com.opensymphony.xwork2.util.InstantiatingNullHandler Maven / Gradle / Ivy
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XWork is an command-pattern framework that is used to power WebWork
as well as other applications. XWork provides an Inversion of Control
container, a powerful expression language, data type conversion,
validation, and pluggable configuration.
/*
* Copyright (c) 2002-2006 by OpenSymphony
* All rights reserved.
*/
package com.opensymphony.xwork2.util;
import com.opensymphony.xwork2.ObjectFactory;
import ognl.NullHandler;
import ognl.Ognl;
import ognl.OgnlRuntime;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.beans.PropertyDescriptor;
import java.util.*;
/**
*
*
* Provided that the key {@link #CREATE_NULL_OBJECTS} is in the action context with a value of true (this key is set
* only during the execution of the {@link com.opensymphony.xwork2.interceptor.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 {@link Collection} or {@link List}, then an ArrayList shall be
* returned and assigned to the null references.
*
* - If the property is declared as a {@link 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 {@link
* 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.
*
*