详细错误及处理方法如下：
[ERROR] Failed to execute goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.5:generate (default-cli) on project spring_boot_mybatis: Execution default-cli of goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.5:generate failed: Cannot resolve classpath entry: mysql-connector-java-5.1.38.jar -> [Help 1]
是由于这个节点：
<classPathEntry location="mysql-connector-java-5.1.38.jar"/>
location要指定绝对路径如：
<classPathEntry location="D:\MyBatisGenerator\mysql-connector-java-5.1.38.jar"/>