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SqlSessionFactorysqlSessionFactory = new SqlSessionFactoryBuilder().build(stream);} catch (Exception e) {e.printStackTrace();}}//获取sqlSessionpublic static SqlSession getSqlSession() {return sqlSessionFactory.openSession();}//提交事务 关闭sqlSessionpublic 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 mapperPUBLIC "-//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 configurationPUBLIC "-//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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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@Testpublic 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。
