How to map a map/hashtable of elements
Intended Audience
Prerequisites
Simple Maps
Basic concept
Mapping file
XML output
Nested Maps
References
Intended Audience
Anyone who wants to map a Map/Hashtable of elements.
This document helps people to get familiar with the basic concepts
of mapping and shows an example.
Prerequisites
None.
Simple Maps
Basic concept
Assume you have two classes Items and Item, where an Items instance holds a Map/Hashtable
of Item instances.
public class Items {
private Map itemlist;
public Map getItemlist() {
return itemlist;
}
public void setItemlist(Map itemlist) {
this.itemlist = itemlist;
}
}
public class Item {
private String id;
private String description;
private String supplier;
private String contact;
public String getContact() {
return contact;
}
public void setContact(String contact) {
this.contact = contact;
}
public String getSupplier() {
return supplier;
}
public void setSupplier(String supplier) {
this.supplier = supplier;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
} |
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As shown above, the Items instance has a field 'itemList' to hold a Map
of Item instances.
Mapping file
Here's the mapping file to instruct Castor XML about the relation of those two
classes, Items and Item respectively:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<mapping>
<class name="nl.vodafone.castorbinding.demo.Items">
<map-to xml="Items"/>
<field name="Itemlist" collection="hashtable">
<bind-xml name="MyItem">
<class name="org.exolab.castor.mapping.MapItem">
<field name="key" type="java.lang.String">
<bind-xml name="id" node="attribute"/>
</field>
<field name="value" type="nl.vodafone.castorbinding.demo.Item">
<bind-xml name="Item"/>
</field>
</class>
</bind-xml>
</field>
</class>
<class name="nl.vodafone.castorbinding.demo.Item">
<map-to xml="Item"/>
<field name="Id" type="java.lang.String">
<bind-xml name="id" node="element"/>
</field>
<field name="Description" type="java.lang.String">
<bind-xml name="description" node="element"/>
</field>
<field name="Supplier" type="java.lang.String">
<bind-xml name="supplier" node="element"/>
</field>
<field name="Contact" type="java.lang.String">
<bind-xml name="contact" node="element"/>
</field>
</class>
</mapping> |
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Please note the use of the org.exolab.castor.mapping.MapItem definition within the
<bind-xml> element in above mapping to map the elements contained in the
Map/Hashtable.
XML output
Using the Castor XML marshaller with the mapping file shown above, the XML
generated by Castor XML might look as follows:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Items>
<MyItem id="1">
<Item>
<id>1</id>
<description>desc1</description>
<supplier>supp1</supplier>
<contact>cont1</contact>
</Item>
</MyItem>
<MyItem id="2">
<Item>
<id>2</id>
<description>desc2</description>
<supplier>supp2</supplier>
<contact>cont2</contact>
</Item>
</MyItem>
<MyItem id="3">
<Item>
<id>3</id>
<description>desc3</description>
<supplier>supp3</supplier>
<contact>cont3</contact>
</Item>
</MyItem>
</Items> |
|
Nested Maps
It is equally possible to nest Collections/Arrays within Maps, incl. Maps within
Maps. The following Java class has a member 'map' of type java.util.Map.
public class MapOfArrays {
private Map map;
public Map getMap() {
return this.map;
}
public void setMap(Map map) {
this.map = map;
}
} |
|
The following code shows how this Map instance is filled with
String arrays before marshalling.
this.map.put("key1", new String[] { "key1_value1", "key1_Value2" });
this.map.put("key2", new String[] { "key2_value1", "key2_Value2" }); |
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Based upon the following mapping file, ...
<class name="MapOfArrays">
<field name="map" collection="map">
<bind-xml name="map">
<class name="org.exolab.castor.mapping.MapItem">
<field name="key" type="java.lang.String">
<bind-xml name="string1" node="attribute" />
</field>
<field name="value" collection="array" type="java.lang.String">
<bind-xml name="nested" />
</field>
</class>
</bind-xml>
</field>
</class> |
|
the following XML will be generated during marshalling.
<?xml version="1.0" encoding="UTF-8"?>
<map-of-arrays>
<map string1="key1">
<nested>key1_value1</nested>
<nested>key1_Value2</nested>
</map>
<map string1="key2">
<nested>key2_value1</nested>
<nested>key2_Value2</nested>
</map>
</map-of-arrays> |
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References
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