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TagAdapter.javaAPI DocGlassfish v2 API6336Fri May 04 22:34:16 BST 2007javax.servlet.jsp.tagext

TagAdapter

public class TagAdapter extends Object implements Tag
Wraps any SimpleTag and exposes it using a Tag interface. This is used to allow collaboration between classic Tag handlers and SimpleTag handlers.

Because SimpleTag does not extend Tag, and because Tag.setParent() only accepts a Tag instance, a classic tag handler (one that implements Tag) cannot have a SimpleTag as its parent. To remedy this, a TagAdapter is created to wrap the SimpleTag parent, and the adapter is passed to setParent() instead. A classic Tag Handler can call getAdaptee() to retrieve the encapsulated SimpleTag instance.

since
2.0

Fields Summary
private SimpleTag
simpleTagAdaptee
The simple tag that's being adapted.
private Tag
parent
The parent, of this tag, converted (if necessary) to be of type Tag.
private boolean
parentDetermined
Constructors Summary
public TagAdapter(SimpleTag adaptee)
Creates a new TagAdapter that wraps the given SimpleTag and returns the parent tag when getParent() is called.

param
adaptee The SimpleTag being adapted as a Tag.

        if( adaptee == null ) {
	    // Cannot wrap a null adaptee.
	    throw new IllegalArgumentException();
        }
        this.simpleTagAdaptee = adaptee;
Methods Summary
public intdoEndTag()
Must not be called.

return
always throws UnsupportedOperationException
throws
UnsupportedOperationException Must not be called
throws
JspException never thrown

        throw new UnsupportedOperationException( 
            "Illegal to invoke doEndTag() on TagAdapter wrapper" );
public intdoStartTag()
Must not be called.

return
always throws UnsupportedOperationException
throws
UnsupportedOperationException Must not be called
throws
JspException never thrown

        throw new UnsupportedOperationException( 
            "Illegal to invoke doStartTag() on TagAdapter wrapper" );
public JspTaggetAdaptee()
Gets the tag that is being adapted to the Tag interface. This should be an instance of SimpleTag in JSP 2.0, but room is left for other kinds of tags in future spec versions.

return
the tag that is being adapted

        return this.simpleTagAdaptee;
public TaggetParent()
Returns the parent of this tag, which is always getAdaptee().getParent(). This will either be the enclosing Tag (if getAdaptee().getParent() implements Tag), or an adapter to the enclosing Tag (if getAdaptee().getParent() does not implement Tag).

return
The parent of the tag being adapted.

	if (!parentDetermined) {
	    JspTag adapteeParent = simpleTagAdaptee.getParent();
	    if (adapteeParent != null) {
		if (adapteeParent instanceof Tag) {
		    this.parent = (Tag) adapteeParent;
		} else {
		    // Must be SimpleTag - no other types defined.
		    this.parent = new TagAdapter((SimpleTag) adapteeParent);
		}
	    }
	    parentDetermined = true;
	}

	return this.parent;
public voidrelease()
Must not be called.

throws
UnsupportedOperationException Must not be called

        throw new UnsupportedOperationException( 
            "Illegal to invoke release() on TagAdapter wrapper" );
public voidsetPageContext(PageContext pc)
Must not be called.

param
pc ignored.
throws
UnsupportedOperationException Must not be called

        throw new UnsupportedOperationException( 
            "Illegal to invoke setPageContext() on TagAdapter wrapper" );
public voidsetParent(Tag parentTag)
Must not be called. The parent of this tag is always getAdaptee().getParent().

param
parentTag ignored.
throws
UnsupportedOperationException Must not be called.

        throw new UnsupportedOperationException( 
            "Illegal to invoke setParent() on TagAdapter wrapper" );