001 // Copyright 2007, 2008 The Apache Software Foundation
002 //
003 // Licensed under the Apache License, Version 2.0 (the "License");
004 // you may not use this file except in compliance with the License.
005 // You may obtain a copy of the License at
006 //
007 // http://www.apache.org/licenses/LICENSE-2.0
008 //
009 // Unless required by applicable law or agreed to in writing, software
010 // distributed under the License is distributed on an "AS IS" BASIS,
011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012 // See the License for the specific language governing permissions and
013 // limitations under the License.
014
015 package org.apache.tapestry5.internal.services;
016
017 import static org.apache.tapestry5.ioc.internal.util.CollectionFactory.newList;
018 import static org.apache.tapestry5.ioc.internal.util.Defense.notBlank;
019 import org.apache.tapestry5.services.PersistentFieldChange;
020 import org.apache.tapestry5.services.PersistentFieldStrategy;
021 import org.apache.tapestry5.services.Request;
022 import org.apache.tapestry5.services.Session;
023
024 import java.util.Collection;
025 import java.util.Collections;
026 import java.util.List;
027
028 /**
029 * Base class for strategies that store their values as keys in the session. Implements a uniform format for the keys,
030 * based on a prefix to identify the particular strategy.
031 */
032 public abstract class AbstractSessionPersistentFieldStrategy implements PersistentFieldStrategy
033 {
034 private final String prefix;
035
036 private final Request request;
037
038 protected AbstractSessionPersistentFieldStrategy(String prefix, Request request)
039 {
040 this.prefix = prefix;
041 this.request = request;
042 }
043
044 public final Collection<PersistentFieldChange> gatherFieldChanges(String pageName)
045 {
046 Session session = request.getSession(false);
047
048 if (session == null) return Collections.emptyList();
049
050 List<PersistentFieldChange> result = newList();
051
052 String fullPrefix = prefix + pageName + ":";
053
054 for (String name : session.getAttributeNames(fullPrefix))
055 {
056 Object persistedValue = session.getAttribute(name);
057
058 Object applicationValue = persistedValue == null ? null : convertPersistedToApplicationValue(
059 persistedValue);
060
061 PersistentFieldChange change = buildChange(name, applicationValue);
062
063 result.add(change);
064
065 didReadChange(session, name);
066 }
067
068 return result;
069 }
070
071 public void discardChanges(String pageName)
072 {
073 Session session = request.getSession(false);
074
075 if (session == null) return;
076
077 String fullPrefix = prefix + pageName + ":";
078
079 for (String name : session.getAttributeNames(fullPrefix))
080 {
081 session.setAttribute(name, null);
082 }
083 }
084
085 /**
086 * Called after each key is read by {@link #gatherFieldChanges(String)}. This implementation does nothing,
087 * subclasses may override.
088 *
089 * @param session the session from which a value was just read
090 * @param attributeName the name of the attribute used to read a value
091 */
092 protected void didReadChange(Session session, String attributeName)
093 {
094 }
095
096 private PersistentFieldChange buildChange(String name, Object newValue)
097 {
098 String[] chunks = name.split(":");
099
100 // Will be empty string for the root component
101 String componentId = chunks[2];
102 String fieldName = chunks[3];
103
104 return new PersistentFieldChangeImpl(componentId, fieldName, newValue);
105 }
106
107 public final void postChange(String pageName, String componentId, String fieldName,
108 Object newValue)
109 {
110 notBlank(pageName, "pageName");
111 notBlank(fieldName, "fieldName");
112
113 Object persistedValue = newValue == null ? null : convertApplicationValueToPersisted(newValue);
114
115 StringBuilder builder = new StringBuilder(prefix);
116 builder.append(pageName);
117 builder.append(':');
118
119 if (componentId != null) builder.append(componentId);
120
121 builder.append(':');
122 builder.append(fieldName);
123
124 Session session = request.getSession(persistedValue != null);
125
126 // TAPESTRY-2308: The session will be false when newValue is null and the session
127 // does not already exist.
128
129 if (session != null)
130 {
131 session.setAttribute(builder.toString(), persistedValue);
132 }
133 }
134
135 /**
136 * Hook that allows a value to be converted as it is written to the session. Passed the new value provided by the
137 * application, returns the object to be stored in the session. This implementation simply returns the provided
138 * value.
139 *
140 * @param newValue non-null value
141 * @return persisted value
142 * @see #convertPersistedToApplicationValue(Object)
143 */
144 protected Object convertApplicationValueToPersisted(Object newValue)
145 {
146 return newValue;
147 }
148
149 /**
150 * Converts a persisted value stored in the session back into an application value. This implementation returns
151 * the persisted value as is.
152 *
153 * @param persistedValue non-null persisted value
154 * @return application value
155 * @see #convertPersistedToApplicationValue(Object)
156 */
157 protected Object convertPersistedToApplicationValue(Object persistedValue)
158 {
159 return persistedValue;
160 }
161 }