FileDocCategorySizeDatePackage
XMLReader.javaAPI DocJava SE 6 API14977Tue Jun 10 00:27:36 BST 2008org.xml.sax

XMLReader

public interface XMLReader
Interface for reading an XML document using callbacks.
This module, both source code and documentation, is in the Public Domain, and comes with NO WARRANTY. See http://www.saxproject.org for further information.

Note: despite its name, this interface does not extend the standard Java {@link java.io.Reader Reader} interface, because reading XML is a fundamentally different activity than reading character data.

XMLReader is the interface that an XML parser's SAX2 driver must implement. This interface allows an application to set and query features and properties in the parser, to register event handlers for document processing, and to initiate a document parse.

All SAX interfaces are assumed to be synchronous: the {@link #parse parse} methods must not return until parsing is complete, and readers must wait for an event-handler callback to return before reporting the next event.

This interface replaces the (now deprecated) SAX 1.0 {@link org.xml.sax.Parser Parser} interface. The XMLReader interface contains two important enhancements over the old Parser interface (as well as some minor ones):

  1. it adds a standard way to query and set features and properties; and
  2. it adds Namespace support, which is required for many higher-level XML standards.

There are adapters available to convert a SAX1 Parser to a SAX2 XMLReader and vice-versa.

since
SAX 2.0
author
David Megginson
version
2.0.1+ (sax2r3pre1)
see
org.xml.sax.XMLFilter
see
org.xml.sax.helpers.ParserAdapter
see
org.xml.sax.helpers.XMLReaderAdapter

Fields Summary
Constructors Summary
Methods Summary
public org.xml.sax.ContentHandlergetContentHandler()
Return the current content handler.

return
The current content handler, or null if none has been registered.
see
#setContentHandler

public org.xml.sax.DTDHandlergetDTDHandler()
Return the current DTD handler.

return
The current DTD handler, or null if none has been registered.
see
#setDTDHandler

public org.xml.sax.EntityResolvergetEntityResolver()
Return the current entity resolver.

return
The current entity resolver, or null if none has been registered.
see
#setEntityResolver

public org.xml.sax.ErrorHandlergetErrorHandler()
Return the current error handler.

return
The current error handler, or null if none has been registered.
see
#setErrorHandler

public booleangetFeature(java.lang.String name)
Look up the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for an XMLReader 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 parse. Also, some feature values may not be programmatically accessible. (In the case of an adapter for SAX1 {@link Parser}, there is no implementation-independent way to expose whether the underlying parser is performing validation, expanding external entities, and so forth.)

All XMLReaders are required to recognize the http://xml.org/sax/features/namespaces and the http://xml.org/sax/features/namespace-prefixes feature names.

Typical usage is something like this:

XMLReader r = new MySAXDriver();

// try to activate validation
try {
r.setFeature("http://xml.org/sax/features/validation", true);
} catch (SAXException e) {
System.err.println("Cannot activate validation.");
}

// register event handlers
r.setContentHandler(new MyContentHandler());
r.setErrorHandler(new MyErrorHandler());

// parse the first document
try {
r.parse("http://www.foo.com/mydoc.xml");
} catch (IOException e) {
System.err.println("I/O exception reading XML document");
} catch (SAXException e) {
System.err.println("XML exception reading document.");
}

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

param
name The feature name, which is a fully-qualified URI.
return
The current value of the feature (true or false).
exception
org.xml.sax.SAXNotRecognizedException If the feature value can't be assigned or retrieved.
exception
org.xml.sax.SAXNotSupportedException When the XMLReader recognizes the feature name but cannot determine its value at this time.
see
#setFeature

public java.lang.ObjectgetProperty(java.lang.String name)
Look up the value of a property.

The property name is any fully-qualified URI. It is possible for an XMLReader 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 parse.

XMLReaders are not required to recognize any specific property names, though an initial core set is documented for SAX2.

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

param
name The property name, which is a fully-qualified URI.
return
The current value of the property.
exception
org.xml.sax.SAXNotRecognizedException If the property value can't be assigned or retrieved.
exception
org.xml.sax.SAXNotSupportedException When the XMLReader recognizes the property name but cannot determine its value at this time.
see
#setProperty

public voidparse(org.xml.sax.InputSource input)
Parse an XML document.

