Module jakarta.el

Package jakarta.el

Class OptionalELResolver

java.lang.Object

jakarta.el.ELResolver

jakarta.el.OptionalELResolver

public class OptionalELResolver
extends ELResolver

Defines property resolution, method invocation and type conversion behaviour on Optionals.

This resolver handles base objects that are instances of Optional.

This resolver is always a read-only resolver since Optional instances are immutable.

Constructor Summary

Constructors

Constructor	Description
OptionalELResolver()

Method Summary

Modifier and Type	Method	Description
<T> T	convertToType(ELContext context, Object obj, Class<T> type)	Converts an object to a specific type.
Class<?>	getCommonPropertyType(ELContext context, Object base)	Returns the most general type that this resolver accepts for the property argument, given a base object.
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 ELResolver.setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) method.
Object	getValue(ELContext context, Object base, Object property)	Attempts to resolve the given property object on the given base object.
Object	invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params)	Attempts to resolve and invoke the given method on the given base object.
boolean	isReadOnly(ELContext context, Object base, Object property)	For a given base and property, attempts to determine whether a call to ELResolver.setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always fail.
void	setValue(ELContext context, Object base, Object property, Object value)	Attempts to set the value of the given property object on the given base object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

OptionalELResolver

public OptionalELResolver()

Method Details

getValue

public Object getValue(ELContext context,
 Object base,
 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.

Specified by:

getValue in class ELResolver

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 base object is an Optional and Optional.isEmpty() returns true then the resulting value is null.

If the base object is an Optional, Optional.isPresent() returns true and the property is null then the resulting value is the result of calling Optional.get() on the base object.

If the base object is an Optional, Optional.isPresent() returns true and the property is not null then the resulting value is the result of calling ELResolver.getValue(ELContext, Object, Object) using the ELResolver obtained from ELContext.getELResolver() with the following parameters:

• The ELContext is the current context
• The base object is the result of calling Optional.get() on the current base object
• The property object is the current property object

If the base object is not an Optional then the return value is undefined.

getType

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 ELResolver.setValue(jakarta.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.

If the resolver or the property is read-only, this method must return null.

Specified by:

getType in class ELResolver

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 base object is an Optional this method always returns null since instances of this resolver are always read-only.

If the base object is not an Optional then the return value is undefined.

setValue

public void setValue(ELContext context,
 Object base,
 Object property,
 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.

If the base object is an Optional this method always throws a PropertyNotWritableException since instances of this resolver are always read-only.

Specified by:

setValue in class ELResolver

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.

isReadOnly

public boolean isReadOnly(ELContext context,
 Object base,
 Object property)

For a given base and property, attempts to determine whether a call to ELResolver.setValue(jakarta.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.

Specified by:

isReadOnly in class ELResolver

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 base object is an Optional this method always returns true since instances of this resolver are always read-only.

If the base object is not an Optional then the return value is undefined.

getCommonPropertyType

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.

This assists tools in auto-completion and also provides a way to express that the resolver accepts a primitive value, such as an integer index into an array. For example, the ArrayELResolver will accept any int as a property, so the return value would be Integer.class.

Specified by:

getCommonPropertyType in class ELResolver

Parameters:

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.

Returns:

If the base object is an Optional this method always returns Object.class.

If the base object is not an Optional then the return value is undefined.

convertToType

public <T> T convertToType(ELContext context,
 Object obj,
 Class<T> type)

Converts an object to a specific type.

An ELException is thrown if an error occurs during the conversion.

Overrides:

convertToType in class ELResolver

Parameters:

context - The context of this evaluation.

obj - The object to convert.

type - The target type for the conversion.

Returns:

If the base object is an Optional and Optional.isEmpty() returns true then this method returns the result of coercing null to the requested type.

If the base object is an Optional and Optional.isPresent() returns true then this method returns the result of coercing Optional#get() to the requested type.

If the base object is not an Optional then the return value is undefined.

invoke

public Object invoke(ELContext context,
 Object base,
 Object method,
 Class<?>[] paramTypes,
 Object[] params)

Attempts to resolve and invoke the given 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.

Overrides:

invoke in class ELResolver

Parameters:

context - The context of this evaluation.

base - The bean on which to invoke the method

method - 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.

Returns:

If the base object is an Optional and Optional.isEmpty() returns true then this method returns null.

If the base object is an Optional and Optional.isPresent() returns true then this method returns the result of invoking the specified method on the object obtained by calling Optional.get() with the specified parameters.

If the base object is not an Optional then the return value is undefined.