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使用maven最烦人的可能就是类包之间的版本冲突引发的问题了，类包冲突的一个很大的原因即产类包之间的间接依赖引起的。每个显式声明的类包都会依赖于一些其它的隐式类包，这些隐式的类包会被maven间接引入进来，因而可能造成一个我们不想要的类包的载入，严重的甚至会引起类包之间的冲突。
要解决这个问题，首先就是要查看pom.xml显式和隐式的依赖类包，然后通过这个类包树找出我们不想要的依赖类包，手工将其排除在外就可以了。
下面，通过一个例子来说明：
我的项目使用testng进行测试，使用了untilis，由于unitils的类包会隐式依赖于junit，这是我不想看到的，下面的目的就是找出junit会谁隐式载入了，然后exculte掉它。
通过idea的maven依赖分析将不需要的依赖exclude掉
打开maven的pom.xml，在某个<dependency>中通过右键菜单：maven->show dependency 打开分析的图形化页面，如下所示： 
通过菜单的exclude即解决这个间接依赖。
通过这个依赖树，我们还可以看到Junit还通过“unitils-spring”的依赖间接载入了，如下所示： 
从上面的依赖树中，我们可以看出junit通过unitils-spring的unitils-database间接引入了，由于我的项目都不需要数据库的测试，因此，可以把unitils-database项整个exclude掉。
下面，是处理完成后的pom.xml关键片断：
Xml代码 
<dependency>
<groupId>org.unitils</groupId>
<artifactId>unitils-testng</artifactId>
<version>${unitils.version}</version>
<scope>test</scope>
<exclusions>
<exclusion>
<artifactId>junit</artifactId>
<groupId>junit</groupId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.unitils</groupId>
<artifactId>unitils-spring</artifactId>
<version>${unitils.version}</version>
<scope>test</scope>
<exclusions>
<exclusion>
<artifactId>unitils-database</artifactId>
<groupId>org.unitils</groupId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
这样，被间接隐式引入的junit就被我们exclude在外了。
有时通过idea的依赖分析工具产生的树不够全，这时就需要使用mvn dependency:tree来查看依赖树了。
通过mvn dependency:tree 查看依赖树
引用
mvn dependency:tree
以下是使用这个工具产生的依赖树：
引用
E:\01workspace\chenxh\09research\rop\rop>mvn dependency:tree
[WARNING]
[WARNING] Some problems were encountered while building the effective settings
[WARNING] ‘pluginRepositories.pluginRepository.id‘ must not be ‘local‘, this identifier is reserved for the local re
tory, using it for other repositories will corrupt your repository metadata. @ C:\Users\Administrator\.m2\settings.x
[WARNING]
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building rop 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.1:tree (default-cli) @ rop ---
[INFO] com.rop:rop:jar:1.0-SNAPSHOT
[INFO] +- javax.validation:validation-api:jar:1.0.0.GA:compile
[INFO] +- org.hibernate:hibernate-validator:jar:4.2.0.Final:compile
[INFO] +- org.codehaus.jackson:jackson-core-asl:jar:1.9.5:compile
[INFO] +- org.codehaus.jackson:jackson-mapper-asl:jar:1.9.5:compile
[INFO] +- org.codehaus.jackson:jackson-jaxrs:jar:1.9.5:compile
[INFO] +- org.codehaus.jackson:jackson-xc:jar:1.9.5:compile
[INFO] +- com.fasterxml.jackson.dataformat:jackson-dataformat-xml:jar:2.0.0-RC2:compile
[INFO] | +- com.fasterxml.jackson.core:jackson-core:jar:2.0.0-RC2:compile
[INFO] | +- com.fasterxml.jackson.core:jackson-annotations:jar:2.0.0-RC2:compile
[INFO] | +- com.fasterxml.jackson.core:jackson-databind:jar:2.0.0-RC2:compile
[INFO] | +- com.fasterxml.jackson.module:jackson-module-jaxb-annotations:jar:2.0.0-RC2:compile
[INFO] | \- org.codehaus.woodstox:stax2-api:jar:3.1.1:compile
[INFO] | \- javax.xml.stream:stax-api:jar:1.0-2:compile
