MyBatis

MyBatis环境搭建

我这个是使用IDEA，基于Maven搭建的

• 首先建立一个空的Maven项目或者模块
• 在pom.xml中引入所需依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>ssm</artifactId>
        <groupId>com.itzhh.ssm</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <packaging>jar</packaging>

    <artifactId>mybatis</artifactId>
    <dependencies>
    <!-- Mybatis核心 -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.7</version>
    </dependency>
    <!-- junit测试 -->
    <dependency>
    <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
        <!-- MySQL驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>

        <!-- log4j日志 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

</project>

• 在resources下面创建核心配置文件mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
<!--    顺序
properties?,settings?,typeAliases?,typeHandlers?,
objectFactory?,objectWrapperFactory?,reflectorFactory?,
plugins?,environments?,databaseIdProvider?,mappers?)".
-->



<!--引入properties文件-->
    <properties resource="jdbc.properties"/>
    
    <settings>
<!--        将下划线映射为驼峰-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

<!--    设置类型别名-->
    <typeAliases>
<!--        <typeAlias type="com.itzhh.mybatisOne.Entity.User" alias="abc"/>-->
<!--        <typeAlias type="com.itzhh.mybatisOne.Entity.User" />-->
<!--        默认别名：类名，不区分大小写-->
<!--        通过包名指定别名，此包下所有类都有别名-->
        <package name="com.itzhh.mybatisOne.Entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
<!--    引入mybatis的映射文件-->
    <mappers>
<!--        <mapper resource="mappers\UserMapper.xml"/>-->
<!--        以包的形式引入，有注意点，要注意可能会出错-->
        <package name="com.itzhh.mybatisOne.Mapper"/>
    </mappers>
</configuration>

• 所需的jdbc.properties根据自己的实际情况进行配置

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC
jdbc.username=root
jdbc.password=123456

• 如果需要配置日志，在pom中引入相应依赖，同时创建log4j.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
        <param name="Encoding" value="UTF-8" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS}
%m (%F:%L) \n" />
        </layout>
    </appender>
    <logger name="java.sql">
        <level value="debug" />
    </logger>
    <logger name="org.apache.ibatis">
        <level value="info" />
    </logger>
    <root>
        <level value="debug" />
        <appender-ref ref="STDOUT" />
    </root>
</log4j:configuration>

• 创建Maven工程对应的目录结构

• 创建Mapper接口

package com.itzhh.mybatisOne.Mapper;

import com.itzhh.mybatisOne.Entity.User;

import java.util.List;

/**
 * Author: zhh
 * Date: 2022-12-21 10:48
 * Description: <描述>
 */
public interface UserMapper {
    int insertUser();
    void updateUser();
    void deleteUser();
    User selectUserById();

    List<User> selectAllUsers();
}

• 创建对应的mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itzhh.mybatisOne.Mapper.UserMapper">
<!--int insertUser();-->
<insert id="insertUser">
    insert into t_user values(null,'admin','123456',23,'男','12345@qq.com')
</insert>
    <update id="updateUser">
        update t_user set username='zhh' where id = 2
    </update>
    <delete id="deleteUser">
        delete from t_user where id = 4
    </delete>
    <select id="selectUserById" resultType="com.itzhh.mybatisOne.Entity.User">
        select * from t_user where id = 3
    </select>
    <select id="selectAllUsers" resultType="com.itzhh.mybatisOne.Entity.User">
        select * from t_user ;
    </select>
</mapper>

注意：因为我在mybatis核心配置文件中是通过包形式引入mybatis依赖文件的，所以只需要完整类名和包名对应即可，不需要每次都引入。但要注意对应的包的位置和名字必须一致。

• 至此，一个简单的mybatis环境搭建完成。
• 获取sqlsession的工具类

package com.itzhh.mybatisOne.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;

/**
 * Author: zhh
 * Date: 2022-12-21 11:20
 * Description: <描述>
 */
public class SqlSessionUtil {
    public static SqlSession getSqlSession(){
        SqlSession sqlSession = null;
        try {
            //读取MyBatis的核心配置文件
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            //创建SqlSessionFactoryBuilder对象
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            //通过核心配置文件所对应的字节输入流创建工厂类SqlSessionFactory，生产SqlSession对象
            SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
            //创建SqlSession对象，此时通过SqlSession对象所操作的sql都必须手动提交或回滚事务
            //SqlSession sqlSession = sqlSessionFactory.openSession();
            //创建SqlSession对象，此时通过SqlSession对象所操作的sql都会自动提交
            sqlSession = sqlSessionFactory.openSession(true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sqlSession;
    }
}

• 简单测试案例

package com.itzhh.mybatisOne;

import com.itzhh.mybatisOne.Entity.User;
import com.itzhh.mybatisOne.Mapper.UserMapper;
import com.itzhh.mybatisOne.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

/**
 * Author: zhh
 * Date: 2022-12-21 11:16
 * Description: <描述>
 */
public class TestMybatis {

    @Test
    public void testInsert(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int result = mapper.insertUser();
        sqlSession.close();
    }

    @Test
    public void testDelete(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUser();
        sqlSession.close();
    }

    @Test
    public void testUpdate(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUser();
        sqlSession.close();
    }

    @Test
    public void testSelect(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.selectUserById();
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void testSelectAll(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = mapper.selectAllUsers();
        users.forEach(System.out::println);
        sqlSession.close();
    }
}

