[Java知识库] MyBatis总结

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[Java知识库]MyBatis总结

回顾JDBC

层

Service是业务层，Dao层是数据访问层，这样的分层是基于MVC架构来说的，分层的主要作用是解耦。
对于Spring这样的框架，（View/Web）表示层调用控制层（Controller），控制层调用业务层（Service），业务层调用数据访问层（Dao）
具体起来，Dao的作用是封装对数据库的访问：增删查改，不涉及业务逻辑，只是达到按某个条件获得指定数据的要求；而Service，则是专注业务逻辑，对于其中需要的数据库操作，都通过Dao去实现；

看官方文档

MyBatis是一款优秀的持久层框架，本是apache的一个开源项目iBatis，后迁移到google code ，后迁移到GitHub
定制化sql
几乎避免了所有的jdbc代码

如何获得mybatis

maven
GitHub

框架主要的配置文件

mybatis-config.xml

<?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>
    <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=true&amp;useUnicode=true&amp;character=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/yst/dao/UserMapper.xml"/>
    </mappers>
</configuration>

UserMapper.xml

<?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="com.yst.dao.UserMapper">

    <select id="getUserList" resultType="com.yst.pojo.User">
        select * from mybatis.user
    </select>

    <select id="getUserByID" parameterType="int" resultType="com.yst.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>

    <insert id="insertUser" parameterType="com.yst.pojo.User">
        insert into mybatis.user(id, name, password) values(#{id},#{name},#{password})
    </insert>

    <update id="updateUser" parameterType="com.yst.pojo.User">
        update mybatis.user set name = #{name},password = #{password} where id =#{id}
    </update>

    <delete id="deleteUser" parameterType="com.yst.pojo.User">
        delete from mybatis.user where id = #{id}
    </delete>
</mapper>

MyBatisUtils

package com.yst.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 {
        try {
            // 使用mybatis第一步先获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";// 加载配置文件
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // 既然有了sqlSessionFactory 顾名思义就可以获取sqlSession的实例了
    // sqlSession 包含了面向数据库执行sql命令所需要的所有方法
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }

}

test

package com.yst.dao;

import com.yst.pojo.User;
import com.yst.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    @Test
    public void test(){
        // 第一步获得 sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        // getMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        // 测试查看结果
        for (User user : userList) {
            System.out.println(user);
        }

        // 关闭sqlSession
        sqlSession.close();
    }
    @Test
    public void getUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User userByID = mapper.getUserByID(1);
        System.out.println(userByID);
        sqlSession.close();
    }
    @Test
    public void insertUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.insertUser(new User(6,"yst","123345"));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUser(new User(1,"yst","123456"));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUser(2);
        sqssion.commit();
        sqlSession.close();
    }



}

配置优化

导入外部properties
typeAliase 别名
settings设置

总结

创建一个干净的maven项目

配置pom.xml

<?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">
    <modelVersion>4.0.0</modelVersion>

    <!--父工程-->
    <groupId>org.example</groupId>
    <artifactId>MyBatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>MyBatis-01</module>
        <module>MyBatis-02</module>
        <module>MyBatis-03</module>
        <module>Mybatis-04</module>
        <module>Mybatis-05</module>
        <module>Mybatis-06</module>
        <module>MyBatis-07</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <!--导入依赖-->
    <dependencies>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.24</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/log4j/log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>
    </dependencies>

    <!--在build中配置resources，来防止我们资源导出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

在src/java目录下创建package （dao、pojo、utils）

dao下写接口和映射mapper（名字最好一样）

UserMapper.java

package com.yst.dao;

import com.yst.pojo.User;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface UserMapper {
    // 通过 userCode 获取 User
    public User getLoginUser(@Param("userCode") String userCode);
    // 增加用户信息
    public int add(User user);
    // 通过条件查询-userList
    public List<User> getUserList(@Param("userPassword") String userPassword,@Param("userRole") Integer userRole,
                                  @Param("from") Integer currentPageNo,@Param("pageSize") Integer PageSize);
}

UseMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.yst.dao.UserMapper">
    <select id="getLoginUser" parameterType="String" resultType="user">
        select * from smbms.smbms_user
        where userCode=#{userCode}
    </select>
    <insert id="add" parameterType="user">
        insert into smbms.smbms_user(id, userCode, userName, userPassword,
                                     gender, birthday, phone, address, userRole, 									createdBy, creationDate, modifyBy, modifyDate)
                                     VALUES
                                    (#{id},#{userCode},#{userName},#{userPassword},
                                     #{gender},#{birthday},#{phone},#{address},#{userRole},#{createdBy},
                                     #{creationDate},#{modifyBy},#{modifyDate})
    </insert>
    <select id="getUserList" resultType="user">
        select * from smbms.smbms_user
        where userPassword=#{userPassword}
          and userRole=#{userRole}
        limit #{from},#{pageSize}
    </select>
</mapper>

utils工具类

package com.yst.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 {
        try {
            // 使用mybatis第一步先获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";// 加载配置文件
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // 既然有了sqlSessionFactory 顾名思义就可以获取sqlSession的实例了
    // sqlSession 包含了面向数据库执行sql命令所需要的所有方法
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

resources目录下放最主要的配置文件

db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useSSL=true&useUnicode=true&characterEncoding=utf8
username=root
password=123456

log4j.properties

#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n

#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/kuang.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n

#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

mybatis-config.xml MyBatis核心配置文件

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="db.properties"/>
    <settings>
        <setting name="logImpl" value="log4j"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <typeAliases>
        <package name="com.yst.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/yst/dao/UserMapper.xml"/>
    </mappers>
</configuration>

test/java 测试

import com.yst.dao.UserMapper;
import com.yst.pojo.User;
import com.yst.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.Date;
import java.util.List;

public class MyTest {
    @Test
    public void getLoginUserByUserCode(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User admin = mapper.getLoginUser("admin");
        System.out.println(admin);
        sqlSession.close();
    }
    @Test
    public void insertUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.add(new User(18,"zhangqiang","张强","000000",1,new Date(),"13230992245","Beijing,China",1,1,new Date(),1,new Date()));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void getUserList() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList("0000000", 3, 1, 99);
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
}