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ObjectView.javaAPI DocJava SE 5 API5125Fri Aug 26 14:58:18 BST 2005javax.swing.text.html

ObjectView

public class ObjectView extends ComponentView
Component decorator that implements the view interface for <object> elements.

This view will try to load the class specified by the classid attribute. If possible, the Classloader used to load the associated Document is used. This would typically be the same as the ClassLoader used to load the EditorKit. If the document's ClassLoader is null, Class.forName is used.

If the class can successfully be loaded, an attempt will be made to create an instance of it by calling Class.newInstance. An attempt will be made to narrow the instance to type java.awt.Component to display the object.

This view can also manage a set of parameters with limitations. The parameters to the <object> element are expected to be present on the associated elements attribute set as simple strings. Each bean property will be queried as a key on the AttributeSet, with the expectation that a non-null value (of type String) will be present if there was a parameter specification for the property. Reflection is used to set the parameter. Currently, this is limited to a very simple single parameter of type String.

A simple example HTML invocation is: 

<object classid="javax.swing.JLabel">
<param name="text" value="sample text">
</object>
author
Timothy Prinzing
version
1.13 12/19/03

Fields Summary
Constructors Summary
public ObjectView(Element elem)
Creates a new ObjectView object.

param
elem the element to decorate

	super(elem);
Methods Summary
protected java.awt.ComponentcreateComponent()
Create the component. The classid is used as a specification of the classname, which we try to load.

	AttributeSet attr = getElement().getAttributes();
	String classname = (String) attr.getAttribute(HTML.Attribute.CLASSID);
	try {
            Class c = Class.forName(classname, true,Thread.currentThread().
                                    getContextClassLoader());
	    Object o = c.newInstance();
	    if (o instanceof Component) {
		Component comp = (Component) o;
		setParameters(comp, attr);
		return comp;
	    }
	} catch (Throwable e) {
	    // couldn't create a component... fall through to the 
	    // couldn't load representation.
	}
	
	return getUnloadableRepresentation();
private java.lang.ClassgetClass(java.lang.String classname)
Get a Class object to use for loading the classid. If possible, the Classloader used to load the associated Document is used. This would typically be the same as the ClassLoader used to load the EditorKit. If the documents ClassLoader is null, Class.forName is used.

	Class klass;

	Class docClass = getDocument().getClass();
	ClassLoader loader = docClass.getClassLoader();
	if (loader != null) {
	    klass = loader.loadClass(classname);
	} else {
	    klass = Class.forName(classname);
	}
	return klass;
java.awt.ComponentgetUnloadableRepresentation()
Fetch a component that can be used to represent the object if it can't be created.

	// PENDING(prinz) get some artwork and return something
	// interesting here.
	Component comp = new JLabel("??");
	comp.setForeground(Color.red);
	return comp;
private voidsetParameters(java.awt.Component comp, javax.swing.text.AttributeSet attr)
Initialize this component according the KEY/VALUEs passed in via the <param> elements in the corresponding <object> element.

	Class k = comp.getClass();
	BeanInfo bi;
	try {
	    bi = Introspector.getBeanInfo(k);
	} catch (IntrospectionException ex) {
	    System.err.println("introspector failed, ex: "+ex);
	    return;		// quit for now
	}
	PropertyDescriptor props[] = bi.getPropertyDescriptors();
	for (int i=0; i < props.length; i++) {
	    //	    System.err.println("checking on props[i]: "+props[i].getName());
	    Object v = attr.getAttribute(props[i].getName());
	    if (v instanceof String) {
		// found a property parameter
		String value = (String) v;
		Method writer = props[i].getWriteMethod();
		if (writer == null) {
		    // read-only property. ignore
		    return;	// for now
		}
		Class[] params = writer.getParameterTypes();
		if (params.length != 1) {
		    // zero or more than one argument, ignore
		    return;	// for now
		}
		String [] args = { value };
		try {
		    writer.invoke(comp, args);
		} catch (Exception ex) {
		    System.err.println("Invocation failed");
		    // invocation code
		}
	    }
	}