通用Mapper简单使用

Posted 2021-01-25 myx-ah

 

通用Mapper

 

1、通用Mapper的使用

1.1、导入依赖

1 <!-- 通用mapper -->
2         <dependency>
3             <groupId>tk.mybatis</groupId>
4             <artifactId>mapper-spring-boot-starter</artifactId>
5             <version>2.0.2</version>
6         </dependency>

1.2、开启包扫描

注意导入的包，一定要和导入的的依赖有关的包

 

 1 import org.springframework.boot.SpringApplication;
 2 import org.springframework.boot.autoconfigure.SpringBootApplication;
 3 import tk.mybatis.spring.annotation.MapperScan;
 4 
 5 @SpringBootApplication
 6 @MapperScan("com.myx.demo.mapper")
 7 public class Application {
 8     public static void main(String[] args) {
 9         SpringApplication.run(Application.class);
10     }
11 }

 

1.3、UserMapper接口继承通用Mapper

1 package com.myx.demo.mapper;
2 import com.myx.demo.pojo.User;
3 import tk.mybatis.mapper.common.Mapper;
4 
5 public interface UserMapper extends Mapper<User>{
6 
7 }

1.4、SpringBoot默认的文件名Application.yml配置

 1 server:
 2   port: 8080
 3 
 4 logging:
 5   level:
 6     com.myx.demo:
 7       debug
 8 spring:
 9   datasource: #spring数据源的配置
10     url: jdbc:mysql://localhost:3306/day11mybatis
11     username: root
12     password: 123

1.5、通用Mapper的测试类

1 @RunWith(SpringRunner.class)
2 @SpringBootTest(classes = Application.class)
3 public class NewUserMapperTest {
4 
5     @Autowired
6     private UserMapper userMapper;
7 
8 
9 }

1.5.1 id 的专用查询方法

1 @Test
2     public void testSelectId() {
3         userMapper.selectByPrimaryKey(1L);//id专用查询方法
4         System.out.println( userMapper.selectByPrimaryKey(1L));
5     }

1.5.2 属性查询

1 @Test
2     public void testSelectName() {
3         User user = new User();
4         user.setName("张三");//哪个属性有值where条件就根据哪个属性生成，id除外
5         List<User> select = userMapper.select(user);
6         System.out.println(select);
7     }

1.5.3 属性值唯一查询

1 @Test
2     public void testSelectOne() {
3         User user = new User();
4         user.setUserName("zhangsan");//查询值有多个会报错
5 
6         System.out.println(userMapper.selectOne(user));
7 
8     }

1.5.4 统计个数

1 @Test
2     public void testSelectCount() {
3         System.out.println(userMapper.selectCount(null));//没有查询条件就全查
4     }

1.5.5 插入

 1 @Test
 2     public void testInsert() {
 3         User user = new User();
 4         user.setUserName("孙悟空");
 5         user.setName("sunwukong");
 6         user.setAge(500);
 7         user.setId(50L);
 8         user.setPassword("234");
 9         int insert = userMapper.insert(user);
10         System.out.println(insert);
11     }

1.5.6 selective插入

 1 /*
 2     * insertSelective方法：有值才操作，没有值不理会，比上insert方法效率高
 3     * */
 4     @Test
 5     public void testInsertSelective() {
 6         User user = new User();
 7         user.setUserName("猪八戒");
 8         user.setName("sunwukong");
 9         user.setAge(500);
10         user.setId(51L);
11         user.setPassword("234");
12         user.setCreated(new Date());
13         int insert = userMapper.insertSelective(user);
14         System.out.println(insert);
15     }

1.5.7 删除

1  @Test
2     public void testDelete() {
3         User user = new User();
4         user.setUserName("孙悟空");
5         int delete = userMapper.delete(user);
6         System.out.println(delete);
7     }

 

 1.5.8 根据id删除，主键的特有方法

 1  @Test 2 public void testDeleteByPrimaryKey() { 3 userMapper.deleteByPrimaryKey(51L); 4 } 

 1.5.9 修改

 1 /*
 2     * 指定的属性改变为指定的值，其余的为null
 3     * */
 4     @Test
 5     public void testUpdateByPrimaryKey() {
 6         User user = new User();
 7         user.setId(36L);
 8         user.setUserName("李白");
 9         user.setName("libai");
10 
11         userMapper.updateByPrimaryKey(user);
12     }

1.5.10 selecttive修改

    /*
    * 只改变指定的属性，其余属性不变
    * */
    @Test
    public void testUpdatePriimarySelective() {
        User user = new User();
        user.setId(33L);
        user.setUserName("王昭君");
        user.setName("wangzhaojun");
        user.setUpdated(new Date());
        userMapper.updateByPrimaryKeySelective(user);
    }

2 通用Mapper分页

2.1 分页的依赖

<!--分页的依赖-->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </dependency>

2.2 分页方法的测试

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)

public class MapperPageQueryTest {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void testPageQuery() {
        //开启分页
        PageHelper.startPage(3,5);
        //不包含总的页数，总的元素个数
        List<User> select = userMapper.select(null);
        System.out.println(select);
    }

    @Test
    public void testPageInfoQuery() {
        //开启分页
        PageHelper.startPage(3,5);
        //用page类型或者pageInfo类型目的就是获取总页数以及总条数
        Page<User> userPage = (Page<User>) userMapper.select(null);
        //分页返回的结果
        //PageInfo<User> pageInfo = new PageInfo<>(select);
        System.out.println(userPage);
    }
}

3 通用Mapper组合查询和排序

3.1 添加普通条件

/*
    * example要表达的含义为？？？
    * 组合的查询条件
    * */
    @Test
    public void testSelectByExample(){
        //条件的组合工具
        Example example = new Example(User.class);
        //条件,一个criteria中可以组合无数个条件，但是这些条件都是and关系
        Example.Criteria criteria = example.createCriteria();
        criteria.andEqualTo("sex","1");
        criteria.andBetween("age",20,30);
        List<User> users = userMapper.selectByExample(example);
        System.out.println("users = " + users);

    }

3.2 添加or条件的组合查询

@Test
    public void testSelectByExampleOr(){
        //条件的组合工具
        Example example = new Example(User.class);
        //条件,一个criteria中可以组合无数个条件，但是这些条件都是and关系
        Example.Criteria criteria = example.createCriteria();
        criteria.andEqualTo("sex","1");
        Example.Criteria criteria1 = example.createCriteria();
        criteria1.andLike("name","%李%");
        //直接使用example的or方法使得第二个条件和原来的条件组合or关系
        example.or(criteria1);
        System.out.println(userMapper.selectByExample(example));

    }

3.3 排序

@Test
    public void testSelectByExampleOrder(){
        //条件的组合工具
        Example example = new Example(User.class);
        //条件,一个criteria中可以组合无数个条件，但是这些条件都是and关系
        Example.Criteria criteria = example.createCriteria();
        criteria.andEqualTo("sex","1");
        Example.Criteria criteria1 = example.createCriteria();
        criteria1.andLike("name","%李%");
        //直接使用example的or方法使得第二个条件和原来的条件组合or关系
        example.or(criteria1);
        //排序
        example.setOrderByClause("id DESC");
        System.out.println(userMapper.selectByExample(example));

    }