1.1 简介

1.1.1 概述

  通用 Mapper 都可以极大的方便开发人员。可以随意的按照自己的需要选择通用方法，还可以很方便的开发自己的通用方法。极其方便的使用 MyBatis 单表的增删改查。支持单表操作，不支持通用的多表联合查询。

1.1.2 相关依赖

<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper</artifactId>
    <version>4.1.5</version>
</dependency>

1.2 通用 Mapper 详解

1.2.1 修改配置

<!-- 扫描 mapper 所在的包，为 mapper 创建实现类【org 包改为 tk 包】-->
<bean class="tk.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="com.software.ssm.mapper"></property>
</bean>

1.2.2 常用注解

1.3 通用 Mapper 接口

1.3.1 继承体系

1.3.2 继承核心接口

@Repository
public interface StudentMapper extends Mapper<Student> { }

1.3.3 操作接口

1.3.4 Example 接口

创建接口

// Condition 和 Example 作用完全一样
Example example = new Example(JavaBean.class);
Example.Criteria criteria = example.createCriteria();

接口方法

1.4 示例

1.4.1 select

@SpringJUnitConfig(locations = "classpath:application.xml")
public class Demo { 

    @Autowired
    private StudentMapper studentMapper;

    @Test
    public void TestSelect() { 
    	// 查询所有
        List<Student> students = studentMapper.selectAll();
        System.out.println(students);

		// 匹配实体类属性查询
        Student student = new Student();
        student.setId(1L);
        List<Student> select = studentMapper.select(student);
        System.out.println(select);
    }
}

1.4.2 update

@SpringJUnitConfig(locations = "classpath:application.xml")
public class Demo { 

    @Autowired
    private StudentMapper studentMapper;

    @Test
    public void TestUpdate() { 
        // 查询参数
        Student student = new Student();
        student.setId(1L);
        // 修改前
        Student result_1 = studentMapper.selectOne(student);
        System.out.println(result_1);

        // 修改
        Student update = new Student();
        update.setId(1L);
        update.setName("王五");
        studentMapper.updateByPrimaryKeySelective(update);

        // 修改后
        Student result_2 = studentMapper.selectOne(student);
        System.out.println(result_2);
    }
}

1.4.3 insert

@SpringJUnitConfig(locations = "classpath:application.xml")
public class Demo { 

    @Autowired
    private StudentMapper studentMapper;

    @Test
    public void TestInsert() { 
    	// 新增数据
        Student student = new Student();
        student.setName("张良");
        student.setAge(800);

		// 新增操作
        studentMapper.insertSelective(student);

		// 打印，新增成功之后可以从实体类对象中获取 id
        System.out.println(student);
    }
}

1.4.4 delete

@SpringJUnitConfig(locations = "classpath:application.xml")
public class Demo { 

    @Autowired
    private StudentMapper studentMapper;

    @Test
    public void TestDel() { 
        // 删除参数
        Student student = new Student();
        student.setId(1L);

        // 删除操作
        studentMapper.delete(student);

        // 查询
        Student result = studentMapper.selectOne(student);
        System.out.println(result);
    }
}

1.4.5 Example

@SpringJUnitConfig(locations = "classpath:application.xml")
public class Demo { 

    @Autowired
    private StudentMapper studentMapper;

    @Test
    public void Test() { 
        Example example = new Example(Student.class);

        Example.Criteria criteria = example.createCriteria();
        criteria.andEqualTo("id", 2L)
                .andLike("name", "%李%");

        List<Student> students = studentMapper.selectByExample(example);
        System.out.println(students);
    }
}