EmmmuaCode
wufan
2022-04-15
目录

MyBatis-Plus 基本CRUD

# MyBatis-Plus 基本CRUD

# BaseMapper

MyBatis-Plus中的基本CRUD在内置的BaseMapper中都已得到了实现，我们可以直接使用，接口如下：

public interface BaseMapper<T> extends Mapper<T> {

    /**
     * 插入一条记录
     *
     * @param entity 实体对象
     */
    int insert(T entity);

    /**
     * 根据 ID 删除
     *
     * @param id 主键ID
     */
    int deleteById(Serializable id);

    /**
     * 根据实体(ID)删除
     *
     * @param entity 实体对象
     * @since 3.4.4
     */
    int deleteById(T entity);

    /**
     * 根据 columnMap 条件，删除记录
     *
     * @param columnMap 表字段 map 对象
     */
    int deleteByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);

    /**
     * 根据 entity 条件，删除记录
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句）
     */
    int delete(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 删除（根据ID或实体 批量删除）
     *
     * @param idList 主键ID列表或实体列表(不能为 null 以及 empty)
     */
    int deleteBatchIds(@Param(Constants.COLLECTION) Collection<?> idList);

    /**
     * 根据 ID 修改
     *
     * @param entity 实体对象
     */
    int updateById(@Param(Constants.ENTITY) T entity);

    /**
     * 根据 whereEntity 条件，更新记录
     *
     * @param entity        实体对象 (set 条件值,可以为 null)
     * @param updateWrapper 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句）
     */
    int update(@Param(Constants.ENTITY) T entity, @Param(Constants.WRAPPER) Wrapper<T> updateWrapper);

    /**
     * 根据 ID 查询
     *
     * @param id 主键ID
     */
    T selectById(Serializable id);

    /**
     * 查询（根据ID 批量查询）
     *
     * @param idList 主键ID列表(不能为 null 以及 empty)
     */
    List<T> selectBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);

    /**
     * 查询（根据 columnMap 条件）
     *
     * @param columnMap 表字段 map 对象
     */
    List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);

    /**
     * 根据 entity 条件，查询一条记录
     * <p>查询一条记录，例如 qw.last("limit 1") 限制取一条记录, 注意：多条数据会报异常</p>
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    default T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper) {
        List<T> ts = this.selectList(queryWrapper);
        if (CollectionUtils.isNotEmpty(ts)) {
            if (ts.size() != 1) {
                throw ExceptionUtils.mpe("One record is expected, but the query result is multiple records");
            }
            return ts.get(0);
        }
        return null;
    }

    /**
     * 根据 Wrapper 条件，判断是否存在记录
     *
     * @param queryWrapper 实体对象封装操作类
     * @return
     */
    default boolean exists(Wrapper<T> queryWrapper) {
        Long count = this.selectCount(queryWrapper);
        return null != count && count > 0;
    }

    /**
     * 根据 Wrapper 条件，查询总记录数
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    Long selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 根据 entity 条件，查询全部记录
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 根据 Wrapper 条件，查询全部记录
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    List<Map<String, Object>> selectMaps(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 根据 Wrapper 条件，查询全部记录
     * <p>注意： 只返回第一个字段的值</p>
     *
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    List<Object> selectObjs(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 根据 entity 条件，查询全部记录（并翻页）
     *
     * @param page         分页查询条件（可以为 RowBounds.DEFAULT）
     * @param queryWrapper 实体对象封装操作类（可以为 null）
     */
    <P extends IPage<T>> P selectPage(P page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

    /**
     * 根据 Wrapper 条件，查询全部记录（并翻页）
     *
     * @param page         分页查询条件
     * @param queryWrapper 实体对象封装操作类
     */
    <P extends IPage<Map<String, Object>>> P selectMapsPage(P page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154

# 插入

    @Test
    public void testInsert(){
        User user = new User();
        user.setName("张三");
        user.setAge(23);
        user.setEmail("zhangsan@atschool.com");
        int result = userMapper.insert(user);
        System.out.println("result:"+result);
        System.out.println("id:"+user.getId());
    }
1
2
3
4
5
6
7
8
9
10

# 结果

...
==>  Preparing: INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? )
==> Parameters: 1514632107652923393(Long), 张三(String), 23(Integer), zhangsan@atschool.com(String)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7e00ed0f]
result:1
id:1514632107652923393
2022-04-14 23:50:10.135  INFO 23036 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-14 23:50:10.155  INFO 23036 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11

最终执行的结果，所获取的id为1514632107652923393

这是因为MyBatis-Plus在实现插入数据时，会默认基于雪花算法的策略生成id

# 删除

# 通过id删除记录

    @Test
    public void testDelete(){
        //通过id删除用户信息
        int result = userMapper.deleteById(1514558344269680641L);
        System.out.println("result:"+result);
    }
1
2
3
4
5
6

# 结果

...
==>  Preparing: DELETE FROM user WHERE id=?
==> Parameters: 1514558344269680641(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7e00ed0f]
result:1
2022-04-14 23:47:52.921  INFO 3000 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-14 23:47:52.962  INFO 3000 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10

