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## How to work with wrapper elements around collections

Intended Audience
Prerequisites
Basic concept
Java entities
Required XML output and XML schema
Mapping file

## Intended Audience

How to work with wrapper elements around collections.

This document helps people to get familiar with the basic concepts and shows an example.

## Prerequisites

None.

## Basic concept

When you have a class that holds a collection of objects of the same type, and you want to wrap the XML produced for the collection members with an additional XML artefact, then read on.

## Java entities

For example, assume you have the following Java class `Foo`:

    package com.example;
    import java.util.Collection;

    public class Foo {
        private String name;
        private Collection children;

        public Foo(){}
        public Foo(String name){
            setName(name);
        }
        public Collection getChildren() {
            return children;
        }
        public void setChildren(Collection children) {
            this.children = children;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
    }

## Required XML output and XML schema

and you want to have Castor generate XML which looks like:

    <foo:foo xmlns:foo="http://example.com/foo" name="foo">
        <foo:children>
            <foo:foo name="foo1" />
            <foo:foo name="foo2" />
        </foo:children>
    </foo:foo>

where the structure of the output is defined by the following XML schema:

    <?xml version="1.0" encoding="UTF-8"?>
    <schema xmlns="http://www.w3.org/2001/XMLSchema"
        targetNamespace="http://example.com/foo"
        xmlns:tns="http://example.com/foo" elementFormDefault="qualified">
        <complexType name="fooType">
            <sequence>
                <element name="children" minOccurs="0">
                    <complexType>
                        <sequence>
                            <element name="foo" type="tns:fooType"
                                maxOccurs="unbounded">
                            </element>
                        </sequence>
                    </complexType>
                </element>
            </sequence>
            <attribute name="name"></attribute>
        </complexType>
    </schema>

## Mapping file

then you would use a mapping like where the `location` attribute on the field mapping for `children` defines the wrapper XML artifact to be used:

    <?xml version="1.0"?>
    <!DOCTYPE mapping PUBLIC "-//EXOLAB/Castor Mapping DTD Version 1.0//EN"
                             "http://castor.org/mapping.dtd">
    <mapping>
        <class name="com.example.Foo" auto-complete="false">
            <map-to xml="foo" ns-uri="http://example.com/foo" ns-prefix="foo" />
            <field name="name" type="java.lang.String">
                <bind-xml name="name" node="attribute" />
            </field>
            <field name="children" collection="collection" type="com.example.Foo">
                <bind-xml name="foo" location="children" />
            </field>
        </class>
    </mapping>

<notice> Copyright © 1999-2005 ExoLab Group, Intalio Inc., and Contributors. All rights reserved. </notice>
<notice> Java, EJB, JDBC, JNDI, JTA, Sun, Sun Microsystems are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and in other countries. XML, XML Schema, XSLT and related standards are trademarks or registered trademarks of MIT, INRIA, Keio or others, and a product of the World Wide Web Consortium. All other product names mentioned herein are trademarks of their respective owners. </notice>