[INFO] +- org.slf4j:slf4j-api:jar:1.6.1:compile
[INFO] +- org.slf4j:slf4j-log4j12:jar:1.6.1:compile
[INFO] +- log4j:log4j:jar:1.2.16:compile
[INFO] +- org.springframework:spring-core:jar:3.1.1.RELEASE:compile
[INFO] | +- org.springframework:spring-asm:jar:3.1.1.RELEASE:compile
[INFO] | \- commons-logging:commons-logging:jar:1.1.1:compile
[INFO] +- org.springframework:spring-context:jar:3.1.1.RELEASE:compile
[INFO] | +- org.springframework:spring-aop:jar:3.1.1.RELEASE:compile
[INFO] | +- org.springframework:spring-beans:jar:3.1.1.RELEASE:compile
[INFO] | \- org.springframework:spring-expression:jar:3.1.1.RELEASE:compile
[INFO] +- org.springframework:spring-context-support:jar:3.1.1.RELEASE:compile
[INFO] +- org.springframework:spring-web:jar:3.1.1.RELEASE:compile
[INFO] | \- aopalliance:aopalliance:jar:1.0:compile
[INFO] +- org.springframework:spring-test:jar:3.1.1.RELEASE:compile
[INFO] +- org.springframework:spring-webmvc:jar:3.1.1.RELEASE:compile
[INFO] +- org.testng:testng:jar:6.3:test
[INFO] | +- org.beanshell:bsh:jar:2.0b4:test
[INFO] | +- com.beust:jcommander:jar:1.12:test
[INFO] | \- org.yaml:snakeyaml:jar:1.6:test
[INFO] +- org.mockito:mockito-all:jar:1.8.5:test
[INFO] +- javax.servlet:servlet-api:jar:2.5:provided
[INFO] +- org.unitils:unitils-core:jar:3.3:test
[INFO] | +- commons-lang:commons-lang:jar:2.3:test
[INFO] | +- commons-collections:commons-collections:jar:3.2:test
[INFO] | \- ognl:ognl:jar:2.6.9:test
[INFO] +- org.unitils:unitils-testng:jar:3.3:test
[INFO] | \- org.testng:testng:jar:jdk15:5.8:test
[INFO] | \- junit:junit:jar:3.8.1:test
[INFO] \- org.unitils:unitils-spring:jar:3.3:test
[INFO] +- org.springframework:spring-tx:jar:2.5.2:test
[INFO] \- org.unitils:unitils-database:jar:3.3:test
[INFO] +- org.unitils:unitils-dbmaintainer:jar:3.3:test
[INFO] | +- org.hibernate:hibernate:jar:3.2.5.ga:test
[INFO] | | +- net.sf.ehcache:ehcache:jar:1.2.3:test
[INFO] | | +- asm:asm-attrs:jar:1.5.3:test
[INFO] | | +- dom4j:dom4j:jar:1.6.1:test
[INFO] | | +- antlr:antlr:jar:2.7.6:test
[INFO] | | +- cglib:cglib:jar:2.1_3:test
[INFO] | | \- asm:asm:jar:1.5.3:test
[INFO] | \- org.dbunit:dbunit:jar:2.2.2:test
[INFO] | +- junit-addons:junit-addons:jar:1.4:test
[INFO] | | +- xerces:xercesImpl:jar:2.6.2:test
[INFO] | | \- xerces:xmlParserAPIs:jar:2.6.2:test
[INFO] | +- poi:poi:jar:2.5.1-final-20040804:test
[INFO] | \- org.slf4j:slf4j-nop:jar:1.4.3:test
[INFO] +- commons-dbcp:commons-dbcp:jar:1.2.2:test
[INFO] | \- commons-pool:commons-pool:jar:1.3:test
[INFO] \- org.springframework:spring-jdbc:jar:2.5.2:test
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 8.250s
[INFO] Finished at: Fri Jun 08 09:08:09 CST 2012
[INFO] Final Memory: 7M/245M
[INFO] ------------------------------------------------------------------------
我原来一个使用idea分析不出的隐式依赖就是通用mvn dependency:tree找到的。
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原文地址：http://my.oschina.net/muou/blog/477742
