The Spring Framework

## org.springframework.beans.factory.annotation
Class RequiredAnnotationBeanPostProcessor

    java.lang.Object
      org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter
          org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor

All Implemented Interfaces:
  BeanPostProcessor, InstantiationAwareBeanPostProcessor, SmartInstantiationAwareBeanPostProcessor, Ordered, PriorityOrdered

    public class RequiredAnnotationBeanPostProcessor

extends InstantiationAwareBeanPostProcessorAdapter
implements PriorityOrdered

`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<? extends java.lang.annotation.Annotation>)`, `Required`

Field Summary

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 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` `setOrder(int order)`
`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, getEarlyBeanReference, 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

### RequiredAnnotationBeanPostProcessor

    public RequiredAnnotationBeanPostProcessor()

Method Detail

### setRequiredAnnotationType

    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.

### getRequiredAnnotationType

    protected Class<? extends Annotation> getRequiredAnnotationType()

  Return the 'required' annotation type.

### 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 or 1, with `Ordered.LOWEST_PRECEDENCE` indicating greatest. Same order values will result in arbitrary positions for the affected objects.

  Higher value can be interpreted as lower priority, consequently the first object has highest priority (somewhat analogous to Servlet "load-on-startup" values).

  Note that order values below 0 are reserved for framework purposes. Application-specified values should always be 0 or greater, with only framework components (internal or third-party) supposed to use lower values.

  Specified by:
    `getOrder` in interface `Ordered`
  Returns:
    the order value
  See Also:
    `Ordered.LOWEST_PRECEDENCE`

### postProcessPropertyValues

    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`
  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`

### isRequiredProperty

    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`.

  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

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