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Non validating sax parser tutorial

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Validation is a powerful tool. It enables you to quickly check that input is roughly in the form you expect and quickly reject any document that is too far away Non validating sax parser tutorial what your process can handle.

Using the Validating Parser

If there's a problem with the data, it's better to find out earlier than later. Sometimes validation is performed while parsing, sometimes immediately after.

Choosing the Parser Implementation

However, it's usually Non validating sax parser tutorial before any further processing of the input takes place.

This description is painted with broad strokes -- there are exceptions. Until recently, the exact Application Programming Interface API by which programs requested validation varied with the schema language and parser.

Java 5 introduced the javax.

By now, you have done...

This package is also available in Java 1. Among other products, an implementation of this library is included with Xerces 2. SchemaFactorySchemaand Validator. It also makes extensive use of the javax.

The Schema object creates a Validator object. Element 'legalnotice' cannot have character [children], because the type's content type is element-only. You can easily change the schema to validate against, the document to validate, and even the schema language.

However, in all cases, validation follows these five steps:. You can reuse the same validator and the same schema multiple times in series. However, only the schema is thread safe. Validators and schema factories are not. If you validate in multiple threads simultaneously, make sure each one has its own Validator and SchemaFactory objects. Some documents specify the schema they expect to be Non validating sax parser tutorial against, typically using xsi: If you create a schema without specifying a URL, file, or source, then the Java language Non validating sax parser tutorial one that looks in the document being validated to Non validating sax parser tutorial the schema it should use.

However, normally this isn't what you want. Usually the document consumer should choose the schema, not the document producer. Furthermore, this approach works only for XSD. All other schema languages require an explicitly specified Non validating sax parser tutorial location.

SchemaFactory is an abstract factory. The abstract factory design pattern enables this one API to support many different schema languages and object models. A single implementation usually supports only a subset of the numerous languages and models. It's almost identical to Listing 1. The only things that have changed are the location of the schema and the URL Non validating sax parser tutorial identifies the schema language. If you run this program with the stock Sun JDK and no extra libraries, you'll probably see something like this:.

When the schema language isn't recognized, SchemaFactory. This isn't a closed list.

Quickstart

Implementations are free to add other URLs to this list to identify other schema languages. For example, the URL http: Although DTD validation is supported, it isn't accessible through the javax.

The sample program SAXLocalNameCount uses...

However, you can install additional libraries that Non validating sax parser tutorial support for these and other schema languages. The Java programming language isn't limited to a single schema factory.

To Non validating sax parser tutorial support for your own custom schema language and corresponding validator, all you have to do is Non validating sax parser tutorial subclasses of SchemaFactorySchemaand Validator that know how to process your schema language.

Then, install your JAR in one of these four locations. This is useful for adding constraints that Non validating sax parser tutorial more easily checked in a Turing-complete language like Java than in a declarative language like the W3C XML Schema language.

You can define a mini-schema language, write a quick implementation, and plug it into the validation layer. The default response from a schema is to throw a SAXException if there's a problem and do nothing if there isn't.

However, you can provide a SAX ErrorHandler to receive more detailed information about the document's problems. For example, suppose you want to log all validation errors, but you don't want to stop processing when you encounter one. You can install an error handler such as that in Listing Non validating sax parser tutorial. To install this error handler, you create an instance of it and pass that instance to the Validator 's setErrorHandler method:.

Some schemas do more than validate. As well as providing a true-false answer to the Non validating sax parser tutorial of whether a document is valid, they also augment the document with additional information.

For example, they can provide default attribute values. They might also assign types like int or gYear to an element or attribute. The validator can create such type-augmented documents and write them onto a javax.

All you need to do is pass a Result as the second argument to validate. For example, Listing 4 both validates an input document and creates an augmented DOM document from the combination of the input with the schema. This procedure can't transform an arbitrary source into an arbitrary result. It doesn't work at all for stream sources and results.

This technique isn't recommended, though. Putting all the information the document requires in Non validating sax parser tutorial instance is far more reliable than splitting it between the instance and the schema. You might validate, but not everyone will. Elements and attributes are declared to be of type int, Non validating sax parser tutorial, date, duration, person, PhoneNumber, or anything else you can imagine.

The Java Validation API includes a means to report such types, although it's surprisingly independent of the rest of the package. Types are identified by an org. This simple interface, summarized in Listing 5tells you the local name and namespace URI of a type.

You can also tell whether and how a type is derived from another type. Beyond that, understanding the type is Non validating sax parser tutorial to your program. The Java language doesn't tell you what it means or convert the data to a Java type such as double Non validating sax parser tutorial java. Non validating sax parser tutorial, you install this handler in a SAX parser. You also install your own ContentHandler in the ValidatorHandler not the parser ; the ValidatorHandler will forward the augmented events on to your ContentHandler.

The ValidatorHandler makes available a TypeInfoProvider that your ContentHandler can call at any time to find out the type of the current element or one of its attributes. It can also tell you whether an attribute is an ID, and whether the attribute was explicitly specified in the document or defaulted in from the schema. Listing 6 summarizes this class. Listing 7 shows a simple program Non validating sax parser tutorial uses Non validating sax parser tutorial these classes and interfaces to print out the names of all the types of the elements in a document.

As you can see, the DocBook schema assigns most elements anonymous complex types. Obviously, this will vary from one schema to the next. The world would be a poorer place if everyone spoke just one language.

Non validating sax parser tutorial would be unhappy if they had only one programming language to choose from. Different languages suit different tasks better, and some tasks Non validating sax parser tutorial more than one language. XML schemas are no different. You can choose from a plethora of useful schema languages. In Java 5 with javax. Sign in or register to add and subscribe to comments.

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