendOnSuccess>



        <sendOnWarning>false</sendOnWarning>



        <configuration>



          <address>manjingtou-ren@hotmail.com</address>



        </configuration>



      </notifier>



    </notifiers>



  </ciManagement>



  <inceptionYear>2007-05</inceptionYear>



  <developers>



    <developer>



      <name>kylin.dai</name>



      <email>kylin.dai@gehouse.cn</email>



    </developer>



    <developer>



      <name>larrin.luo</name>



      <email>larrin.luo@gehouse.cn</email>



    </developer>



    <developer>



      <name>jason.ren</name>



      <email>jason.ren@gehouse.cn</email>



    </developer>



  </developers>



  <scm>



    <connection>scm:svn:svn://svn.gehouse.cn/sandbox/kylin/admin.gehouse.cn/trunk</connection>



  </scm>



  <organization>



    <name>gehouse.cn</name>



    <url>http://www.gehouse.cn</url>



  </organization>



  <build>



    <plugins>



      <plugin>



        <artifactId>maven-compiler-plugin</artifactId>



        <version>2.0.2</version>



        <configuration>



          <source>1.6</source>



          <target>1.6</target>



        </configuration>



      </plugin>



    </plugins>



  </build>



  <profiles>



    <profile>



      <id>default-tools.jar</id>



      <activation>



        <property>



          <name>java.vendor</name>



          <value>Sun Microsystems Inc.</value>



        </property>



      </activation>



      <dependencies>



        <dependency>



          <groupId>com.sun</groupId>



          <artifactId>tools</artifactId>



          <version>1.5.0</version>



          <scope>system</scope>



          <systemPath>${java.home}/../lib/tools.jar</systemPath>



        </dependency>



      </dependencies>



    </profile>



  </profiles>



  <dependencies>



    <dependency>



      <groupId>log4j</groupId>



      <artifactId>log4j</artifactId>



      <version>1.2.14</version>



    </dependency>



    <dependency>



      <groupId>javax.servlet</groupId>



      <artifactId>servlet-api</artifactId>



      <version>2.5</version>



    </dependency>



    <dependency>



      <groupId>dom4j</groupId>



      <artifactId>dom4j</artifactId>



      <version>1.6.1</version>



    </dependency>



    <dependency>



      <groupId>com.ibatis</groupId>



      <artifactId>ibatis</artifactId>



      <version>2.3.0.667</version>



    </dependency>



    <dependency>



      <groupId>junit</groupId>



      <artifactId>junit</artifactId>



      <version>4.1</version>



    </dependency>



    <dependency>



      <groupId>mysql</groupId>



      <artifactId>mysql-connector-java</artifactId>



      <version>5.0.5</version>



    </dependency>



    <dependency>



      <groupId>org.extremecomponents</groupId>



      <artifactId>extremecomponents</artifactId>



      <version>1.0.1</version>



    </dependency>



    <dependency>



      <groupId>commons-dbcp</groupId>



      <artifactId>commons-dbcp</artifactId>



      <version>1.2.1</version>



    </dependency>



    <dependency>



      <groupId>org.springframework</groupId>



      <artifactId>spring</artifactId>



      <version>2.0.5</version>



    </dependency>



    <dependency>



      <groupId>org.springframework</groupId>



      <artifactId>spring-mock</artifactId>



      <version>2.0.5</version>



    </dependency>



    <dependency>



      <groupId>org.springframework</groupId>



      <artifactId>spring-aspects</artifactId>



      <version>2.0.5</version>



    </dependency>



    <dependency>



      <groupId>org.apache.struts</groupId>



      <artifactId>struts2-core</artifactId>



      <version>2.0.6</version>



    </dependency>



  </dependencies>



  <reporting>



    <plugins>



      <plugin>



        <artifactId>maven-changelog-plugin</artifactId>



      </plugin>



      <plugin>



        <artifactId>maven-checkstyle-plugin</artifactId>



      </plugin>



      <plugin>



        <artifactId>maven-pmd-plugin</artifactId>



      </plugin>



      <plugin>



        <artifactId>maven-changes-plugin</artifactId>



        <reportSets>



          <reportSet>



            <reports>



              <report>jira-report</report>



            </reports>



          </reportSet>



        </reportSets>



      </plugin>



    </plugins>



  </reporting>



</project>











这个pom.xml 在eclipse里加载的时候总是报告：







Missing:



1) com.sun:tools:jar:1.4.2



Try downloading the file manually from the project website.



