使用maven shade插件解决项目版本冲突详解

首先，需要清楚的是，当我们使用Maven构建项目时，会引入许多第三方依赖，有时这些依赖版本存在冲突，会导致我们的项目无法正常编译和运行。这时候就需要使用Maven Shade Plugin来解决依赖版本冲突问题。

以下是Maven Shade Plugin的使用教程：

1. 添加Maven Shade Plugin插件到项目中

在项目中的pom.xml文件中添加以下代码：

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-shade-plugin</artifactId>
     <version>3.2.4</version>
      <configuration>
        <createDependencyReducedPom>false</createDependencyReducedPom>
      </configuration>
      <executions>
        <execution>
          <phase>package</phase>
          <goals>
            <goal>shade</goal>
          </goals>
          <configuration>
            <transformers>
              <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer" />
              <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                <mainClass>com.example.Main</mainClass>
              </transformer>
            </transformers>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

在这个例子中，我们定义了Maven Shade Plugin在package阶段运行，并且指定了插件要使用的transformers。

2. 配置transformers

Maven Shade Plugin中的transformers可以用来修改打包后的jar包文件，实现依赖版本冲突的解决。

注意：以下示例中的groupId、artifactId、version仅作为示例，实际使用时需要根据项目的实际情况进行修改。

2.1 重复类合并处理Transformer

在项目中，有可能会存在多个依赖包中都存在同名的类，这时候需要使用Maven Shade Plugin的重复类合并处理transformer将这些类合并成一个，从而避免冲突。具体实现步骤如下：

• 在pom.xml文件中添加以下代码：

<build>
   <plugins>
     <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-shade-plugin</artifactId>
       <version>3.2.4</version>
       <executions>
         <execution>
           <phase>package</phase>
           <goals>
             <goal>shade</goal>
           </goals>
           <configuration>
             <transformers>
               <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                 <mainClass>org.example.Main</mainClass>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.DontIncludeTestResourcesTransformer" />
               <transformer implementation="org.apache.maven.plugins.shade.plugins.IncludeResourceTransformer">
                 <resource>log4j.properties</resource>
                 <file>src/main/resources/log4j.properties</file>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.JarTransformer">
                 <mainClass>org.example.Main</mainClass>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ReproducibleJarTransformer" />
               <transformer implementation="org.apache.maven.plugins.shade.plugins.MinimalMainArtifactFilter">
                <groupId>commons-cli</groupId>
                 <artifactId>commons-cli</artifactId>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.AppendingTransformer">
                 <resource>
                   META-INF/spring.handlers
                 </resource>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ComponentsXmlAggregatorTransformer">
                 <components>
                   <component>
                     <resource>META-INF/cxf/bus-extensions.xml</resource>
                     <implementation>org.apache.cxf.bus.spring.BusExtensionPostProcessor</implementation>
                   </component>
                 </components>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ClasspathAppendingTransformer">
                 <resource>log4j.properties</resource>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.RenamingTransformer">
                 <artifactSet>
                   <includes>
                     <include>com.google.guava:guava*</include>
                   </includes>
                   <excludes>
                     <exclude>com.google.guava:*-source</exclude>
                     <exclude>com.google.guava:*-javadoc</exclude>
                   </excludes>
                 </artifactSet>
                 <regex>guava-([0-9.]+).jar</regex>
                 <replacement>guava-$1-repackaged.jar</replacement>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.DontIncludeJarsWithGroupIdArtifactIdTransformer">
                 <groupId>commons-logging</groupId>
                 <artifactId>commons-logging</artifactId>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ServicesResourceTransformer" />
               <transformer implementation="org.apache.maven.plugins.shade.plugins.XmlAppendingTransformer">
                 <resource>spring.xml</resource>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.IncludeAsResourceTransformer">
                 <resource>META-INF/my-file.txt</resource>
                 <file>${basedir}/target/classes/META-INF/my-file.txt</file>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ExcludeResourceTransformer">
                 <resource>**/*-linux-x86*</resource>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.JarResourceTransformer">
                 <targetPath>conf</targetPath>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.FilteringTransformer">
                 <resource>**/*.properties</resource>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.CustomManifestTransformer">
                 <mainClass>org.example.Main</mainClass>
                 <manifestEntries>
                   <Owner>my company name</Owner>
                 </manifestEntries>
                 <merges>
                   <merge></merge>
                 </merges>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.VersionResourceTransformer" />
               <transformer implementation="org.apache.maven.plugins.shade.plugins.DependencyReducedPomTransformer" />
               <transformer implementation="org.apache.maven.plugins.shade.plugins.XmlAppendingTransformer">
                 <resource>META-INF/maven/com.google.guava/guava/pom.xml</resource> <!-- source of pom file -->
                 <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                   <!-- xpath expression to match parent node in target -->
                   <xpath>/project/dependencies</xpath>
                   <!-- xpath expression of element to append -->
                   <resource>META-INF/maven/com.google.guava/guava/pom.xml</resource> <!-- source of dependency -->
                 </transformer>
               </transformer>
               <transformer implementation="org.apache.maven.plugins.shade.plugins.ManifestResourceTransformer" />
             </transformers>
           </configuration>
         </execution>
       </executions>
     </plugin>
   </plugins>
 </build>

• 在运行命令时，使用命令mvn package来将项目打包成jar包。

2.2 指定依赖版本

Maven Shade Plugin中的relocating transformer可以用来修改依赖包的包路径，从而避免依赖版本冲突。具体实现步骤如下：

• 在pom.xml文件中添加以下代码：

<build>
   <plugins>
     <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-shade-plugin</artifactId>
       <version>3.2.4</version>
       <executions>
         <execution>
           <phase>package</phase>
           <goals>
             <goal>shade</goal>
           </goals>
           <configuration>
             <relocations>
               <relocation>
                 <pattern>commons-logging</pattern>
                 <shadedPattern>com.sample.commons.logging</shadedPattern>
               </relocation>
             </relocations>
           </configuration>
         </execution>
       </executions>
     </plugin>
   </plugins>
 </build>

• 在运行命令时，使用命令mvn package来将项目打包成jar包。

以上就是使用Maven Shade Plugin解决依赖版本冲突的详细攻略。