abstractxmlwriter.java

一个即时消息系统的源码（J2ME编程部分）。

package org.kxml.io;

import java.io.*;
import java.util.*;

import org.kxml.*;


/** An abstract XmlWriter including namespace handling. */


public abstract class AbstractXmlWriter extends Writer {

    protected State current = new State (null, new PrefixMap (), //null, null, 
			       null);

    protected class State {
	public State prev;
	public PrefixMap prefixMap;
	//	String namespace;
	//	String name;
	public String tag;   // for auto-endtag writing

	public State (State prev, PrefixMap prefixMap, 
	       //String namespace, String name, 
	       String tag) {

	    this.prev = prev;
	    this.prefixMap = prefixMap;
	    //	    this.namespace = namespace;
	    //	    this.name = name;
	    this.tag = tag;
	}
    }


    /** writes an attribute. Only allowed immediately after
        startTag or attribute.  */

    public abstract void attribute (String name, 
				    String value) throws IOException;



    /** writes an attribute with the given namespace. Only allowed
	immediately after startTag or another attribute
	call. */

    public void attribute (String namespace, 
				String name, 
				String value) throws IOException {

	if (namespace == null || "".equals (namespace))
	    attribute (name, value);
	else {
	    String prefix = current.prefixMap.getPrefix (namespace);
	    if (prefix == null || prefix.equals ("")) {
		int cnt = 0;
		do {
		    prefix = "p"+(cnt++);
		}
		while (current.prefixMap.getNamespace (prefix) != null);
		current.prefixMap = new PrefixMap 
		    (current.prefixMap, prefix, namespace);

		attribute ("xmlns:"+prefix, namespace);
	    }
	    attribute (prefix + ":" + name, value);
	}
    }
                   
    public PrefixMap getPrefixMap () {
	return current.prefixMap;
    }


    /** writes a start tag with the given name, using the given prefix
        map.  This method cares about the namespace prefixes and calls
        startTag (PrefixMap prefixMap, String tag) for concrete
        writing. */

    public void startTag (PrefixMap prefixMap,
			  String namespace, 
			  String name) throws IOException {

	// check if namespace is default. 
	
	if (prefixMap == null) prefixMap = current.prefixMap;
	if (namespace == null) namespace = "";

	String prefix = prefixMap.getPrefix (namespace);
	
	if (prefix == null) { 
	    prefixMap = new PrefixMap (prefixMap, "", namespace);
	    prefix = "";
	}

	String tag = prefix.length () == 0 
	    ? name
	    : prefix + ':' + name;

	PrefixMap oldMap = current.prefixMap;

	startTag (prefixMap, tag);

	// if namespace has changed, write out changes...

	if (prefixMap != oldMap) {
	    for (Enumeration e = prefixMap.prefixEnumeration (); 
		 e.hasMoreElements ();) {

		String p2 = (String) e.nextElement (); 
		String ns = prefixMap.getNamespace (p2);

		if (ns != oldMap.getNamespace (p2)) {
		    if (p2.equals ("")) 
			attribute ("xmlns", ns);
		    else 
			attribute ("xmlns:"+p2, ns);
		}
	    }
	}
    }
    

    /** writes a start tag with the given namespace and name */

    public void startTag (String namespace, 
			       String name) throws IOException {
	startTag (null, namespace, name);
    }
    

    /** convenience method for startTag (Xml.NO_NAMESPACE, name) */

    public void startTag (String name) throws IOException {
	startTag (null, Xml.NO_NAMESPACE, name);
    }


    /** abstract method that must be overwritten by
	a method actually writing the resolved start tag 
	without namespace checking. This implementation
        just puts the state on the stack.<br /><br />
        
        Attention: The actual implementation include the
	following line in order to 
        put the current State on the stack!<br /><br />

	current = new State (current, prefixMap, tag);
    */


    protected abstract void startTag (PrefixMap prefixMap, 
					   String tag) throws IOException;   



    /** @deprecated 

	Old method for writing a (possibly degenerated)
        tag including the given attributes. Please use subsequent
	calls of the other methods instead! */

    public void startTag (String name, 
			  String [] attrs,  			       
			  boolean degenerated) throws IOException {
	
	startTag (name); 
	for (int i = 0; i < attrs.length; i+=2)  
	    attribute (attrs [i], attrs [i+1]); 
  	if (degenerated) endTag ();
    } 



    /** Abstract method for writing an end tag.  <b>Attention:</b>
	Concrete implementations must pop the previous state from the
	stack:<br /><br />

	current = current.prev; */
	
    public abstract void endTag () throws IOException;

    /** writes Xml.DOCTYPE, Xml.PROCESSING_INSTRUCTION or Xml.COMMENT */

    public abstract void writeLegacy (int type, String text) throws IOException;
}