Class ValidatorHandler

All Implemented Interfaces:
ContentHandler

public abstract class ValidatorHandler
extends Object
implements ContentHandler

Streaming validator that works on SAX stream.

A ValidatorHandler object is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one ValidatorHandler object is not used from more than one thread at any given time.

ValidatorHandler checks if the SAX events follow the set of constraints described in the associated Schema, and additionally it may modify the SAX events (for example by adding default values, etc.)

ValidatorHandler extends from ContentHandler, but it refines the underlying ContentHandler in the following way:

  1. startElement/endElement events must receive non-null String for uri, localName, and qname, even though SAX allows some of them to be null. Similarly, the user-specified ContentHandler will receive non-null Strings for all three parameters.
  2. Applications must ensure that ValidatorHandler's ContentHandler.startPrefixMapping(String,String) and ContentHandler.endPrefixMapping(String) are invoked properly. Similarly, the user-specified ContentHandler will receive startPrefixMapping/endPrefixMapping events. If the ValidatorHandler introduces additional namespace bindings, the user-specified ContentHandler will receive additional startPrefixMapping/endPrefixMapping events.
  3. Attributes for the ContentHandler.startElement(String,String,String,Attributes) method may or may not include xmlns* attributes.

A ValidatorHandler is automatically reset every time the startDocument method is invoked.

Recognized Properties and Features

This spec defines the following feature that must be recognized by all ValidatorHandler implementations.

http://xml.org/sax/features/namespace-prefixes

This feature controls how a ValidatorHandler introduces namespace bindings that were not present in the original SAX event stream. When this feature is set to true, it must make sure that the user's ContentHandler will see the corresponding xmlns* attribute in the Attributes object of the ContentHandler.startElement(String,String,String,Attributes) callback. Otherwise, xmlns* attributes must not be added to Attributes that's passed to the user-specified ContentHandler.

(Note that regardless of this switch, namespace bindings are always notified to applications through ContentHandler.startPrefixMapping(String,String) and ContentHandler.endPrefixMapping(String) methods of the ContentHandler specified by the user.)

Note that this feature does NOT affect the way a ValidatorHandler receives SAX events. It merely changes the way it augments SAX events.

This feature is set to false by default.

Since:
1.5

Constructors

Modifier Constructor and Description
protected ValidatorHandler()

Constructor for derived classes.

Methods

Modifier and Type Method and Description
abstract ContentHandler getContentHandler()

Gets the ContentHandler which receives the augmented validation result.
abstract ErrorHandler getErrorHandler()

Gets the current ErrorHandler set to this ValidatorHandler.
boolean getFeature(String name)

Look up the value of a feature flag.
Object getProperty(String name)

Look up the value of a property.
abstract LSResourceResolver getResourceResolver()

Gets the current LSResourceResolver set to this ValidatorHandler.
abstract TypeInfoProvider getTypeInfoProvider()

Obtains the TypeInfoProvider implementation of this ValidatorHandler.
abstract void setContentHandler(ContentHandler receiver)

Sets the ContentHandler which receives the augmented validation result.
abstract void setErrorHandler(ErrorHandler errorHandler)

Sets the ErrorHandler to receive errors encountered during the validation.
void setFeature(String name, boolean value)

Set a feature for this ValidatorHandler.
void setProperty(String name, Object object)

Set the value of a property.
abstract void setResourceResolver(LSResourceResolver resourceResolver)

Sets the LSResourceResolver to customize resource resolution while in a validation episode.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.xml.sax.ContentHandler

characters, endDocument, endElement, endPrefixMapping, ignorableWhitespace, processingInstruction, setDocumentLocator, skippedEntity, startDocument, startElement, startPrefixMapping

Constructors

ValidatorHandler

protected ValidatorHandler()

Constructor for derived classes.

The constructor does nothing.

Derived classes must create ValidatorHandler objects that have null ErrorHandler and null LSResourceResolver.

Methods

setContentHandler

public abstract void setContentHandler(ContentHandler receiver)

Sets the ContentHandler which receives the augmented validation result.

When a ContentHandler is specified, a ValidatorHandler will work as a filter and basically copy the incoming events to the specified ContentHandler.

