maven打包，配置中指定主类

<build>
　　　　
　<!-- 指定源码包和测试包的位置 -->

　　<sourceDirectory>src/main/scala</sourceDirectory>
　　<testSourceDirectory>src/test/scala</testSourceDirectory>

<plugins>

<!-- 指定编译scala的插件 -->
  <plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <!-- <version>3.2.2</version>  -->
　　　　<version>3.4.6</version>
    <executions>
      <execution>
        <goals>
          <goal>compile</goal>
          <goal>testCompile</goal>
        </goals>
        <configuration>
          <args>
            <arg>-dependencyfile</arg>
            <arg>${project.build.directory}/.scala_dependencies</arg>
          </args>
        </configuration>
      </execution>
    </executions>
  </plugin>

   
            <!-- maven打包的插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                 <version>3.2.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                    <resource>reference.conf</resource>
                                </transformer>
                                <!-- 指定main方法 -->
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>xxx</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build> 

二、将项目打jar 包时，将依赖的 jar 包一起并入到项目 jar 包中
在 pom.xml 的 build-plugins 节点上添加以下配置即可

<!-- 配置将依赖包一并打入到项目的 jar 包中 -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>3.0.0</version>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass></mainClass>
                    </manifest>
                </archive>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id> <!-- this is used for inheritance merges -->
                    <phase>package</phase> <!-- 指定在打包节点执行jar包合并操作 -->
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>