ObjectMapping

Use either <resultMap> or <entity> to map query results:

<resultMap>: map SQL result sets.
<entity>: map a concrete table.

How to choose between resultMap and entity?

For the same table with different query shapes, entity is good when columns all come from one table; resultMap when columns span multiple tables.
Using the Fluent API requires entity or object-mapping annotations.
If the SELECT uses aliases, functions, CASE, or columns from multiple tables, resultMap is safer.

entity tag

定义和使用 resultMap
<entity id="user_resultMap" table="users" type="com.example.dto.UserBean">
    <id column="id" property="id"/>
    <mapping column="name" property="name"/>
    <mapping column="age" property="age"/>
    <mapping column="create_time" property="createTime"/>
</entity>

<select id="queryById" resultMap="user_resultMap">
    select
        id, name, age, create_time
    from
        users
    where
        id = #{id}
</select>

Attributes

entity tag*

Property	Description
id	可选 Identifier; if empty, `type` is used.
catalog	可选 Catalog of the mapped table.
schema	可选 Schema of the mapped table.
table	可选 Table name.
type	必选 Fully qualified Java type to map to.
caseInsensitive	可选 Case-insensitive mapping for column/property names. Default `true`.
autoMapping	可选 Whether to perform auto-mapping. Default `true`.
mapUnderscoreToCamelCase	可选 With auto-mapping, convert camelCase property names to snake_case columns (e.g., `createTime` → `create_time`). Default `false`.
useDelimited	可选 Force quoting/delimiters on table/column names when generating SQL. Default `false`.
character-set	可选 Table character set (available via TableDescription).
collation	可选 Table collation (TableDescription).
comment	可选 Table comment (TableDescription).
other	可选 Other table options (TableDescription).
ddlAuto	可选 Auto DDL strategy: `none`, `create`, `add`, `update`, `create-drop` (auto DDL not yet supported).

id tag and mapping tag

Property	Description
column	必选 Column name in the result set.
property	必选 Property name in the target type.
javaType	可选 Usually inferred; specify when the property is abstract or an interface.
jdbcType	可选 Overrides the default Java↔JDBC mapping.
typeHandler	可选 Override the type handler to use.
keyType	可选 For Fluent API only. Key generation strategy when the value is null. See key generator.
insert	可选 For Fluent API only. Whether it participates in insert. See write policy.
update	可选 For Fluent API only. Whether it participates in update. See write policy.
selectTemplate	可选 For Fluent API only. Column expression when used in SELECT. Default empty (column name). See templates.
insertTemplate	可选 For Fluent API only. Argument expression for INSERT. Default `?`. See templates.
setValueTemplate	可选 For Fluent API only. Argument expression in UPDATE SET. Default `?`. See templates.
whereColTemplate	可选 For Fluent API only. Column expression in WHERE for update/delete. Default empty (column name). See templates.
whereValueTemplate	可选 For Fluent API only. Argument expression in WHERE for update/delete. Default `?`. See templates.
orderByColTemplate	可选 For Fluent API only. Column expression in ORDER BY. Default empty (column name). See templates.
sqlType	可选 Column data type (TableDescription).
length	可选 Column length (TableDescription).
precision	可选 Numeric precision (TableDescription).
scale	可选 Numeric scale (TableDescription).
character-set	可选 Column character set (TableDescription).
collation	可选 Column collation (TableDescription).
nullable	可选 Whether the column allows NULL; for <id> this is always true and cannot be set (TableDescription).
default	可选 Column default value (TableDescription).
comment	可选 Column comment (TableDescription).
other	可选 Other column options (TableDescription).

entity tag​

Attributes​

entity tag

Attributes