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Designing XML Based Applications

  When you want to implement a flexible mapping design where each 

component may manipulate a common document in the most suitable manner 

for itself.

  When requirements might evolve (such as a new schema to be supported or a 

new version of the same schema) to where they would necessitate changes to 

the XML processing implementation. Generally, you do not want to alter the 

application logic to accommodate these XML processing changes. Addition 

ally, since several XML processing APIs (SAX, DOM, XSLT, JAXB technol 

ogy, and so forth) may be relevant, you want to allow for subsequent changes 

to later address such issues as performance and integration. 

  When different developer skill sets exist. For example, you may want the busi 

ness domain and XML processing experts to work independently. Or, you may 

want to leverage particular skill sets within XML processing techniques. 

Figure 4.12 and Code Example 4.9 give an example of a supplier Web service

endpoint using an XML document editor to preprocess incoming purchase order

documents.

public class SupplierOrderXDE extends 

XMLDocumentEditor.DefaultXDE {

public static final String DEFAULT_ENCODING = "UTF 8";

private Source source = null;

private String orderId = null;

public SupplierOrderXDE(boolean validating, ...) {

// Initialize XML processing logic

}

// Sets the document to be processed

public void setDocument(Source source) throws ... {

this.source = source;

}

// Invokes XML processing logic to validate the source document,

// extract its orderId, transform it into a different format,

// and copy the resulting document into the Result object

public void copyDocument(Result result) throws ... {

orderId = null;

// XML processing...

}