运行时发现报错信息是169行

然后，检查169行的代码（自然包括169行调用的代码啦）并没有发现明显的问题，然后我们可以注释掉169行的代码，然后重新运行，比如：

此时的运行报错信息如下：

"C:\Program Files\Java\jdk1.8.0_162\bin\java.exe" -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.5\lib\idea_rt.jar=54192:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.5\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.5\lib\idea_rt.jar;D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.5\plugins\junit\lib\junit5-rt.jar;D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.5\plugins\junit\lib\junit-rt.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_162\jre\lib\rt.jar;E:\java\mybatis\target\test-classes;E:\java\mybatis\target\classes;C:\Users\dell\.m2\repository\org\mybatis\mybatis\3.5.1\mybatis-3.5.1.jar;C:\Users\dell\.m2\repository\mysql\mysql-connector-java\5.1.47\mysql-connector-java-5.1.47.jar;C:\Users\dell\.m2\repository\junit\junit\4.12\junit-4.12.jar;C:\Users\dell\.m2\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;C:\Users\dell\.m2\repository\org\dom4j\dom4j\2.1.3\dom4j-2.1.3.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.imooc.mybatis.MyBatisTestor,testInsert

java.lang.ExceptionInInitializerError
	at com.imooc.mybatis.MyBatisTestor.testInsert(MyBatisTestor.java:152)
	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$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in mappers/goods.xml
### The error occurred while processing mapper_resultMap[rmGoods]
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mappers/goods.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for goods.insert. please check mappers/goods.xml and mappers/goods.xml
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:52)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:36)
	at com.imooc.mybatis.utils.MyBatisUtils.<clinit>(MyBatisUtils.java:22)
	... 23 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mappers/goods.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for goods.insert. please check mappers/goods.xml and mappers/goods.xml
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:121)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:98)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:50)
	... 25 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mappers/goods.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for goods.insert. please check mappers/goods.xml and mappers/goods.xml
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:122)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:94)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:373)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:119)
	... 27 more
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for goods.insert. please check mappers/goods.xml and mappers/goods.xml
	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:930)
	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:887)
	at org.apache.ibatis.session.Configuration.addMappedStatement(Configuration.java:686)
	at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:296)
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:110)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:137)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:130)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:120)
	... 30 more


Process finished with exit code -1

通过上面的报错信息，可以帮助我们定位错误：

在goods.xml中果然发现了重复的insert；；；；

将其修改后：

再次运行就OK了：

即，这个报错信息背后的原因，说白了就是xml配置文件出错了，导致MybatisUtils类（这个类中包含初始化SqlSessionFactory这个对象；获得SqlSession对象的方法；关闭SqlSession对象的方法；的内容；；；即这个类的主要功能是初始化Mybatis）在动态运行初始化加载Mybatis的时候出错了。（PS：mybatis的配置文件出错了，自然Mybatis的初始化加载会出错了~~~）

---

（1）声明一下，可能有很多原因都可以导致【java.lang.NoClassDefFoundError: Could not initialize class】。本篇博客，可以帮助提升【如何定位错误的能力】。

（2）然后，MyBatisUtils类是工具类，中间后很多静态变量和静态代码块：可能有些在加载类或者静态变量或者静态代码块执行的时候，也会报【java.lang.NoClassDefFoundError: Could not initialize class】，但是这涉及到了JVM的一些东西，目前并不能很好的理解，望在以后能更好的理解这儿的定西。

package com.imooc.mybatis.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import sun.misc.ExtensionInstallationException;

import java.io.IOException;
import java.io.Reader;

/**
 * MyBatis工具类
 * （1）创建全局唯一的SqlSessionFactory对象；（2）获取SqlSession的方法；（3）关闭SqlSession的方法；
 */
public class MyBatisUtils {
    //sqlSessionFactory对象设置成静态的，这个对象属于类的；
    private static SqlSessionFactory sqlSessionFactory = null;
    static{
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            e.printStackTrace();
            // 如果出现了异常，除了上面打印异常，还需要将这个异常向上抛，让使用这个类的程序也知道这儿报错了；
            // 这儿主动抛了ExceptionInInitializerError，即在类的初始化过程中产生了错误；即调用者捕获了这个异常，就能够明白，
            // mybatis在初始化的时候产生了错误，
            throw new ExceptionInInitializerError(e);
        }
    }

    /**
     * 获得SqlSession对象的方法；；；；
     * 在其他地方调用这个方法获得SqlSession对象后，后续就可以利用SqlSession完成数据表的增删改查了;
     * 说明：工具类中的方法，一般使用static进行描述，这样以后通过类名就能直接调用了；
     * @return
     */
    public static SqlSession openSession(){
        return sqlSessionFactory.openSession();
    }

    /**
     * 关闭SqlSession的方法；
     * @param sqlSession
     */
    public static void closeSession(SqlSession sqlSession){
        if (sqlSession != null){
            sqlSession.close();
        }
    }
}

---

（20210619加）：

其也报了【java.lang.NoClassDefFoundError: Could not initialize class】；修改后，就OK了，，，，，但是，后来又把上面的xml该错后，又不报这个异常了，，，，挺操蛋的，其背后的根本原因尚不明确。