Have you ever had the issue of trying to do a deep nested mapping using Dozer, but you keep running into issues because the destination object doesn't have a set method for the property you need to populate?
We see this a lot when dealing with generated JAX-WS code. The JAXB classes generated from the schema typically do not create set methods for collections. So, if you are trying to create a Dozer mapping to map from the JAX-WS/JAXB generated code to and from your application domain classes, you can run into some issues if you start trying to do deep mappings.
Here are the classes I want to populate via Dozer (made up for an example... all in package com.barry.to). Starting with the first one and going down each class contains the class below it. Usually in a List.
public class StartDestObject {
private HaveNestedListNoSetter haveNestedListNoSetter;
public HaveNestedListNoSetter getHaveNestedListNoSetter() {
return haveNestedListNoSetter;
}
public void setHaveNestedListNoSetter(HaveNestedListNoSetter haveNestedListNoSetter) {
this.haveNestedListNoSetter = haveNestedListNoSetter;
}
}
public class HaveNestedListNoSetter {
private List<HaveListNoSetter> haveListNoSetterList = new ArrayList<HaveListNoSetter>();
public List<HaveListNoSetter> getHaveListNoSetterList() {
return haveListNoSetterList;
}
}
public class HaveListNoSetter {
private List<Thing> things = new ArrayList<Thing>();
public List<Thing> getThings() {
return things;
}
}
public class Thing {
private String name;
private String value;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
Notice that none of my classes that contain collections have any set methods for the List.
So, the idea is that I want to map a much simpler object into this object tree... Here's my much simpler object structure:
package com.barry.from;
import java.util.List;
public class ItemHolder {
private List<Item> items;
public List<Item> getItems() {
return items;
}
public void setItems(List<Item> items) {
this.items = items;
}
}
public class Item {
private String itemName;
private String itemValue;
public Item getItem(){
return this;
}
public String getItemName() {
return itemName;
}
public void setItemName(String name) {
this.itemName = name;
}
public String getItemValue() {
return itemValue;
}
public void setItemValue(String value) {
this.itemValue = value;
}
}
Here's my test to validate it's working:
public class DozerTest {
Mapper mapper;
Item item = new Item();
@Before
public void setup(){
List<String> files = new ArrayList<String>();
files.add("dozer-bean-mappings.xml");
mapper = new DozerBeanMapper(files);
item = new Item();
item.setItemName("gear");
item.setItemValue("Value");
}
@Test
public void testEvenMoreNestedMapping(){
ItemHolder itemHolder = new ItemHolder();
itemHolder.setItems(new ArrayList<Item>());
itemHolder.getItems().add(item);
StartDestObject startDestObject = mapper.map(itemHolder, StartDestObject.class);
assertNotNull(startDestObject);
assertEquals(item.getItemName(), startDestObject.getHaveNestedListNoSetter().getHaveListNoSetterList().get(0).getThings().get(0).getName());
assertEquals(item.getItemValue(), startDestObject.getHaveNestedListNoSetter().getHaveListNoSetterList().get(0).getThings().get(0).getValue());
}
I'm creating a single Item instance and then set that in the ItemHolder's list. Then I want to map that Item instance into the Thing class that is deeply nested down at the bottom of my StartDestObject tree.
The trick to allow this deep mapping to work with nested collections that have no set methods is to Not do a deep mapping. Instead, you break the mappings up into smaller chunks. You create a mapping that goes from the ItemHolder's item to the StartDestObject's haveNestedListNoSetter property. That gets us to the first step. Then Dozer would try to figure out how to map from Item to HaveNestedListNoSetter class. So, you create a mapping for this which actually just passes the Item (via "this") onto the first item in the HaveNestedListNoSetter's list. Then you just keep this pattern up, utilizing the "this" to keep passing the Item instance along and then use the is-accessible="true" attribute to access the lists with no set method.
If you're not following my description, here's the dozer mapping to make it all work:
<?xml version="1.0" encoding="UTF-8"?>
<mappings xmlns="http://dozer.sourceforge.net"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://dozer.sourceforge.net
http://dozer.sourceforge.net/schema/beanmapping.xsd">
<configuration>
<stop-on-errors>true</stop-on-errors>
<wildcard>true</wildcard>
</configuration>
<mapping>
<class-a>com.barry.from.ItemHolder</class-a>
<class-b>com.barry.to.StartDestObject</class-b>
<field>
<a>items[0]</a>
<b>haveNestedListNoSetter</b>
<a-hint>com.barry.from.Item</a-hint>
</field>
</mapping>
<mapping>
<class-a>com.barry.from.Item</class-a>
<class-b>com.barry.to.HaveNestedListNoSetter</class-b>
<field>
<a>this</a>
<b is-accessible="true">haveListNoSetterList[0]</b>
<a-hint>com.barry.from.Item</a-hint>
<b-hint>com.barry.to.HaveListNoSetter</b-hint>
</field>
</mapping>
<mapping>
<class-a>com.barry.from.Item</class-a>
<class-b>com.barry.to.HaveListNoSetter</class-b>
<field>
<a>this</a>
<b is-accessible="true">things[0]</b>
<b-hint>com.barry.to.Thing</b-hint>
</field>
</mapping>
<mapping>
<class-a>com.barry.from.Item</class-a>
<class-b>com.barry.to.Thing</class-b>
<field>
<a>itemName</a>
<b>name</b>
</field>
<field>
<a>itemValue</a>
<b>value</b>
</field>
</mapping>
</mappings>
This may make for more mappings, but I don't know of a better solution without creating custom mapping classes or adding setters to the generated code (which sometimes you don't have access to).
If this isn't perfectly clear or you have a better way, please post in the comments.
Thanks!
