Bootstrap

Web学习day04

mybatis

目录

mybatis

文章目录

一、查询

1.1结果映射

1.2多条件查询

1.3模糊查询

二、XML

书写规范

三、动态SQL

四、配置文件

4.1settings标签

4.2mappers标签

4.3environments标签

五、案例

5.1数据表

5.2实现类

5.3mapper实现

5.4工具类实现

5.5XML动态SQL实现

5.6XML配置实现

5.7测试实现

5.8pom.xml配置

总结

一、查询

1.1结果映射

开启驼峰映射：如果字段名与属性名符合驼峰命名规则，mybatis会自动通过驼峰命名规则映射。

字段起别名：在SQL语句中，对不一样的列名起别名，别名和实体类属性名一样。

@Results @Result：通过 @Results及@Result 进行手动结果映射。

1.2多条件查询

@Param 标注在方法参数的前面,用于声明参数在#{}中的名字

1.3模糊查询

${}性能低，不安全，存在SQL注入问题：

#{}推荐：

二、XML

书写规范

XML文件的名称与Mapper接口名称一致，并且放置在相同包下（同包同名）。

XML文件的namespace属性为Mapper接口全限定名一致。

XML文件中sql语句的id与Mapper 接口中的方法名一致。

XML文件中sql语句的返回类型与Mapper 接口中的方法返回类型一致。

三、动态SQL

<if>

用于判断条件是否成立，如果条件为true，则拼接SQL

<where>

where 元素只会在子元素有内容的情况下才插入where子句

而且会自动去除子句的开头的AND 或OR

<set>

动态地在行首插入SET关键字，并会删掉额外的逗号（用在update语句中）

<foreach >

用来批量处理的 比如批量删除拼接 in后面的值

<sql>

定义一个sql片段 就是提取公共的sql

<include>

引入sql片段

四、配置文件

4.1settings标签

控制一些全局配置项的开闭

4.2mappers标签

加载Mapper接口位置

4.3environments标签

Druid(德鲁伊):  阿里巴巴提供的数据库连接池技术，国内使用率很高，提供了完善的监控机制

HikariCP:  日本人开发的连接池技术，号称性能之王，速度最快，SpringBoot2.0默认使用此连接池

五、案例

5.1数据表

5.2实现类

代码如下（示例）：

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.LocalDate;
import java.time.LocalDateTime;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Emp {
    private Integer id;
    private String username;
    private String password;
    private String name;
    private Short gender;
    private String image;
    private Short job;

    //注意:这四个属性跟数据表中的字段不一致
    private LocalDate ed;

    private Integer deptId;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;
}

5.3mapper实现

代码如下：

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.time.LocalDate;
import java.util.Date;
import java.util.List;

public interface EmpMapper {

    @Select("select * from emp")
    public List<Emp> findAll();

    @Select("select * from emp")
    public List<Emp> findAll1();

    @Select("select id,username,password,name,gender,image,job,entrydate ed,dept_id,create_time,update_time from emp")
    public List<Emp> findAll2();

    @Select("select * from emp")
    @Results({
            @Result(column = "entrydate",property = "ed")
    })
    public List<Emp> findAll3();

    @Select("select * from emp where name =#{name} and gender = #{gender} and entrydate between #{begin} and #{end} ")
    @Results({
            @Result(column = "entrydate",property = "ed")
    })
    public List<Emp> findByCondition(@Param("name") String name,@Param("gender") Integer gender,@Param("begin") LocalDate begin,@Param("end") LocalDate end);

    @Select("select * from emp where name like concat('%',#{name},'%') and gender = #{gender} and entrydate between #{begin} and #{end} ")
    @Results({
            @Result(column = "entrydate",property = "ed")
    })
    public List<Emp> findByCondition2(@Param("name") String name,@Param("gender") Integer gender,@Param("begin") LocalDate begin,@Param("end") LocalDate end);

    public Emp findById(Integer id);

    List<Emp> findByCondition3(@Param("name") String name,@Param("gender") Short gender,@Param("begin") LocalDate begin,@Param("end") LocalDate end);
    
    void update(Emp emp);

    void deleteByIds(@Param("ids") List<Integer> ids);
}

5.4工具类实现

代码如下：

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.InputStream;

public class MybatisUtil {

    private static SqlSessionFactory sqlSessionFactory = null;

    //保证SqlSessionFactory仅仅创建一次
    static {
        try {
            //读取配置文件
            InputStream stream = Resources.getResourceAsStream("SqlMapConfig.xml");
            //创建SqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(stream);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //获取sqlSession
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }

    //提交事务 关闭sqlSession
    public static void close(SqlSession sqlSession) {
        if (sqlSession != null) {
            //提交事务
            sqlSession.commit();
            //释放资源
            sqlSession.close();
        }
    }
}

5.5XML动态SQL实现

代码如下：

<?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.itheima.mapper.EmpMapper">

