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## How to use a binding file with source generation Intended Audience Background The Supply Chain XSD Binding file? - IT IS REQUIRED! References ## Intended Audience Anyone who wants to use a binding file with the Castor XML source generator. This document discusses various main concepts in the context of a non-trivial real word example, and intends to help people to get familiar with the basic concepts and discusses some implementation details. The example given describes the steps required to build a binding file that helps users to overcome typical problems related to the use of more complex XML Schemas. ## Background Two companies wish to trade with each other using a Supply Chain messaging system. This system sends and receives Purchase Orders and Order Receipt messages. After many months of discussion they have finally decided upon the structure of the Version 1.0 of their message XSD and both are presently developing solutions for it. One of the companies decides to use Java and Castor XML supprt for (un)marshalling and Castor's code generator to accelerate their development process. ## The Supply Chain XSD
supplyChainV1.0.xsd
    <?xml version="1.0" encoding="UTF-8"?>
    <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
                  elementFormDefault="qualified"
                  attributeFormDefault="unqualified">
        <xs:element name="Data">
          <xs:annotation>
            <xs:documentation>This section contains the supply chain message
    		  data</xs:documentation>
          </xs:annotation>
          <xs:complexType>
            <xs:choice>
              <xs:element name="PurchaseOrder">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="LineItem" type="LineItemType" maxOccurs="unbounded"/>
                  </xs:sequence>
                  <xs:attribute name="OrderNumber" type="xs:string" use="required"/>
                </xs:complexType>
              </xs:element>
              <xs:element name="OrderReceipt">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="LineItem" type="ReceiptLineItemType" maxOccurs="unbounded"/>
                  </xs:sequence>
                  <xs:attribute name="OrderNumber" type="xs:string" use="required"/>
                </xs:complexType>
        	  </xs:element>
        	</xs:choice>
          </xs:complexType>
        </xs:element>
        <xs:complexType name="SkuType">
          <xs:annotation>
            <xs:documentation>Contains Product Identifier</xs:documentation>
          </xs:annotation>
          <xs:sequence>
            <xs:element name="Number" type="xs:integer"/>
            <xs:element name="ID" type="xs:string"/>
          </xs:sequence>
        </xs:complexType>
        <xs:complexType name="ReceiptSkuType">
          <xs:annotation>
            <xs:documentation>Contains Product Identifier</xs:documentation>
          </xs:annotation>
          <xs:complexContent>
            <xs:extension base="SkuType">
              <xs:sequence>
                <xs:element name="InternalID" type="xs:string"/>
              </xs:sequence>
            </xs:extension>
          </xs:complexContent>
        </xs:complexType>
        <xs:complexType name="LineItemType">
          <xs:sequence>
            <xs:element name="Sku" type="SkuType"/>
            <xs:element name="Value" type="xs:double"/>
            <xs:element name="BillingInstructions" type="xs:string"/>
            <xs:element name="DeliveryDate" type="xs:date"/>
            <xs:element name="Number" type="xs:integer"/>
          </xs:sequence>
        </xs:complexType>
        <xs:complexType name="ReceiptLineItemType">
          <xs:sequence>
            <xs:element name="Sku" type="ReceiptSkuType"/>
            <xs:element name="Value" type="xs:double"/>
            <xs:element name="PackingDescription" type="xs:string"/>
            <xs:element name="ShipDate" type="xs:dateTime"/>
            <xs:element name="Number" type="xs:integer"/>
          </xs:sequence>
        </xs:complexType>
    </xs:schema>
## Binding file? - IT IS REQUIRED! If you run the Castor CodeGenerator on the above XSD you end up with the following set of classes. [You also get lots of warning messages with the present 0.99 version.]
    Data.java
    DataDescriptor.java
    LineItem.java
    LineItemDescriptor.java
    LineItemType.java
    LineItemTypeDescriptor.java
    OrderReceipt.java
    OrderReceiptDescriptor.java
    PurchaseOrder.java
    PurchaseOrderDescriptor.java
    ReceiptLineItemType.java
    ReceiptLineItemTypeDescriptor.java
    ReceiptSkuType.java
    ReceiptSkuTypeDescriptor.java
    Sku.java
    SkuDescriptor.java
    SkuType.java
    SkuTypeDescriptor.java
The problem here is that there are two different elements with the same name in different locations in the XSD. This causes a java code generation conflict. Castor uses the element name as the name of the class. So the second class generated for the LineItem definition, which is different than the first, overwrites the first class generated. A binding file is therefore necessary to help the Castor code generator differentiate between these generated classes. [i.e. You can 'bind' an element in the XSD to a differently named class file that you want to generate. Thus keeping different elements seperate]
Tip: | The warning messages for Castor 0.99+ are very usefull in assisting you in your creation of the binding file. For the example the warning messages for the example are; `Warning: A class name generation conflict has occured between element '/Data/OrderReceipt/LineItem' and element '/Data/PurchaseOrder/LineItem'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y Warning: A class name generation conflict has occured between element '/Data/OrderReceipt/LineItem' and element '/Data/PurchaseOrder/LineItem'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y Warning: A class name generation conflict has occured between element '/Data/OrderReceipt/LineItem' and element '/Data/PurchaseOrder/LineItem'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y Warning: A class name generation conflict has occured between element 'complexType:ReceiptLineItemType/Sku' and element 'complexType:LineItemType/Sku'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y Warning: A class name generation conflict has occured between element 'complexType:ReceiptLineItemType/Sku' and element 'complexType:LineItemType/Sku'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y Warning: A class name generation conflict has occured between element 'complexType:ReceiptLineItemType/Sku' and element 'complexType:LineItemType/Sku'. Please use a Binding file to solve this problem.Continue anyway [not recommended] (y|n|?)y`
The following binding file definition will overcome the naming issues for the generated classes.
binding.xml
    <binding xmlns="http://www.castor.org/SourceGenerator/Binding"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:schemaLocation="http://www.castor.org/SourceGenerator/Binding
                    C:\\Castor\\xsd\\binding.xsd"
                defaultBinding="element">

