maven-pom

maven的scope

compile:（默认的范围）编译，测试，运行

provided:编译，测试的时候有效，在运行时不会被加入 如:servlet api

runtime:在测试，运行时有效;如jdbc驱动包

test:在测试时有效

system:在编译，测试时有效（和provided相似），和系统相关联，可移埴性差

import: 用在dependencyManagent中。如：把a中的依赖导入b 中

dependencyManagent

一般定义在父模块中用于定义常用的依赖，maven并不会真正去加载，给子模块继承用。在子模块中定义时才会真正加载。例如：

<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>com.phl.test</groupId>  <artifactId>test</artifactId>  <packaging>pom</packaging>  <version>1.0-SNAPSHOT</version>  <name>test Maven Webapp</name>  <url>http://maven.apache.org</url>  <modules>    <module>loadresources</module>    <module>designmodel</module>    <module>javacase</module>  </modules>  <dependencyManagement>    <dependencies>      <dependency>        <groupId>junit</groupId>        <artifactId>junit</artifactId>        <version>3.8.1</version>        <scope>test</scope>      </dependency>      <dependency>        <groupId>org.springframework</groupId>        <artifactId>spring-context</artifactId>        <version>4.2.0.RELEASE</version>      </dependency>      <dependency>        <groupId>org.springframework</groupId>        <artifactId>spring-core</artifactId>        <version>4.2.0.RELEASE</version>      </dependency>    </dependencies>  </dependencyManagement>  <build>    <finalName>test</finalName>  </build></project>

build plugins

在build的时候执行插件.

plugin就是用来向maven提供goal的。一个plugin里面可以有多个goal，这就是为什么我们在指明goal时，前面会用一个冒号与plugin的名字。

一个plugin自己可以指定自己的goal绑定到哪个lifecycle的哪一个Phase上，另外也可以配置一个goal绑定到哪个phase上。可以在pom.xml里面配置。

在build里面列出要执行的插件列表

<build>    <finalName>${app.warFile}</finalName>    <resources>        <resource>            <directory>src/main/resources</directory>            <filtering>true</filtering>        </resource>        <resource>            <directory>src/main/resources-${profile.name}</directory>            <filtering>true</filtering>        </resource>    </resources>    <plugins>        <plugin>            <groupId>org.codehaus.mojo</groupId>            <artifactId>build-helper-maven-plugin</artifactId>            <version>1.9.1</version>            <executions>                <execution>                    <id>add-resource</id>                    <phase>generate-resources</phase>                    <goals>                        <goal>add-resource</goal>                    </goals>                    <configuration>                        <resources>                            <resource>                                <directory>src/main/resources-${profile.name}</directory>                            </resource>                        </resources>                    </configuration>                </execution>            </executions>        </plugin>        <plugin>            <groupId>org.apache.tomcat.maven</groupId>            <artifactId>tomcat7-maven-plugin</artifactId>            <version>2.2</version>            <configuration>                <path>/</path>                <uriEncoding>utf-8</uriEncoding>                <port>${app.port}</port>                <server>tomcat</server>                <systemProperties>                    <systemProperty>                        <name>JAVA_OPTS</name>                        <value>-Xms256m -Xmx768m -XX:+UseConcMarkSweepGC -XX:MaxPermSize=256m -XX:NewRatio=6                            -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled                        </value>                    </systemProperty>                </systemProperties>            </configuration>        </plugin>    </plugins></build>

build lifecycle & build phase & goal

maven有一套build的生命周期，是按照一套顺序走下来的，这一套顺序就叫一个生命周期(lifecycle)。maven内置三种生命周期：default, clean 和 site。一个生命周期分为多个build phase，下面是default生命周期全部的build phase：

• validate：validate the project is correct and all necessary information is available.
• initialize：initialize build state, e.g. set properties or create directories.
• generate-sources：generate any source code for inclusion in compilation.
• process-sources：process the source code, for example to filter any values.
• generate-resources：generate resources for inclusion in the package.
• process-resources：copy and process the resources into the destination directory, ready for packaging.
• compile：compile the source code of the project.
• process-classes：post-process the generated files from compilation, for example to do bytecode enhancement on Java classes.
• generate-test-sources：generate any test source code for inclusion in compilation.
• process-test-sources：process the test source code, for example to filter any values.
• generate-test-resources：create resources for testing.
• process-test-resources：copy and process the resources into the test destination directory.
• test-compile：compile the test source code into the test destination directory
• process-test-classes：post-process the generated files from test compilation, for example to do bytecode enhancement on Java classes. For Maven 2.0.5 and above.
• test：run tests using a suitable unit testing framework. These tests should not require the code be packaged or deployed.
• prepare-package：perform any operations necessary to prepare a package before the actual packaging. This often results in an unpacked, processed version of the package. (Maven 2.1 and above)
• package：take the compiled code and package it in its distributable format, such as a JAR.
• pre-integration-test：perform actions required before integration tests are executed. This may involve things such as setting up the required environment.
• integration-test：process and deploy the package if necessary into an environment where integration tests can be run.
• post-integration-test：perform actions required after integration tests have been executed. This may including cleaning up the environment.
• verify：run any checks to verify the package is valid and meets quality criteria.
• install：install the package into the local repository, for use as a dependency in other projects locally.
• deploy：done in an integration or release environment, copies the final package to the remote repository for sharing with other developers and projects.

这些build phase是按照顺序执行的，如果执行后面的build phase，前面的build phase 也会被执行。例如如果执行：

mvn deploy

前面的install、verify一直到validate这些build phase都会执行。

每一个build phase是由goal组成的，一个goal其实就是一个任务，一个goal可以关联到一个build phase也可以不关联到任何build phase 。 不关联到任何phase的goal是可以独立执行的，例如：

mvn clean dependency:copy-dependencies package

上面的命令会导致先执行clean这个phase，然后拷贝依赖项，最后打包。注意，这里clean这个goal是clean这个lifecycle里面的一个goal，所以可以看到不同lifecycle的build phase和goal是可以混合在一起执行的。 如果一个goal被绑定到多个phase上，那么goal就会被执行多次。

phase的顺序是已经固定的，如果一个phase没有绑定到任何goal，那么phase就不会被执行。 一个goal可以通过两种方式绑定到一个phase，一个是指定packaging，另一个就是plugin。