Then, install it using the command: 







mvn install:install-file -DgroupId=com.sun -DartifactId=tools "



-Dversion=1.4.2 -Dpackaging=jar -Dfile=/path/to/file



Path to dependency: 







原来，是${java.home}在作怪，eclipse 没有使用 JAVA_HOME



默认，eclipse 使用 C:"windows"system32"javaw.exe 作为 JVM，当然找不到tools.jar







解决方法如下：



修改 eclipse.exe 目录下的 eclipse.ini 指定vm，加入红色黑体字部分，注意 -vm后面不能有空格。







-vm



D:"Program Files"Java"jdk1.6.0_01"bin"javaw.exe



-vmargs



-Xms128m



-Xmx512m







再次启动 eclipse，问题解决。







上面的pom.xml文件，也是一个 Mavne2 & Continuum 的例子，由我写的 Maven2 &

Continuum 持续整合 (3)，发布时，网络故障丢失了，也不打算重新再写一篇了，上述的pom.xml，可以在continuum的 add









maven2 projects 里，添加使用，设好 scheduler，可以设1小时 build 一次，半小时 test 一次，等不同的任务

Prerequisites and Assumptions

• Maven is already installed
• A local instance of Tomcat is already installed and configured to run on port 8080
• Optional - Eclipse is installed

Step One - Prepare the Tomcat Manager application

In order to deploy a web app to your Tomcat server, you will need to ensure that you can access the Tomcat Manager application at: http://localhost:8080/manager/html. Typically, you just need to ensure that your <tomcat>/conf/tomcat-users.xml file has the following defined:

In this case, we will be logging in to the Tomcat Manager app using:

Step Two - Create a New Web App Using Maven

Next, we will use a Maven archetype to generate a new web application project.

Assuming that you will primarily use Eclipse as your IDE, you may wish to start the project within Eclipse. We'll start the project within Eclipse and then use Maven to fill the project in with the proper Maven web app structure.

• In Eclipse create a new General project. New > Project... > General > Project
• Project name: "sw" (name it what you wish, but remember to replace 'sw' with your project name in all instances where that appears in this document from here on out.)

The steps above just create a General project in your Eclipse workspace (e.g. a folder with a .project settings file inside of it).

Next, open a command prompt, cd into the 'sw' project directory, and then execute the following Maven command (all on one line):

You project will now have the following structure:

• sw
  • webapp
    • src
      • main
        • resources
        • webapp
          • WEB-INF
            • web.xml
          • index.jsp
    • pom.xml
  • .project

In Eclipse, right-click on the project and select Refresh to see this stuff within Eclipse. (Note that the .project file will typically not appear within Eclipse, but it is there.)

Step Three - Define Your Tomcat Server in Maven Settings

Open your Maven settings.xml file (e.g. C:"Documents and Settings"Administrator".m2"settings.xml) and add a server 'myserver' with the credentials for logging into the Tomcat Manager application:

Step Four - Point Your Pom to Your Tomcat Server

Open the pom.xml file in the 'sw' project and replace the <build> section so that it looks like this:

Here, we have added the Tomcat plugin for Maven. Note that the <configuration> section needs to point to the server you defined in settings.xml ('myserver'). The <finalName> and the <path> are used to tell the web context that you want to deploy to. In this case, we'll be able to access our application at http://localhost:8080/sw.

Step Five - Build and Deploy the Web App

On a command prompt, you can now cd into the sw/webapp directory where the project pom exists. The execute the following command:

If you get a BUILD SUCCESSFUL message, you should then be able to access your web application at http://localhost:8080/sw/.

You should see "Hello World!" in your web browser (from the index.jsp page). Now you're all set and ready to start building the next killer web app!

If you try to deploy again with the same command, you will likely get a FAIL message because the application already exists at the path. For successive deployments, use the following command instead:

Next, you may want to enable log4j logging for your new application; check out How to setup Log4j in a web app - fast.

