第一步：环境搭建1.新建一个普通的maven项目 2.删除src目录 3.导入maven依赖
一共需要四个jar包
junit用于@Test对程序测试
mysql-connector-java用于连接数据库
mybatis用于导入mybatis环境
lombok负责简化实体类
mysql mysql-connector-java8.0.25 junit junit4.11 test org.mybatis mybatis3.4.6 org.projectlombok lombok1.18.20
第二步：导入MyBatis1.编写配置文件
在maven下新建一个子maven项目
在resources目录下建立mybatis-config.xml
导入官方的配置文件，并配置dirver，url，username，password用于连接数据库
2.编写工具类
在java模具下建立utils包并编写MybatisUtils工具类
在官网中找到配置的三条语句并抛出异常，然后编写getSqlSession方法返回
package com.kuang.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.InputStream;
public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static{
String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream=null;
try {
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}
第三步：编写代码1.编写工具类
在java目录下建立pojo包并构建User类用于对应数据库中Mybatis下的User表，并用lombok简化方法
package com.kuang.pojo;
import lombok.*;
@Getter
@Setter
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class User {
private int id;
private String name;
private String pwd;
}
2.编写Dao接口
建立UserDao接口并创建一个返回User数组的方法
package com.kuang.dao;
import com.kuang.pojo.User;
import java.util.List;
public interface UserDao {
List getUserList();
}
3.创建UserMapper.xml链接UserDao接口
注意：
测试要在test文件夹下绿色的java文件夹进行，而且测试类要与被测试类位置对应 编写测试类 1、2统一是因为在MybatisUtils类中 在官网中复制的resource地址为 而实际上应该删掉部分变成 修改后即可排除两个错误 没有在Mybatis-config.xml中配置UserMapping，添加配置文件即可 在pom.xml文件中添加如下代码，然后刷新maven（重要，一定记得刷新）即可
4.在mabatis-config.xml中注册UserMapper
路径一定要用 / 不能用 .
第四步：用junit测试
package com.kuang.dao;
import com.kuang.pojo.User;
import com.kuang.utils.MybatisUtils;
import jdk.swing.interop.SwingInterOpUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserDaoTest {
@Test
public void test(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
List
出现问题及解决
1.IO异常
java.io.IOException: Could not find resource org/mybatis/example/mybatis-config.xml
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:114)
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:100)
at com.kuang.utils.MybatisUtils.
2.空指针异常
java.lang.NullPointerException
at com.kuang.utils.MybatisUtils.getSqlSession(MybatisUtils.java:31)
at com.kuang.dao.UserDaoTest.test(UserDaoTest.java:15)
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:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.frameworkMethod.invokeExplosively(frameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
解决方法
org/mybatis/example/mybatis-config.xml
String resource = "mybatis-config.xml";
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.ibatis.reflection.Reflector (file:/C:/Users/86156/.m2/repository/org/mybatis/mybatis/3.4.6/mybatis-3.4.6.jar) to method java.lang.Class.checkPackageAccess(java.lang.SecurityManager,java.lang.ClassLoader,boolean)
WARNING: Please consider reporting this to the maintainers of org.apache.ibatis.reflection.Reflector
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
org.apache.ibatis.binding.BindingException: Type interface com.kuang.dao.UserDao is not known to the MapperRegistry.
at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:745)
at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:292)
at com.kuang.dao.UserDaoTest.test(UserDaoTest.java:17)
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 junit.framework.TestCase.runTest(TestCase.java:176)
at junit.framework.TestCase.runBare(TestCase.java:141)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:129)
at junit.framework.TestSuite.runTest(TestSuite.java:255)
at junit.framework.TestSuite.run(TestSuite.java:250)
at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Process finished with exit code -1
解决方法
4.UserMapper.xml不存在
"C:Program FilesJavajdk-13.0.1binjava.exe" -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2021.2.1libidea_rt.jar=61991:C:Program FilesJetBrainsIntelliJ IDEA 2021.2.1bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJetBrainsIntelliJ IDEA 2021.2.1libidea_rt.jar;C:Program FilesJetBrainsIntelliJ IDEA 2021.2.1pluginsjunitlibjunit5-rt.jar;C:Program FilesJetBrainsIntelliJ IDEA 2021.2.1pluginsjunitlibjunit-rt.jar;C:Users86156IdeaProjects1Mybatis-StudyMybatis-01targettest-classes;C:Users86156IdeaProjects1Mybatis-StudyMybatis-01targetclasses;C:Users86156.m2repositoryorgprojectlomboklombok1.18.20lombok-1.18.20.jar;C:Users86156.m2repositorymysqlmysql-connector-java8.0.25mysql-connector-java-8.0.25.jar;C:Users86156.m2repositorycomgoogleprotobufprotobuf-java3.11.4protobuf-java-3.11.4.jar;C:Users86156.m2repositoryjunitjunit4.11junit-4.11.jar;C:Users86156.m2repositoryorghamcresthamcrest-core1.3hamcrest-core-1.3.jar;C:Users86156.m2repositoryorgmybatismybatis3.4.6mybatis-3.4.6.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.kuang.dao.UserDaoTest
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.ibatis.reflection.Reflector (file:/C:/Users/86156/.m2/repository/org/mybatis/mybatis/3.4.6/mybatis-3.4.6.jar) to method java.lang.Class.checkPackageAccess(java.lang.SecurityManager,java.lang.ClassLoader,boolean)
WARNING: Please consider reporting this to the maintainers of org.apache.ibatis.reflection.Reflector
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
java.lang.ExceptionInInitializerError
at com.kuang.dao.UserDaoTest.test(UserDaoTest.java:15)
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 junit.framework.TestCase.runTest(TestCase.java:176)
at junit.framework.TestCase.runBare(TestCase.java:141)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:129)
at junit.framework.TestSuite.runTest(TestSuite.java:255)
at junit.framework.TestSuite.run(TestSuite.java:250)
at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error building SqlSession.
### The error may exist in com/kuang/dao/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/kuang/dao/UserMapper.xml
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:80)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:64)
at com.kuang.utils.MybatisUtils.
解决方法