# 通过id批量删除记录

   @Test
   public void testDeleteBatchIds(){
       List<Long> list = Arrays.asList(1L, 2L, 3L);
       int result = userMapper.deleteBatchIds(list);
       System.out.println("result:"+result);
   }
1
2
3
4
5
6

# 结果

...
==>  Preparing: DELETE FROM user WHERE id IN ( ? , ? , ? )
==> Parameters: 1(Long), 2(Long), 3(Long)
<==    Updates: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@62db0521]
result:3
2022-04-15 00:00:56.260  INFO 9828 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:00:56.270  INFO 9828 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10

# 通过map条件删除记录

    @Test
    public  void testDeleteByMap(){
        Map<String,Object> map=new HashMap<>();
        //删除name为张三，年龄为23的所有用户
        map.put("name","张三");
        map.put("age",23);
        int result = userMapper.deleteByMap(map);
        System.out.println("result:"+result);

    }
1
2
3
4
5
6
7
8
9
10

# 结果

...
==>  Preparing: DELETE FROM user WHERE name = ? AND age = ?
==> Parameters: 张三(String), 23(Integer)
<==    Updates: 0
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@65f2f9b0]
result:0
2022-04-15 01:40:24.693  INFO 23248 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 01:40:24.713  INFO 23248 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10

# 修改

# 通过Id修改记录

    @Test
    public void testUpdateById(){
        User user = new User();
        user.setId(4L);
        user.setName("李四");//修改name
        user.setEmail("lisi@atSchool.com");
        int result = userMapper.updateById(user);
        System.out.println("result:"+result);
    }
1
2
3
4
5
6
7
8
9

# 结果

...
==>  Preparing: UPDATE user SET name=?, email=? WHERE id=?
==> Parameters: 李四(String), lisi@atSchool.com(String), 4(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@62db0521]
result:1
2022-04-15 00:05:46.724  INFO 7772 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:05:46.774  INFO 7772 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10

# 查询

# 根据id查询用户信息

  	@Test
    public void testSelectById(){
        //通过Id查询用户信息
        User user = userMapper.selectById(1L);
        System.out.println(user);
    }
1
2
3
4
5
6

# 结果

...
==>  Preparing: SELECT id,name,age,email FROM user WHERE id=?
==> Parameters: 1(Long)
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3964d79]
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
2022-04-15 00:10:50.204  INFO 11976 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:10:50.219  INFO 11976 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12

# 根据多个id查询多个用户信息

  	@Test
    public void testSelectBatchIds(){
        //根据多个id查询多个用户信息
        List<Long> list = Arrays.asList(1L, 2L, 3L);
        List<User> users = userMapper.selectBatchIds(list);
        users.forEach(System.out :: println);
    }
1
2
3
4
5
6
7

# 结果

...
=>  Preparing: SELECT id,name,age,email FROM user WHERE id IN ( ? , ? , ? )
==> Parameters: 1(Long), 2(Long), 3(Long)
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==        Row: 2, Jack, 20, test2@baomidou.com
<==        Row: 3, Tom, 28, test3@baomidou.com
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@65753040]
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
2022-04-15 00:16:56.186  INFO 19452 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:16:56.202  INFO 19452 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

# 通过map条件查询用户信息

   	@Test
    public void testSelectByMap(){
        //通过map条件查询用户信息
        Map<String,Object> map=new HashMap<>();
        map.put("name","Jack");
        map.put("age",20);
        List<User> users = userMapper.selectByMap(map);
        users.forEach(System.out :: println);
    }
1
2
3
4
5
6
7
8
9

# 结果

...
==>  Preparing: SELECT id,name,age,email FROM user WHERE name = ? AND age = ?
==> Parameters: Jack(String), 20(Integer)
<==    Columns: id, name, age, email
<==        Row: 2, Jack, 20, test2@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@4acb2510]
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
2022-04-15 00:20:34.390  INFO 20808 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:20:34.404  INFO 20808 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12

# 查询所有数据

  	@Test
    public void testSelectList(){
        //通过条件构造器查询一个list集合，若没有条件，则可以设置null为参数
        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }
1
2
3
4
5
6

通过观察BaseMapper中的方法，大多方法中都有Wrapper类型的形参，此为条件构造器，可针对于SQL语句设置不同的条件，若没有条件，则可以为该形参赋值null，即查询（删除/修改）所有数据

# 结果

...
==>  Preparing: SELECT id,name,age,email FROM user
==> Parameters: 
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==        Row: 2, Jack, 20, test2@baomidou.com
<==        Row: 3, Tom, 28, test3@baomidou.com
<==        Row: 4, 李四, 21, lisi@atSchool.com
<==        Row: 5, Billie, 24, test5@baomidou.com
<==        Row: 6, Sandy, 21, test4@baomidou.com
<==        Row: 7, Billie, 24, test5@baomidou.com
<==      Total: 7
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@65753040]
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=李四, age=21, email=lisi@atSchool.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)
User(id=6, name=Sandy, age=21, email=test4@baomidou.com)
User(id=7, name=Billie, age=24, email=test5@baomidou.com)
2022-04-15 00:23:56.531  INFO 19052 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:23:56.548  INFO 19052 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

