SSM学习笔记16 MyBatis注解开发（小总结）_mybatis的注解开发实验总结

先学xml，再学注解

MyBatis的常用注解

@Insert:实现新增
@Update:实现更新
@Delete:实现删除
@Select:实现查询
@Result:实现结果集封装
@Results:可以与@Result-一起使用，封装多个结果集（比Result范围大）
@One：实现一对结果集封装
@Many:实现一对多结果集封装（一对多可能部分要手动映射）

简单查询

只是把xml的关系，用注解的方式配置到接口的方法上

usermapper

    @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
    public void save(User user);
 
    @Update("update user set username=#{username},password=#{password} where id=#{id}")
    public void update(User user);
 
    @Delete("delete from user where id=#{id}")
    public void delete(int id);
 
    @Select("select * from user where id=#{id}")
    public User findById(int id);
 
    @Select("select * from user")
    public List<User> findAll();

sqlMapConfig.xml

    <!--加载映射关系-->
    <mappers>
        <!--指定接口所在的包-->
        <package name="com.itheima.mapper"></package>
    </mappers>

复杂查询

 demo：一对一查询：查询订单的同时查询与该订单相关的用户

ordermapper.java

package com.itheima.mapper;
 
import com.itheima.domain.Order;
import com.itheima.domain.User;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
 
import java.util.List;
 
public interface OrderMapper {
 
 
 
    @Select("select * from orders where uid=#{uid}")
    public List<Order> findByUid(int uid);
 
 
 
    @Select("select * from orders")
    //用@Results封装映射参数，一对一查询
    //分表查询，不用加user.id了
    @Results({
            @Result(column = "id",property = "id"),
            @Result(column = "ordertime",property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(
                    property = "user", //要封装的属性名称
                    column = "uid", //根据哪个字段去查询user表的数据
                    javaType = User.class, //要封装的实体类型
                    //select属性 代表查询哪个接口的方法获得数据,引用要查的那个表的接口方法进行查询
                    one = @One(select = "com.itheima.mapper.UserMapper.findById")
            )
    })
    public List<Order> findAll();
 
 
 
    /*@Select("select *,o.id oid from orders o,user u where o.uid=u.id")
    //总表查询
    @Results({
            @Result(column = "oid",property = "id"),
            @Result(column = "ordertime",property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(column = "uid",property = "user.id"),
            @Result(column = "username",property = "user.username"),
            @Result(column = "password",property = "user.password")
    })
    public List<Order> findAll();*/
 
}

mybatistest2.java

package com.itheima.test;
 
import com.itheima.domain.Order;
import com.itheima.domain.User;
import com.itheima.mapper.OrderMapper;
import com.itheima.mapper.UserMapper;
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.Before;
import org.junit.Test;
 
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
 
public class MyBatisTest2 {
 
    private OrderMapper mapper;
 
    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        mapper = sqlSession.getMapper(OrderMapper.class);
    }
 
 
    @Test
    public void testSave(){
        List<Order> all = mapper.findAll();
        for (Order order : all) {
            System.out.println(order);
        }
    }
 
 
 
}

sqlMapConfig.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>
 
    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>
 
    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.User" alias="user"></typeAlias>
    </typeAliases>
 
 
    <!--数据源环境-->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    
 
    <!--加载映射关系-->
    <mappers>
        <!--指定接口所在的包-->
        <package name="com.itheima.mapper"></package>
    </mappers>
 
 
</configuration>

一对多的注解开发

    @Select("select * from user")
    @Results({
            @Result(id=true ,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "orderList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid")
            )
    })
    public List<User> findUserAndOrderAll();

多对多查询的需求：查询用户同时查询出该用户的所有角色

（一对多查询与多对多查询 ，差不多）

    @Select("SELECT * FROM USER")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "roleList",
                    column = "id",//根据谁去查询
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")//调用了rolemapper中的sql语句
            )
    })
    public List<User> findUserAndRoleAll();