对于web项目,会涉及到许多依赖关系。以jar包为例,可能项目本身只需要用到spring的一些jar包,但是spring又会依赖于其他jar包,而其他的jar包又有可能依赖于别的jar包,这样的传递关系可能会很长,层次会很深,这导致lib下的jar包很多,而且有时候我们并不知道所有的依赖关系。我们打开服务器运行项目时会提示依赖包缺失,我们又要花很长时间去寻找依赖包,这大大增加开发时间。
有了Maven,情况就不一样了,我们可以通过Maven来进行依赖管理
Spring MVC项目的搭建可以使用Maven,通过一个配置文件来完成依赖管理。配置文件中包括对依赖包和插件等的配置。依赖的管理是通过坐标来完成的。
POM(Project Object Model)
pom.xml
<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>eseBookSys</groupId> <artifactId>eseBookSys</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>war</packaging> <name>eseBookSys</name> <description/> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>org.glassfish</groupId> <artifactId>bean-validator</artifactId> <version>3.0-JBoss-4.0.2</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.enterprise.deploy</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.jms</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.management.j2ee</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>javax.persistence</artifactId> <version>2.0.0</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.resource</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.security.auth.message</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.security.jacc</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.servlet</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.servlet.jsp</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.servlet.jsp.jstl</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.xml.bind</groupId> <artifactId>jaxb-api-osgi</artifactId> <version>2.2.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.ws.rs</groupId> <artifactId>jsr311-api</artifactId> <version>1.1.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>jstl-impl</artifactId> <version>1.2</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.mail</groupId> <artifactId>mail</artifactId> <version>1.4.3</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.xml</groupId> <artifactId>webservices-api-osgi</artifactId> <version>2.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.jboss.weld</groupId> <artifactId>weld-osgi-bundle</artifactId> <version>1.0.1-SP3</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.servlet.jsp.jstl</artifactId> <version>1.2.1</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.2</version> <configuration> <source>1.7</source> <target>1.7</target> </configuration> </plugin> <plugin> <artifactId>maven-war-plugin</artifactId> <version>2.2</version> <configuration> <version>3.0</version> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> </plugins> </build> </project>
总结:Maven通过一个xml文件来完成依赖管理,包括直接依赖和传递依赖
Maven的安装:
1)下载解压Maven
2) 配置环境变量(MAVEN_HOME,Path)
MAVEN_HOME:为maven的解压路径
Path:在后面加上;%MAVEN_HOME%bin
配置完成后,在命令行下输入 mvn -version,出现如下内容,则配置成功,否则检查路径
3) 配置Maven配置文件(本地仓库路径,镜像)
找到maven安装路径下的conf文件,里面有个setting.xml配置文件
这里也可以不进行配置,但最好还是要修改一下。尤其是镜像文件,下载的maven中的镜像文件连接的是英国的一个库,所以myeclipse总是会一直在后台更新工作空间,导入相关jar包,导致无法进行其他操作,速度特别慢,之前我就是没有修改,所以总是出现这个问题。后来我把它改成开源中国上的一个镜像,就没有出现问题了。修改如下:
<mirror> <id>CN</id> <name>OSChina Central</name> <url>http://maven.oschina.net/content/groups/public/</url> <mirrorOf>central</mirrorOf> </mirror>
还有一个是对localRepository的配置,如果不配置默认在${user.home}/.m2/repository 路径下,也可以进行配置,改为指定的路径
<!-- localRepository | The path to the local repository maven will use to store artifacts. | | Default: ${user.home}/.m2/repository <localRepository>/path/to/local/repo</localRepository> -->
这里说明一下,我们可以把setting.xml文件放到user的.m2路径下, 这样以后maven版本更新后,我们不需要再修改配置文件。