    <sql id="mySql">
        select * from emp
    </sql>

    <resultMap id="MyMap" type="com.itheima.domain.Emp">
        <result column="entrydate" property="ed"/>
    </resultMap>
    <select id="findById" resultMap="MyMap">
        <include refid="mySql"/>
        where id = #{id}
    </select>


    <select id="findByCondition3" resultType="com.itheima.domain.Emp">
        <include refid="mySql"/>
        <where>
            <if test="name != null and name !=''">
                name like concat('%',#{name},'%')
            </if>
            <if test="gender != null">
                and gender = #{gender}
            </if>
            <if test="begin != null and end != null">
                and entrydate between #{begin} and #{end}
            </if>
        </where>
    </select>

    <update id="update">
        update emp
        <set>
            <if test="username != null and username != ''">
                username = #{username},
            </if>
            <if test="password != null and password != ''">
                password = #{password},
            </if>
            <if test="name != null and name != ''">
                name = #{name},
            </if>
            <if test="gender != null">
                gender = #{gender},
            </if>
            <if test="image != null and image != ''">
                image = #{image},
            </if>
            <if test="job != null">
                job = #{job},
            </if>
            <if test="ed != null">
                entrydate = #{ed},
            </if>
            <if test="deptId != null">
                dept_id = #{deptId},
            </if>
            <if test="createTime != null">
                create_time = #{createTime},
            </if>
            <if test="updateTime != null">
                update_time = #{updateTime},
            </if>
        </set>
        where id = #{id}
    </update>

    <delete id="deleteByIds">
        delete from emp where id in
        <foreach collection="ids" item="id" separator="," open="(" close=")">
            #{id}
        </foreach>
    </delete>


</mapper>

5.6XML配置实现

代码如下：

<?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>

    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <!--在控制台输出发送的sql日志-->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>


    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>

            <!--目前只关注这部分内容,它的作用就是声明要连接的数据信息-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <!--声明含有sql的接口所在包-->
        <package name="com.itheima.mapper"/>
    </mappers>
</configuration>

5.7测试实现

代码如下：

package com.itheima.test;

import com.itheima.domain.Emp;
import com.itheima.mapper.EmpMapper;
import com.itheima.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.Arrays;
import java.util.List;

public class EmpMapperTest {

    // 测试查询所有
    @Test
    public void testFindAll(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findAll();
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试结果集映射开启驼峰命名规则
    @Test
    public void testFindAll1(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findAll1();
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试结果集映射起别名
    @Test
    public void testFindAll2(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findAll2();
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试结果集映射手动结果映射@Results @Result
    @Test
    public void testFindAll3(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findAll3();
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试条件查询
    @Test
    public void testFindCondition(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findByCondition("张三丰",1, LocalDate.of(2000,1,1),LocalDate.of(2020,1,1));
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试模糊查询
    @Test
    public void testFindCondition2(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        List<Emp> empList = empMapper.findByCondition2("张",1, LocalDate.of(2000,1,1),LocalDate.of(2020,1,1));
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        MybatisUtil.close(sqlSession);
    }
    // 测试根据id查询
    @Test
    public void testFindById(){

        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
        Emp emp1 = empMapper.findById(4);
        System.out.println(emp1);
        MybatisUtil.close(sqlSession);
    }

    //条件查询
    @Test
    public void testFindByCondition() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        //List<Emp> empList = empMapper.findByCondition3("张", (short) 1, LocalDate.of(2002, 01, 01), LocalDate.of(2023, 12, 31));
        //List<Emp> empList = empMapper.findByCondition3("张", (short) 1, null, null);
        List<Emp> empList = empMapper.findByCondition3("", (short) 1, null, null);
        empList.forEach(e -> System.out.println(e));//lambda方式打印

        MybatisUtil.close(sqlSession);
    }

    //更新
    @Test
    public void testUpdate() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        Emp emp = new Emp();
        emp.setId(2);
        emp.setUsername("haha2");
        emp.setName("sdnajn");
        emp.setGender( (short) 1);
        emp.setImage("haha.jpg");
        emp.setJob((short) 2);
        emp.setDeptId(1);
        emp.setCreateTime(LocalDateTime.of(2023, 1, 1, 1, 1,1));
        emp.setUpdateTime(LocalDateTime.now());

        empMapper.update(emp);

        MybatisUtil.close(sqlSession);
    }

    //批量删除
    @Test
    public void deleteByIds() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        empMapper.deleteByIds(Arrays.asList(13, 14, 15));

        MybatisUtil.close(sqlSession);
    }

}

5.8pom.xml配置

<?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>

    <groupId>com.itheima</groupId>
    <artifactId>day04-01-mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
    </properties>

    <dependencies>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.9</version>
        </dependency>
        <!--junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.26</version>
        </dependency>
    </dependencies>

</project>

总结

以上就是今天学习的内容。

悦读

道可道，非常道；名可名，非常名。 无名，天地之始，有名，万物之母。 故常无欲，以观其妙，常有欲，以观其徼。 此两者，同出而异名，同谓之玄，玄之又玄，众妙之门。

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