java.lang.NoClassDefFoundError: Could not initialize class com.imooc.mybatis.utils.MyBatisUtils

at com.imooc.mybatis.MyBatisTestor.testOneToMany(MyBatisTestor.java:242)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)

at org.junit.runners.ParentRunner.run(ParentRunner.java:363)

at org.junit.runner.JUnitCore.run(JUnitCore.java:137)

at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)

at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)

at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)

at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

   <!--
       resultMap可用于说明一对多或者多对一的映射逻辑
       id是resultMap属性引用的标志
       type指one的实体
   -->
   <resultMap id="rmGoods1" type="com.imooc.mybatis.entity.Goods">
       <!--映射goods对象的主键到goods_id字段-->
       <id column="goods_id" property="goodsId"></id>
       <!--
           collection的含义是在
           select * from t_goods limit 0,1 得到结果后，对所有的Goods对象遍历得到goods_id字段值
           并带入到goodsDetail命名空间的findByGoodsId的SQL中执行查询
           将得到的“商品详情”集合赋值给goodsDetails list对象。
       -->
       <collection property="goodsDetails" select="goodsDetail.selectByGoodsId"/>
   </resultMap>
   <select id="selectOneToMany" resultMap="rmGoods1">
       select * from t_goods limit 0,1
   </select>

</mapper>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
       PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
       "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
   <settings>
       <!-- goods_id转换成goodsId -->
       <setting name="mapUnderscoreToCamelCase" value="true"/>
   </settings>
   <!-- 设置默认指向的数据库 -->
   <environments default="dev">
       <!-- 根据环境，不同的环境不同的名字 -->
       <environment id="dev">
           <!-- 采用JDBC的方法对数据库事物进行commit/rollback -->
           <transactionManager type="JDBC"></transactionManager>
           <dataSource type="POOLED">
               <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
               <property name="url" value="jdbc:mysql://localhost:3306/babytun?useUnicode=true&amp;characterEncoding=UTF-8"/>
               <property name="username" value="root"/>
               <property name="password" value="Fy13636857477"/>
           </dataSource>
       </environment>
   </environments>
   <mappers>
       <mapper resource="mappers/goods.xml"/>
       <mapper resource="mappers/goods_detail.xml"/>
   </mappers>
</configuration>

public void testOneToMany() {
   SqlSession session = null;
   try {
       session = MyBatisUtils.openSession();
       List<Goods> list = session.selectList("goods.selectOneToMany");
       for(Goods goods:list){
           System.out.println(goods.getTitle()+":"+goods.getGoodsDetails().size());
       }
   } catch(Exception e) {
       e.printStackTrace();
   }finally {
       MyBatisUtils.closeSession(session);
   }
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
       PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
       "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="goodsDetail">
   <select id="selectByGoodsId" parameterType="Integer" resultType="com.imooc.mybatis.entity.GoodsDetail">
       select * from t_goods_detail where goods_id = #{value}
   </select>
</mapper>