oracle.adfnmc.el
Interface ELResolver

All Known Implementing Classes:

AdapterOperationBinding, AttributeBindingImpl, BeanELResolver, BeanResolver, CompositeELResolver, ControlBindingImpl, CredentialsBean, CustomOperationBinding, DynamicListBindingImpl, IndexedAttributeBindingImpl, IteratorExecutableBindingImpl, ListELResolver, MapELResolver, MethodIteratorBindingImpl, MobileSyncBean, OperationBindingBase, RangeBindingImpl, RowBindingImpl, StaticListBindingImpl, UiThreadBeanELResolver

public interface ELResolver

Enables customization of variable and property resolution behavior for EL expression evaluation.

While evaluating an expression, the ELResolver associated with the ELContext is consulted to do the initial resolution of the first variable of an expression. It is also consulted when a . or [] operator is encountered, except for the last such operator in a method expression, in which case the resultion rules are hard coded.

For example, in the EL expression ${employee.lastName}, the ELResolver determines what object employee refers to, and what it means to get the lastName property on that object.

Most methods in this class accept a base and property parameter. In the case of variable resolution (e.g. determining what employee refers to in ${employee.lastName}), the base parameter will be null and the property parameter will always be of type String. In this case, if the property is not a String, the behavior of the ELResolver is undefined.

In the case of property resolution, the base parameter identifies the base object and the property object identifies the property on that base. For example, in the expression ${employee.lastName}, base is the result of the variable resolution for employee and property is the string "lastName". In the expression ${y[x]}, base is the result of the variable resolution for y and property is the result of the variable resolution for x.

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 CompositeELResolvers, to define rich semantics for evaluating an expression.

For the getValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object), getType(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object), setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) and isReadOnly(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object) 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 #getFeatureDescriptors and #getCommonPropertyType methods are primarily designed for design-time tool support, but must handle invocation at runtime as well. The java.beans.Beans#isDesignTime method can be used to determine if the resolver is being consulted at design-time or runtime.

Since:

JSP 2.1

See Also:

CompositeELResolver, ELContext.getELResolver()

Field Summary

static java.lang.String	RESOLVABLE_AT_DESIGN_TIME The attribute name of the named attribute in the FeatureDescriptor that specifies whether the variable or property can be resolved at runtime.
static java.lang.String	TYPE The attribute name of the named attribute in the FeatureDescriptor that specifies the runtime type of the variable or property.

Method Summary

java.lang.Class	getType(ELContext context, java.lang.Object base, java.lang.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 setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) method.
java.lang.Object	getValue(ELContext context, java.lang.Object base, java.lang.Object property) Attempts to resolve the given property object on the given base object.
boolean	isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property) For a given base and property, attempts to determine whether a call to setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always fail.
void	setValue(ELContext context, java.lang.Object base, java.lang.Object property, java.lang.Object value) Attempts to set the value of the given property object on the given base object.

Field Detail

TYPE

static final java.lang.String TYPE

The attribute name of the named attribute in the FeatureDescriptor that specifies the runtime type of the variable or property.

See Also:

Constant Field Values

RESOLVABLE_AT_DESIGN_TIME

static final java.lang.String RESOLVABLE_AT_DESIGN_TIME

The attribute name of the named attribute in the FeatureDescriptor that specifies whether the variable or property can be resolved at runtime.

See Also:

Constant Field Values

Method Detail

getValue

java.lang.Object getValue(ELContext context,
                          java.lang.Object base,
                          java.lang.Object property)

Attempts to resolve the given property object on the given base object.

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.

Parameters:

context - The context of this evaluation.

base - The base object whose property value is to be returned, or null to resolve a top-level variable.

property - The property or variable to be resolved.

Returns:

If the propertyResolved property of ELContext was set to true, then the result of the variable or property resolution; otherwise undefined.

Throws:

java.lang.NullPointerException - if context is null

PropertyNotFoundException - if the given (base, property) pair is handled by this ELResolver but the specified variable or property does not exist or is not readable.

ELException - if an exception was thrown while performing the property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

getType

java.lang.Class getType(ELContext context,
                        java.lang.Object base,
                        java.lang.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 setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) method.

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.

This is not always the same as getValue().getClass(). For example, in the case of an ArrayELResolver, the getType method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element.

Parameters:

context - The context of this evaluation.

base - The base object whose property value is to be analyzed, or null to analyze a top-level variable.

property - The property or variable to return the acceptable type for.

Returns:

If the propertyResolved property of ELContext was set to true, then the most general acceptable type; otherwise undefined.

Throws:

java.lang.NullPointerException - if context is null

PropertyNotFoundException - if the given (base, property) pair is handled by this ELResolver but the specified variable or property does not exist or is not readable.

ELException - if an exception was thrown while performing the property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

setValue

void setValue(ELContext context,
              java.lang.Object base,
              java.lang.Object property,
              java.lang.Object value)

Attempts to set the value of the given property object on the given base object.

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.

Parameters:

context - The context of this evaluation.

base - The base object whose property value is to be set, or null to set a top-level variable.

property - The property or variable to be set.

value - The value to set the property or variable to.

Throws:

java.lang.NullPointerException - if context is null

PropertyNotFoundException - if the given (base, property) pair is handled by this ELResolver but the specified variable or property does not exist.

PropertyNotWritableException - if the given (base, property) pair is handled by this ELResolver but the specified variable or property is not writable.

ELException - if an exception was thrown while attempting to set the property or variable. The thrown exception must be included as the cause property of this exception, if available.

isReadOnly

boolean isReadOnly(ELContext context,
                   java.lang.Object base,
                   java.lang.Object property)

For a given base and property, attempts to determine whether a call to setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always fail.

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.

Parameters:

context - The context of this evaluation.

base - The base object whose property value is to be analyzed, or null to analyze a top-level variable.

property - The property or variable to return the read-only status for.

Returns:

If the propertyResolved property of ELContext was set to true, then true if the property is read-only or false if not; otherwise undefined.

Throws:

java.lang.NullPointerException - if context is null

PropertyNotFoundException - if the given (base, property) pair is handled by this ELResolver but the specified variable or property does not exist.

ELException - if an exception was thrown while performing the property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.