javolution.xml.XMLBinding Maven / Gradle / Ivy
/*
* Javolution - Java(TM) Solution for Real-Time and Embedded Systems
* Copyright (C) 2012 - Javolution (http://javolution.org/)
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software is
* freely granted, provided that this notice is preserved.
*/
package javolution.xml;
import javolution.util.FastMap;
import javolution.xml.stream.XMLStreamException;
import javolution.xml.stream.XMLStreamReader;
import javolution.xml.stream.XMLStreamWriter;
/**
* This class represents the binding between Java classes and
* their XML representation.
*
* Custom bindings are used to alias class names and
* ensure that the XML representation is:
* - Impervious to obfuscation.
* - Unaffected by any class refactoring.
* - Can be mapped to multiple implementations. For example:
* [code]
* // Creates a binding to serialize Swing components into high-level XML
* // and deserialize the same XML into SWT components.
* XMLBinding swingBinding = new XMLBinding();
* swingBinding.setAlias(javax.swing.JButton.class, "Button");
* swingBinding.setAlias(javax.swing.JTable.class, "Table");
* ...
* XMLBinding swtBinding = new XMLBinding();
* swtBinding.setAlias(org.eclipse.swt.widgets.Button.class, "Button");
* swtBinding.setAlias(org.eclipse.swt.widgets.Table.class, "Table");
* ...
*
* // Writes Swing desktop to XML.
* XMLObjectWriter writer = new XMLObjectWriter().setBinding(swingBinding);
* writer.setOutput(new FileOutputStream("C:/desktop.xml"));
* writer.write(swingDesktop, "Desktop", SwingDesktop.class);
* writer.close();
*
* // Reads back desktop to a SWT implementation!
* XMLObjectReader reader = new XMLObjectReader().setXMLBinding(swtBinding);
* reader.setInput(new FileInputStream("C:/desktop.xml"));
* SWTDesktop swtDesktop = reader.read("Desktop", SWTDesktop.class);
* reader.close();[/code]
*
*
* More advanced bindings can be created by sub-classing this class.
* [code]
* // XML binding using reflection.
* public ReflectionBinding extends XMLBinding {
* protected XMLFormat getFormat(Class forClass) {
* Field[] fields = forClass.getDeclaredFields();
* return new XMLReflectionFormat(fields);
* }
* }
*
* // XML binding read from DTD input source.
* public DTDBinding extends XMLBinding {
* public DTDBinding(InputStream dtd) {
* ...
* }
* }
*
* // Custom XML binding overriding XML formats (from XMLContext).
* public MyBinding extends XMLBinding {
* XMLFormat myStringFormat = new XMLFormat() {...}
* XMLFormat myCollectionFormat = new XMLFormat() {...}
* protected XMLFormat getFormat(Class forClass) throws XMLStreamException {
* if (String.class.equals(forClass)) return myStringFormat;
* if (Collection.class.isAssignableFrom(forClass)) return myCollectionFormat;
* return super.getFormat(cls); // Returns XMLFormat from XMLContext
* }
* }[/code]
*
* @author Jean-Marie Dautelle
* @version 5.4, December 1, 2009
*/
public class XMLBinding implements XMLSerializable {
/**
* Holds the class attribute.
*/
private QName _classAttribute = QName.valueOf("class");
/**
* Holds the class to alias (QName) mapping.
*/
private final FastMap, QName> _classToAlias = new FastMap, QName>();
/**
* Holds the alias (QName) to class mapping.
*/
private final FastMap> _aliasToClass = new FastMap>();
/**
* Default constructor.
*/
public XMLBinding() {}
/**
* Sets the qualified alias for the specified class.
*
* @param cls the class being aliased.
* @param qName the qualified name.
*/
public void setAlias(Class cls, QName qName) {
_classToAlias.put(cls, qName);
_aliasToClass.put(qName, cls);
}
/**
* Convenient method equivalent to {@link #setAlias(Class, QName)
* setAlias(cls, QName.valueOf(alias))}.
*
* @param cls the class being aliased.
* @param alias the alias for the specified class.
*/
public final void setAlias(Class cls, String alias) {
setAlias(cls, QName.valueOf(alias));
}
/**
* Sets the qualified name of the attribute holding the
* class identifier. If the local name is null the class
* attribute is never read/written (which may prevent unmarshalling).
*
* @param classAttribute the qualified name of the class attribute or
* null.
