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()
Constructor and Description |
---|
JspContext()
Sole constructor.
|
Modifier and Type | Method and Description |
---|---|
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<String> |
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 javax.el.ELContext |
getELContext()
Returns the
ELContext associated with this JspContext . |
abstract ExpressionEvaluator |
getExpressionEvaluator()
Deprecated.
As of JSP 2.1, replaced by
JspApplicationContext.getExpressionFactory() |
abstract JspWriter |
getOut()
The current value of the out object (a JspWriter).
|
abstract VariableResolver |
getVariableResolver()
Deprecated.
As of JSP 2.1, replaced by
ELContext.getELResolver() , which can be obtained by
jspContext.getELContext().getELResolver() . |
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.
|
public JspContext()
public abstract void setAttribute(String name, Object value)
null
,
this has the same effect as calling removeAttribute( name, PageContext.PAGE_SCOPE )
.name
- the name of the attribute to setvalue
- the value to associate with the name, or null if the attribute is to be removed from the page scope.NullPointerException
- if the name is nullpublic abstract void setAttribute(String name, Object value, int scope)
null
, this has the same effect as calling removeAttribute( name, scope )
.name
- the name of the attribute to setvalue
- 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/objectNullPointerException
- if the name is nullIllegalArgumentException
- if the scope is invalidIllegalStateException
- 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.public abstract Object getAttribute(String name)
name
- the name of the attribute to getNullPointerException
- if the name is nullpublic abstract Object getAttribute(String name, int scope)
name
- the name of the attribute to setscope
- the scope with which to associate the name/objectNullPointerException
- if the name is nullIllegalArgumentException
- if the scope is invalidIllegalStateException
- 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.public abstract Object findAttribute(String name)
name
- the name of the attribute to search forNullPointerException
- if the name is nullpublic abstract void removeAttribute(String name)
name
- The name of the object to remove.NullPointerException
- if the name is nullpublic abstract void removeAttribute(String name, int scope)
name
- The name of the object to remove.scope
- The scope where to look.IllegalArgumentException
- if the scope is invalidIllegalStateException
- 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 nullpublic abstract int getAttributesScope(String name)
name
- the name of the attribute to return the scope forNullPointerException
- if the name is nullpublic abstract Enumeration<String> getAttributeNamesInScope(int scope)
scope
- the scope to enumerate all the attributes forIllegalArgumentException
- if the scope is invalidIllegalStateException
- 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.public abstract JspWriter getOut()
public abstract ExpressionEvaluator getExpressionEvaluator()
JspApplicationContext.getExpressionFactory()
public abstract VariableResolver getVariableResolver()
ELContext.getELResolver()
, which can be obtained by
jspContext.getELContext().getELResolver()
.public abstract javax.el.ELContext getELContext()
ELContext
associated with this JspContext
.
The ELContext
is created lazily and is reused if it already exists. There is a new
ELContext
for each JspContext
.
The ELContext
must contain the ELResolver
described in the JSP specification (and in
the javadocs for JspApplicationContext.addELResolver(javax.el.ELResolver)
).
ELContext
associated with this JspContext
.public JspWriter pushBody(Writer writer)
The returned JspWriter must implement all methods and behave as though it were unbuffered. More specifically:
writer
- The Writer for the returned JspWriter to send output to.public JspWriter popBody()
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