Spring Framework

org.springframework.beans.factory.annotation
Class RequiredAnnotationBeanPostProcessor

java.lang.Object
  extended by org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter
      extended by org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor
All Implemented Interfaces:
Aware, BeanFactoryAware, BeanPostProcessor, InstantiationAwareBeanPostProcessor, SmartInstantiationAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor, Ordered, PriorityOrdered

public class RequiredAnnotationBeanPostProcessor
extends InstantiationAwareBeanPostProcessorAdapter
implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware

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.

Since:
2.0
Author:
Rob Harrop, Juergen Hoeller
See Also:
setRequiredAnnotationType(java.lang.Class), Required

Field Summary
static java.lang.String SKIP_REQUIRED_CHECK_ATTRIBUTE
          Bean definition attribute that may indicate whether a given bean is supposed to be skipped when performing this post-processor's required property check.
 
Fields inherited from interface org.springframework.core.Ordered
HIGHEST_PRECEDENCE, LOWEST_PRECEDENCE
 
Constructor Summary
RequiredAnnotationBeanPostProcessor()
           
 
Method Summary
 int getOrder()
          Return the order value of this object, with a higher value meaning greater in terms of sorting.
protected  java.lang.Class<? extends java.lang.annotation.Annotation> getRequiredAnnotationType()
          Return the 'required' annotation type.
protected  boolean isRequiredProperty(java.beans.PropertyDescriptor propertyDescriptor)
          Is the supplied property required to have a value (that is, to be dependency-injected)?
 void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, java.lang.Class<?> beanType, java.lang.String beanName)
          Post-process the given merged bean definition for the specified bean.
 PropertyValues postProcessPropertyValues(PropertyValues pvs, java.beans.PropertyDescriptor[] pds, java.lang.Object bean, java.lang.String beanName)
          Post-process the given property values before the factory applies them to the given bean.
 void setBeanFactory(BeanFactory beanFactory)
          Callback that supplies the owning factory to a bean instance.
 void setOrder(int order)
           
 void setRequiredAnnotationType(java.lang.Class<? extends java.lang.annotation.Annotation> requiredAnnotationType)
          Set the 'required' annotation type, to be used on bean property setter methods.
protected  boolean shouldSkip(ConfigurableListableBeanFactory beanFactory, java.lang.String beanName)
          Check whether the given bean definition is not subject to the annotation-based required property check as performed by this post-processor.
 
Methods inherited from class org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter
determineCandidateConstructors, getEarlyBeanReference, postProcessAfterInitialization, postProcessAfterInstantiation, postProcessBeforeInitialization, postProcessBeforeInstantiation, predictBeanType
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface org.springframework.beans.factory.config.BeanPostProcessor
postProcessAfterInitialization, postProcessBeforeInitialization
 

Field Detail

SKIP_REQUIRED_CHECK_ATTRIBUTE

public static final java.lang.String SKIP_REQUIRED_CHECK_ATTRIBUTE
Bean definition attribute that may indicate whether a given bean is supposed to be skipped when performing this post-processor's required property check.

See Also:
shouldSkip(org.springframework.beans.factory.config.ConfigurableListableBeanFactory, java.lang.String)
Constructor Detail

RequiredAnnotationBeanPostProcessor

public RequiredAnnotationBeanPostProcessor()
Method Detail

setRequiredAnnotationType

public void setRequiredAnnotationType(java.lang.Class<? extends java.lang.annotation.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.


getRequiredAnnotationType

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


setBeanFactory

public void setBeanFactory(BeanFactory beanFactory)
Description copied from interface: BeanFactoryAware
Callback that supplies the owning factory to a bean instance.

Invoked after the population of normal bean properties but before an initialization callback such as InitializingBean.afterPropertiesSet() or a custom init-method.

Specified by:
setBeanFactory in interface BeanFactoryAware
Parameters:
beanFactory - owning BeanFactory (never null). The bean can immediately call methods on the factory.
See Also:
BeanInitializationException

setOrder

public void setOrder(int order)

getOrder

public int getOrder()
Description copied from interface: Ordered
Return the order value of this object, with a higher value meaning greater in terms of sorting.

Normally starting with 0, with Integer.MAX_VALUE indicating the greatest value. Same order values will result in arbitrary positions for the affected objects.

Higher values can be interpreted as lower priority. As a consequence, the object with the lowest value has highest priority (somewhat analogous to Servlet "load-on-startup" values).

Specified by:
getOrder in interface Ordered
Returns:
the order value

postProcessMergedBeanDefinition

public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition,
                                            java.lang.Class<?> beanType,
                                            java.lang.String beanName)
Description copied from interface: MergedBeanDefinitionPostProcessor
Post-process the given merged bean definition for the specified bean.

Specified by:
postProcessMergedBeanDefinition in interface MergedBeanDefinitionPostProcessor
Parameters:
beanDefinition - the merged bean definition for the bean
beanType - the actual type of the managed bean instance
beanName - the name of the bean

postProcessPropertyValues

public PropertyValues postProcessPropertyValues(PropertyValues pvs,
                                                java.beans.PropertyDescriptor[] pds,
                                                java.lang.Object bean,
                                                java.lang.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
Overrides:
postProcessPropertyValues in class InstantiationAwareBeanPostProcessorAdapter
Parameters:
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
Returns:
the actual property values to apply to to the given bean (can be the passed-in PropertyValues instance), or null to skip property population
Throws:
BeansException - in case of errors
See Also:
MutablePropertyValues

shouldSkip

protected boolean shouldSkip(ConfigurableListableBeanFactory beanFactory,
                             java.lang.String beanName)
Check whether the given bean definition is not subject to the annotation-based required property check as performed by this post-processor.

The default implementations check for the presence of the SKIP_REQUIRED_CHECK_ATTRIBUTE attribute in the bean definition, if any.

Parameters:
beanFactory - the BeanFactory to check against
beanName - the name of the bean to check against
Returns:
true to skip the bean; false to process it

isRequiredProperty

protected boolean isRequiredProperty(java.beans.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.

Parameters:
propertyDescriptor - the target PropertyDescriptor (never null)
Returns:
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

Spring Framework