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BaseMapper Interface

The generic BaseMapper interface provides a set of predefined database operations that work with Object Mapping metadata to perform CRUD — no SQL required.

Highlights
  • Zero-SQL development: just define entity mappings to get a full set of CRUD methods — insert, update, delete, selectById, etc.
  • Built-in sample query listBySample: pass an entity object and non-null properties automatically become equality conditions.
  • Built-in paginated query pageBySample: auto-calculates total records and total pages.
  • Built-in batch operations: selectByIds for batch primary-key lookup, insert(List) for batch insert.
  • Switch to the Fluent API via mapper.query() for complex conditional queries.
  • Can be combined with the Declarative API — mix predefined methods and custom SQL in the same interface.

Declare Entity Class​

Establish mapping with @Table and @Column annotations
@Table("users")
public class User {
    @Column(name = "id", primary = true, keyType = KeyTypeEnum.Auto)
    private Long id;
    @Column("name")
    private String name;
    @Column("age")
    private Integer age;
    @Column("email")
    private String email;
    ...
}

Create BaseMapper​

Create via Session
Configuration config = new Configuration();
Session session = config.newSession(dataSource);
BaseMapper<User> mapper = session.createBaseMapper(User.class);

CRUD​

Basic CRUD operations
// Insert one row
User user = ...
int result = mapper.insert(user);

// Insert multiple rows
int result = mapper.insert(Arrays.asList(user1, user2));

// Query by primary key
User loaded = mapper.selectById(1);

// Batch primary key query
List<User> users = mapper.selectByIds(Arrays.asList(1, 2, 3));

// Update by primary key
user.setAge(30);
int result = mapper.update(user);

// Delete by primary key
int result = mapper.deleteById(1);

Sample Query and Pagination​

Conditional queries and pagination via sample object
// Sample query: non-null properties become equality conditions
User sample = new User();
sample.setAge(30);
List<User> result = mapper.listBySample(sample);

// Count query
int count = mapper.countBySample(sample);

// Paginated query
Page pageInfo = mapper.pageInitBySample(sample, 0, 20); // page number starts at 0
PageResult<User> result = mapper.pageBySample(sample, pageInfo);

Switch to Fluent API​

Get a builder directly for complex conditions
List<User> result = mapper.query()
                          .like(User::getName, "A%")
                          .ge(User::getAge, 20)
                          .queryForList();
For more details, see: