javax.servlet.jsp.tagext

Class TagSupport

public class TagSupport extends Object implements IterationTag, Serializable

A base class for defining new tag handlers implementing Tag.

The TagSupport class is a utility class intended to be used as the base class for new tag handlers. The TagSupport class implements the Tag and IterationTag interfaces and adds additional convenience methods including getter methods for the properties in Tag. TagSupport has one static method that is included to facilitate coordination among cooperating tags.

Many tag handlers will extend TagSupport and only redefine a few methods.

Field Summary
protected Stringid
The value of the id attribute of this tag; or null.
protected PageContextpageContext
The PageContext.
Constructor Summary
TagSupport()
Default constructor, all subclasses are required to define only a public constructor with the same signature, and to call the superclass constructor.
Method Summary
intdoAfterBody()
Default processing for a body.
intdoEndTag()
Default processing of the end tag returning EVAL_PAGE.
intdoStartTag()
Default processing of the start tag, returning SKIP_BODY.
static TagfindAncestorWithClass(Tag from, Class klass)
Find the instance of a given class type that is closest to a given instance.
StringgetId()
The value of the id attribute of this tag; or null.
TaggetParent()
The Tag instance most closely enclosing this tag instance.
ObjectgetValue(String k)
Get a the value associated with a key.
EnumerationgetValues()
Enumerate the keys for the values kept by this tag handler.
voidrelease()
Release state.
voidremoveValue(String k)
Remove a value associated with a key.
voidsetId(String id)
Set the id attribute for this tag.
voidsetPageContext(PageContext pageContext)
Set the page context.
voidsetParent(Tag t)
Set the nesting tag of this tag.
voidsetValue(String k, Object o)
Associate a value with a String key.

Field Detail

id

protected String id
The value of the id attribute of this tag; or null.

pageContext

protected PageContext pageContext
The PageContext.

Constructor Detail

TagSupport

public TagSupport()
Default constructor, all subclasses are required to define only a public constructor with the same signature, and to call the superclass constructor. This constructor is called by the code generated by the JSP translator.

Method Detail

doAfterBody

public int doAfterBody()
Default processing for a body.

Returns: SKIP_BODY

Throws: JspException if an error occurs while processing this tag

See Also: doAfterBody

doEndTag

public int doEndTag()
Default processing of the end tag returning EVAL_PAGE.

Returns: EVAL_PAGE

Throws: JspException if an error occurs while processing this tag

See Also: doEndTag

doStartTag

public int doStartTag()
Default processing of the start tag, returning SKIP_BODY.

Returns: SKIP_BODY

Throws: JspException if an error occurs while processing this tag

See Also: doStartTag

findAncestorWithClass

public static final Tag findAncestorWithClass(Tag 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 interface. This method is used for coordination among cooperating tags.

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 Tag or interface to be matched

Returns: the nearest ancestor that implements the interface or is an instance of the class specified

getId

public String getId()
The value of the id attribute of this tag; or null.

Returns: the value of the id attribute, or null

getParent

public Tag getParent()
The Tag instance most closely enclosing this tag instance.

Returns: the parent tag instance or null

See Also:

getValue

public Object getValue(String k)
Get a the value associated with a key.

Parameters: k The string key.

Returns: The value associated with the key, or null.

getValues

public Enumeration getValues()
Enumerate the keys for the values kept by this tag handler.

Returns: An enumeration of all the keys for the values set, or null or an empty Enumeration if no values have been set.

release

public void release()
Release state.

See Also: release

removeValue

public void removeValue(String k)
Remove a value associated with a key.

Parameters: k The string key.

setId

public void setId(String id)
Set the id attribute for this tag.

Parameters: id The String for the id.

setPageContext

public void setPageContext(PageContext pageContext)
Set the page context.

Parameters: pageContext The PageContext.

See Also: Tag

setParent

public void setParent(Tag t)
Set the nesting tag of this tag.

Parameters: t The parent Tag.

See Also: setParent

setValue

public void setValue(String k, Object o)
Associate a value with a String key.

Parameters: k The key String. o The value to associate.

Copyright © 2004 Mortbay Consulting Pty. Ltd. All Rights Reserved.