# MyBatis-Plus 基本CRUD
- BaseMapper
- 插入
- 结果
- 删除
- 通过id删除记录
- 通过id批量删除记录
- 通过map条件删除记录
- 修改
- 通过Id修改记录
- 查询
- 根据id查询用户信息
- 根据多个id查询多个用户信息
- 通过map条件查询用户信息
- 查询所有数据
- 自定义功能
- 通用Service
- IService
- 创建Service接口和实现类
- 测试查询记录数
- 测试批量插入
# 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：
代码语言：javascript复制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);
}# 插入
代码语言：javascript复制 @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());
}# 结果
代码语言：javascript复制...
==> 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
代码语言：javascript复制 @Test
public void testDelete(){
//通过id删除用户信息
int result = userMapper.deleteById(1514558344269680641L);
System.out.println("result:" result);
}# 结果
代码语言：javascript复制...
==> 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# 通过id批量删除记录
代码语言：javascript复制 @Test
public void testDeleteBatchIds(){
List<Long> list = Arrays.asList(1L, 2L, 3L);
int result = userMapper.deleteBatchIds(list);
System.out.println("result:" result);
}# 结果
代码语言：javascript复制...
==> 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# 通过map条件删除记录
代码语言：javascript复制 @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);
}# 结果
代码语言：javascript复制...
==> 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# 修改
# 通过Id修改记录
代码语言：javascript复制 @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);
}# 结果
代码语言：javascript复制...
==> 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# 查询
# 根据id查询用户信息
代码语言：javascript复制 @Test
public void testSelectById(){
//通过Id查询用户信息
User user = userMapper.selectById(1L);
System.out.println(user);
}# 结果
代码语言：javascript复制...
==> 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# 根据多个id查询多个用户信息
代码语言：javascript复制 @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);
}# 结果
代码语言：javascript复制...
=> 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# 通过map条件查询用户信息
代码语言：javascript复制 @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);
}# 结果
代码语言：javascript复制...
==> 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# 查询所有数据
代码语言：javascript复制 @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);
}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
代码语言：javascript复制...
==> 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# 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);
}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># 测试
代码语言：javascript复制 @Test
public void selectMapById(){
Map<String, Object> map = userMapper.selectMapById(1L);
System.out.println(map);
}# 结果
代码语言：javascript复制...
==> 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# 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-接�% 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
代码语言：javascript复制/**
* UserService继承IService模板提供的基础功能
*/
public interface UserService extends IService<User> {
}/**
* 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 {
}# 测试查询记录数
代码语言：javascript复制@SpringBootTest
public class MyBatisPlusServiceTest {
@Autowired
private UserService userService;
@Test
public void testGetCount(){
long count = userService.count();
System.out.println("总记录数:" count);
}
}# 结果
代码语言：javascript复制...
==> 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# 测试批量插入
代码语言：javascript复制 @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");
}# 结果
代码语言：javascript复制...
==> 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
