MyBaits概念

ORM：对象关系映射，是一个程序设计技术，用于实现面向对象编程语言里不同类型的数据之间的转换。

mybaits：对象关系映射（ORM）框架。常见的ORM框架还有：Hibernate，EclipseLink，JFinal等。

MyBatis的使用案例

添加依赖
1. mybaits依赖
2. 数据库驱动
3. junit
创建数据库映射的实体类
配置mybatis-config.xml配置文件
配置mapper.xml接口映射的配置文件

测试

<?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.quail</groupId>
 <artifactId>MyBatis-01</artifactId>
 <version>1.0-SNAPSHOT</version>
 <dependencies>
     <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.11</version>
         <scope>test</scope>
     </dependency>
     <!--mybatis依赖-->
     <dependency>
         <groupId>org.mybatis</groupId>
         <artifactId>mybatis</artifactId>
         <version>3.5.1</version>
     </dependency>
     <!--mysql驱动-->
     <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
         <version>8.0.22</version>
     </dependency>
 </dependencies>
   <!-- 
             此配置用于编译mapper.xml
              如果没有这个配置，将映射文件配置在接口下时，编译器不会读取
             这个配置是告诉编译器去这个目录找xml，进行编译
     -->
 <build>
     <resources>
         <resource>
             <directory>src/main/java</directory>
             <includes>
                 <include>**/*.xml</include>
             </includes>
         </resource>
     </resources>
 </build>
</project>

<?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:控制mybatis全局行为。
 setting name=“logImpl”：设置mybatis输出日志
 -->
 <!--    <settings>-->
 <!--        <setting name="logImpl" value="STDOUT_LOGGING"/>-->
 <!--    </settings>-->
 <!--
     环境配置：数据库的连接信息
     default:必须和某个environment的id值一样。
     告诉mybatis使用哪个数据库的连接信息。就是访问哪个数据库
 -->
 <environments default="mybatis">
     <!--
         environment:一个数据库信息的配置，环境
         id：唯一值，自定义，表示环境名称
     -->
     <environment id="mybatis">
         <!--
             transactionManager:mybatis的事务类型
             type:JDBC(表示使用jdbc中的Connection对象的commit，rollback做事务处理)
         -->
         <transactionManager type="JDBC"></transactionManager>
         <!--
             dataSource:表示数据源，连接数据库
             type：表示数据源的类型，POOLED表示使用连接池
         -->
         <dataSource type="POOLED">
             <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
             <property name="url" value="jdbc:mysql://localhost:3306/mis?useUnicode=true&amp;characterEncoding=utf-8&amp;serverTimezone=UTC"/>
             <property name="username" value="root"/>
             <property name="password" value="root"/>
         </dataSource>
     </environment>
 </environments>

 <!--sql mapper（sql映射文件）的位置-->
 <mappers>
     <mapper resource="com/quail/dao/TeacherMapper.xml"/>
 </mappers>
</configuration>

```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">

```java
package com.quail.test;

import com.quail.pojo.Teacher;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;

/**
 * @author quail
 * @date 2021/3/19 20:53
 * @TODO
 */
public class MybatisTest {
    @Test
    public void test(){
        // 获取配置文件流
        InputStream in = this.getClass().getClassLoader().getResourceAsStream("mybatis-config.xml");
        // 创建连接
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        SqlSession sqlSession = factory.openSession();
        // 执行sql语句
        Teacher teacher = sqlSession.selectOne("TeacherDao.queryById", 3l);
        System.out.println(teacher);
    }
}

MyBatis实现简单的CRUD

tips：-

（DML）增删改操作需要提交事务
模糊查询时使用${}替换符，因为#{}占位符在’’（单引号）中不生效

像分页查询这样需要传入多个参数的方法，要使用map来配合。mybatis的sqlSession执行sql语句的方法中没有可以创多个参数的方法，所以只能用map。

<?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="TeacherDao">
  <select id="queryById" resultType="com.quail.pojo.Teacher">
      select * from teacher where teacherId = #{teacherId};
  </select>

  <insert id="create" parameterType="com.quail.pojo.Teacher">
      insert into teacher(teacherName,loginPass,teacherGender,teacherTel,status)
       values(#{teacherName},#{loginPass},#{teacherGender},#{teacherTel},#{status})
  </insert>

  <delete id="delete" parameterType="long">
      delete from teacher where teacherId = #{teacherId}
  </delete>

  <update id="update" parameterType="com.quail.pojo.Teacher">
      update teacher set teacherName = #{teacherName} where teacherId = #{teacherId}
  </update>

  <select id="limitQuery" parameterType="int" resultType="com.quail.pojo.Teacher">
      select * from teacher limit #{start},#{count}
  </select>

  <select id="likeQuery" parameterType="string" resultType="com.quail.pojo.Teacher">
      select * from teacher where teacherName like '%${value}%'
  </select>
</mapper>

```java package com.quail.test;

import com.quail.pojo.Teacher; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.junit.Test;

import java.io.InputStream; import java.util.HashMap; import java.util.List; import java.util.Map;

/**

@author quail
@date 2021/3/19 20:53

@TODO */ public class MybatisTest { // 获取配置文件流 private InputStream in = this.getClass().getClassLoader().getResourceAsStream(“mybatis-config.xml”); // 创建连接 private SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in); private SqlSession sqlSession = factory.openSession();

private String mapper = “TeacherDao.”;

@Test public void test(){

 Teacher teacher = sqlSession.selectOne("TeacherDao.queryById", 3l);
 System.out.println(teacher);

}

@Test public void testCreate(){

 Teacher teacher = new Teacher();
 teacher.setLoginPass("123");
 teacher.setStatus(1);
 teacher.setTeacherGender(2);
 teacher.setTeacherName("quail");
 teacher.setTeacherTel("1829392123");
 int insert = sqlSession.insert(mapper + "create", teacher);
 System.out.println(insert);
 // 增删改操作需要手动提交事务,DML
 sqlSession.commit();

}

@Test public void testDelete(){

 int delete = sqlSession.delete(mapper + "delete", 20l);
 sqlSession.commit();

}

@Test public void testUpdate(){

 Teacher teacher = new Teacher();
 teacher.setTeacherId(18l);
 teacher.setTeacherName("鹌鹑");
 int delete = sqlSession.delete(mapper + "update", teacher);
 System.out.println(delete);
 sqlSession.commit();

}

@Test public void testLimitQuery(){

 Map<String,Integer> map = new HashMap<String,Integer>();
 map.put("start",0);
 map.put("count",5);
 List<Teacher> list = sqlSession.selectList(mapper + "limitQuery",map);
 System.out.println(list);

}

@Test public void testLikeQuery(){

 String data = "双虎";
 List<Teacher> list = sqlSession.selectList(mapper + "likeQuery",data);
 System.out.println(list);

} }

```

SSM框架学习

MyBaits从头开始

MyBaits概念

MyBatis的使用案例

MyBatis实现简单的CRUD