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来源：5-2 自由编程

慕沐0220913

2020-02-28 15:35:07

@Test
public void testInsert(){
SqlSession sqlSession=null;
try {
sqlSession=MyBatisUtils.openSession();
Goods goods=new Goods();
goods.setRegNo(20171208);
goods.setName("言豫津");
goods.setSex("男");
goods.setAge(26);
goods.setGrade("2013");
goods.setMajor("哲学系");
//insert()方法返回值代表本次成功插入的记录次数
int num =sqlSession.insert("goods.insert",goods);
if(num>0){
List<Goods> list=sqlSession.selectList("goods.selectAll");
for (Goods g:list) {
System.out.println(g);
}
}else{
System.out.println("添加失败");
}
sqlSession.commit();
}catch (Exception e){
if(sqlSession!=null){
sqlSession.rollback();
}
throw e;
}finally {
MyBatisUtils.closeSession(sqlSession);
}
}

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

public class MyBatisUtils {
//为保证唯一，利用static（静态）属于类，不属于对象，就可以保证唯一
private static SqlSessionFactory sqlSessionFactory=null;
//静态代码块可以初始化静态对象，
static {
Reader reader = null;
try {
reader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

} catch (IOException e) {
e.printStackTrace();
//初始化错误时通过抛出异常ExceptionInInitializerError通知调用者
throw new ExceptionInInitializerError(e);
}
}
/**
* openSession 创建一个新的 SqlSession对象
*/
public static SqlSession openSession(){
//默认sqlSession 对自动提交事务数据（commit）
//设置false代表关闭自动提交，改为手动提交数据
return sqlSessionFactory.openSession(false);
}

/**
* 关闭连接
* @param session
*/
public static void closeSession(SqlSession session){
if (session!=null){
session.close();
}
}

}

<?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="goods">
<select id="selectAll" resultType="com.imooc.mybatis.entity.Goods">
select * from student order by id desc limit 5
</select>

<insert id="insert" parameterType="com.imooc.mybatis.entity.Goods">
INSERT INTO student(reg_no,name,sex,age,grade,major)
VALUES (#{regNo},#{name},#{sex},#{age},#{grade},#{major})
<selectKey resultType="Integer" keyProperty="Id" order="AFTER">
select last_insert_id()
</selectKey>
</insert>
</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>
goodsId即开启驼峰命名转换-->
<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
<environments default="dev">
<environment id="dev">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/message?userSSL=false&serverTimezone=UTC&useUnicode=true&CharacterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="18351337068cC"/>
</dataSource>

</environment>
</environments>
<mappers>
<mapper resource="mappers/goods.xml"></mapper>
</mappers>
</configuration>

报错

"C:\Program Files\Java\jdk-12.0.2\bin\java.exe" -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:D:\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=54825:D:\JetBrains\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar;D:\JetBrains\IntelliJ IDEA 2019.3.3\plugins\junit\lib\junit5-rt.jar;D:\JetBrains\IntelliJ IDEA 2019.3.3\plugins\junit\lib\junit-rt.jar;D:\idea\mybatis\target\test-classes;D:\idea\mybatis\target\classes;D:\maven\repo\org\mybatis\mybatis\3.5.3\mybatis-3.5.3.jar;D:\maven\repo\mysql\mysql-connector-java\8.0.19\mysql-connector-java-8.0.19.jar;D:\maven\repo\com\google\protobuf\protobuf-java\3.6.1\protobuf-java-3.6.1.jar;D:\maven\repo\junit\junit\4.12\junit-4.12.jar;D:\maven\repo\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.imooc.mybatis.MyBatisTestor,testInsert

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

at com.imooc.mybatis.MyBatisTestor.testInsert(MyBatisTestor.java:103)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
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)