MyBatis Plus (MP for short) is a MyBatis enhancement tool designed to simplify development and improve efficiency. It provides many convenient features, one of which isIServiceinterface.IServiceThe interface is a service layer interface provided by MyBatis Plus, encapsulating commonly used CRUD operations, allowing developers to perform database operations more conveniently. This article will explain in detailIServiceInterfaces include its basic concepts, common methods and practical application scenarios.
1. Basic concepts
IServiceThe interface is a service layer interface provided by MyBatis Plus, which defines a series of commonly used CRUD operation methods. By implementingIServiceInterfaces can quickly build service layers and simplify development processes.
1.1 Interface definition
IServiceThe interface is defined as follows:
public interface IService<T> {
// Insert a record (select field, policy insertion) boolean save(T entity);
// Insert (batch) boolean saveBatch(Collection<T> entityList);
// Insert (batch) boolean saveBatch(Collection<T> entityList, int batchSize);
// Delete by ID boolean removeById(Serializable id);
// Delete according to entity (ID) boolean removeById(T entity);
// Delete the record according to the columnMap condition boolean removeByMap(Map<String, Object> columnMap);
// Delete the record according to entity conditions boolean remove(Wrapper<T> queryWrapper);
// Delete (batch deletion according to ID) boolean removeByIds(Collection<? extends Serializable> idList);
// Select Modify according to ID boolean updateById(T entity);
// Update records according to whereEntity conditions boolean update(T entity, Wrapper<T> updateWrapper);
// Query by ID T getById(Serializable id);
// Query (batch query based on ID) List<T> listByIds(Collection<? extends Serializable> idList);
// Query (according to columnMap conditions) List<T> listByMap(Map<String, Object> columnMap);
// Query a record according to entity conditions T getOne(Wrapper<T> queryWrapper);
// Query all records according to Wrapper conditions List<T> list(Wrapper<T> queryWrapper);
// Query all List<T> list();
// Query the total number of records int count();
// Query the total number of records int count(Wrapper<T> queryWrapper);
// Query all lists List<Map<String, Object>> listMaps(Wrapper<T> queryWrapper);
// Query all lists List<Map<String, Object>> listMaps();
// Query all records List<Object> listObjs();
// Query all records <V> List<V> listObjs(Function<? super Object, V> mapper);
// Query all records according to Wrapper conditions List<Object> listObjs(Wrapper<T> queryWrapper);
// Query all records according to Wrapper conditions <V> List<V> listObjs(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);
// Unconditional pagination query IPage<T> page(IPage<T> page);
// Conditional pagination query IPage<T> page(IPage<T> page, Wrapper<T> queryWrapper);
// Unconditional pagination query IPage<Map<String, Object>> pageMaps(IPage<T> page);
// Conditional pagination query IPage<Map<String, Object>> pageMaps(IPage<T> page, Wrapper<T> queryWrapper);
}
1.2 Implementation Class
For useIServiceInterfaces usually require creating an implementation class, inheritingServiceImplclass and implementIServiceinterface.ServiceImplClass is a default implementation class provided by MyBatis Plus, encapsulating commonly used CRUD operations.
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IService<User> {
// Custom method}
In the above code,UserServiceImplInheritedServiceImplclass and implementedIService<User>interface.ServiceImplThe constructor of the class needs to be passed into the Mapper interface and entity class.
2. Common methods
2.1 Insert operation
- save: Insert a record (select field, policy insertion)
- saveBatch: Insert (batch)
User user = new User();
("John");
(25);
(user);
List<User> userList = new ArrayList<>();
(new User("John", 25, "john@"));
(new User("Jane", 30, "jane@"));
(userList);
2.2 Delete operation
- removeById: Delete according to ID
- removeByMap: Delete according to columnMap conditions
- remove: Delete according to entity conditions
- removeByIds: Batch deletion according to ID
(1);
Map<String, Object> columnMap = new HashMap<>();
("age", 25);
(columnMap);
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
("age", 25);
(queryWrapper);
List<Integer> idList = (1, 2, 3);
(idList);
2.3 Update operation
- updateById: Updated by ID
- update: Updated according to whereEntity conditions
User user = new User();
(1);
("John Doe");
(26);
(user);
User user = new User();
(1);
QueryWrapper<User> updateWrapper = new QueryWrapper<>();
("age", 25);
(user, updateWrapper);
2.4 Query operation
- getById: Query based on ID
- listByIds: Batch query based on ID
- listByMap: Query according to columnMap conditions
- getOne: Query a record according to entity conditions
- list: Query all records according to Wrapper conditions
- list: Query all
- count: Query the total number of records
- page: Unconditional pagination query
- page: Conditional pagination query
User user = (1);
List<Integer> idList = (1, 2, 3);
List<User> userList = (idList);
Map<String, Object> columnMap = new HashMap<>();
("age", 25);
List<User> userList = (columnMap);
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
("age", 25);
User user = (queryWrapper);
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
("age", 25);
List<User> userList = (queryWrapper);
List<User> userList = ();
int count = ();
Page<User> page = new Page<>(1, 10);
IPage<User> userPage = (page);
Page<User> page = new Page<>(1, 10);
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
("age", 25);
IPage<User> userPage = (page, queryWrapper);
3. Practical application scenarios
3.1 User Management
Suppose we have a user management system that needs to add, delete, modify and check the users. passIServiceInterface, these functions can be easily implemented.
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IService<User> {
// Custom method public User getUserByName(String name) {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
("name", name);
return getOne(queryWrapper);
}
}
In the above code, we define a custom methodgetUserByName, query user information based on user name.
3.2 Order Management
Suppose we have an order management system that requires adding, deleting, modifying and checking orders. passIServiceInterface, these functions can be easily implemented.
@Service
public class OrderServiceImpl extends ServiceImpl<OrderMapper, Order> implements IService<Order> {
// Custom method public List<Order> getOrdersByUserId(int userId) {
QueryWrapper<Order> queryWrapper = new QueryWrapper<>();
("user_id", userId);
return list(queryWrapper);
}
}
In the above code, we define a custom methodgetOrdersByUserId, query order information based on user ID.
4. Summary
MyBatis PlusIServiceThe interface provides a series of commonly used CRUD operation methods, allowing developers to perform database operations more conveniently. By implementingIServiceInterface and inheritServiceImplclass, which can quickly build a service layer and simplify the development process. In practical applications, combining custom methods can further improve development efficiency and code maintainability.
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