报错信息： Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.1.3.RELEASE:repackage (repackage) on project jeecg-boot-module-system: Execution repackage of goal org.springframework.boot:spring-boot-maven-plugin:2.1.3.RELEASE:repackage failed: Unable to find a single main class from the following candidates [org.jeecg.JeecgApplication, org.jeecg.URuleApplication]
原因及解决方法：看了网上说spring-boot-maven-plugin 改成普通的maven-plugin，或者把启动类放在src/main/java下，我这个问题的原因是在一个模块中出现了两个SpringBoot启动类（@SpringBootApplication修饰的类）冲突了，将两个启动类合并就解决了。