org.springframework.expression

Interface PropertyAccessor

All Known Subinterfaces:

CompilablePropertyAccessor

All Known Implementing Classes:

BeanExpressionContextAccessor, BeanFactoryAccessor, DataBindingPropertyAccessor, EnvironmentAccessor, MapAccessor, ReflectivePropertyAccessor, ReflectivePropertyAccessor.OptimalPropertyAccessor

public interface PropertyAccessor

A property accessor is able to read from (and possibly write to) an object's properties. This interface places no restrictions, and so implementors are free to access properties directly as fields or through getters or in any other way they see as appropriate.

A resolver can optionally specify an array of target classes for which it should be called. However, if it returns null from getSpecificTargetClasses(), it will be called for all property references and given a chance to determine if it can read or write them.

Property resolvers are considered to be ordered and each will be called in turn. The only rule that affects the call order is that any naming the target class directly in getSpecificTargetClasses() will be called first, before the general resolvers.

Since:

3.0

Author:

Andy Clement

Method Summary

Modifier and Type	Method and Description
boolean	canRead(EvaluationContext context, Object target, String name) Called to determine if a resolver instance is able to access a specified property on a specified target object.
boolean	canWrite(EvaluationContext context, Object target, String name) Called to determine if a resolver instance is able to write to a specified property on a specified target object.
Class<?>[]	getSpecificTargetClasses() Return an array of classes for which this resolver should be called.
TypedValue	read(EvaluationContext context, Object target, String name) Called to read a property from a specified target object.
void	write(EvaluationContext context, Object target, String name, Object newValue) Called to write to a property on a specified target object.

Method Detail

getSpecificTargetClasses

@Nullable
Class<?>[] getSpecificTargetClasses()

Return an array of classes for which this resolver should be called.

>Returning null indicates this is a general resolver that can be called in an attempt to resolve a property on any type.

Returns:

an array of classes that this resolver is suitable for (or null if a general resolver)

canRead

boolean canRead(EvaluationContext context,
                @Nullable
                Object target,
                String name)
         throws AccessException

Called to determine if a resolver instance is able to access a specified property on a specified target object.

Parameters:

context - the evaluation context in which the access is being attempted

target - the target object upon which the property is being accessed

name - the name of the property being accessed

Returns:

true if this resolver is able to read the property

Throws:

AccessException - if there is any problem determining whether the property can be read

read

TypedValue read(EvaluationContext context,
                @Nullable
                Object target,
                String name)
         throws AccessException

Called to read a property from a specified target object. Should only succeed if canRead(org.springframework.expression.EvaluationContext, java.lang.Object, java.lang.String) also returns true.

Parameters:

context - the evaluation context in which the access is being attempted

target - the target object upon which the property is being accessed

name - the name of the property being accessed

Returns:

a TypedValue object wrapping the property value read and a type descriptor for it

Throws:

AccessException - if there is any problem accessing the property value

canWrite

boolean canWrite(EvaluationContext context,
                 @Nullable
                 Object target,
                 String name)
          throws AccessException

Called to determine if a resolver instance is able to write to a specified property on a specified target object.

Parameters:

context - the evaluation context in which the access is being attempted

target - the target object upon which the property is being accessed

name - the name of the property being accessed

Returns:

true if this resolver is able to write to the property

Throws:

AccessException - if there is any problem determining whether the property can be written to

write

void write(EvaluationContext context,
           @Nullable
           Object target,
           String name,
           @Nullable
           Object newValue)
    throws AccessException

Called to write to a property on a specified target object. Should only succeed if canWrite(org.springframework.expression.EvaluationContext, java.lang.Object, java.lang.String) also returns true.

Parameters:

context - the evaluation context in which the access is being attempted

target - the target object upon which the property is being accessed

name - the name of the property being accessed

newValue - the new value for the property

Throws:

AccessException - if there is any problem writing to the property value