xmlencoder.java

JGraph扩展应用。自定义Renderer,自定义视图View实现自定义工作流控件

/*
 * @(#)XMLEncoder.java	1.33 03/12/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package flow.graph.gui.graph.encoder;

import java.beans.Encoder;
import java.beans.Expression;
import java.beans.Introspector;
import java.beans.Statement;
import java.beans.XMLDecoder;
import java.io.*;
import java.util.*;
import java.lang.reflect.*;

/**
 * The <code>XMLEncoder</code> class is a complementary alternative to
 * the <code>ObjectOutputStream</code> and can used to generate
 * a textual representation of a <em>JavaBean</em> in the same
 * way that the <code>ObjectOutputStream</code> can
 * be used to create binary representation of <code>Serializable</code>
 * objects. For example, the following fragment can be used to create
 * a textual representation the supplied <em>JavaBean</em>
 * and all its properties:
 * <pre>
 *       XMLEncoder e = new XMLEncoder(
 *                          new BufferedOutputStream(
 *                              new FileOutputStream("Test.xml")));
 *       e.writeObject(new JButton("Hello, world"));
 *       e.close();
 * </pre>
 * Despite the similarity of their APIs, the <code>XMLEncoder</code>
 * class is exclusively designed for the purpose of archiving graphs
 * of <em>JavaBean</em>s as textual representations of their public
 * properties. Like Java source files, documents written this way
 * have a natural immunity to changes in the implementations of the classes
 * involved. The <code>ObjectOutputStream</code> continues to be recommended
 * for interprocess communication and general purpose serialization.
 * <p>
 * The <code>XMLEncoder</code> class provides a default denotation for
 * <em>JavaBean</em>s in which they are represented as XML documents
 * complying with version 1.0 of the XML specification and the
 * UTF-8 character encoding of the Unicode/ISO 10646 character set.
 * The XML documents produced by the <code>XMLEncoder</code> class are:
 * <ul>
 * <li>
 * <em>Portable and version resilient</em>: they have no dependencies
 * on the private implementation of any class and so, like Java source
 * files, they may be exchanged between environments which may have
 * different versions of some of the classes and between VMs from
 * different vendors.
 * <li>
 * <em>Structurally compact</em>: The <code>XMLEncoder</code> class
 * uses a <em>redundancy elimination</em> algorithm internally so that the
 * default values of a Bean's properties are not written to the stream.
 * <li>
 * <em>Fault tolerant</em>: Non-structural errors in the file,
 * caused either by damage to the file or by API changes
 * made to classes in an archive remain localized
 * so that a reader can report the error and continue to load the parts
 * of the document which were not affected by the error.
 * </ul>
 * <p>
 * Below is an example of an XML archive containing
 * some user interface components from the <em>swing</em> toolkit:
 * <pre>
 * &lt;?xml version="1.0" encoding="UTF-8"?&gt;
 * &lt;java version="1.0" class="java.beans.XMLDecoder"&gt;
 * &lt;object class="javax.swing.JFrame"&gt;
 *   &lt;void property="name"&gt;
 *     &lt;string&gt;frame1&lt;/string&gt;
 *   &lt;/void&gt;
 *   &lt;void property="bounds"&gt;
 *     &lt;object class="java.awt.Rectangle"&gt;
 *       &lt;int&gt;0&lt;/int&gt;
 *       &lt;int&gt;0&lt;/int&gt;
 *       &lt;int&gt;200&lt;/int&gt;
 *       &lt;int&gt;200&lt;/int&gt;
 *     &lt;/object&gt;
 *   &lt;/void&gt;
 *   &lt;void property="contentPane"&gt;
 *     &lt;void method="add"&gt;
 *       &lt;object class="javax.swing.JButton"&gt;
 *         &lt;void property="label"&gt;
 *           &lt;string&gt;Hello&lt;/string&gt;
 *         &lt;/void&gt;
 *       &lt;/object&gt;
 *     &lt;/void&gt;
 *   &lt;/void&gt;
 *   &lt;void property="visible"&gt;
 *     &lt;boolean&gt;true&lt;/boolean&gt;
 *   &lt;/void&gt;
 * &lt;/object&gt;
 * &lt;/java&gt;
 * </pre>
 * The XML syntax uses the following conventions:
 * <ul>
 * <li>
 * Each element represents a method call.
 * <li>
 * The "object" tag denotes an <em>expression</em> whose value is
 * to be used as the argument to the enclosing element.
 * <li>
 * The "void" tag denotes a <em>statement</em> which will
 * be executed, but whose result will not be used as an
 * argument to the enclosing method.
 * <li>
 * Elements which contain elements use those elements as arguments,
 * unless they have the tag: "void".
 * <li>
 * The name of the method is denoted by the "method" attribute.
 * <li>
 * XML's standard "id" and "idref" attributes are used to make
 * references to previous expressions - so as to deal with
 * circularities in the object graph.
 * <li>
 * The "class" attribute is used to specify the target of a static
 * method or constructor explicitly; its value being the fully
 * qualified name of the class.
 * <li>
 * Elements with the "void" tag are executed using
 * the outer context as the target if no target is defined
 * by a "class" attribute.
 * <li>
 * Java's String class is treated specially and is
 * written &lt;string&gt;Hello, world&lt;/string&gt; where
 * the characters of the string are converted to bytes
 * using the UTF-8 character encoding.
 * </ul>
 * <p>
 * Although all object graphs may be written using just these three
 * tags, the following definitions are included so that common
 * data structures can be expressed more concisely:
 * <p>
 * <ul>
 * <li>
 * The default method name is "new".
 * <li>
 * A reference to a java class is written in the form
 *  &lt;class&gt;javax.swing.JButton&lt;/class&gt;.
 * <li>
 * Instances of the wrapper classes for Java's primitive types are written
 * using the name of the primitive type as the tag. For example, an
 * instance of the <code>Integer</code> class could be written:
 * &lt;int&gt;123&lt;/int&gt;. Note that the <code>XMLEncoder</code> class
 * uses Java's reflection package in which the conversion between
 * Java's primitive types and their associated "wrapper classes"
 * is handled internally. The API for the <code>XMLEncoder</code> class
 * itself deals only with <code>Object</code>s.
 * <li>
 * In an element representing a nullary method whose name
 * starts with "get", the "method" attribute is replaced
 * with a "property" attribute whose value is given by removing
 * the "get" prefix and decapitalizing the result.
 * <li>
 * In an element representing a monadic method whose name
 * starts with "set", the "method" attribute is replaced
 * with a "property" attribute whose value is given by removing
 * the "set" prefix and decapitalizing the result.
 * <li>
 * In an element representing a method named "get" taking one
 * integer argument, the "method" attribute is replaced
 * with an "index" attribute whose value the value of the
 * first argument.
 * <li>
 * In an element representing a method named "set" taking two arguments,
 * the first of which is an integer, the "method" attribute is replaced
 * with an "index" attribute whose value the value of the
 * first argument.
 * <li>
 * A reference to an array is written using the "array"
 * tag. The "class" and "length" attributes specify the
 * sub-type of the array and its length respectively.
 * </ul>
 *
 *<p>
 * For more information you might also want to check out 
 * <a
 href="http://java.sun.com/products/jfc/tsc/articles/persistence4">Using XMLEncoder</a>,
 * an article in <em>The Swing Connection.</em>
 * @see XMLDecoder
 * @see java.io.ObjectOutputStream
 *
 * @since 1.4
 *
 * @version 1.33 12/19/03
 * @author Philip Milne
 */
public class XMLEncoder extends Encoder {

