| java.lang.Object
 javax.el.ELResolver
javax.el.CompositeELResolver
| CompositeELResolver | | public class CompositeELResolver extends ELResolver (Code) | | Maintains an ordered composite list of child ELResolvers.
Though only a single ELResolver is associated with an
ELContext, there are usually multiple resolvers considered
for any given variable or property resolution. ELResolvers
are combined together using a CompositeELResolver, to define
rich semantics for evaluating an expression.
For the
CompositeELResolver.getValue ,
CompositeELResolver.getType ,
CompositeELResolver.setValue and
CompositeELResolver.isReadOnly methods, an ELResolver is not
responsible for resolving all possible (base, property) pairs. In fact,
most resolvers will only handle a base of a single type.
To indicate that a resolver has successfully resolved a particular
(base, property) pair, it must set the propertyResolved
property of the ELContext to true. If it could
not handle the given pair, it must leave this property alone. The caller
must ignore the return value of the method if propertyResolved
is false.
The CompositeELResolver initializes the
ELContext.propertyResolved flag to false, and uses
it as a stop condition for iterating through its component resolvers.
The ELContext.propertyResolved flag is not used for the
design-time methods
CompositeELResolver.getFeatureDescriptors and
CompositeELResolver.getCommonPropertyType . Instead, results are collected and
combined from all child ELResolvers for these methods.
See Also: ELContext
See Also: ELResolver
since:
JSP 2.1 |
| Method Summary | |
| public void | add(ELResolver elResolver)
Adds the given resolver to the list of component resolvers. | | public Class | getCommonPropertyType(ELContext context, Object base)
Returns the most general type that this resolver accepts for the
property argument, given a base object.
One use for this method is to assist tools in auto-completion. | | public Iterator<FeatureDescriptor> | getFeatureDescriptors(ELContext context, Object base)
Returns information about the set of variables or properties that
can be resolved for the given base object. | | public Class | getType(ELContext context, Object base, Object property)
For a given base and property, attempts to
identify the most general type that is acceptable for an object to be
passed as the value parameter in a future call
to the
CompositeELResolver.setValue method. | | public Object | getValue(ELContext context, Object base, Object property)
Attempts to resolve the given property object on the given
base object by querying all component resolvers.
If this resolver handles the given (base, property) pair,
the propertyResolved property of the
ELContext object must be set to true
by the resolver, before returning. | | public boolean | isReadOnly(ELContext context, Object base, Object property)
For a given base and property, attempts to
determine whether a call to
CompositeELResolver.setValue will always fail. | | public void | setValue(ELContext context, Object base, Object property, Object val)
Attempts to set the value of the given property
object on the given base object. |
| add | | public void add(ELResolver elResolver)(Code) | | Adds the given resolver to the list of component resolvers.
Resolvers are consulted in the order in which they are added.
Parameters:
elResolver - The component resolver to add.
throws:
NullPointerException - If the provided resolver isnull. |
| getCommonPropertyType | | public Class getCommonPropertyType(ELContext context, Object base)(Code) | | Returns the most general type that this resolver accepts for the
property argument, given a base object.
One use for this method is to assist tools in auto-completion. The
result is obtained by querying all component resolvers.
The Class returned is the most specific class that is
a common superclass of all the classes returned by each component
resolver's getCommonPropertyType method. If
null is returned by a resolver, it is skipped.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object to return the most general propertytype for, or null to enumerate the set oftop-level variables that this resolver can evaluate. null if this ELResolver does notknow how to handle the given base object; otherwiseObject.class if any type of propertyis accepted; otherwise the most general propertytype accepted for the given base. |
| getFeatureDescriptors | | public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)(Code) | | Returns information about the set of variables or properties that
can be resolved for the given base object. One use for
this method is to assist tools in auto-completion. The results are
collected from all component resolvers.
The propertyResolved property of the
ELContext is not relevant to this method.
The results of all ELResolvers are concatenated.
The Iterator returned is an iterator over the
collection of FeatureDescriptor objects returned by
the iterators returned by each component resolver's
getFeatureDescriptors method. If null is
returned by a resolver, it is skipped.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object whose set of valid properties is tobe enumerated, or null to enumerate the set oftop-level variables that this resolver can evaluate. An Iterator containing zero or more (possiblyinfinitely more) FeatureDescriptor objects, or null if this resolver does not handle the given base object or that the results are too complex to represent with this method |
| getType | | public Class getType(ELContext context, Object base, Object property)(Code) | | For a given base and property, attempts to
identify the most general type that is acceptable for an object to be
passed as the value parameter in a future call
to the
CompositeELResolver.setValue method. The result is obtained by
querying all component resolvers.
If this resolver handles the given (base, property) pair,
the propertyResolved property of the
ELContext object must be set to true
by the resolver, before returning. If this property is not
true after this method is called, the caller should ignore
the return value.
