配置

<pluginRepositories>
    <pluginRepository>
        <name>oss.sonatype.org</name>
        <id>oss.sonatype.org</id>
        <url>http://oss.sonatype.org/content/groups/public</url>
    </pluginRepository>
</pluginRepositories>
<plugin>
            <groupId>net.alchim31.maven</groupId>
            <artifactId>yuicompressor-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>compress</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <nosuffix>true</nosuffix>
                <sourceDirectory>${project.basedir}/web</sourceDirectory>
                <outputDirectory>${project.build.directory}/web</outputDirectory>
            </configuration>
        </plugin>

注意事项

这个plugin拷贝js/css文件到制定的目录中，并且会保留原有的目录结构，比如web目录下有js,css这两个文件夹，那么输出的目录target/web中也会有同样的目录结构。但是如果你的web目录下还有其他文件，比如html等，这个plugin不会帮你拷贝到target/web目录下的，这时候需要结合使用maven-resources插件，举例:

    <resources>
        <resource>
            <directory>${project.basedir}/web/public/images</directory>
            <targetPath>${project.build.directory}/web/public/images</targetPath>
        </resource>
        <resource>
            <directory>${project.basedir}/web/public/static</directory>
            <targetPath>${project.build.directory}/web/public/static</targetPath>
        </resource>
    </resources>

参考

YUI Compressor Maven Mojo