The application can use this method to instruct the XML reader to begin parsing an XML document from any valid input source (a character stream, a byte stream, or a URI).

Applications may not invoke this method while a parse is in progress (they should create a new XMLReader instead for each nested XML document). Once a parse is complete, an application may reuse the same XMLReader object, possibly with a different input source. Configuration of the XMLReader object (such as handler bindings and values established for feature flags and properties) is unchanged by completion of a parse, unless the definition of that aspect of the configuration explicitly specifies other behavior. (For example, feature flags or properties exposing characteristics of the document being parsed.)

During the parse, the XMLReader will provide information about the XML document through the registered event handlers.

This method is synchronous: it will not return until parsing has ended. If a client application wants to terminate parsing early, it should throw an exception.

param
input The input source for the top-level of the XML document.
exception
org.xml.sax.SAXException Any SAX exception, possibly wrapping another exception.
exception
java.io.IOException An IO exception from the parser, possibly from a byte stream or character stream supplied by the application.
see
org.xml.sax.InputSource
see
#parse(java.lang.String)
see
#setEntityResolver
see
#setDTDHandler
see
#setContentHandler
see
#setErrorHandler

public voidparse(java.lang.String systemId)
Parse an XML document from a system identifier (URI).

This method is a shortcut for the common case of reading a document from a system identifier. It is the exact equivalent of the following:

parse(new InputSource(systemId));

If the system identifier is a URL, it must be fully resolved by the application before it is passed to the parser.

param
systemId The system identifier (URI).
exception
org.xml.sax.SAXException Any SAX exception, possibly wrapping another exception.
exception
java.io.IOException An IO exception from the parser, possibly from a byte stream or character stream supplied by the application.
see
#parse(org.xml.sax.InputSource)

public voidsetContentHandler(org.xml.sax.ContentHandler handler)
Allow an application to register a content event handler.

If the application does not register a content handler, all content events reported by the SAX parser will be silently ignored.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

param
handler The content handler.
see
#getContentHandler

public voidsetDTDHandler(org.xml.sax.DTDHandler handler)
Allow an application to register a DTD event handler.

If the application does not register a DTD handler, all DTD events reported by the SAX parser will be silently ignored.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

param
handler The DTD handler.
see
#getDTDHandler

public voidsetEntityResolver(org.xml.sax.EntityResolver resolver)
Allow an application to register an entity resolver.

If the application does not register an entity resolver, the XMLReader will perform its own default resolution.

Applications may register a new or different resolver in the middle of a parse, and the SAX parser must begin using the new resolver immediately.

param
resolver The entity resolver.
see
#getEntityResolver

public voidsetErrorHandler(org.xml.sax.ErrorHandler handler)
Allow an application to register an error event handler.

If the application does not register an error handler, all error events reported by the SAX parser will be silently ignored; however, normal processing may not continue. It is highly recommended that all SAX applications implement an error handler to avoid unexpected bugs.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

param
handler The error handler.
see
#getErrorHandler

public voidsetFeature(java.lang.String name, boolean value)
Set the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for an XMLReader 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 parse.

All XMLReaders are required to support setting http://xml.org/sax/features/namespaces to true and http://xml.org/sax/features/namespace-prefixes to false.

param
name The feature name, which is a fully-qualified URI.
param
value The requested value of the feature (true or false).
exception
org.xml.sax.SAXNotRecognizedException If the feature value can't be assigned or retrieved.
exception
org.xml.sax.SAXNotSupportedException When the XMLReader recognizes the feature name but cannot set the requested value.
see
#getFeature

public voidsetProperty(java.lang.String name, java.lang.Object value)
Set the value of a property.

The property name is any fully-qualified URI. It is possible for an XMLReader 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 parse.

XMLReaders are not required to recognize setting any specific property names, though a core set is defined by SAX2.

This method is also the standard mechanism for setting extended handlers.

param
name The property name, which is a fully-qualified URI.
param
value The requested value for the property.
exception
org.xml.sax.SAXNotRecognizedException If the property value can't be assigned or retrieved.
exception
org.xml.sax.SAXNotSupportedException When the XMLReader recognizes the property name but cannot set the requested value.