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Oracle Fusion Middleware Java API Reference for Oracle ADF Mobile 11g Release 2 (11.1.2.4.0) E27204-03 |
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java.lang.Object
javax.el.ELResolver
public abstract class 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 resolution 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 CompositeELResolver
s, to define rich semantics for evaluating an expression. For the getValue(ELContext, Object, Object)
, getType(ELContext, Object, Object)
, setValue(ELContext, Object, Object, Object)
and isReadOnly(ELContext, Object, 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(ELContext, Object)
and getCommonPropertyType(ELContext, Object)
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.
Field Summary | |
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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. |
Constructor Summary | |
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ELResolver() |
Method Summary | |
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abstract java.lang.Class |
getCommonPropertyType(ELContext context, java.lang.Object base) Returns the most general type that this resolver accepts for the property argument, given a base object. |
abstract 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(ELContext, Object, Object, Object) method. |
abstract 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. |
java.lang.Object |
invoke(ELContext context, java.lang.Object base, java.lang.Object method, java.lang.Class[] paramTypes, java.lang.Object[] params) Attempts to resolve and invoke the given method on the given base object. |
abstract 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(ELContext, Object, Object, Object) will always fail. |
abstract 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. |
Methods inherited from class java.lang.Object |
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equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final java.lang.String RESOLVABLE_AT_DESIGN_TIME
public static final java.lang.String TYPE
Constructor Detail |
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public ELResolver()
Method Detail |
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public abstract java.lang.Class getCommonPropertyType(ELContext context, java.lang.Object base)
ArrayELResolver
will accept any int as a property, so the return value would be Integer.class.context
- The context of this evaluation.base
- The base object to return the most general property type for, or null to enumerate the set of top-level variables that this resolver can evaluate.public abstract java.lang.Class getType(ELContext context, java.lang.Object base, java.lang.Object property)
setValue(ELContext, Object, Object, 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.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.java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- 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.public abstract java.lang.Object getValue(ELContext context, java.lang.Object base, java.lang.Object property)
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.java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- 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.public abstract boolean isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property)
setValue(ELContext, Object, Object, 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.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.java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- 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.public abstract void setValue(ELContext context, java.lang.Object base, java.lang.Object property, java.lang.Object value)
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.java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- 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.public java.lang.Object invoke(ELContext context, java.lang.Object base, java.lang.Object method, java.lang.Class[] paramTypes, java.lang.Object[] params)
method
on the given base
object.
If this resolver handles the given (base, method) 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.
A default implementation is provided that returns null so that existing classes that extend ELResolver can continue to function.
context
- The context of this evaluation.base
- The bean on which to invoke the methodmethod
- The simple name of the method to invoke. Will be coerced to a String
.paramTypes
- An array of Class objects identifying the method's formal parameter types, in declared order. Use an empty array if the method has no parameters. Can be null
, in which case the method's formal parameter types are assumed to be unknown.params
- The parameters to pass to the method, or null
if no parameters.null
if the method has a void
return type).MethodNotFoundException
- if no suitable method can be found.ELException
- if an exception was thrown while performing (base, method) resolution. The thrown exception must be included as the cause property of this exception, if available. If the exception thrown is an InvocationTargetException
, extract its cause
and pass it to the ELException
constructor.
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Oracle Fusion Middleware Java API Reference for Oracle ADF Mobile 11g Release 2 (11.1.2.4.0) E27204-03 |
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