Initial revision

From-SVN: r102074

libjava/classpath/gnu/java/beans/decoder/ObjectHandler.java

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+/* gnu.java.beans.decoder.ObjectHandler
+   Copyright (C) 2004 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package gnu.java.beans.decoder;
+
+import java.beans.ExceptionListener;
+
+import org.xml.sax.Attributes;
+
+/** An ObjectHandler parses the <object> tag and thereby creates various
+ * Context implementations.
+ *
+ * @author Robert Schuster
+ *
+ */
+public class ObjectHandler extends AbstractElementHandler
+{
+  /**
+   * XXX: Can all results be stored with an object id?
+   *
+   *
+   * @param PersistenceParser
+   */
+  ObjectHandler(ElementHandler parent)
+  {
+    super(parent, true);
+  }
+
+  protected Context startElement(Attributes attributes, ExceptionListener exceptionListener)
+    throws AssemblyException
+  {
+    String className = attributes.getValue("class");
+    String methodName = attributes.getValue("method");
+    String fieldName = attributes.getValue("field");
+    String index = attributes.getValue("index");
+    String propertyName = attributes.getValue("property");
+    String id = attributes.getValue("id");
+    String idRef = attributes.getValue("idref");
+
+    /* first check if we just want to access an existing object (idref present)
+     *
+     * note: <object idref="foo" method="bar"/> is not valid to call method "bar"
+     * on the object with id "foo". Instead this should return the object "foo"
+     * itself. The right way to this is:
+     * <object idref="foo">
+     *         <object method="bar"/>
+     * </object>
+     *
+     * This means that if idref is present class, method, field, index and
+     * property are obsolete.
+     */
+    if (idRef != null)
+      // reactivates an existing object and giving it another name if id exists
+      return new ObjectContext(id, getObject(idRef));
+
+    // decides whether we are in a static (className present) or dynamic context
+    if (className != null)
+      {
+	try
+	  {
+	    Class klass = instantiateClass(className);
+
+	    // class name exists which means that we are in a static context.
+	    // so we may want to ...
+	    // access a static field if the fieldName exists
+	    if (fieldName != null)
+	      {
+		try
+		  {
+		    return new ObjectContext(id,
+		                             klass.getField(fieldName).get(null));
+		  }
+		catch (NoSuchFieldException nsfe)
+		  {
+		    throw new AssemblyException(nsfe);
+		  }
+		catch (IllegalAccessException iae)
+		  {
+		    throw new AssemblyException(iae);
+		  }
+	      }
+
+	    // (falling through is important!)
+	    // run a constructor if methodName is "new" or null
+	    if (methodName == null || methodName.equals("new"))
+	      return new ConstructorContext(id, klass);
+
+	    // (falling through is important!)
+	    // run a static method on the given class (if methodName exists, which is implied already) 
+	    return new StaticMethodContext(id, klass, methodName);
+	    // XXX: should fail if unexpected attributes are present?
+	  }
+	catch (ClassNotFoundException cnfe)
+	  {
+	    throw new AssemblyException(cnfe);
+	  }
+      }
+    else
+      {
+	// className does not exist which means we are in the context of
+	// some object and want to ...
+	// access the get(int index) method if index != null
+	if (index != null)
+	  {
+	    try
+	      {
+		// Note: http://java.sun.com/products/jfc/tsc/articles/persistence3/ says
+		// that <void index="4"/> will make up a get()-call. But this is wrong because
+		// <void/> tags never return values (to the surrounding context)
+		return new IndexContext(id, Integer.parseInt(index));
+	      }
+	    catch (NumberFormatException nfe)
+	      {
+		throw new AssemblyException(nfe);
+	      }
+	  }
+
+	// access a method if methodName exists
+	if (methodName != null)
+	  return new MethodContext(id, methodName);
+
+	// (falling through is important!)
+	// access a property if a propertyName exists
+	if (propertyName != null && propertyName.length() > 0)
+	  // this is reported as an ordinary method access where the propertyName is
+	  // converted into a 'getter'-method name: convert first character of property name
+	  // to upper case and prepend 'get'
+	  // Note: This will be a getter-method because the <object> tag implies that a return
+	  // value is expected.
+	  return new PropertyContext(id, propertyName);
+      }
+
+    throw new AssemblyException(new IllegalArgumentException("Wrong or missing attributes for <object> tag."));
+  }
+}