package org.apache.velocity.app.event;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import org.apache.velocity.context.Context;
import org.apache.velocity.util.introspection.Info;
/**
* Event handler called when an invalid reference is encountered. Allows
* the application to report errors or substitute return values. May be chained
* in sequence; the behavior will differ per method.
*
* <p>This feature should be regarded as experimental.
*
* @author <a href="mailto:[email protected]">Will Glass-Husain</a>
* @version $Id: InvalidReferenceEventHandler.java 832324 2009-11-03 07:33:03Z wglass $
* @since 1.5
*/
public interface InvalidReferenceEventHandler extends EventHandler
{
/**
* Called when object is null or there is no getter for the given
* property. Also called for invalid references without properties.
* invalidGetMethod() will be called in sequence for
* each link in the chain until the first non-null value is
* returned.
*
* @param context the context when the reference was found invalid
* @param reference string with complete invalid reference. If silent reference, will start with $!
* @param object the object referred to, or null if not found
* @param property the property name from the reference
* @param info contains template, line, column details
* @return substitute return value for missing reference, or null if no substitute
*/
public Object invalidGetMethod(Context context, String reference,
Object object, String property, Info info);
/**
* Called when object is null or there is no setter for the given
* property. invalidSetMethod() will be called in sequence for
* each link in the chain until a true value is returned. It's
* recommended that false be returned as a default to allow
* for easy chaining.
*
* @param context the context when the reference was found invalid
* @param leftreference left reference being assigned to
* @param rightreference invalid reference on the right
* @param info contains info on template, line, col
*
* @return if true then stop calling invalidSetMethod along the
* chain.
*/
public boolean invalidSetMethod(Context context, String leftreference,
String rightreference, Info info);
/**
* Called when object is null or the given method does not exist.
* invalidMethod() will be called in sequence for each link in
* the chain until the first non-null value is returned.
*
* @param context the context when the reference was found invalid
* @param reference string with complete invalid reference. If silent reference, will start with $!
* @param object the object referred to, or null if not found
* @param method the name of the (non-existent) method
* @param info contains template, line, column details
* @return substitute return value for missing reference, or null if no substitute
*/
public Object invalidMethod(Context context, String reference,
Object object, String method, Info info);
/**
* Defines the execution strategy for invalidGetMethod
*/
static class InvalidGetMethodExecutor implements EventHandlerMethodExecutor
{
private Context context;
private String reference;
private Object object;
private String property;
private Info info;
private Object result;
InvalidGetMethodExecutor(
Context context,
String reference,
Object object,
String property,
Info info)
{
this.context = context;
this.reference = reference;
this.object = object;
this.property = property;
this.info = info;
}
/**
* Call the method invalidGetMethod()
*
* @param handler call the appropriate method on this handler
*/
public void execute(EventHandler handler)
{
result = ((InvalidReferenceEventHandler) handler).invalidGetMethod(
context, reference, object, property, info);
}
public Object getReturnValue()
{
return result;
}
public boolean isDone()
{
return (result != null);
}
}
/**
* Defines the execution strategy for invalidGetMethod
*/
static class InvalidSetMethodExecutor implements EventHandlerMethodExecutor
{
private Context context;
private String leftreference;
private String rightreference;
private Info info;
private boolean result;
InvalidSetMethodExecutor(
Context context,
String leftreference,
String rightreference,
Info info)
{
this.context = context;
this.leftreference = leftreference;
this.rightreference = rightreference;
this.info = info;
}
/**
* Call the method invalidSetMethod()
*
* @param handler call the appropriate method on this handler
*/
public void execute(EventHandler handler)
{
result = ((InvalidReferenceEventHandler) handler).invalidSetMethod(
context, leftreference, rightreference, info);
}
public Object getReturnValue()
{
return null;
}
public boolean isDone()
{
return result;
}
}
/**
* Defines the execution strategy for invalidGetMethod
*/
static class InvalidMethodExecutor implements EventHandlerMethodExecutor
{
private Context context;
private String reference;
private Object object;
private String method;
private Info info;
private Object result;
private boolean executed = false;
InvalidMethodExecutor(
Context context,
String reference,
Object object,
String method,
Info info)
{
this.context = context;
this.reference = reference;
this.object = object;
this.method = method;
this.info = info;
}
/**
* Call the method invalidMethod()
*
* @param handler call the appropriate method on this handler
*/
public void execute(EventHandler handler)
{
executed = true;
result = ((InvalidReferenceEventHandler) handler).invalidMethod(
context, reference, object, method, info);
}
public Object getReturnValue()
{
return result;
}
public boolean isDone()
{
return executed && (result != null);
}
}
}
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