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

Typically parsing is done in while loop that will work until {@link org.gjt.xpp.XmlPullParser#next} returns {@link org.gjt.xpp.XmlPullParser#END_DOCUMENT} event. All possible types of events that {@link org.gjt.xpp.XmlPullParser#next} can return:

If there is parsing error {@link org.gjt.xpp.XmlPullParser#next} will throw {@link org.gjt.xpp.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 {@link org.gjt.xpp.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 $