Can MyBatis choose the unique public constructor when multiple constructors exist (e.g., with Lombok @SuperBuilder)?

[chastro3]

I’m using Lombok’s @SuperBuilder together with fluent getters to define immutable and inheritance-friendly entity classes.
For example:

@Getter
@Accessors(fluent = true)
@SuperBuilder(toBuilder = true)
@AllArgsConstructor
public class Question {
    private final Long id;
    private final String content;
    private final Integer type;
}

Lombok generates two constructors:

public Question(Long id, String content, Integer type) { ... } // Normal constructor
protected Question(QuestionBuilder<?, ?> builder) { ... } // Builder constructor

When MyBatis performs constructor-based result mapping,
argNameBasedConstructorAutoMapping is enabled and the class 'xxx' has multiple constructors

Expected Behavior

If an entity defines exactly one public constructor,
it would be helpful if MyBatis could automatically choose that constructor when multiple constructors exist.
This would make constructor-based result mapping compatible with immutable, fluent-style entities often generated by Lombok’s @SuperBuilder.
I’m not using record because I sometimes need inheritance, which records do not support.

[harawata]

Hello @chastro3 ,

I am pretty sure that the error message mentions the solution:

argNameBasedConstructorAutoMapping is enabled and the class 'xxx' has multiple constructors, so @AutomapConstructor must be added to one of the constructors.

I am not familiar with Lombok, but there seems to be an experimental feature to achieve this.

import org.apache.ibatis.annotations.AutomapConstructor;
...
@AllArgsConstructor(onConstructor_ = @__({@AutomapConstructor}))

---

If an entity defines exactly one public constructor, it would be helpful if MyBatis could automatically choose that constructor when multiple constructors exist.

That behavior may be what you want, but not necessarily what other people want.

[chastro3]

Hello,

Yes, this indeed solves the issue. However, in our project structure, the entity module does not depend on MyBatis (it only defines pure data models).
Adding a MyBatis dependency just to use @AutomapConstructor would break the module decoupling and make the design less elegant.

[harawata]

Well, then you may have to use a result map.

With XML:

<resultMap id="userRM" type="xxx.Question">
  <constructor>
    <idArg column="id" javaType="long" />
    <arg column="content" javaType="string" />
    <arg column="type" javaType="int" />
  </constructor>
</resultMap>

With annotation:

@Arg(column = "id", javaType = Long.class, id = true)
@Arg(column = "content", javaType = String.class)
@Arg(column = "type", javaType = Integer.class)
@Select("select ...")
List<Question> getAllQuestions();