Nested fields and multiple targets annotations mapping.
In this guide, we'll review mapping nested fields, as well as defining mappings to multiple targets.
Classes
We start by defining our source and destination classes, and additionally a child class which will be used by both.
Starting with the child class:
data class AdvancedChildEntity(
val childName: String
)
public class AdvancedChildEntity {
private String childName;
public String getChildName() {
return childName;
}
public void setChildName(String childName) {
this.childName = childName;
}
}
Followed by our source class:
data class AdvancedEntity(
val name: String,
val firstChild: AdvancedChildEntity,
val secondChild: AdvancedChildEntity
)
public class AdvancedEntity {
private String name;
private AdvancedChildEntity firstChild;
private AdvancedChildEntity secondChild;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public AdvancedChildEntity getFirstChild() {
return firstChild;
}
public void setFirstChild(AdvancedChildEntity firstChild) {
this.firstChild = firstChild;
}
public AdvancedChildEntity getSecondChild() {
return secondChild;
}
public void setSecondChild(AdvancedChildEntity secondChild) {
this.secondChild = secondChild;
}
}
In this example, we will have two separate destination classes, AdvancedEntityDisplay and ReducedAdvancedEntityDisplay.
data class AdvancedEntityDisplay(
val name: String = "",
val firstChildName: String = "",
val secondChildName: String = ""
)
public class AdvancedEntityDisplay {
private String name = "";
private String firstChildName = "";
private String secondChildName = "";
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getFirstChildName() {
return firstChildName;
}
public void setFirstChildName(String firstChildName) {
this.firstChildName = firstChildName;
}
public String getSecondChildName() {
return secondChildName;
}
public void setSecondChildName(String secondChildName) {
this.secondChildName = secondChildName;
}
}
data class ReducedAdvancedEntityDisplay(
val name: String = "",
val firstChildName: String = ""
)
public class ReducedAdvancedEntityDisplay {
private String name = "";
private String firstChildName = "";
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getFirstChildName() {
return firstChildName;
}
public void setFirstChildName(String firstChildName) {
this.firstChildName = firstChildName;
}
}
Annotations
Let's start adding annotations to the source class. We will define a @DefaultMappingTarget annotation on the AdvancedEntity class, which will indicate that all fields annotated with @MappedField that do not specify a target should be mapped to the AdvancedEntityDisplay class. Seeing as we have two destinations in this example, we will have to define some of the mapping targets manually.
We'll start by defining a simple @MappedField on the name field for both targets. We will also define a @MappedField annotation on the firstChild field, which will indicate that it should be mapped to the firstChildName field on the AdvancedEntityDisplay class, and repeat the same annotation for secondChild. To achieve this we will use the mapFrom and mapTo parameters. Notice that by doing this, we have extracted the name field from the AdvancedEntity class, and mapped it directly to the *ChildName field on the AdvancedEntityDisplay class. The ReducedAdvancedEntityDisplay class will have the same mapping as the AdvancedEntityDisplay class, but will omit the secondChildName field;
@DefaultMappingTarget(AdvancedEntityDisplay::class)
data class AdvancedEntity(
@MappedField
@MappedField(target = ReducedAdvancedEntityDisplay::class)
val name: String,
@MappedField(mapFrom = "childName", mapTo = "firstChildName")
@MappedField(target = ReducedAdvancedEntityDisplay::class, mapFrom = "childName", mapTo = "firstChildName")
val firstChild: AdvancedChildEntity,
@MappedField(mapFrom = "childName", mapTo = "secondChildName")
val secondChild: AdvancedChildEntity
)
