/*
* Copyright (c) 2002-2006 by OpenSymphony
* All rights reserved.
*/
package com.opensymphony.xwork2.conversion.impl;
import com.opensymphony.xwork2.ObjectFactory;
import com.opensymphony.xwork2.conversion.NullHandler;
import com.opensymphony.xwork2.conversion.ObjectTypeDeterminer;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import com.opensymphony.xwork2.util.reflection.ReflectionContextState;
import com.opensymphony.xwork2.util.reflection.ReflectionProvider;
import java.beans.PropertyDescriptor;
import java.util.*;
/**
* <!-- START SNIPPET: javadoc -->
*
* Provided that the key {@link ReflectionContextState#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.
*
* <p/> The following rules are used when handling null references:
*
* <ul>
*
* <li>If the property is declared <i>exactly</i> as a {@link Collection} or {@link List}, then an ArrayList shall be
* returned and assigned to the null references.</li>
*
* <li>If the property is declared as a {@link Map}, then a HashMap will be returned and assigned to the null
* references.</li>
*
* <li>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.</li>
*
* </ul>
*
* <!-- END SNIPPET: javadoc -->
*
* <!-- START SNIPPET: example -->
*
* For example, if a form element has a text field named <b>person.name</b> and the expression <i>person</i> evaluates
* to null, then this class will be invoked. Because the <i>person</i> expression evaluates to a <i>Person</i> 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.
*
* <!-- END SNIPPET: example>
*
* @author Matt Ho
* @author Patrick Lightbody
*/
public class InstantiatingNullHandler implements NullHandler {
/**
* @deprecated Use {@link ReflectionContextState#CREATE_NULL_OBJECTS} instead
*/
@Deprecated public static final String CREATE_NULL_OBJECTS = ReflectionContextState.CREATE_NULL_OBJECTS;
private static final Logger LOG = LoggerFactory.getLogger(InstantiatingNullHandler.class);
private ReflectionProvider reflectionProvider;
private ObjectFactory objectFactory;
private ObjectTypeDeterminer objectTypeDeterminer;
@Inject
public void setObjectTypeDeterminer(ObjectTypeDeterminer det) {
this.objectTypeDeterminer = det;
}
@Inject
public void setReflectionProvider(ReflectionProvider prov) {
this.reflectionProvider = prov;
}
@Inject
public void setObjectFactory(ObjectFactory fac) {
this.objectFactory = fac;
}
public Object nullMethodResult(Map<String, Object> context, Object target, String methodName, Object[] args) {
if (LOG.isDebugEnabled()) {
LOG.debug("Entering nullMethodResult ");
}
return null;
}
public Object nullPropertyValue(Map<String, Object> context, Object target, Object property) {
if (LOG.isDebugEnabled()) {
LOG.debug("Entering nullPropertyValue [target="+target+", property="+property+"]");
}
boolean c = ReflectionContextState.isCreatingNullObjects(context);
if (!c) {
return null;
}
if ((target == null) || (property == null)) {
return null;
}
try {
String propName = property.toString();
Object realTarget = reflectionProvider.getRealTarget(propName, context, target);
Class clazz = null;
if (realTarget != null) {
PropertyDescriptor pd = reflectionProvider.getPropertyDescriptor(realTarget.getClass(), propName);
if (pd == null) {
return null;
}
clazz = pd.getPropertyType();
}
if (clazz == null) {
// can't do much here!
return null;
}
Object param = createObject(clazz, realTarget, propName, context);
reflectionProvider.setValue(propName, context, realTarget, param);
return param;
} catch (Exception e) {
LOG.error("Could not create and/or set value back on to object", e);
}
return null;
}
private Object createObject(Class clazz, Object target, String property, Map<String, Object> context) throws Exception {
if (Collection.class.isAssignableFrom(clazz)) {
return new ArrayList();
} else if (clazz == Map.class) {
return new HashMap();
} else if (clazz == EnumMap.class) {
Class keyClass = objectTypeDeterminer.getKeyClass(target.getClass(), property);
return new EnumMap(keyClass);
}
return objectFactory.buildBean(clazz, context);
}
}
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