maven-dependency-plugin最大的用途是帮助分析项目依赖，dependency:list能够列出项目最终解析到的依赖列表，dependency:tree能进一步的描绘项目依赖树，dependency:analyze可以告诉你项目依赖潜在的问题，如果你有直接使用到的却未声明的依赖，该目标就会发出警告。maven-dependency-plugin还有很多目标帮助你操作依赖文件，例如dependency:copy-dependencies能将项目依赖从本地Maven仓库复制到某个特定的文件夹下面。

比如查看maven项目的依赖，我们可以用下面命令：

mvn dependency:tree [INFO] Scanning for projects... [WARNING] [WARNING] Some problems were encountered while building the effective model for com.alibaba:dubbo-demo-provider:jar:2.5.4-SNAPSHOT [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-surefire-plugin is missing. @ com.alibaba:dubbo-parent:2.5.4-SNAPSHOT, /Users/ghj1976/project/github/alibaba/dubbo/pom.xml, line 379, column 12 [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-jar-plugin is missing. @ com.alibaba:dubbo-parent:2.5.4-SNAPSHOT, /Users/ghj1976/project/github/alibaba/dubbo/pom.xml, line 365, column 12 [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-deploy-plugin is missing. @ com.alibaba:dubbo-parent:2.5.4-SNAPSHOT, /Users/ghj1976/project/github/alibaba/dubbo/pom.xml, line 449, column 12 [WARNING] [WARNING] It is highly recommended to fix these problems because they threaten the stability of your build. [WARNING] [WARNING] For this reason, future Maven versions might no longer support building such malformed projects. [WARNING] [INFO]                                                                         [INFO] ------------------------------------------------------------------------ [INFO] Building dubbo-demo-provider 2.5.4-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ dubbo-demo-provider --- [INFO] com.alibaba:dubbo-demo-provider:jar:2.5.4-SNAPSHOT [INFO] +- com.alibaba:dubbo-demo-api:jar:2.5.4-SNAPSHOT:compile [INFO] +- com.alibaba:dubbo:jar:2.5.4-SNAPSHOT:compile [INFO] |  \- commons-logging:commons-logging:jar:1.1.1:compile [INFO] +- org.springframework:spring:jar:2.5.6.SEC03:compile [INFO] +- org.javassist:javassist:jar:3.15.0-GA:compile [INFO] +- org.jboss.netty:netty:jar:3.2.5.Final:compile [INFO] +- org.apache.mina:mina-core:jar:1.1.7:compile [INFO] +- org.glassfish.grizzly:grizzly-core:jar:2.1.4:compile [INFO] |  +- org.glassfish.grizzly:grizzly-framework:jar:2.1.4:compile [INFO] |  |  \- org.glassfish.gmbal:gmbal-api-only:jar:3.0.0-b023:compile [INFO] |  |     \- org.glassfish.external:management-api:jar:3.0.0-b012:compile [INFO] |  +- org.glassfish.grizzly:grizzly-portunif:jar:2.1.4:compile [INFO] |  \- org.glassfish.grizzly:grizzly-rcm:jar:2.1.4:compile [INFO] +- org.apache.httpcomponents:httpclient:jar:4.1.2:compile [INFO] |  +- org.apache.httpcomponents:httpcore:jar:4.1.2:compile [INFO] |  \- commons-codec:commons-codec:jar:1.4:compile [INFO] +- com.alibaba:fastjson:jar:1.1.39:compile [INFO] +- com.thoughtworks.xstream:xstream:jar:1.4.1:compile [INFO] |  +- xmlpull:xmlpull:jar:1.1.3.1:compile [INFO] |  \- xpp3:xpp3_min:jar:1.1.4c:compile [INFO] +- org.apache.bsf:bsf-api:jar:3.1:compile [INFO] +- org.apache.zookeeper:zookeeper:jar:3.3.3:compile [INFO] |  \- jline:jline:jar:0.9.94:compile [INFO] +- com.github.sgroschupf:zkclient:jar:0.1:compile [INFO] +- com.netflix.curator:curator-framework:jar:1.1.16:compile [INFO] |  +- com.netflix.curator:curator-client:jar:1.1.16:compile [INFO] |  \- com.google.guava:guava:jar:11.0.1:compile [INFO] |     \- com.google.code.findbugs:jsr305:jar:1.3.9:compile [INFO] +- com.googlecode.xmemcached:xmemcached:jar:1.3.6:compile [INFO] +- org.apache.cxf:cxf-rt-frontend-simple:jar:2.6.1:compile [INFO] |  +- org.apache.cxf:cxf-api:jar:2.6.1:compile [INFO] |  |  +- org.codehaus.woodstox:woodstox-core-asl:jar:4.1.2:runtime [INFO] |  |  |  \- org.codehaus.woodstox:stax2-api:jar:3.1.1:runtime [INFO] |  |  +- org.apache.ws.xmlschema:xmlschema-core:jar:2.0.2:compile [INFO] |  |  +- org.apache.geronimo.specs:geronimo-javamail_1.4_spec:jar:1.7.1:compile [INFO] |  |  \- wsdl4j:wsdl4j:jar:1.6.2:compile [INFO] |  +- org.apache.cxf:cxf-rt-core:jar:2.6.1:compile [INFO] |  |  \- com.sun.xml.bind:jaxb-impl:jar:2.1.13:compile [INFO] |  \- org.apache.cxf:cxf-rt-bindings-soap:jar:2.6.1:compile [INFO] |     \- org.apache.cxf:cxf-rt-databinding-jaxb:jar:2.6.1:compile [INFO] +- org.apache.cxf:cxf-rt-transports-http:jar:2.6.1:compile [INFO] +- org.apache.thrift:libthrift:jar:0.8.0:compile [INFO] |  \- commons-lang:commons-lang:jar:2.5:compile [INFO] +- com.caucho:hessian:jar:4.0.7:compile [INFO] +- javax.servlet:servlet-api:jar:2.5:compile [INFO] +- org.mortbay.jetty:jetty:jar:6.1.26:compile [INFO] |  +- org.mortbay.jetty:jetty-util:jar:6.1.26:compile [INFO] |  \- org.mortbay.jetty:servlet-api:jar:2.5-20081211:compile [INFO] +- log4j:log4j:jar:1.2.16:compile [INFO] +- org.slf4j:slf4j-api:jar:1.6.2:compile [INFO] +- redis.clients:jedis:jar:2.1.0:compile [INFO] |  \- commons-pool:commons-pool:jar:1.5.5:compile [INFO] +- javax.validation:validation-api:jar:1.0.0.GA:compile [INFO] +- org.hibernate:hibernate-validator:jar:4.2.0.Final:compile [INFO] +- javax.cache:cache-api:jar:0.4:compile [INFO] +- junit:junit:jar:4.10:test [INFO] |  \- org.hamcrest:hamcrest-core:jar:1.1:test [INFO] +- org.easymock:easymock:jar:3.0:test [INFO] |  +- cglib:cglib-nodep:jar:2.2:test [INFO] |  \- org.objenesis:objenesis:jar:1.2:test [INFO] +- org.easymock:easymockclassextension:jar:3.0:test [INFO] \- com.googlecode.jmockit:jmockit:jar:0.999.8:test [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.057 s [INFO] Finished at: 2016-03-29T15:41:31+08:00 [INFO] Final Memory: 12M/309M [INFO] ------------------------------------------------------------------------

unpack和copy类似，只不过它会把拷来的包解开，例如：

                        maven-dependency-plugin                                                 unpack                     package                                             unpack                                                                                                                             com.alibaba                                 dubbo                                 ${project.parent.version}                                 ${project.build.directory}/dubbo                                 META-INF/assembly/**                                                                                                            

…

dependency:unpack 中常用参数有：

artifactItems：用来包含声明需要解压的文件元素；

artifactItem：声明需要解压的文件；

outputDirectory：定义解压后输出的文件夹；

includes：定义输出包含的规则；

excludes：定义输出排除的规则。

Apache Maven Dependency Plugin中比较常用的功能有：

dependency:copy  用来拷贝某一个或多个特定文件到指定目录；

dependency:copy-dependencies  用来拷贝依赖的文件到指定目录；

dependency:unpack  与 copy 类似，但会解压文件；

dependency:unpack-dependencies 与 copy-dependencies 类似，但会解压文件；

参考资料：

使用maven命令来分析jar包之间的依赖关系 http://outofmemory.cn/code-snippet/10914/maven-command-dependency