javax.servlet.jsp
public abstract class JspContext extends Object
JspContext
serves as the base class for the
PageContext class and abstracts all information that is not specific
to servlets. This allows for Simple Tag Extensions to be used
outside of the context of a request/response Servlet.
The JspContext provides a number of facilities to the page/component author and page implementor, including:
Methods Intended for Container Generated Code
The following methods enable the management of nested JspWriter
streams to implement Tag Extensions: pushBody()
and
popBody()
Methods Intended for JSP authors
Some methods provide uniform access to the diverse objects
representing scopes.
The implementation must use the underlying machinery
corresponding to that scope, so information can be passed back and
forth between the underlying environment (e.g. Servlets) and JSP pages.
The methods are:
setAttribute()
, getAttribute()
,
findAttribute()
, removeAttribute()
,
getAttributesScope()
and
getAttributeNamesInScope()
.
The following methods provide convenient access to implicit objects:
getOut()
The following methods provide programmatic access to the
Expression Language evaluator:
getExpressionEvaluator()
, getVariableResolver()
Since: 2.0
Constructor Summary | |
---|---|
JspContext()
Sole constructor. |
Method Summary | |
---|---|
abstract Object | findAttribute(String name)
Searches for the named attribute in page, request, session (if valid),
and application scope(s) in order and returns the value associated or
null.
|
abstract Object | getAttribute(String name)
Returns the object associated with the name in the page scope or null
if not found.
|
abstract Object | getAttribute(String name, int scope)
Return the object associated with the name in the specified
scope or null if not found.
|
abstract Enumeration | getAttributeNamesInScope(int scope)
Enumerate all the attributes in a given scope.
|
abstract int | getAttributesScope(String name)
Get the scope where a given attribute is defined.
|
abstract ExpressionEvaluator | getExpressionEvaluator()
Provides programmatic access to the ExpressionEvaluator.
|
abstract JspWriter | getOut()
The current value of the out object (a JspWriter).
|
abstract VariableResolver | getVariableResolver()
Returns an instance of a VariableResolver that provides access to the
implicit objects specified in the JSP specification using this JspContext
as the context object.
|
JspWriter | popBody()
Return the previous JspWriter "out" saved by the matching
pushBody(), and update the value of the "out" attribute in
the page scope attribute namespace of the JspContext.
|
JspWriter | pushBody(Writer writer)
Return a new JspWriter object that sends output to the
provided Writer. |
abstract void | removeAttribute(String name)
Remove the object reference associated with the given name
from all scopes. |
abstract void | removeAttribute(String name, int scope)
Remove the object reference associated with the specified name
in the given scope. |
abstract void | setAttribute(String name, Object value)
Register the name and value specified with page scope semantics.
|
abstract void | setAttribute(String name, Object value, int scope)
Register the name and value specified with appropriate
scope semantics. |
Parameters: name the name of the attribute to search for
Returns: the value associated or null
Throws: NullPointerException if the name is null
Parameters: name the name of the attribute to get
Returns: the object associated with the name in the page scope or null if not found.
Throws: NullPointerException if the name is null
Parameters: name the name of the attribute to set scope the scope with which to associate the name/object
Returns: the object associated with the name in the specified scope or null if not found.
Throws: NullPointerException if the name is null IllegalArgumentException if the scope is invalid IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does not participate in a session or the session has been invalidated.
Parameters: scope the scope to enumerate all the attributes for
Returns: an enumeration of names (java.lang.String) of all the attributes the specified scope
Throws: IllegalArgumentException if the scope is invalid IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does not participate in a session or the session has been invalidated.
Parameters: name the name of the attribute to return the scope for
Returns: the scope of the object associated with the name specified or 0
Throws: NullPointerException if the name is null
Returns: A valid instance of an ExpressionEvaluator.
Since: 2.0
Returns: the current JspWriter stream being used for client response
Returns: A valid instance of a VariableResolver.
Since: 2.0
Returns: the saved JspWriter.
The returned JspWriter must implement all methods and behave as though it were unbuffered. More specifically:
Parameters: writer The Writer for the returned JspWriter to send output to.
Returns: a new JspWriter that writes to the given Writer.
Since: 2.0
Parameters: name The name of the object to remove.
Throws: NullPointerException if the name is null
Parameters: name The name of the object to remove. scope The scope where to look.
Throws: IllegalArgumentException if the scope is invalid IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does not participate in a session or the session has been invalidated. NullPointerException if the name is null
null
, this has the same
effect as calling
removeAttribute( name, PageContext.PAGE_SCOPE )
.
Parameters: name the name of the attribute to set value the value to associate with the name, or null if the attribute is to be removed from the page scope.
Throws: NullPointerException if the name is null
null
,
this has the same effect as calling
removeAttribute( name, scope )
.
Parameters: name the name of the attribute to set value the object to associate with the name, or null if the attribute is to be removed from the specified scope. scope the scope with which to associate the name/object
Throws: NullPointerException if the name is null IllegalArgumentException if the scope is invalid IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does not participate in a session or the session has been invalidated.