1 package org.apache.velocity.app.event; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import org.apache.velocity.context.Context; 23 import org.apache.velocity.util.introspection.Info; 24 25 /** 26 * Event handler called when an invalid reference is encountered. Allows 27 * the application to report errors or substitute return values. May be chained 28 * in sequence; the behavior will differ per method. 29 * 30 * <p>This feature should be regarded as experimental. 31 * 32 * @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a> 33 * @version $Id$ 34 * @since 1.5 35 */ 36 public interface InvalidReferenceEventHandler extends EventHandler 37 { 38 39 /** 40 * Called when object is null or there is no getter for the given 41 * property. Also called for invalid references without properties. 42 * invalidGetMethod() will be called in sequence for 43 * each link in the chain until the first non-null value is 44 * returned. 45 * 46 * @param context the context when the reference was found invalid 47 * @param reference string with complete invalid reference 48 * @param object the object referred to, or null if not found 49 * @param property the property name from the reference 50 * @param info contains template, line, column details 51 * @return substitute return value for missing reference, or null if no substitute 52 */ invalidGetMethod(Context context, String reference, Object object, String property, Info info)53 Object invalidGetMethod(Context context, String reference, 54 Object object, String property, Info info); 55 56 /** 57 * Called when object is null or there is no setter for the given 58 * property. invalidSetMethod() will be called in sequence for 59 * each link in the chain until a true value is returned. It's 60 * recommended that false be returned as a default to allow 61 * for easy chaining. 62 * 63 * @param context the context when the reference was found invalid 64 * @param leftreference left reference being assigned to 65 * @param rightreference invalid reference on the right 66 * @param info contains info on template, line, col 67 * 68 * @return if true then stop calling invalidSetMethod along the 69 * chain. 70 */ invalidSetMethod(Context context, String leftreference, String rightreference, Info info)71 boolean invalidSetMethod(Context context, String leftreference, 72 String rightreference, Info info); 73 74 /** 75 * Called when object is null or the given method does not exist. 76 * invalidMethod() will be called in sequence for each link in 77 * the chain until the first non-null value is returned. 78 * 79 * @param context the context when the reference was found invalid 80 * @param reference string with complete invalid reference 81 * @param object the object referred to, or null if not found 82 * @param method the name of the (non-existent) method 83 * @param info contains template, line, column details 84 * @return substitute return value for missing reference, or null if no substitute 85 */ invalidMethod(Context context, String reference, Object object, String method, Info info)86 Object invalidMethod(Context context, String reference, 87 Object object, String method, Info info); 88 } 89