First, propertyResolved is set to false on
the provided ELContext.
Next, for each component resolver in this composite:
- The
getType() method is called, passing in
the provided context, base and
property.
- If the
ELContext's propertyResolved
flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are
considered. The value returned by
getType() is
returned by this method.
If none of the component resolvers were able to perform this
operation, the value null is returned and the
propertyResolved flag remains set to
false .
Any exception thrown by component resolvers during the iteration
is propagated to the caller of this method.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object whose property value is to be analyzed,or null to analyze a top-level variable.
Parameters:
property - The property or variable to return the acceptable type for. If the propertyResolved property of ELContext was set to true, thenthe most general acceptable type; otherwise undefined.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if the given (base, property) pairis handled by this ELResolver but the specifiedvariable or property does not exist or is not readable.
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| getValue | | public Object getValue(ELContext context, Object base, Object property)(Code) | | Attempts to resolve the given property object on the given
base object by querying all component resolvers.
If this resolver handles the given (base, property) pair,
the propertyResolved property of the
ELContext object must be set to true
by the resolver, before returning. If this property is not
true after this method is called, the caller should ignore
the return value.
First, propertyResolved is set to false on
the provided ELContext.
Next, for each component resolver in this composite:
- The
getValue() method is called, passing in
the provided context, base and
property.
- If the
ELContext's propertyResolved
flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are
considered. The value returned by
getValue() is
returned by this method.
If none of the component resolvers were able to perform this
operation, the value null is returned and the
propertyResolved flag remains set to
false .
Any exception thrown by component resolvers during the iteration
is propagated to the caller of this method.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object whose property value is to be returned,or null to resolve a top-level variable.
Parameters:
property - The property or variable to be resolved. If the propertyResolved property of ELContext was set to true, thenthe result of the variable or property resolution; otherwiseundefined.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if the given (base, property) pairis handled by this ELResolver but the specifiedvariable or property does not exist or is not readable.
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| isReadOnly | | public boolean isReadOnly(ELContext context, Object base, Object property)(Code) | | For a given base and property, attempts to
determine whether a call to
CompositeELResolver.setValue will always fail. The
result is obtained by querying all component resolvers.
If this resolver handles the given (base, property) pair,
the propertyResolved property of the
ELContext object must be set to true
by the resolver, before returning. If this property is not
true after this method is called, the caller should ignore
the return value.
First, propertyResolved is set to false on
the provided ELContext.
Next, for each component resolver in this composite:
- The
isReadOnly() method is called, passing in
the provided context, base and
property.
- If the
ELContext's propertyResolved
flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are
considered. The value returned by
isReadOnly() is
returned by this method.
If none of the component resolvers were able to perform this
operation, the value false is returned and the
propertyResolved flag remains set to
false .
Any exception thrown by component resolvers during the iteration
is propagated to the caller of this method.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object whose property value is to be analyzed,or null to analyze a top-level variable.
Parameters:
property - The property or variable to return the read-only statusfor. If the propertyResolved property of ELContext was set to true, thentrue if the property is read-only orfalse if not; otherwise undefined.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if the given (base, property) pairis handled by this ELResolver but the specifiedvariable or property does not exist.
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| setValue | | public void setValue(ELContext context, Object base, Object property, Object val)(Code) | | Attempts to set the value of the given property
object on the given base object. All component
resolvers are asked to attempt to set the value.
If this resolver handles the given (base, property) pair,
the propertyResolved property of the
ELContext object must be set to true
by the resolver, before returning. If this property is not
true after this method is called, the caller can
safely assume no value has been set.
First, propertyResolved is set to false on
the provided ELContext.
Next, for each component resolver in this composite:
- The
setValue() method is called, passing in
the provided context, base,
property and value.
- If the
ELContext's propertyResolved
flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are
considered.
If none of the component resolvers were able to perform this
operation, the propertyResolved flag remains set to
false .
Any exception thrown by component resolvers during the iteration
is propagated to the caller of this method.
Parameters:
context - The context of this evaluation.
Parameters:
base - The base object whose property value is to be set,or null to set a top-level variable.
Parameters:
property - The property or variable to be set.
Parameters:
val - The value to set the property or variable to.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if the given (base, property) pairis handled by this ELResolver but the specifiedvariable or property does not exist.
throws:
PropertyNotWritableException - if the given (base, property)pair is handled by this ELResolver but the specifiedvariable or property is not writable.
throws:
ELException - if an exception was thrown while attempting toset the property or variable. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| Methods inherited from javax.el.ELResolver | abstract public Class getCommonPropertyType(ELContext context, Object base)(Code)(Java Doc)
abstract public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)(Code)(Java Doc)
abstract public Class getType(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public Object getValue(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public boolean isReadOnly(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public void setValue(ELContext context, Object base, Object property, Object value)(Code)(Java Doc)
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