Package org.apache.struts2.conversion.impl

Class InstantiatingNullHandler

java.lang.Object
org.apache.struts2.conversion.impl.InstantiatingNullHandler
All Implemented Interfaces:
NullHandler
public class InstantiatingNullHandler extends Object implements NullHandler

Provided that the key ReflectionContextState.CREATE_NULL_OBJECTS is in the action context with a value of true (this key is set only during the execution of the ParametersInterceptor), OGNL expressions that have caused a NullPointerException will be temporarily stopped for evaluation while the system automatically tries to solve the null references by automatically creating the object.

The following rules are used when handling null references:

  • If the property is declared exactly as a Collection or List, then an ArrayList shall be returned and assigned to the null references.
  • If the property is declared as a Map, then a HashMap will be returned and assigned to the null references.
  • If the null property is a simple bean with a no-arg constructor, it will simply be created using the ObjectFactory.buildBean(java.lang.Class, java.util.Map) method.

For example, if a form element has a text field named person.name and the expression person evaluates to null, then this class will be invoked. Because the person expression evaluates to a Person class, a new Person is created and assigned to the null reference. Finally, the name is set on that object and the overall effect is that the system automatically created a Person object for you, set it by calling setUsers() and then finally called getUsers().setName() as you would typically expect.

Author:
Matt Ho, Patrick Lightbody

  • Constructor Details

    • InstantiatingNullHandler

      public InstantiatingNullHandler()

  • Method Details

    • setObjectTypeDeterminer

      public void setObjectTypeDeterminer(ObjectTypeDeterminer det)

    • setReflectionProvider

      public void setReflectionProvider(ReflectionProvider prov)

    • setObjectFactory

      public void setObjectFactory(ObjectFactory fac)

    • nullMethodResult

      public Object nullMethodResult(Map<String,Object> context, Object target, String methodName, Object[] args)
      Description copied from interface: NullHandler
      Method called on target returned null.
      Specified by:
      nullMethodResult in interface NullHandler
      Parameters:
      context - context
      target - target object
      methodName - method name
      args - arguments
      Returns:
      object

    • nullPropertyValue

      public Object nullPropertyValue(Map<String,Object> context, Object target, Object property)
      Description copied from interface: NullHandler
      Property in target evaluated to null. Property can be a constant String property name or a DynamicSubscript.
      Specified by:
      nullPropertyValue in interface NullHandler
      Parameters:
      context - context
      target - target object
      property - property
      Returns:
      object