详解 maven的pom.xml用<exclusion>解决版本问题

<!-- Struts2 -->     <dependency>       <groupId>org.apache.struts</groupId>       <artifactId>struts2-core</artifactId>       <version>${struts.version}</version>       <exclusions>         <exclusion>           <groupId>javassist</groupId>           <artifactId>javassist</artifactId>         </exclusion>         <exclusion> <!-- we prefer our explicit version, though it should be the same -->           <groupId>asm</groupId>           <artifactId>asm</artifactId>         </exclusion>         <exclusion> <!-- we prefer our explicit version, though it should be the same -->           <groupId>asm</groupId>           <artifactId>asm-commons</artifactId>         </exclusion>         <exclusion> <!-- we prefer our explicit version, though it should be the same -->           <groupId>org.ow2.asm</groupId>           <artifactId>asm</artifactId>         </exclusion>         <exclusion> <!-- we prefer our explicit version, though it should be the same -->           <groupId>org.ow2.asm</groupId>           <artifactId>asm-commons</artifactId>         </exclusion>       </exclusions>     </dependency>