    private static String encoding = "gb2312";

    private OutputStream out;
    private Object owner;
    private int indentation = 0;
    private boolean internal = false;
    private Map valueToExpression;
    private Map targetToStatementList;
    private boolean preambleWritten = false;
    private NameGenerator nameGenerator;

    private class ValueData {
        public int refs = 0;
        public boolean marked = false; // Marked -> refs > 0 unless ref was a target.
        public String name = null;
        public Expression exp = null;
    }

    /**
     * Creates a new output stream for sending <em>JavaBeans</em>
     * to the stream <code>out</code> using an XML encoding.
     *
     * @param out The stream to which the XML representation of
     * the objects will be sent.
     *
     * @see XMLDecoder#XMLDecoder(InputStream)
     */
    public XMLEncoder(OutputStream out) {
        this.out = out;
        valueToExpression = new IdentityHashMap();
        targetToStatementList = new IdentityHashMap();
	nameGenerator = new NameGenerator();
    }

    /**
     * Sets the owner of this encoder to <code>owner</code>.
     *
     * @param owner The owner of this encoder.
     *
     * @see #getOwner
     */
    public void setOwner(Object owner) {
        this.owner = owner;
        writeExpression(new Expression(this, "getOwner", new Object[0]));
    }

    /**
     * Gets the owner of this encoder.
     *
     * @return The owner of this encoder.
     *
     * @see #setOwner
     */
    public Object getOwner() {
	return owner;
    }

    /**
     * Write an XML representation of the specified object to the output.
     *
     * @param o The object to be written to the stream.
     *
     * @see XMLDecoder#readObject
     */
    public void writeObject(Object o) {
        if (internal) {
            super.writeObject(o);
        }
        else {
            writeStatement(new Statement(this, "writeObject", new Object[]{o}));
        }
    }

    private Vector statementList(Object target) {
        Vector list = (Vector)targetToStatementList.get(target);
        if (list != null) {
            return list;
        }
        list = new Vector();
        targetToStatementList.put(target, list);
        return list;
    }

    
    private void mark(Object o, boolean isArgument) {
        if (o == null || o == this) {
            return;
        }
        ValueData d = getValueData(o);
        Expression exp = d.exp; 
        // Do not mark liternal strings. Other strings, which might,  
        // for example, come from resource bundles should still be marked. 
        if (o.getClass() == String.class && exp == null) { 
            return; 
        } 
        
        // Bump the reference counts of all arguments
        if (isArgument) {
            d.refs++;
        }
        if (d.marked) {
            return;
        }
        d.marked = true;
        Object target = exp.getTarget();
        if (!(target instanceof Class)) {
            statementList(target).add(exp);
	    // Pending: Why does the reference count need to
	    // be incremented here?
            d.refs++;
        }
        mark(exp);
    }
    
    private void mark(Statement stm) {
        Object[] args = stm.getArguments();
        for (int i = 0; i < args.length; i++) {
            Object arg = args[i];
            mark(arg, true);
        }
        mark(stm.getTarget(), false);
    }


    /**
     * Records the Statement so that the Encoder will
     * produce the actual output when the stream is flushed.
     * <P>
     * This method should only be invoked within the context
     * of initializing a persistence delegate.
     *
     * @param oldStm The statement that will be written
     *               to the stream.