In doing so, a ValidatorHandler may modify the events, for example by adding defaulted attributes.

A ValidatorHandler may buffer events to certain extent, but to allow ValidatorHandler to be used by a parser, the following requirement has to be met.

  1. When ContentHandler.startElement(String, String, String, Attributes), ContentHandler.endElement(String, String, String), ContentHandler.startDocument(), or ContentHandler.endDocument() are invoked on a ValidatorHandler, the same method on the user-specified ContentHandler must be invoked for the same event before the callback returns.
  2. ValidatorHandler may not introduce new elements that were not present in the input.
  3. ValidatorHandler may not remove attributes that were present in the input.

When a callback method on the specified ContentHandler throws an exception, the same exception object must be thrown from the ValidatorHandler. The ErrorHandler should not be notified of such an exception.

This method can be called even during a middle of a validation.

Parameters:
receiver - A ContentHandler or a null value.

getContentHandler

public abstract ContentHandler getContentHandler()

Gets the ContentHandler which receives the augmented validation result.

Returns:
This method returns the object that was last set through the getContentHandler() method, or null if that method has never been called since this ValidatorHandler has created.
See Also:
setContentHandler(ContentHandler)

setErrorHandler

public abstract void setErrorHandler(ErrorHandler errorHandler)

Sets the ErrorHandler to receive errors encountered during the validation.

Error handler can be used to customize the error handling process during a validation. When an ErrorHandler is set, errors found during the validation will be first sent to the ErrorHandler.

The error handler can abort further validation immediately by throwing SAXException from the handler. Or for example it can print an error to the screen and try to continue the validation by returning normally from the ErrorHandler

If any Throwable is thrown from an ErrorHandler, the same Throwable object will be thrown toward the root of the call stack.

ValidatorHandler is not allowed to throw SAXException without first reporting it to ErrorHandler.

When the ErrorHandler is null, the implementation will behave as if the following ErrorHandler is set: 

class DraconianErrorHandler implements ErrorHandler {
     public void fatalError( SAXParseException e ) throws SAXException {
         throw e;
     }
     public void error( SAXParseException e ) throws SAXException {
         throw e;
     }
     public void warning( SAXParseException e ) throws SAXException {
         // noop
     }
 }

When a new ValidatorHandler object is created, initially this field is set to null.

Parameters:
errorHandler - A new error handler to be set. This parameter can be null.

getErrorHandler

public abstract ErrorHandler getErrorHandler()

Gets the current ErrorHandler set to this ValidatorHandler.

Returns:
This method returns the object that was last set through the setErrorHandler(ErrorHandler) method, or null if that method has never been called since this ValidatorHandler has created.
See Also:
setErrorHandler(ErrorHandler)

setResourceResolver

public abstract void setResourceResolver(LSResourceResolver resourceResolver)

Sets the LSResourceResolver to customize resource resolution while in a validation episode.

ValidatorHandler uses a LSResourceResolver when it needs to locate external resources while a validation, although exactly what constitutes "locating external resources" is up to each schema language.

When the LSResourceResolver is null, the implementation will behave as if the following LSResourceResolver is set: 

class DumbLSResourceResolver implements LSResourceResolver {
     public LSInput resolveResource(
         String publicId, String systemId, String baseURI) {

         return null; // always return null
     }
 }

If a LSResourceResolver throws a RuntimeException (or instances of its derived classes), then the ValidatorHandler will abort the parsing and the caller of the validate method will receive the same RuntimeException.

When a new ValidatorHandler object is created, initially this field is set to null.

Parameters:
resourceResolver - A new resource resolver to be set. This parameter can be null.

getResourceResolver

public abstract LSResourceResolver getResourceResolver()

Gets the current LSResourceResolver set to this ValidatorHandler.

Returns:
This method returns the object that was last set through the setResourceResolver(LSResourceResolver) method, or null if that method has never been called since this ValidatorHandler has created.
See Also:
setErrorHandler(ErrorHandler)

getTypeInfoProvider

public abstract TypeInfoProvider getTypeInfoProvider()

Obtains the TypeInfoProvider implementation of this ValidatorHandler.

