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Mybatis 入门实战(2)--简单使用

且行且码 2023-04-18 原文

本文主要介绍 Mybatis 的实际使用，相关的环境及软件信息如下：Mybatis 3.5.11。

1、工程整体结构

这里使用 Maven 来构建样例工程，工程目录结构如下：

2、引入依赖

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.11</version>
</dependency>

其他相关依赖如分页插件、日志登，根据需要引入：

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.11</version>
    </dependency>
    <!--分页插件-->
    <dependency>
        <groupId>com.github.pagehelper</groupId>
        <artifactId>pagehelper</artifactId>
        <version>5.3.2</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.30</version>
    </dependency>

    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.2.11</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.24</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
        </resource>
    </resources>
</build>
View Code

3、Mybatis 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>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <plugins>
        <!--分页插件-->
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <property name="reasonable" value="true"/>
        </plugin>
    </plugins>

    <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://10.49.196.23:3306/test?characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/abc/mapper/StudentMapper.xml"/>
        <mapper class="com.abc.mapper.TeacherMapper"/>
    </mappers>
</configuration>

4、创建实体类

4.1、Student.java

package com.abc.entity;

import lombok.Data;
import lombok.ToString;

import java.time.LocalDateTime;

@ToString
@Data
public class Student {
    private Long id;

    private LocalDateTime createTime;

    private LocalDateTime modifyTime;

    private String name;

    private Integer age;

    private String homeAddress;
}

4.2、Teacher.java

package com.abc.entity;

import lombok.Data;
import lombok.ToString;

import java.time.LocalDateTime;

@ToString
@Data
public class Teacher {
    private Long id;

    private LocalDateTime createTime;

    private LocalDateTime modifyTime;

    private String name;

    private Integer age;

    private String homeAddress;
}

5、创建 Provider

provider 主要用来提供 SQL。

package com.abc.provider;


import org.apache.ibatis.builder.annotation.ProviderMethodResolver;
import org.apache.ibatis.jdbc.SQL;

public class TeacherProvider implements ProviderMethodResolver {
    public static String select2(String name, String homeAddress) {
        return new SQL(){{
            SELECT("*");
            FROM("a_teacher");
            if (name != null && !"".equals(name)) {
                WHERE("name like #{name}");
            }
            if (name != null && !"".equals(homeAddress)) {
                WHERE("home_address like #{name}");
            }
        }}.toString();
    }
}

6、创建 Mapper

6.1、StudentMapper.java

package com.abc.mapper;

import com.abc.entity.Student;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

public interface StudentMapper {
    void insert(Student student);

    void update(Student student);

    Student selectById(Long id);

    List<Student> select(@Param("name") String name, @Param("homeAddress") String homeAddress);

    List<Map<String, Object>> select2(String name, String homeAddress);

    void delete(Long[] ids);
}

StudentMapper 使用 XML 来编写 SQL，对应 XML 文件(StudentMapper.xml)内容为：

<?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.abc.mapper.StudentMapper">
    <insert id="insert" parameterType="com.abc.entity.Student" useGeneratedKeys="true" keyProperty="id">
        insert into a_student(create_time,modify_time,name,age,home_address)
        values(#{createTime},#{modifyTime},#{name},#{age},#{homeAddress})
    </insert>

    <update id="update" parameterType="com.abc.entity.Student">
        update a_student set id=id
        <if test="name != null and name != ''">
            ,name=#{name}
        </if>
        <if test="age != null">
            ,age=#{age}
        </if>
        <if test="homeAddress != null and homeAddress != ''">
            ,home_address=#{homeAddress}
        </if>
        where id=#{id}
    </update>

    <select id="selectById" resultType="com.abc.entity.Student">
        select * from a_student where id=#{id}
    </select>

    <select id="select" resultType="com.abc.entity.Student">
        select * from a_student where 1=1
        <if test="name != null and name != ''">
            and name like #{name}
        </if>
        <if test="homeAddress != null and homeAddress != ''">
            and home_address like #{homeAddress}
        </if>
    </select>

    <select id="select2" resultType="map">
        select * from a_student where 1=1
        <if test="param1 != null and param1 != ''">
            and name like #{param1}
        </if>
        <if test="param2 != null and param2 != ''">
            and home_address like #{param2}
        </if>
    </select>

    <delete id="delete">
        delete from a_student where id in
        <foreach collection="array" item="id" index="index" open="(" close=")" separator=",">
            #{id}
        </foreach>
    </delete>
</mapper>

表 a_student 的字段与实体类的属性一一对应(表中字段使用下划线写法，实体类属性使用驼峰写法)，字段 id 为自增字段。

6.2、TeacherMapper.java

package com.abc.mapper;

import com.abc.entity.Teacher;
import com.abc.provider.TeacherProvider;
import org.apache.ibatis.annotations.*;

import java.util.List;
import java.util.Map;

public interface TeacherMapper {
    @Options(useGeneratedKeys = true, keyProperty = "id")
    @Insert({"insert into a_teacher(create_time,modify_time,name,age,home_address)",
            " values(#{createTime},#{modifyTime},#{name},#{age},#{homeAddress})"})
    void insert(Teacher teacher);

    @Update({"<script>",
            "update a_teacher set id=id",
            "<if test='name != null and name != \"\"'>",
            "   ,name=#{name}",
            "</if>",
            "<if test='age != null'>",
            "   ,age=#{age}",
            "</if>",
            "<if test='homeAddress != null and homeAddress != \"\"'>",
            "   ,home_address=#{homeAddress}",
            "</if>",
            "where id=#{id}",
            "</script>"
    })
    void update(Teacher teacher);

