5.1 何爲Maven座標
世界上任何一個構件都可以使用Maven座標唯一標識,Maven座標的元素包括groupId、artifactId、version、packageing、classfier。
Maven內置了Maven倉庫:http://repo1.maven.org/maven2
5.2 座標詳解
5.3 account-email
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.lxm.mkfriend</groupId>
<artifactId>mkfriend-email</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>email</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>2.5.6</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>2.5.6</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>2.5.6</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>2.5.6</version>
</dependency>
<dependency>
<groupId>javax.mail</groupId>
<artifactId>mail</artifactId>
<version>1.4.1</version>
</dependency>
<dependency>
<groupId>com.icegreen</groupId>
<artifactId>greenmail</artifactId>
<version>1.3.1b</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.7</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
5.4 依賴的配置
<dependency>
<groupId></groupId>
<artifactId></artifactId>
<version></version>
<type></type>
<scope></scope>
<optional></optional>
<exclusions>
<exclusion></exclusion>
</exclusions>
</dependency>
groupId、artifactId、version:依賴的基本座標,對於任何一個依賴來說,基本座標是最重要的,Maven可以根據座標才能找到需要的依賴。5.5 依賴的範圍
<dependency>
<groupId>javax.sql</groupId>
<artifactId>jdbc-stdext</artifactId>
<version>2.0</version>
<scope>system</scope>
<systemPath>${java.home}/lib/rt.jar</systemPath>
</dependency>
import:(Maven2.0.9及以上):導入依賴範圍。該依賴不會對三種classpath產生實際的影響,將在介紹8.3.3 Maven依賴時進行詳細介紹。5.6 傳遞性依賴
5.6.1 何爲傳遞依賴
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.1</version>
</dependency>
該依賴沒有聲明依賴範圍,那麼其依賴範圍就是默認的compile。同時回顧一下account-email,spring-core的依賴範圍也是compile。5.6.2 傳遞性依賴和依賴範圍
5.7 依賴調節
5.8 可選依賴
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.10</version>
<optional>true</optional>
</dependency>
<dependency>
<groupId>postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>8.4-701.jdbc3</version>
<optional>true</optional>
</dependency>
</dependencies>
使用<optional>標識依賴是可選依賴,他們只對當前項目B產生影響,當其他項目依賴於B的時候,這兩個依賴不會被傳遞。因此,當項目A依賴於項目B的時候,如果其實際使用基於Mysql數據庫,那麼需要在項目A中就需要顯式地聲明mysql-connector-java這一個依賴。
5.9 最佳實踐
5.9.1 排除依賴
<project>
<groupId>com.liuxm.com</groupId>
<artifactId>project-a</artifactId>
<version></version>
<dependencies>
<dependency>
<groupId>com.liuxm.group</groupId>
<artifactId>project-b</artifactId>
<version>1.0.0</version>
<exclusions>
<exclusion>
<groupId>com.liuxm.group</groupId>
<artifactId>project-c<artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>com.liuxm.group</groupId>
<artifactId>project-c</artifactId>
<version>1.1.0</version>
</dependency>
</dependencies>
</project>
5.9.2 歸類依賴
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.lxm.mkfriend</groupId>
<artifactId>guileidependency</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>guileidependency</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<springframework.version>2.5.6</springframework.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${springframework.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${springframework.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${springframework.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${springframework.version}</version>
</dependency>
</dependencies>
</project>
這裏簡單用了Maven屬性,首先使用properties元素定義Maven定義屬性,該例中定義了一個springframework.version子元素,其值爲2.5.6.