Eclipse->Windows->Preferences->java->Build Path->Classpath Variable->New

名字:M2_REPO，属性选folder，指向C:\Documents and Settings\your name\.m2\repository

The next section documents the directory layout expected by Maven and the directory layout created by Maven. Please try to conform to this structure as much as possible; however, if you can't these settings can be overridden via the project descriptor.

At the top level files descriptive of the project: a pom.xml file (and any properties, maven.xml or build.xml if using Ant). In addition, there are textual documents meant for the user to be able to read immediately on receiving the source: README.txt, LICENSE.txt, etc.

There are just two subdirectories of this structure: src and target. The only other directories that would be expected here are metadata like CVS or .svn, and any subprojects in a multiproject build (each of which would be laid out as above).

The target directory is used to house all output of the build.

The src directory contains all of the source material for building the project, its site and so on. It contains a subdirectory for each type: main for the main build artifact, test for the unit test code and resources, site and so on.

Within artifact producing source directories (ie. main and test), there is one directory for the language java (under which the normal package hierarchy exists), and one for resources (the structure which is copied to the target classpath given the default resource definition).

If there are other contributing sources to the artifact build, they would be under other subdirectories: for example src/main/antlr would contain Antlr grammar definition files.

对于使用maven的骨架创建工程，想必大家都已经熟悉了，这里是一些常用的工程类型，如想看到更多的骨架可以使用mvn的交互式Interactive generate Goal创建指令：mvn archetype:generate

// Creating a simple java application
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id]

// Creating a webapp
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id] -DarchetypeArtifactId=maven-archetype-webapp

// Creating a site
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id] -DarchetypeArtifactId=maven-archetype-site-simple

// Creating a mojo
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id] -DarchetypeArtifactId=maven-archetype-mojo

// Creating a portlet
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id] -DarchetypeArtifactId=maven-archetype-portlet

现在想介绍的是多模块的工程的构建。

典型的多模块划分，即按MVC的分层方式来构建多个模块，如工程包括web,business,core3个模块。好我们先看看主工程的pom中应添加些什么，请注意红色文字部分

1.主工程的pom文件中内容：

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.your-company.xxxx</groupId>
    <artifactId>xxxx</artifactId>
    <packaging>pom</packaging>
    <version>1.0</version>
    <name>xxxx Project</name>
    <url>http://maven.apache.org</url>

    <!-- 工程所包含的模块 -->

    <modules>
        <module>xxxx-core</module>
        <module>xxxx-business</module>
        <module>xxxx-web</module>
    </modules>

2.Web模块的pom文件：

    <!-- 父级的pom文件位置 -->

    <parent>
        <groupId>com.your-company.xxxx</groupId>
        <artifactId>xxxx</artifactId>
        <version>1.0</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <groupId>com.your-company.xxxx</groupId>
    <artifactId>xxxx-web</artifactId>
    <packaging>war</packaging>
    <version>1.0</version>
    <name>xxxx-web/name>
    <url>http://maven.apache.org</url>

    <dependencies>
        <!-- Application Dependencies -->
        <!-- Web层所依赖的上两层模块 -->

        <dependency>
            <groupId>com.your-company.xxxx</groupId>
            <artifactId>xxxx-core</artifactId>
            <version>${version}</version>
        </dependency>
        <dependency>
            <groupId>com.your-company.xxxx</groupId>
            <artifactId>xxxx-business</artifactId>
            <version>${version}</version>
        </dependency>

        ...

    <dependencies>

3.完成后，mvn eclipse:eclipse后的文件目录为：

xxxx

├─xxxx-core

│ ├─pom.xml
│ ├─.settings
│ ├─src
│ │ ├─main
│ │ │ ├─java
│ │ │ └─resources
│ │ └─test
│ │      ├─java
│ │      └─resources
│ └─target
│      ├─classes
│      └─test-classes

├─xxxx-business
│ ├─pom.xml
│ ├─.settings
│ ├─src
│ │ ├─main
│ │ │ ├─java
│ │ │ └─resources
│ │ └─test
│ │      ├─java
│ │      └─resources
│ └─target
│      ├─classes
│      └─test-classes

├─xxxx-web

│ ├─pom.xml
│ ├─.settings
│ ├─src
│ │ ├─main
│ │ │ ├─java
│ │ │ └─resources
│ │ └─test
│ │      ├─java
│ │      └─resources
│ └─target
│      ├─classes
│      └─test-classes

|--pox.xml