逆向工程的创建

• 在pom.xml中添加相应的依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>SSM</artifactId>
        <groupId>com.itzhh.ssm</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis_mbg</artifactId>
    <packaging>jar</packaging>


    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!-- junit测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!-- log4j日志 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
    </dependencies>
    <!-- 控制Maven在构建过程中相关配置 -->
    <build>
        <!-- 构建过程中用到的插件 -->
        <plugins>
            <!-- 具体插件，逆向工程的操作是以构建过程中插件形式出现的 -->
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.0</version>
                <!-- 插件的依赖 -->
                <dependencies>
                    <!-- 逆向工程的核心依赖 -->
                    <dependency>
                        <groupId>org.mybatis.generator</groupId>
                        <artifactId>mybatis-generator-core</artifactId>
                        <version>1.3.2</version>
                    </dependency>
                    <!-- MySQL驱动 -->
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>8.0.16</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>


</project>

• 在resources下创建generatorConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <!--
    targetRuntime: 执行生成的逆向工程的版本
    MyBatis3Simple: 生成基本的CRUD（清新简洁版）
    MyBatis3: 生成带条件的CRUD（奢华尊享版）
    -->
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <!-- 数据库的连接信息 -->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/ssm?
serverTimezone=UTC"
                        userId="root"
                        password="123456">
        </jdbcConnection>
        <!-- javaBean的生成策略-->
        <javaModelGenerator targetPackage="com.itzhh.mybatis.entity"
                            targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>
        <!-- SQL映射文件的生成策略 -->
        <sqlMapGenerator targetPackage="com.itzhh.mybatis.mapper"
                         targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>
        <!-- Mapper接口的生成策略 -->
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.itzhh.mybatis.mapper" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>
        <!-- 逆向分析的表 -->
        <!-- tableName设置为*号，可以对应所有表，此时不写domainObjectName -->
        <!-- domainObjectName属性指定生成出来的实体类的类名 -->
        <table tableName="t_emp" domainObjectName="Emp"/>
        <table tableName="t_dept" domainObjectName="Dept"/>
    </context>
</generatorConfiguration>

• 双击执行
  
• 逆向工程只是帮助生成了一部分代码，其它步骤照旧。

分页插件的使用

• 在pom.xml中添加相关依赖

<!--        分页插件依赖-->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>5.2.0</version>
        </dependency>

• 在mybatis-config.xml中添加相关插件，注意放到environment标签之前

<!--    设置分页插件-->
    <plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor"/>
    </plugins>

• 在测试类中使用分页插件

package com.itzhh.mybatis;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.itzhh.mybatis.entity.Emp;
import com.itzhh.mybatis.entity.EmpExample;
import com.itzhh.mybatis.mapper.EmpMapper;
import com.itzhh.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

/**
 * Author: zhh
 * Date: 2022-12-26 15:17
 * Description: <描述>
 */
public class TestPage {
    @Test
    public void testPage(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
        //查询之前开启分页功能
        Page<Object> page = PageHelper.startPage(1, 4);
        List<Emp> emps = mapper.selectByExample(null);
        //查询功能之后可以获取分页相关的所有数据
        PageInfo<Emp> pageInfo = new PageInfo<>(emps, 5);
        emps.forEach(System.out::println);
        System.out.println(pageInfo);

    }

}

• 结果：

DEBUG 12-26 15:23:43,224 Cache Hit Ratio [SQL_CACHE]: 0.0 (LoggingCache.java:60) 
DEBUG 12-26 15:23:43,293 ==>  Preparing: SELECT count(0) FROM t_emp (BaseJdbcLogger.java:137) 
DEBUG 12-26 15:23:43,315 ==> Parameters:  (BaseJdbcLogger.java:137) 
DEBUG 12-26 15:23:43,331 <==      Total: 1 (BaseJdbcLogger.java:137) 
DEBUG 12-26 15:23:43,333 ==>  Preparing: select emp_id, emp_name, emp_age from t_emp LIMIT ? (BaseJdbcLogger.java:137) 
DEBUG 12-26 15:23:43,333 ==> Parameters: 4(Integer) (BaseJdbcLogger.java:137) 
DEBUG 12-26 15:23:43,334 <==      Total: 4 (BaseJdbcLogger.java:137) 
Emp{empId=1, empName='zhh', empAge=34}
Emp{empId=2, empName='zhh', empAge=34}
Emp{empId=3, empName='abc', empAge=null}
Emp{empId=4, empName='fcd', empAge=null}
PageInfo{pageNum=1, pageSize=4, size=4, 
startRow=1, endRow=4, total=34, pages=9, 
list=Page{count=true, pageNum=1, pageSize=4, 
startRow=0, endRow=4, total=34, pages=9, reasonable=false, pageSizeZero=false}
[Emp{empId=1, empName='zhh', empAge=34}, 
Emp{empId=2, empName='zhh', empAge=34}, 
Emp{empId=3, empName='abc', empAge=null}, 
Emp{empId=4, empName='fcd', empAge=null}], 
prePage=0, nextPage=2, isFirstPage=true, 
isLastPage=false, hasPreviousPage=false, 
hasNextPage=true, navigatePages=5, 
navigateFirstPage=1, navigateLastPage=5, 
navigatepageNums=[1, 2, 3, 4, 5]}