Apache Maven项目提供的Dependency插件详解

川长思鸟来 2022-07-15 07:23 430阅读 0赞

Dependency插件可以操作Maven构件（artifact），如复制并解压缩本地或远程Maven库中的构件到某个指定路径。Dependency插件的最新版本是2015.1.24发布的2.10。

Dependency插件提供了大量的goals，常用的如下：

*  [dependency:analyze][dependency_analyze] analyzes the dependencies of this project and determines which are: used and declared; used and undeclared; unused and declared.
 *  [dependency:display-ancestors][dependency_display-ancestors] displays all ancestor POMs of the project. This may be useful in a continuous integration system where you want to know all parent poms of the project. This goal can also be run from the command line.
 *  [dependency:list][dependency_list] alias for resolve that lists the dependencies for this project.
 *  [dependency:resolve][dependency_resolve] tells Maven to resolve all dependencies and displays the version.
 *  [dependency:resolve-plugins][dependency_resolve-plugins] tells Maven to resolve plugins and their dependencies.
 *  [dependency:tree][dependency_tree] displays the dependency tree for this project.
 *  [dependency:unpack][dependency_unpack] like copy but unpacks.

1.利用dependency:analyze-only分析依赖

对Maven项目的依赖的分析默认属于verify阶段，即执行mvn verify默认将会执行dependency:analyze。

但是也可以将dependency:analyze与构建阶段绑定。pom.xml配置如下：

<build>
        <plugins>
          <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <version>2.10</version>
            <executions>
              <execution>
                <id>analyze-only-in-package</id>
                <phase>package</phase>
                <goals>
                  <goal>analyze-only</goal>
                </goals>
                <configuration>
                  
                </configuration>
              </execution>
            </executions>
          </plugin>
        </plugins>
      </build>

另外与dependency:analyze相比，dependency:analyze-only的优势是无需额外的编译任务，只要利用test-compile阶段的编译类即可。

2.利用dependency:tree解决依赖冲突

找出在哪里使用了log4j类库，可以执行如下命令：

mvn dependency:tree -Dverbose -Dincludes=log4j

输出如下：

[INFO] Building MS Extension 1.7.1384-SNAPSHOT
    [INFO] ------------------------------------------------------------------------
    [INFO] 
    [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ ms-extension ---
    [INFO] com.mydoamin.ms:extension:jar:1.7.1384-SNAPSHOT
    [INFO] \- com.mydoamin.core:jar:R4C21-alpha-1:compile
    [INFO]    \- log4j:log4j:jar:1.2.16:compile
    ...

可以看到，这里只有一个对log4j的依赖。如果有多个，那么Maven默认采用最上面的类库（即最后被依赖的类库），这就是所谓的“nearest-wins”策略。

参考文献：

http://maven.apache.org/plugins/maven-dependency-plugin/

[dependency_analyze]: http://maven.apache.org/plugins/maven-dependency-plugin/analyze-mojo.html
[dependency_display-ancestors]: http://maven.apache.org/plugins/maven-dependency-plugin/display-ancestors-mojo.html
[dependency_list]: http://maven.apache.org/plugins/maven-dependency-plugin/list-mojo.html
[dependency_resolve]: http://maven.apache.org/plugins/maven-dependency-plugin/resolve-mojo.html
[dependency_resolve-plugins]: http://maven.apache.org/plugins/maven-dependency-plugin/resolve-plugins-mojo.html
[dependency_tree]: http://maven.apache.org/plugins/maven-dependency-plugin/tree-mojo.html
[dependency_unpack]: http://maven.apache.org/plugins/maven-dependency-plugin/unpack-mojo.html