Added in API level 1

XMLReader

public interface XMLReader

org.xml.sax.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 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 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 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.

Summary

Public methods

abstract ContentHandler getContentHandler()

Return the current content handler.

abstract DTDHandler getDTDHandler()

Return the current DTD handler.

abstract EntityResolver getEntityResolver()

Return the current entity resolver.

abstract ErrorHandler getErrorHandler()

Return the current error handler.

abstract boolean getFeature(String name)

Look up the value of a feature flag.

abstract Object getProperty(String name)

Look up the value of a property.

abstract void parse(InputSource input)

Parse an XML document.

abstract void parse(String systemId)

Parse an XML document from a system identifier (URI).

abstract void setContentHandler(ContentHandler handler)

Allow an application to register a content event handler.

abstract void setDTDHandler(DTDHandler handler)

Allow an application to register a DTD event handler.

abstract void setEntityResolver(EntityResolver resolver)

Allow an application to register an entity resolver.

abstract void setErrorHandler(ErrorHandler handler)

Allow an application to register an error event handler.

abstract void setFeature(String name, boolean value)

Set the value of a feature flag.

abstract void setProperty(String name, Object value)

Set the value of a property.

Public methods

getContentHandler

Added in API level 1
public abstract ContentHandler getContentHandler ()

Return the current content handler.

Returns
ContentHandler The current content handler, or null if none has been registered.

getDTDHandler

Added in API level 1
public abstract DTDHandler getDTDHandler ()

Return the current DTD handler.

Returns
DTDHandler The current DTD handler, or null if none has been registered.

getEntityResolver

Added in API level 1
public abstract EntityResolver getEntityResolver ()

Return the current entity resolver.

Returns
EntityResolver The current entity resolver, or null if none has been registered.

getErrorHandler

Added in API level 1
public abstract ErrorHandler getErrorHandler ()

Return the current error handler.

Returns
ErrorHandler The current error handler, or null if none has been registered.

getFeature

Added in API level 1
public abstract boolean getFeature (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 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.

Parameters
name String: The feature name, which is a fully-qualified URI.

Returns
boolean The current value of the feature (true or false).

Throws
SAXNotRecognizedException If the feature value can't be assigned or retrieved.
SAXNotSupportedException When the XMLReader recognizes the feature name but cannot determine its value at this time.

getProperty

Added in API level 1
public abstract Object getProperty (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.

Parameters
name String: The property name, which is a fully-qualified URI.

Returns
Object 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.

parse

Added in API level 1
public abstract void parse (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.

Parameters
input InputSource: The input source for the top-level of the XML document.

Throws
SAXException Any SAX exception, possibly wrapping another exception.
IOException An IO exception from the parser, possibly from a byte stream or character stream supplied by the application.

parse

Added in API level 1
public abstract void parse (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.

Parameters
systemId String: The system identifier (URI).

Throws
SAXException Any SAX exception, possibly wrapping another exception.
IOException An IO exception from the parser, possibly from a byte stream or character stream supplied by the application.

setContentHandler

Added in API level 1
public abstract void setContentHandler (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.

Parameters
handler ContentHandler: The content handler.

setDTDHandler

Added in API level 1
public abstract void setDTDHandler (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.

Parameters
handler DTDHandler: The DTD handler.

See also:

setEntityResolver

Added in API level 1
public abstract void setEntityResolver (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.

Parameters
resolver EntityResolver: The entity resolver.

setErrorHandler

Added in API level 1
public abstract void setErrorHandler (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.

Parameters
handler ErrorHandler: The error handler.

See also:

setFeature

Added in API level 1
public abstract void setFeature (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.

Parameters
name String: The feature name, which is a fully-qualified URI.

value boolean: The requested value of the feature (true or false).

Throws
SAXNotRecognizedException If the feature value can't be assigned or retrieved.
SAXNotSupportedException When the XMLReader recognizes the feature name but cannot set the requested value.

See also:

setProperty

Added in API level 1
public abstract void setProperty (String name, 
                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.

Parameters
name String: The property name, which is a fully-qualified URI.

value Object: The requested value for the property.

Throws
SAXNotRecognizedException If the property value can't be assigned or retrieved.
SAXNotSupportedException When the XMLReader recognizes the property name but cannot set the requested value.