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Performance Considerations

as much as possible without jeopardizing the application processing and to use 

the most appropriate API to process the document.

  It may be memory intensive. XML processing may require creating large num 

bers of objects, especially when dealing with document object models.

  It may be network intensive. A document may be the aggregation of different 

external entities that during parsing may need to be retrieved across the net 

work. It is important to reduce as much as possible the cost of referencing ex 

ternal entities.

Following are some guidelines for improving performance when processing

XML documents. In particular, these guidelines examine ways of improving the

CPU, memory, and input/output or network consumption. 

4.5.1 Limit Parsing of Incoming XML Documents

In general, it is best to parse incoming XML documents only when the request has

been properly formulated. In the case of a Web service application, if a document is

retrieved as a 

Source

 parameter from a request to an endpoint method, it is best first

to enforce security and validate the meta information that may have been passed as

additional parameters with the request.

In a more generic messaging scenario, when a document is wrapped inside

another document (considered an envelope), and the envelope contains meta

information about security and how to process the inner document, you may apply

the same recommendation: Extract the meta information from the envelope, then

enforce security and validate the meta information before proceeding with the

parsing of the inner document. When implementing a SAX handler and assuming

that the meta information is located at the beginning of the document, if either the

security or the validation of the meta information fails, then the handler can throw

a SAX exception to immediately abort the processing and minimize the overall

impact on performance.

4.5.2 Use the Most Appropriate API

It's important to choose the most appropriate XML processing API for your particu 

lar task. In this section, we look at the different processing models in terms of the

situations in which they perform best and where their performance is limited. 

In general, without considering memory consumption, processing using the

DOM API tends to be slower than processing using the SAX API. This is because