Package org.gjt.xpp

This package defines classes compromising public API of XML Pull Parser 2.0 (org.gjt.xpp).

See:
          Description

Interface Summary
XmlEndTag This represent XML end tag.
XmlFormatter This interface extends XmlRecorder to give some control over formattingof XML output.
XmlNode This class represents XML subtree.
XmlPullNode This class represents pullable XML subtree - children are built on demand.
XmlPullParser Generic interface for simple and quick XML Pull Parser.
XmlPullParserBufferControl Additional interface to control XML Pull Parser buffering.
XmlPullParserEventPosition Special interface to retrieve event positioning information.
XmlRecorder This class represents abstract functionality necessary to to persist XML Pull Parser events.
XmlStartTag This class represents abstract functionality necessary to to persist XML Pull Parser events.
XmlTag Base interface that encapsulates common functionality for XML elements: both start tag and end tag (an empty element is equivalent to start tag followed by end tag so for simplicity ti is not modeled as a separate class).
XmlWritable This interface can be used by classes that wishes to implement its own way to persist XML into writer.
 

Class Summary
XmlPullParserFactory This class is used to create implementations of XML Pull Parser.
 

Exception Summary
XmlPullParserException This exception is thrown to signal XML Pull Parser related excepions.
 

Package org.gjt.xpp Description

This package defines classes compromising public API of XML Pull Parser 2.0 (org.gjt.xpp).

Note this package is deprecated by next version of XML Pull Parser called XPP3/MXP1 that implements XmlPull API.

Usage:

Xml Pull Parser (XPP) provides a simple and fast implementation of "pull parsing model" that allows processing application to request parsing events incrementally (ideal for deserializing XML such as SOAP encoding).

Following steps are required to use XPP:

  1. create an instance of XmlPullParserFactory using newInstance() method
  2. create an instance of XmlPullParser using newPullParser() method on instance of XmlPullParserFactory
  3. set options (if they are different than defaults)
  4. set input by calling either XmlPullParser.setInput(Reader) or XmlPullParser.setInput(char[])
  5. start parsing by calling XmlPullParser.next() - this method returns event type and parsing is finished when it returns XmlPullParser.END_DOCUMENT event type.

Typically parsing is done in while loop that will work until XmlPullParser.next() returns XmlPullParser.END_DOCUMENT event. All possible types of events that XmlPullParser.next() can return:

If there is parsing error XmlPullParser.next() will throw XmlPullParserException.

An example Java program may look like this: (for more detailed example please see src/java/samples/)

  // 1. creating instance of parser
  XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
  XmlPullParser pp = factory.newPullParser();

  // 2. setting options
  // ex. disabling mixed content for elements
  // (element can not have elements mixed with non-whitespace string content)
  pp.setAllowedMixedContent(false);

  // 3. setting input
  String data = "<hello>World!</hello>";
  // input will be taken from java.io.Reader
  pp.setInput(new StringReader(data));

  // input could be also taken from String directly:
  //pp.setInput(data.toCharArray());

  // 4. parsing

  //declare variables used during parsing
  byte type;  // received event type
  XmlStartTag stag = factory.newStartTag();
  XmlEndTag etag = factory.newEndTag();

  // start parsing loop
  while((type = pp.next()) != XmlPullParser.END_DOCUMENT) {
    if(type == XmlPullParser.CONTENT) {
      String s = pp.readContent();
      System.out.println("CONTENT={'"+s+"'}");
    } else if(type == XmlPullParser.END_TAG) {
      pp.readEndTag(etag);
      System.out.println(""+etag);
    } else if(type == XmlPullParser.START_TAG) {
      pp.readStartTag(stag);
      System.out.println(""+stag);
    }
  }

After parsing is finished, parser instance may be reused by calling again XmlPullParser.setInput(Reader).

Example Java code that will read string for SOAP encoding

  public String readString(XmlPullParser pp, XmlStartTag stag)
    throws DeserializeException, XmlPullParserException, IOException
  {
    String xs = stag.getAttributeValue(Soap.XSI_NS, "null");
    if( "1".equals(xs) ) {
      if(pp.next() != XmlPullParser.END_TAG)
        throw new DeserializeException("expected end tag");
      return null;
    }
    if(pp.next() != XmlPullParser.CONTENT)
      throw new DeserializeException("expected content");
    String content = pp.readContent();
    if(pp.next() != XmlPullParser.END_TAG)
      throw new DeserializeException("expected end tag");
    return content;
  }


Aleksander Slominski

Last modified: $Id: package.html,v 1.4 2002/12/11 01:49:32 aslom Exp $



Copyright (c) 2003 IU Extreme! Lab http://www.extreme.indiana.edu/ All Rights Reserved.

Note this package is deprecated by XPP3 that implements XmlPull API