Sax parser non validating feelings, choosing the parser implementation
So now you know that a DTD is a requirement for a valid document. After you have learned more about sax parser non validating feelings, you will see how to use XML Schema to validate complex documents that do use them. These are called "Positive Tests" because they ensure that sax parser non validating feelings processor just "does the right thing" without reporting any problems.
There is one kind of error, though, that is generated by the nonvalidating parser you have been working with so far. However, "XML Schema" presents us with a terminology challenge.
The browsable version is Echo You'll do that next. Employees can also optionally have email addresses and URLs. That is a non-trappable error, since the program is not expected to be able to recover from it.
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Such an error might occur if the factory could not find the ognie idirsholas online dating needed to create the parser class not found errorwas not permitted to access it illegal access exceptionor could not instantiate it instantiation error.
Diagnostics for failed tests are presented in italics, with a cherry colored background, to highlight the result. You will see the following error.
The best way to demonstrate the different types of validation is to modify the code of the XML file being parsed, as well as the associated schema and DTDs, to break the processing and get the application to generate exceptions.
This may be done in the case of parsers with severe bugs which completely prevented handling the test case, typically because the parser seems to "hang" by entering an infinite loop.
The following code uses the constants defined above to specify the W3C's XML Schema language as the one to use if the -xsd option is specified when the program is started.
XML Validation Using SAX
You've seen that the parser generates exceptions for fatal errors. To take over error handling, you supply the SAX parser with an ErrorHandlerwhich defines methods for handling fatal errors, nonfatal errors, and warnings.
To be notified of validation errors in an XML document, the parser factory must be configured to create a validating parser, as shown in the preceeding section.
This schema defines what kinds of information are required about each employee in order for an XML document associated with the schema to be considered valid. When the parser delivers the exception back to the code that invoked the parser, it makes sense to use the original exception to generate the stack trace.
Diagnostics with parenthesized comments indicate the reporting path: Again, do not forget to save the file, but leave it open.
Worker One now looks like this: When validating, an error results. Configuring the Factory The SAXParserFactory needs to be set up such that it uses a validating parser instead of the default non-validating parser.
Java Mapping Concepts (DOM and SAX) - Process Integration - SCN Wiki
Because that tag is not defined in the DTD, the attempt to validate the document fails. Next, you'll learn more about errors and warnings and find out how to supply an error handler to process them.
If a combination is not supported by a particular implementation, it is required to generate a factory configuration error. That code is reproduced here as a reminder: Associating a Document with a Schema Now that the program is ready to validate the data using an XML Schema definition, it is only necessary to ensure that the XML document is associated with one.
Error Handling in the Validating Parser It is important to recognize that the only reason an exception is thrown when the file fails validation is as a result of the error-handling code you entered in the early stages of this tutorial.
Cannot find the declaration of element 'personnel'.
Such errors are primarily well-formedness errors, such as the violation of XML 1. Admittedly, there are quite a few error handlers here. The document must be associated with a schema. If you are using a different parser, the error message is likely to be somewhat different. The file you'll create in this exercise is slideSampleBad2.
The appropriate properties must be set on the SAX parser. The SAX parser delivers a SAXParseException to each of these methods, so generating an exception when an error occurs is as simple as throwing it back.
Using the Validating Parser
In addition, the following must be true: Also, note that duplicate definitions of elements always produce a fatal error when validating, as you saw earlier. Here, you configure the factory so that it will produce a validating parser when newSAXParser is invoked.
To configure it to return a namespace-aware parser, you can also use setNamespaceAware true. The following code from the SAXLocalNameCount example's main method shows how to configure the factory so that it implements the validating parser.
The declaration of the email element is now as follows. Such declarations are ignored. Setting the SAX Parser Properties It's helpful to start by defining the constants you'll use when setting the properties: However, in this case it does not make sense to have more than one title in a section of a document.
The output shown here is contained in Echo Our DOM Document implementation class, DocumentImpl class now implements DocumentTraversal, which supplies the factory methods to create the iterators and treewalkers.
To fix the problem, add a question mark to make title an optional element: If DTD validation is activated, the structure of the XML file being parsed will be checked against the structure provided in play. Add the code highlighted below to generate a message when a warning occurs: Activating validation allows the application to tell whether the XML document contains the right tags or whether those tags are in the right sequence.
To be notified of validation errors in an XML document, the parser factory must be configured to create a validating parser, as shown in the preceding section. The code for the program you'll create in this exercise is in Echo The output looks like this: If so, it generates a stack trace originating from where that exception occurred to make it easier to pinpoint the code responsible for the error.
This section examines the validating parser to find out what happens when you use it to parse the sample program. The diagnostic provided by the processor must correspond to the description of the test provided; if the processor does not report the matching error, the seeming "pass" is in fact an error of a type the test harness could not detect or report.
For example, by examining the schema definition, you can see that each person element requires a name, and that each person's name must comprise a family name and a given name.