Class TagAdapter

java.lang.Object
jakarta.servlet.jsp.tagext.TagAdapter
All Implemented Interfaces:
JspTag, Tag
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:
JSP 2.0

  • Constructor Details

    • TagAdapter

      public TagAdapter(SimpleTag adaptee)
      Creates a new TagAdapter that wraps the given SimpleTag and returns the parent tag when getParent() is called.
      Parameters:
      adaptee - The SimpleTag being adapted as a Tag.

  • Method Details

    • setPageContext

      public void setPageContext(PageContext pc)
      Must not be called.
      Specified by:
      setPageContext in interface Tag
      Parameters:
      pc - ignored.
      Throws:
      UnsupportedOperationException - Must not be called

    • setParent

      public void setParent(Tag parentTag)
      Must not be called. The parent of this tag is always getAdaptee().getParent().
      Specified by:
      setParent in interface Tag
      Parameters:
      parentTag - ignored.
      Throws:
      UnsupportedOperationException - Must not be called.

    • getParent

      public Tag getParent()
      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).
      Specified by:
      getParent in interface Tag
      Returns:
      The parent of the tag being adapted.
      See Also:

    • getAdaptee

      public JspTag getAdaptee()
      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.
      Returns:
      the tag that is being adapted

    • doStartTag

      public int doStartTag() throws JspException
      Must not be called.
      Specified by:
      doStartTag in interface Tag
      Returns:
      always throws UnsupportedOperationException
      Throws:
      UnsupportedOperationException - Must not be called
      JspException - never thrown
      See Also:

    • doEndTag

      public int doEndTag() throws JspException
      Must not be called.
      Specified by:
      doEndTag in interface Tag
      Returns:
      always throws UnsupportedOperationException
      Throws:
      UnsupportedOperationException - Must not be called
      JspException - never thrown

    • release

      public void release()
      Must not be called.
      Specified by:
      release in interface Tag
      Throws:
      UnsupportedOperationException - Must not be called