TagSupport (Java EE 5 SDK)

javax.servlet.jsp.tagext Class TagSupport

java.lang.Object
  javax.servlet.jsp.tagext.TagSupport

所有已实现的接口:

Serializable, IterationTag, JspTag, Tag

直接已知子类:

AttributeTag, BodyTagSupport, ConverterELTag, ConverterTag, FacetTag, ValidatorELTag, ValidatorTag

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.

另请参见:

Serialized Form

id

protected String id

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

pageContext

protected PageContext pageContext

The PageContext.

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.

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.

参数:

from - The instance from where to start looking.

klass - The subclass of Tag or interface to be matched

返回:

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.

规范说明:

doStartTag in interface Tag

返回:

SKIP_BODY

抛出异常:

JspException - if an error occurs while processing this tag

另请参见:

Tag.doStartTag()

doEndTag

public int doEndTag()
             throws JspException

Default processing of the end tag returning EVAL_PAGE.

规范说明:

doEndTag in interface Tag

返回:

EVAL_PAGE

抛出异常:

JspException - if an error occurs while processing this tag

另请参见:

Tag.doEndTag()

doAfterBody

public int doAfterBody()
                throws JspException

Default processing for a body.

规范说明:

doAfterBody in interface IterationTag

返回:

SKIP_BODY

抛出异常:

JspException - if an error occurs while processing this tag

另请参见:

IterationTag.doAfterBody()

release

public void release()

Release state.

规范说明:

release in interface Tag

另请参见:

Tag.release()

setParent

public void setParent(Tag t)

Set the nesting tag of this tag.

规范说明:

setParent in interface Tag

参数:

t - The parent Tag.

另请参见:

Tag.setParent(Tag)

getParent

public Tag getParent()

The Tag instance most closely enclosing this tag instance.

规范说明:

getParent in interface Tag

返回:

the parent tag instance or null

另请参见:

Tag.getParent()

setId

public void setId(String id)

Set the id attribute for this tag.

参数:

id - The String for the id.

getId

public String getId()

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

返回:

the value of the id attribute, or null

setPageContext

public void setPageContext(PageContext pageContext)

Set the page context.

规范说明:

setPageContext in interface Tag

参数:

pageContext - The PageContext.

另请参见:

Tag.setPageContext(javax.servlet.jsp.PageContext)

setValue

public void setValue(String k,
                     Object o)

Associate a value with a String key.

参数:

k - The key String.

o - The value to associate.

getValue

public Object getValue(String k)

Get a the value associated with a key.

参数:

k - The string key.

返回:

The value associated with the key, or null.

removeValue

public void removeValue(String k)

Remove a value associated with a key.

参数:

k - The string key.

getValues

public Enumeration<String> getValues()

Enumerate the keys for the values kept by this tag handler.

返回:

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

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