*/
public void setClassAttribute(QName classAttribute) {
_classAttribute = classAttribute;
}
/**
* Convenience method equivalent to {@link #setClassAttribute(QName)
* setClassAttribute(QName.valueOf(name))}.
*
* @param name the name of the class attribute or null.
*/
public final void setClassAttribute(String name) {
setClassAttribute(name == null ? null : QName.valueOf(name));
}
/**
* Returns the XML format for the specified class/interface.
* The default implementation returns the {@link XMLContext#getFormat}
* for the specified class.
*
* @param forClass the class for which the XML format is returned.
* @return the XML format for the specified class (never null).
*/
protected XMLFormat getFormat(Class forClass)
throws XMLStreamException {
return XMLContext.getFormat(forClass);
}
/**
* Reads the class corresponding to the current XML element.
*
* This method is called by {@link XMLFormat.InputElement#getNext()}
* {@link XMLFormat.InputElement#get(String)} and
* {@link XMLFormat.InputElement#get(String, String)} to retrieve the
* Java class corresponding to the current XML element.
*
* If useAttributes is set, the default implementation
* reads the class name from the class attribute; otherwise the class
* name (or alias) is read from the current element qualified name.
*
* @param reader the XML stream reader.
* @param useAttributes indicates if the element's attributes should be
* used to identify the class (e.g. when the element name is
* specified by the user then attributes have to be used).
* @return the corresponding class.
* @throws XMLStreamException
*/
protected Class readClass(XMLStreamReader reader, boolean useAttributes)
throws XMLStreamException {
try {
QName classQName;
if (useAttributes) {
if (_classAttribute == null)
throw new XMLStreamException(
"Binding has no class attribute defined, cannot retrieve class");
classQName = QName.valueOf(reader.getAttributeValue(
_classAttribute.getNamespaceURI(),
_classAttribute.getLocalName()));
if (classQName == null)
throw new XMLStreamException(
"Cannot retrieve class (class attribute not found)");
} else {
classQName = QName.valueOf(reader.getNamespaceURI(),
reader.getLocalName());
}
// Searches aliases with namespace URI.
Class cls = _aliasToClass.get(classQName);
if (cls != null)
return cls;
// Searches aliases without namespace URI.
cls = _aliasToClass.get(QName.valueOf(classQName.getLocalName()));
if (cls != null)
return cls;
// Finally convert the qualified name to a class (ignoring namespace URI).
cls = Class.forName(classQName.getLocalName().toString());
if (cls == null)
throw new XMLStreamException(
"Class "
+ classQName.getLocalName()
+ " not found (see javolution.lang.Reflection to support additional class loader)");
_aliasToClass.put(classQName, cls);
return cls;
} catch (ClassNotFoundException ex) {
throw new RuntimeException(ex);
}
}
/**
* Writes the specified class to the current XML element attributes or to
* a new element if the element attributes cannot be used.
*
* This method is called by
* {@link XMLFormat.OutputElement#add(Object)} and
* {@link XMLFormat.OutputElement#add(Object, String)} and
* {@link XMLFormat.OutputElement#add(Object, String, String)} to
* identify the Java class corresponding to the XML element.
*
*
* @param cls the class to be written.
* @param writer the XML stream writer.
* @param useAttributes indicates if the element's attributes should be
* used to identify the class (e.g. when the element name is
* specified by the user then attributes have to be used).
* @throws XMLStreamException
*/
protected void writeClass(Class cls, XMLStreamWriter writer,
boolean useAttributes) throws XMLStreamException {
QName qName = (QName) _classToAlias.get(cls);
String name = qName != null ? qName.toString() : cls.getName();
if (useAttributes) {
if (_classAttribute == null)
return;
if (_classAttribute.getNamespaceURI() == null) {
writer.writeAttribute(_classAttribute.getLocalName(), name);
} else {
writer.writeAttribute(_classAttribute.getNamespaceURI(),
_classAttribute.getLocalName(), name);
}
} else {
if (qName != null) {
if (qName.getNamespaceURI() == null) {
writer.writeStartElement(qName.getLocalName());
} else {
writer.writeStartElement(qName.getNamespaceURI(),
qName.getLocalName());
}
} else {
writer.writeStartElement(name);
}
}
}
public void reset() {
_classAttribute = QName.valueOf("class");
_aliasToClass.clear();
_classToAlias.clear();
}
private static final long serialVersionUID = 6611041662550083919L;
}