java mybatis 大型项目 mybatis项目搭建

转载

definitely 2023-07-17 00:05:58

文章标签 java mybatis 大型项目 maven java mybatis xml 文章分类 Java 后端开发

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

<dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.25</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>
    </dependencies>

第二步：导入MyBatis

1.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

java mybatis 大型项目 mybatis项目搭建_xml

导入官方的配置文件，并配置dirver，url，username，password用于连接数据库

<?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">
<!--核心配置文件-->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

</configuration>

2.编写工具类

在java模具下建立utils包并编写MybatisUtils工具类

java mybatis 大型项目 mybatis项目搭建_maven_02

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 = "mybatis-config.xml";
        InputStream inputStream=null;
        try {
            /*使用第一步
            * 获取sqlSessionFactory对象*/
            inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /*既然有了SqlSessionFactory，顾名思义，我们就可以从中获得SqlSession的实例了
    * SqlSession 完全包含了面向数据库执行SQL命令所需的方法*/

    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

java mybatis 大型项目 mybatis项目搭建_maven_03

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<User> getUserList();
}

3.创建UserMapper.xml链接UserDao接口

注意：

<mapper namespace=中的内容为上面创建接口的接口地址

<select id =中的内容为上面创建接口的方法名 resultType=中为方法返回值类型的地址

<select>中则编写要输入的sql语句

<?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">
<!--namespace=绑定一个对应的Dao/Mapper接口,改为对应的Dao接口位置-->
<mapper namespace="com.kuang.dao.UserDao">
    <!--这句select相当于重写上面连接的接口的方法,id代表方法名，resultType代表方法的返回值类型-->
    <select id="getUserList" resultType="com.kuang.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

4.在mabatis-config.xml中注册UserMapper

路径一定要用 / 不能用 .

<mappers>
        <mapper resource="com/kuang/dao/UserMapper.xml"/>
    </mappers>

第四步：用junit测试

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

java mybatis 大型项目 mybatis项目搭建_maven_04

编写测试类

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(){
        /*获取SqlSession对象*/
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        /*方式一：getMapper*/
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        for(User user:userList){
            System.out.println(user);
        }
        /*关闭SqlSession*/
        sqlSession.close();
    }
}

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.<clinit>(MybatisUtils.java:19)
	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)

java mybatis 大型项目 mybatis项目搭建_java_05

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)

java mybatis 大型项目 mybatis项目搭建_maven_06

解决方法

1、2统一是因为在MybatisUtils类中

java mybatis 大型项目 mybatis项目搭建_java_07

在官网中复制的resource地址为

org/mybatis/example/mybatis-config.xml

而实际上应该删掉部分变成

String resource = "mybatis-config.xml";

修改后即可排除两个错误

3.BindingException绑定异常

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

java mybatis 大型项目 mybatis项目搭建_java_08

解决方法

没有在Mybatis-config.xml中配置UserMapping，添加配置文件即可

<mappers>
        <mapper resource="com/kuang/dao/UserMapper.xml"/>
    </mappers>

4.UserMapper.xml不存在

"C:\Program Files\Java\jdk-13.0.1\bin\java.exe" -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2021.2.1\lib\idea_rt.jar=61991:C:\Program Files\JetBrains\IntelliJ IDEA 2021.2.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\JetBrains\IntelliJ IDEA 2021.2.1\lib\idea_rt.jar;C:\Program Files\JetBrains\IntelliJ IDEA 2021.2.1\plugins\junit\lib\junit5-rt.jar;C:\Program Files\JetBrains\IntelliJ IDEA 2021.2.1\plugins\junit\lib\junit-rt.jar;C:\Users\86156\IdeaProjects1\Mybatis-Study\Mybatis-01\target\test-classes;C:\Users\86156\IdeaProjects1\Mybatis-Study\Mybatis-01\target\classes;C:\Users\86156\.m2\repository\org\projectlombok\lombok\1.18.20\lombok-1.18.20.jar;C:\Users\86156\.m2\repository\mysql\mysql-connector-java\8.0.25\mysql-connector-java-8.0.25.jar;C:\Users\86156\.m2\repository\com\google\protobuf\protobuf-java\3.11.4\protobuf-java-3.11.4.jar;C:\Users\86156\.m2\repository\junit\junit\4.11\junit-4.11.jar;C:\Users\86156\.m2\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;C:\Users\86156\.m2\repository\org\mybatis\mybatis\3.4.6\mybatis-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.<clinit>(MybatisUtils.java:19)
	... 19 more
Caused by: 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.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:121)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:99)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
	... 21 more
Caused by: java.io.IOException: Could not find resource com/kuang/dao/UserMapper.xml
	at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:114)
	at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:100)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:371)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:119)
	... 23 more

java mybatis 大型项目 mybatis项目搭建_java_09

解决方法

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

<build>
        <resources>
            <resource>
                <!-- 设定主资源目录  -->
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

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