    @Select("select * from a_teacher where id=#{id}")
    Teacher selectById(Long id);

    @Select({"<script>",
            "select * from a_teacher where 1=1",
            "<if test='name != null and name != \"\"'>",
            "   and name like #{name}",
            "</if>",
            "<if test='homeAddress != null and homeAddress != \"\"'>",
            "   and home_address like #{homeAddress}",
            "</if>",
            "</script>"
    })
    List<Teacher> select(@Param("name") String name, @Param("homeAddress") String homeAddress);

    @SelectProvider(type = TeacherProvider.class)
    List<Map<String, Object>> select2(String name, String homeAddress);

    @Delete({"<script>",
            "delete from a_teacher where id in",
            "<foreach collection='array' item='id' index='index' open='(' close=')' separator=','>",
            "   #{id}",
            "</foreach>",
            "</script>"
    })
    void delete(Long[] ids);
}

TeacherMapper 使用注解来编写 SQL，如果使用了动态 SQL，需添加  script 元素；如果 SQL 比较复杂，不太方便使用注解，可以通过 Provider 使用 Java 代码来构建 SQL。

表 a_teacher 的字段与实体类的属性一一对应(表中字段使用下划线写法，实体类属性使用驼峰写法)，字段 id 为自增字段。

7、日志配置

这里使用 Logback 作为日志框架，其配置文件(logback.xml)内容如下：

<?xml version="1.0" encoding="utf-8"?>
<configuration debug="false">
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d %level [%thread] %logger[%L] -> %m%n</pattern>
        </encoder>
    </appender>

    <root level="info">
        <appender-ref ref="STDOUT" />
    </root>
    <logger name="com.abc.mapper" level="debug">
    </logger>
</configuration>

8、分页插件

Mybatis 中分页可以使用 PageHelper 插件，该插件方便好用，具体使用方法及配置说用可参考官网文档：https://pagehelper.github.io。

9、测试用例

9.1、StudentMapperCase.java

 package com.abc.mapper;

import com.abc.entity.Student;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.time.LocalDateTime;
import java.util.List;
import java.util.Map;

public class StudentMapperCase {
    private Logger logger = LoggerFactory.getLogger(StudentMapperCase.class);

    private SqlSession sqlSession;

    @Before
    public void before() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession();
    }

    @After
    public void after() {
        sqlSession.close();
    }

    @Test
    public void insert() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        Student student = new Student();
        student.setCreateTime(LocalDateTime.now());
        student.setName("李白");
        student.setAge(30);
        student.setHomeAddress("长安");
        mapper.insert(student);
        sqlSession.commit();
        logger.info("id={}", student.getId());
    }

    @Test
    public void update() {
        Student student = new Student();
        student.setId(261L);
        student.setName("李白2");
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        mapper.update(student);
        sqlSession.commit();
    }

    @Test
    public void selectById() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        Student student = mapper.selectById(261L);
        logger.info(student.toString());
    }

    @Test
    public void select() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        List<Student> students = mapper.select("%李%", "%长%");
        logger.info(students.toString());
    }

    @Test
    public void selectForPage() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        PageHelper.startPage(1, 5);
        List<Student> students = mapper.select("%李%", "");
        PageInfo<Map<String, String>> pageInfo = new PageInfo(students);
        logger.info(pageInfo.toString());
    }

    @Test
    public void select2() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        List<Map<String, Object>> list = mapper.select2("%李%", "%长%");
        logger.info(list.toString());
    }

    @Test
    public void delete() {
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        mapper.delete(new Long[]{260L, 263L});
    }
}

9.2、TeacherMapperCase.java

package com.abc.mapper;

import com.abc.entity.Teacher;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.time.LocalDateTime;
import java.util.List;
import java.util.Map;

public class TeacherMapperCase {
    private Logger logger = LoggerFactory.getLogger(TeacherMapperCase.class);

    private SqlSession sqlSession;

    @Before
    public void before() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession();
    }

    @After
    public void after() {
        sqlSession.close();
    }

    @Test
    public void insert() {
        Teacher teacher = new Teacher();
        teacher.setCreateTime(LocalDateTime.now());
        teacher.setName("孔子");
        teacher.setAge(30);
        teacher.setHomeAddress("鲁国");
        sqlSession.insert("com.abc.mapper.TeacherMapper.insert", teacher);
        sqlSession.commit();
        logger.info("id={}", teacher.getId());
    }

    @Test
    public void update() {
        Teacher teacher = new Teacher();
        teacher.setId(1865L);
        teacher.setName("孔子2");
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        mapper.update(teacher);
        sqlSession.commit();
    }

    @Test
    public void selectById() {
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        Teacher teacher = mapper.selectById(1865L);
        logger.info(teacher.toString());
    }

    @Test
    public void select() {
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        List<Teacher> teachers = mapper.select("%孔%", "%鲁%");
        logger.info(teachers.toString());
    }

    @Test
    public void selectForPage() {
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        PageHelper.startPage(10, 3);
        List<Teacher> teachers = mapper.select("%孔%", "%鲁%");
        PageInfo<Map<String, String>> pageInfo = new PageInfo(teachers);
        logger.info(pageInfo.toString());
    }

    @Test
    public void select2() {
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        List<Map<String, Object>> list = mapper.select2("%孔%", "%鲁%");
        logger.info(list.toString());
    }

    @Test
    public void delete() {
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        mapper.delete(new Long[]{1853L, 1854L});
    }
}

 

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