The obtained TypeInfoProvider can be queried during a parse to access the type information determined by the validator.

Some schema languages do not define the notion of type, for those languages, this method may not be supported. However, to be compliant with this specification, implementations for W3C XML Schema 1.0 must support this operation.

Returns:
null if the validator / schema language does not support the notion of TypeInfo. Otherwise a non-null valid TypeInfoProvider.

getFeature

public boolean getFeature(String name)
                   throws SAXNotRecognizedException,
                          SAXNotSupportedException

Look up the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for a ValidatorHandler to recognize a feature name but temporarily be unable to return its value. Some feature values may be available only in specific contexts, such as before, during, or after a validation.

Implementors are free (and encouraged) to invent their own features, using names built on their own URIs.

Parameters:
name - The feature name, which is a non-null fully-qualified URI.
Returns:
The current value of the feature (true or false).
Throws:
SAXNotRecognizedException - If the feature value can't be assigned or retrieved.
SAXNotSupportedException - When the ValidatorHandler recognizes the feature name but cannot determine its value at this time.
NullPointerException - When name is null.
See Also:
setFeature(String, boolean)

setFeature

public void setFeature(String name,
                       boolean value)
                throws SAXNotRecognizedException,
                       SAXNotSupportedException

Set a feature for this ValidatorHandler.

Feature can be used to control the way a ValidatorHandler parses schemas. The feature name is any fully-qualified URI. It is possible for a SchemaFactory to expose a feature value but to be unable to change the current value. Some feature values may be immutable or mutable only in specific contexts, such as before, during, or after a validation.

All implementations are required to support the XMLConstants.FEATURE_SECURE_PROCESSING feature. When the feature is:

  • true: the implementation will limit XML processing to conform to implementation limits. Examples include enity expansion limits and XML Schema constructs that would consume large amounts of resources. If XML processing is limited for security reasons, it will be reported via a call to the registered ErrorHandler.fatalError(SAXParseException exception). See setErrorHandler(ErrorHandler errorHandler).
  • false: the implementation will processing XML according to the XML specifications without regard to possible implementation limits.
Parameters:
name - The feature name, which is a non-null fully-qualified URI.
value - The requested value of the feature (true or false).
Throws:
SAXNotRecognizedException - If the feature value can't be assigned or retrieved.
SAXNotSupportedException - When the ValidatorHandler recognizes the feature name but cannot set the requested value.
NullPointerException - When name is null.
See Also:
getFeature(String)

setProperty

public void setProperty(String name,
                        Object object)
                 throws SAXNotRecognizedException,
                        SAXNotSupportedException

Set the value of a property.

The property name is any fully-qualified URI. It is possible for a ValidatorHandler to recognize a property name but to be unable to change the current value. Some property values may be immutable or mutable only in specific contexts, such as before, during, or after a validation.

ValidatorHandlers are not required to recognize setting any specific property names.

Parameters:
name - The property name, which is a non-null fully-qualified URI.
object - The requested value for the property.
Throws:
SAXNotRecognizedException - If the property value can't be assigned or retrieved.
SAXNotSupportedException - When the ValidatorHandler recognizes the property name but cannot set the requested value.
NullPointerException - When name is null.

getProperty

public Object getProperty(String name)
                   throws SAXNotRecognizedException,
                          SAXNotSupportedException

Look up the value of a property.

The property name is any fully-qualified URI. It is possible for a ValidatorHandler to recognize a property name but temporarily be unable to return its value. Some property values may be available only in specific contexts, such as before, during, or after a validation.

ValidatorHandlers are not required to recognize any specific property names.

Implementors are free (and encouraged) to invent their own properties, using names built on their own URIs.

Parameters:
name - The property name, which is a non-null fully-qualified URI.
Returns:
The current value of the property.
Throws:
SAXNotRecognizedException - If the property value can't be assigned or retrieved.
SAXNotSupportedException - When the XMLReader recognizes the property name but cannot determine its value at this time.
NullPointerException - When name is null.
See Also:
setProperty(String, Object)

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https://docs.oracle.com/javase/8/docs/api/javax/xml/validation/ValidatorHandler.html