Interface PropertyAccessor

All Superinterfaces:
TargetedAccessor
All Known Subinterfaces:
CompilablePropertyAccessor
All Known Implementing Classes:
BeanExpressionContextAccessor, BeanFactoryAccessor, DataBindingPropertyAccessor, EnvironmentAccessor, MapAccessor, MapAccessor, ReflectivePropertyAccessor
public interface PropertyAccessor extends TargetedAccessor
A property accessor is able to read from (and possibly write to) an object's properties.

This interface places no restrictions on what constitutes a property. Implementors are therefore free to access properties directly via fields, through getters, or in any other way they deem appropriate.

A property accessor can specify an array of target classes for which it should be called. See TargetedAccessor for details.

SpEL infrastructure may cache a PropertyAccessor instance on a per-node basis once it has successfully served a read or write for a given property name and target type, in order to avoid repeatedly invoking canRead(EvaluationContext, Object, String)/canWrite(EvaluationContext, Object, String) on every registered accessor for subsequent evaluations of that node. Before reusing a cached instance, SpEL confirms that it is still registered with the current EvaluationContext. Consequently, canRead(EvaluationContext, Object, String), canWrite(EvaluationContext, Object, String), read(EvaluationContext, Object, String), and write(EvaluationContext, Object, String, Object) should behave consistently for a given (context, target type, name) combination for as long as the accessor remains registered with a context, since a change in behavior may not be observed until the accessor is re-selected from scratch.

Since:
3.0
Author:
Andy Clement
See Also:

  • Method Details

    • canRead

      boolean canRead(EvaluationContext context, @Nullable Object target, String name) throws AccessException
      Called to determine if this property accessor is able to read 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 property accessor 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(EvaluationContext, Object, 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 reading the property value

    • canWrite

      boolean canWrite(EvaluationContext context, @Nullable Object target, String name) throws AccessException
      Called to determine if this property accessor 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 property accessor 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(EvaluationContext, Object, 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