Package jakarta.servlet.jsp.tagext

Class TagSupport

java.lang.Object

jakarta.servlet.jsp.tagext.TagSupport

All Implemented Interfaces:

IterationTag, JspTag, Tag, Serializable

Direct Known Subclasses:

BodyTagSupport

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.

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected String	id	The value of the id attribute of this tag; or null.
protected PageContext	pageContext	The PageContext.

Fields inherited from interface jakarta.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface jakarta.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

Constructors

Constructor	Description
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

Modifier and Type	Method	Description
int	doAfterBody()	Default processing for a body.
int	doEndTag()	Default processing of the end tag returning EVAL_PAGE.
int	doStartTag()	Default processing of the start tag, returning SKIP_BODY.
static final Tag	findAncestorWithClass(Tag from, Class<?> klass)	Find the instance of a given class type that is closest to a given instance.
String	getId()	The value of the id attribute of this tag; or null.
Tag	getParent()	The Tag instance most closely enclosing this tag instance.
Object	getValue(String k)	Get a the value associated with a key.
Enumeration<String>	getValues()	Enumerate the keys for the values kept by this tag handler.
void	release()	Release state.
void	removeValue(String k)	Remove a value associated with a key.
void	setId(String id)	Set the id attribute for this tag.
void	setPageContext(PageContext pageContext)	Set the page context.
void	setParent(Tag t)	Set the nesting tag of this tag.
void	setValue(String k, Object o)	Associate a value with a String key.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

id

protected String id

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

pageContext

protected transient PageContext pageContext

The PageContext.

Constructor Details

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 Details

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 additional 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

doStartTag

public int doStartTag()
               throws JspException

Default processing of the start tag, returning SKIP_BODY.

Specified by:

doStartTag in interface Tag

Returns:

SKIP_BODY

Throws:

JspException - if an error occurs while processing this tag

See Also:

• Tag.doStartTag()

doEndTag

public int doEndTag()
             throws JspException

Default processing of the end tag returning EVAL_PAGE.

Specified by:

doEndTag in interface Tag

Returns:

EVAL_PAGE

Throws:

JspException - if an error occurs while processing this tag

See Also:

• Tag.doEndTag()

doAfterBody

public int doAfterBody()
                throws JspException

Default processing for a body.

Specified by:

doAfterBody in interface IterationTag

Returns:

SKIP_BODY

Throws:

JspException - if an error occurs while processing this tag

See Also:

• IterationTag.doAfterBody()

release

public void release()

Release state.

Specified by:

release in interface Tag

See Also:

• Tag.release()

setParent

public void setParent(Tag t)

Set the nesting tag of this tag.

Specified by:

setParent in interface Tag

Parameters:

t - The parent Tag.

See Also:

• Tag.setParent(Tag)

getParent

public Tag getParent()

The Tag instance most closely enclosing this tag instance.

Specified by:

getParent in interface Tag

Returns:

the parent tag instance or null

See Also:

• Tag.getParent()

setId

public void setId(String id)

Set the id attribute for this tag.

Parameters:

id - The String for the id.

getId

public String getId()

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

Returns:

the value of the id attribute, or null

setPageContext

public void setPageContext(PageContext pageContext)

Set the page context.

Specified by:

setPageContext in interface Tag

Parameters:

pageContext - The PageContext.

See Also:

• Tag.setPageContext(jakarta.servlet.jsp.PageContext)

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.

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.

removeValue

public void removeValue(String k)

Remove a value associated with a key.

Parameters:

k - The string key.

getValues

public Enumeration<String> 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.