# 自定义功能

UserMapper.java

@Repository
public interface UserMapper extends BaseMapper<User> {

    /**
     * 根据id用户信息为map集合
     * @param id
     * @return
     */
    Map<String,Object> selectMapById(long id);
}
1
2
3
4
5
6
7
8
9
10

UserMapper.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">
<mapper namespace="com.frx01.mybatisplus.mapper.UserMapper">
    <!--Map<String,Object> selectMapById(long id);-->
    <select id="selectMapById" resultType="map">
        select id,name,age,email from user where id=#{id}
    </select>
</mapper>
1
2
3
4
5
6
7
8
9
10

# 测试

    @Test
    public void selectMapById(){
        Map<String, Object> map = userMapper.selectMapById(1L);
        System.out.println(map);
    }
1
2
3
4
5
6

# 结果

...
==>  Preparing: select id,name,age,email from user where id=?
==> Parameters: 1(Long)
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7a904f32]
{name=Jone, id=1, age=18, email=test1@baomidou.com}
2022-04-15 00:53:53.503  INFO 18756 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 00:53:53.516  INFO 18756 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12

# 通用Service

说明:

  • 通用 Service CRUD 封装IService (opens new window)接口，进一步封装 CRUD 采用 get 查询单行 remove 删除 list 查询集合 page 分页 前缀命名方式区分 Mapper 层避免混淆
  • 泛型 T 为任意实体对象
  • 建议如果存在自定义通用 Service 方法的可能，请创建自己的 IBaseService 继承 Mybatis-Plus 提供的基类
  • 对象 Wrapper 为 条件构造器 (opens new window)
  • 官网地址：https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F% A3

# IService

MyBatis-Plus中有一个接口 IService和其实现类 ServiceImpl，封装了常见的业务层逻辑

详情查看源码IService和ServiceImpl

# 创建Service接口和实现类

/**
 * UserService继承IService模板提供的基础功能
 */
public interface UserService extends IService<User> {
}
1
2
3
4
5
/**
 * ServiceImpl实现了IService，提供了IService中基础功能的实现
 * 若ServiceImpl无法满足业务需求，则可以使用自定的UserService定义方法，并在实现类中实现
 */
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}
1
2
3
4
5
6
7

# 测试查询记录数

@SpringBootTest
public class MyBatisPlusServiceTest {

    @Autowired
    private UserService userService;

    @Test
    public void testGetCount(){
        long count = userService.count();
        System.out.println("总记录数:"+count);
    }
}
1
2
3
4
5
6
7
8
9
10
11
12

# 结果

...
==>  Preparing: SELECT COUNT( * ) FROM user
==> Parameters: 
<==    Columns: COUNT( * )
<==        Row: 7
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@59901c4d]
总记录数:7
2022-04-15 01:12:23.828  INFO 1048 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 01:12:23.843  INFO 1048 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12

# 测试批量插入

    @Test
    public void testInsertMore(){
        // SQL长度有限制，海量数据插入单条SQL无法实行，
		// 因此MP将批量插入放在了通用Service中实现，而不是通用Mapper
        List<User> list =new ArrayList<>();
        for (int i = 1; i <=10 ; i++) {
            User user = new User();
            user.setName("frx"+i);
            user.setAge(20+i);
            list.add(user);
        }
        boolean b = userService.saveBatch(list);
        System.out.println(b==true?"操作成功":"操作失败");
    }
1
2
3
4
5
6
7
8
9
10
11
12
13
14

# 结果

...
==>  Preparing: INSERT INTO user ( id, name, age ) VALUES ( ?, ?, ? )
==> Parameters: 1514654840059076610(Long), frx1(String), 21(Integer)
==> Parameters: 1514654840226848770(Long), frx2(String), 22(Integer)
==> Parameters: 1514654840226848771(Long), frx3(String), 23(Integer)
==> Parameters: 1514654840268791810(Long), frx4(String), 24(Integer)
==> Parameters: 1514654840268791811(Long), frx5(String), 25(Integer)
==> Parameters: 1514654840268791812(Long), frx6(String), 26(Integer)
==> Parameters: 1514654840268791813(Long), frx7(String), 27(Integer)
==> Parameters: 1514654840268791814(Long), frx8(String), 28(Integer)
==> Parameters: 1514654840268791815(Long), frx9(String), 29(Integer)
==> Parameters: 1514654840268791816(Long), frx10(String), 30(Integer)
操作成功
2022-04-15 01:20:29.833  INFO 22624 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-04-15 01:20:29.843  INFO 22624 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
#MyBatis-Plus
上次更新: 2024/04/21, 09:42:22
MyBatis-Plus 入门案例
MyBatis-Plus 常用注解

← MyBatis-Plus 常用注解→

最近更新
01
微信支付功能的实现与流程
11-21
02
购物车与结算区域的深入优化与功能完善
11-21
03
购物车与结算区域的功能实现与优化
11-21
更多文章>
Theme by Vdoing | Copyright © 2023-2024 EmmmuaCode | 黔ICP备2022009864号-2