Package jakarta.servlet.jsp.tagext

Class SimpleTagSupport

  • All Implemented Interfaces:
    JspTag, SimpleTag
    public class SimpleTagSupport
extends Object
implements SimpleTag
    A base class for defining tag handlers implementing SimpleTag.

    The SimpleTagSupport class is a utility class intended to be used as the base class for new simple tag handlers. The SimpleTagSupport class implements the SimpleTag interface and adds additional convenience methods including getter methods for the properties in SimpleTag.

    Since:
    JSP 2.0

    • Constructor Detail

      • SimpleTagSupport

        public SimpleTagSupport()
        Sole constructor. (For invocation by subclass constructors, typically implicit.)

    • Method Detail

      • doTag

        public void doTag()
           throws JspException,
                  IOException
        Default processing of the tag does nothing.
        Specified by:
        doTag in interface SimpleTag
        Throws:
        JspException - Subclasses can throw JspException to indicate an error occurred while processing this tag.
        SkipPageException - If the page that (either directly or indirectly) invoked this tag is to cease evaluation. A Simple Tag Handler generated from a tag file must throw this exception if an invoked Classic Tag Handler returned SKIP_PAGE or if an invoked Simple Tag Handler threw SkipPageException or if an invoked Jsp Fragment threw a SkipPageException.
        IOException - Subclasses can throw IOException if there was an error writing to the output stream
        See Also:
        SimpleTag.doTag()

      • setParent

        public void setParent​(JspTag parent)
        Sets the parent of this tag, for collaboration purposes.

        The container invokes this method only if this tag invocation is nested within another tag invocation.

        Specified by:
        setParent in interface SimpleTag
        Parameters:
        parent - the tag that encloses this tag

      • getParent

        public JspTag getParent()
        Returns the parent of this tag, for collaboration purposes.
        Specified by:
        getParent in interface SimpleTag
        Returns:
        the parent of this tag

      • getJspContext

        protected JspContext getJspContext()
        Returns the page context passed in by the container via setJspContext.
        Returns:
        the page context for this invocation

      • getJspBody

        protected JspFragment getJspBody()
        Returns the body passed in by the container via setJspBody.
        Returns:
        the fragment encapsulating the body of this tag, or null if the action element is empty in the page.

      • findAncestorWithClass

        public static final JspTag findAncestorWithClass​(JspTag from,
                                                 Class<?> klass)
        Find the instance of a given class type that is closest to a given instance. This method uses the getParent method from the Tag and/or SimpleTag interfaces. This method is used for coordination among cooperating tags.

        For every instance of TagAdapter encountered while traversing the ancestors, the tag handler returned by TagAdapter.getAdaptee() - instead of the TagAdpater itself - is compared to klass. If the tag handler matches, it - and not its TagAdapter - is returned.

        The current version of the specification only provides one formal way of indicating the observable type of a tag handler: its tag handler implementation class, described in the tag-class subelement of the tag element. This is extended in an informal manner by allowing the tag library author to indicate in the description subelement an observable type. The type should be a subtype of the tag handler implementation class or void. This addititional constraint can be exploited by a specialized container that knows about that specific tag library, as in the case of the JSP standard tag library.

        When a tag library author provides information on the observable type of a tag handler, client programmatic code should adhere to that constraint. Specifically, the Class passed to findAncestorWithClass should be a subtype of the observable type.

        Parameters:
        from - The instance from where to start looking.
        klass - The subclass of JspTag or interface to be matched
        Returns:
        the nearest ancestor that implements the interface or is an instance of the class specified