Object Suppliers

Mapping to destination classes without a no arg constructor.

Due to the fact that ShapeShift uses reflection behind the scenes, destination classes need a no arg constructor. But in some cases you have no control over the destination classes and cannot modify them to add a no arg constructor. This is where Object Suppliers comes into play, you can register object suppliers to the ShapeShift instance to add your own logic for instance generation.
​Instance Mapping is another solution for the no arg constructor issue. The advantage of Object Suppliers is that they also work when mapping classes containing subclasses while Instance Mapping only solves the issue for the top level class instance.
We have two classes, the source class SimpleEntity and the destination class SimpleEntityDisplay. 
Kotlin
Java
@DefaultMappingTarget(SimpleEntityDisplay::class)
data class SimpleEntity(
    @MappedField
    val name: String,
    @MappedField
    val description: String,
    val privateData: String
)
@DefaultMappingTarget(SimpleEntityDisplay.class)
public class SimpleEntity {
    @MappedField
    private String name;
    @MappedField
    private String description;
    private String privateData;
    // Getters and Setters...
}
The destination class does not have a no arg constructor.
Kotlin
Java
data class SimpleEntityDisplay(
    val name: String,
    val description: String
)
public class SimpleEntityDisplay {
    private String name;
    private String description;
​
    public SimpleEntityDisplay(String name, String description) {
        this.name = name;
        this.description = description;
    }
    // Getters and Setters...
}
To solve this issue we need to either use instance mapping or add an object supplier for the class.
Adding Object Suppliers
Adding object suppliers is available through the ShapeShiftBuilder class. Object suppliers can be added inline or as a separate class.
Class Object Suppliers
To create an object supplier class implement the Supplier interface.
Kotlin
Java
class SimpleEntityDisplaySupplier : Supplier<SimpleEntityDisplay> {
    override fun get(): SimpleEntityDisplay {
        return SimpleEntityDisplay("", "")
    }
}
public class SimpleEntityDisplaySupplier implements Supplier<SimpleEntityDisplay> {
    @Override
    public SimpleEntityDisplay get() {
        return new SimpleEntityDisplay("", "");
    }
}
And register it to the ShapeShift instance.
Kotlin
Java
val shapeShift = ShapeShiftBuilder()
    .withObjectSupplier(SimpleEntityDisplaySupplier())
    .build()
ShapeShift shapeShift = new ShapeShiftBuilder()
        .withObjectSupplier(new SimpleEntityDisplaySupplier(), SimpleEntityDisplay.class)
        .build();
Inline Object Suppliers
It is also possible to add the object supplier logic inline.
Kotlin
Java
val shapeShift = ShapeShiftBuilder()
    .withObjectSupplier { SimpleEntityDisplay("", "") }
    .build()
ShapeShift shapeShift = new ShapeShiftBuilder()
        .withObjectSupplier(() -> new SimpleEntityDisplay("", ""), SimpleEntityDisplay.class)
        .build();
Mapping with Object Suppliers
Now that we added an object supplier for the SimpleEntityDisplay class we can map to it as if it has a no arg constructor.
Kotlin
Java
val simpleEntity = SimpleEntity("test", "test description", "private data")
val simpleEntityDisplay = SimpleEntityDisplay("", "")
val result = shapeShift.map<SimpleEntityDisplay>(simpleEntity)
SimpleEntity simpleEntity = new SimpleEntity();
simpleEntity.setName("test");
simpleEntity.setDescription("test description");
simpleEntity.setPrivateData("private data");
SimpleEntityDisplay result = shapeShift.map(simpleEntity, SimpleEntityDisplay.class);

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Last modified 6mo ago