/*
* Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.beans.decoder;
/**
* The base class for element handlers.
*
* @since 1.7
*
* @author Sergey A. Malenkov
*
* @see DocumentHandler
*/
public abstract class ElementHandler {
private DocumentHandler owner;
private ElementHandler parent;
private String id;
/**
* Returns the document handler that creates this element handler.
*
* @return the owner document handler
*/
public final DocumentHandler getOwner() {
return this.owner;
}
/**
* Sets the document handler that creates this element handler.
* The owner document handler should be set after instantiation.
* Such approach is used to simplify the extensibility.
*
* @param owner the owner document handler
* @see DocumentHandler#startElement
*/
final void setOwner(DocumentHandler owner) {
if (owner == null) {
throw new IllegalArgumentException("Every element should have owner");
}
this.owner = owner;
}
/**
* Returns the element handler that contains this one.
*
* @return the parent element handler
*/
public final ElementHandler getParent() {
return this.parent;
}
/**
* Sets the element handler that contains this one.
* The parent element handler should be set after instantiation.
* Such approach is used to simplify the extensibility.
*
* @param parent the parent element handler
* @see DocumentHandler#startElement
*/
final void setParent(ElementHandler parent) {
this.parent = parent;
}
/**
* Returns the value of the variable with specified identifier.
*
* @param id the identifier
* @return the value of the variable
*/
protected final Object getVariable(String id) {
if (id.equals(this.id)) {
ValueObject value = getValueObject();
if (value.isVoid()) {
throw new IllegalStateException("The element does not return value");
}
return value.getValue();
}
return (this.parent != null)
? this.parent.getVariable(id)
: this.owner.getVariable(id);
}
/**
* Returns the value of the parent element.
*
* @return the value of the parent element
*/
protected Object getContextBean() {
if (this.parent != null) {
ValueObject value = this.parent.getValueObject();
if (!value.isVoid()) {
return value.getValue();
}
throw new IllegalStateException("The outer element does not return value");
} else {
Object value = this.owner.getOwner();
if (value != null) {
return value;
}
throw new IllegalStateException("The topmost element does not have context");
}
}
/**
* Parses attributes of the element.
* By default, the following attribute is supported:
* <dl>
* <dt>id
* <dd>the identifier of the variable that is intended to store the result
* </dl>
*
* @param name the attribute name
* @param value the attribute value
*/
public void addAttribute(String name, String value) {
if (name.equals("id")) { // NON-NLS: the attribute name
this.id = value;
} else {
throw new IllegalArgumentException("Unsupported attribute: " + name);
}
}
/**
* This method is called before parsing of the element's body.
* All attributes are parsed at this point.
* By default, do nothing.
*/
public void startElement() {
}
/**
* This method is called after parsing of the element's body.
* By default, it calculates the value of this element.
* The following tasks are executing for any non-void value:
* <ol>
* <li>If the {@code id} attribute is set
* the value of the variable with the specified identifier
* is set to the value of this element.</li>
* <li>This element is used as an argument of parent element if it is possible.</li>
* </ol>
*
* @see #isArgument
*/
public void endElement() {
// do nothing if no value returned
ValueObject value = getValueObject();
if (!value.isVoid()) {
if (this.id != null) {
this.owner.setVariable(this.id, value.getValue());
}
if (isArgument()) {
if (this.parent != null) {
this.parent.addArgument(value.getValue());
} else {
this.owner.addObject(value.getValue());
}
}
}
}
/**
* Adds the character that contained in this element.
* By default, only whitespaces are acceptable.
*
* @param ch the character
*/
public void addCharacter(char ch) {
if ((ch != ' ') && (ch != '\n') && (ch != '\t') && (ch != '\r')) {
throw new IllegalStateException("Illegal character with code " + (int) ch);
}
}
/**
* Adds the argument that is used to calculate the value of this element.
* By default, no arguments are acceptable.
*
* @param argument the value of the element that contained in this one
*/
protected void addArgument(Object argument) {
throw new IllegalStateException("Could not add argument to simple element");
}
/**
* Tests whether the value of this element can be used
* as an argument of the element that contained in this one.
*
* @return {@code true} if the value of this element can be used
* as an argument of the element that contained in this one,
* {@code false} otherwise
*/
protected boolean isArgument() {
return this.id == null;
}
/**
* Returns the value of this element.
*
* @return the value of this element
*/
protected abstract ValueObject getValueObject();
}