SSM——MyBatis注解开发_ssm mybatis注解开发

一. MyBatis的常用注解

这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。

• mybatis最初配置信息是基于 XML ,映射语句(SQL)也是定义在 XML 中的。而到MyBatis 3提供了新的基于注解的配置。不幸的是，Java 注解的的表达力和灵活性十分有限。最强大的 MyBatis 映射并不能用注解来构建

二. MyBatis的增删改查

我们完成简单的user表的增删改查的操作

1. 我们不使用注解

在test文件夹中进行

添加数据、修改数据

删除数据、查询数据

在mybatis的核心配置文件中注入

2. 我们使用注解

1.编写工具类

package com.pudding.utils;

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.IOException;
import java.io.InputStream;

//SqlSessionFactory --> SqlSession
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //使用mybatis第一步：获取SqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例
    //SqlSession 提供了在数据库执行 SQL 命令所需的所有方法
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession(true);
    }
}

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2.编写接口方法注解

package com.pudding.dao;

import com.pudding.pojo.User;
import org.apache.ibatis.annotations.*;

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

public interface UserMapper {
    //查询全部用户
    @Select("select id,name,pwd password from user")
    public List<User> getAllUser();

    //根据id查询用户
    //方法存在多个参数，所有的参数前面必须加上@Param("id")注解
    @Select("select * from user where id = #{id}")
    User selectUserById(@Param("id") int id);

    //添加一个用户
    @Insert("insert into user (id,name,pwd) values (#{id},#{name},#{password})")
    int addUser(User user);

    //修改一个用户
    @Update("update user set name=#{name},pwd=#{password} where id = #{id}")
    int updateUser(User user);

    //根据id删除用
    @Delete("delete from user where id = #{id}")
    int deleteUser(@Param("id")int id);
}

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3.测试

import com.pudding.dao.UserMapper;
import com.pudding.pojo.User;
import com.pudding.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    @Test
    public void test(){
        SqlSession session = MybatisUtils.getSession();
        //本质上利用了jvm的动态代理机制
        UserMapper mapper = session.getMapper(UserMapper.class);

        List<User> users = mapper.getAllUser();
        for (User user : users){
            System.out.println(user);
        }

        session.close();
    }

    @Test
    public void testSelectUserById() {
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);

        User user = mapper.selectUserById(1);
        System.out.println(user);

        session.close();
    }

    @Test
    public void testAddUser() {
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);

        User user = new User(4, "秦疆", "123456");
        mapper.addUser(user);

        session.close();
    }

    @Test
    public void testUpdateUser() {
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);

        User user = new User(4, "秦疆", "zxcvbn");
        mapper.updateUser(user);

        session.close();
    }

    @Test
    public void testDeleteUser() {
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);

        mapper.deleteUser(4);

        session.close();
    }
}

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三. MyBatis的注解实现复杂映射开发

注意：利用注解开发就不需要mapper.xml映射文件了

1. 一对一查询

1.1 一对一查询模型

1.2 一对一查询的语句

1.3 创建Order和User实体

1.4 创建OrderMapper接口

1.5 使用注解配置Mapper

2、我们在我们的接口中添加注解

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);


    /*第二种方式*/
    @Select("select * from orders")
    @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", //根据那个字段去查询user表的数据
                    javaType = User.class, //要封装的实体类型
                    //select属性 代表查询那个接口的方法获得数据
                    one = @One(select = "com.itheima.mapper.UserMapper.findById")
            )
    })
    public List<Order> findAll();



    /*第一种方式
    @Select("select *,o.id oid from orders o,user u where o.uid=u.id")
    @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();*/

}

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1.6 进行测试

3、我们去进行测试

2. 一对多查询

2.1 一对多查询模型

2.2 一对多查询语句

2.3 创建实体类

2.4 创建实体对应的接口

2.5 使用注解配置Mapper

package com.itheima.mapper;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface 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();

    @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();


    @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",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")
            )
    })
    public List<User> findUserAndRoleAll();


}

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2.6 进行测试

3. 多对多查询

3.1 多对多查询模型

3.2 多对多查询的语句

2.3 创建实体

3.4 创建UserMapper接口

3.5 使用注解配置Mapper

package com.itheima.mapper;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface 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();

    @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();


    @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",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")
            )
    })
    public List<User> findUserAndRoleAll();


}

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package com.itheima.mapper;

import com.itheima.domain.Role;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface RoleMapper {

    @Select("SELECT * FROM sys_user_role ur,sys_role r WHERE ur.roleId=r.id AND ur.userId=#{uid}")
    public List<Role> findByUid(int uid);

}

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3.6 进行测试