The Spring Framework

Class RequiredAnnotationBeanPostProcessor

  extended by org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter
      extended by org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor
All Implemented Interfaces:
BeanPostProcessor, InstantiationAwareBeanPostProcessor, SmartInstantiationAwareBeanPostProcessor

public class RequiredAnnotationBeanPostProcessor
extends InstantiationAwareBeanPostProcessorAdapter

BeanPostProcessor implementation that enforces required JavaBean properties to have been configured. Required bean properties are detected through a Java 5 annotation: by default, Spring's Required annotation.

The motivation for the existence of this BeanPostProcessor is to allow developers to annotate the setter properties of their own classes with an arbitrary JDK 1.5 annotation to indicate that the container must check for the configuration of a dependency injected value. This neatly pushes responsibility for such checking onto the container (where it arguably belongs), and obviates the need (in part) for a developer to code a method that simply checks that all required properties have actually been set.

Please note that an 'init' method may still need to implemented (and may still be desirable), because all that this class does is enforce that a 'required' property has actually been configured with a value. It does not check anything else... In particular, it does not check that a configured value is not null.

Note: A default RequiredAnnotationBeanPostProcessor will be registered by the "context:annotation-config" and "context:component-scan" XML tags. Remove or turn off the default annotation configuration there if you intend to specify a custom RequiredAnnotationBeanPostProcessor bean definition.

Rob Harrop, Juergen Hoeller
See Also:
setRequiredAnnotationType(java.lang.Class), Required

Constructor Summary
Method Summary
protected  Class<? extends Annotation> getRequiredAnnotationType()
          Return the 'required' annotation type.
protected  boolean isRequiredProperty(PropertyDescriptor propertyDescriptor)
          Is the supplied property required to have a value (that is, to be dependency-injected)?
 PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName)
          Post-process the given property values before the factory applies them to the given bean.
 void setRequiredAnnotationType(Class<? extends Annotation> requiredAnnotationType)
          Set the 'required' annotation type, to be used on bean property setter methods.
Methods inherited from class org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter
determineCandidateConstructors, postProcessAfterInitialization, postProcessAfterInstantiation, postProcessBeforeInitialization, postProcessBeforeInstantiation, predictBeanType
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public RequiredAnnotationBeanPostProcessor()
Method Detail


public void setRequiredAnnotationType(Class<? extends Annotation> requiredAnnotationType)
Set the 'required' annotation type, to be used on bean property setter methods.

The default required annotation type is the Spring-provided Required annotation.

This setter property exists so that developers can provide their own (non-Spring-specific) annotation type to indicate that a property value is required.


protected Class<? extends Annotation> getRequiredAnnotationType()
Return the 'required' annotation type.


public PropertyValues postProcessPropertyValues(PropertyValues pvs,
                                                PropertyDescriptor[] pds,
                                                Object bean,
                                                String beanName)
                                         throws BeansException
Description copied from interface: InstantiationAwareBeanPostProcessor
Post-process the given property values before the factory applies them to the given bean. Allows for checking whether all dependencies have been satisfied, for example based on a "Required" annotation on bean property setters.

Also allows for replacing the property values to apply, typically through creating a new MutablePropertyValues instance based on the original PropertyValues, adding or removing specific values.

Specified by:
postProcessPropertyValues in interface InstantiationAwareBeanPostProcessor
postProcessPropertyValues in class InstantiationAwareBeanPostProcessorAdapter
pvs - the property values that the factory is about to apply (never null)
pds - the relevant property descriptors for the target bean (with ignored dependency types - which the factory handles specifically - already filtered out)
bean - the bean instance created, but whose properties have not yet been set
beanName - the name of the bean
the actual property values to apply to to the given bean (can be the passed-in PropertyValues instance), or null to skip property population
BeansException - in case of errors
See Also:


protected boolean isRequiredProperty(PropertyDescriptor propertyDescriptor)
Is the supplied property required to have a value (that is, to be dependency-injected)?

This implementation looks for the existence of a "required" annotation on the supplied property.

propertyDescriptor - the target PropertyDescriptor (never null)
true if the supplied property has been marked as being required; false if not, or if the supplied property does not have a setter method

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