       <elementBinding name="/Data/PurchaseOrder/LineItem">
          <java-class name="PurchaseOrderLineItem"/>
       </elementBinding>

       <elementBinding name="/Data/OrderReceipt/LineItem">
          <java-class name="OrderReceiptLineItem"/>
       </elementBinding>

       <elementBinding name="/complexType:ReceiptLineItemType/Sku">
          <java-class name="OrderReceiptSku"/>
       </elementBinding>

       <elementBinding name="/complexType:LineItemType/Sku">
          <java-class name="PurchaseOrderSku"/>
       </elementBinding>

    </binding>
Things to notice in the above binding.xml file are that the name path used is relative to the root of the XSD NOT the root of the target XML. Also notice that the two complex types have the "complexType:" prefix to identify them, and then the name path relative to the root of the XSD. The new list of generated classes is:
    Data.java
    DataDescriptor.java
    LineItem.java
    LineItemDescriptor.java
    LineItemType.java
    LineItemTypeDescriptor.java
    OrderReceipt.java
    OrderReceiptDescriptor.java
    OrderReceiptLineItem.java
    OrderReceiptLineItemDescriptor.java
    OrderReceiptSku.java
    OrderReceiptSkuDescriptor.java
    PurchaseOrder.java
    PurchaseOrderDescriptor.java
    PurchaseOrderLineItem.java
    PurchaseOrderLineItemDescriptor.java
    PurchaseOrderSku.java
    PurchaseOrderSkuDescriptor.java
    ReceiptLineItemType.java
    ReceiptLineItemTypeDescriptor.java
    ReceiptSkuType.java
    ReceiptSkuTypeDescriptor.java
    Sku.java
    SkuDescriptor.java
    SkuType.java
    SkuTypeDescriptor.java
The developers can now use these generated classes with Castor to (un)marshal the supply chain messages sent by their business partner. ## References
- | Castor Source Generator
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