DataGridStateFactory


1   /*
2    * Copyright 2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   *
16   * $Header:$
17   */
18  package org.apache.beehive.netui.databinding.datagrid.api;
19  
20  import java.util.HashMap  ;
21  import javax.servlet.jsp.PageContext  ;
22  import javax.servlet.jsp.JspContext  ;
23  import javax.servlet.ServletRequest  ;
24  
25  import org.apache.beehive.netui.util.Bundle;
26  
27  /**
28   * <p>
29   * Factory class used to construct instances of {@link DataGridState} objects.  This
30   * class is used by the data grid and other clients to obtain the state for a data grid
31   * with a given name.
32   * </p>
33   * <p>
34   * Data grid state information is scoped by a unique data grid String name.  This name
35   * should be unique for a particular scope in a request.  For all factory methods that
36   * take a data grid name as a parameter, the value of the <code>name</code> attribute
37   * should match the value of the
38   * {@link org.apache.beehive.netui.tags.databinding.datagrid.DataGrid#setName(String)}
39   * attribute for the data grid whose state to lookup.
40   * </p>
41   */
42  public final class DataGridStateFactory {
43  
44      private static final String   KEY = DataGridStateFactory.class.getName() + "REQUEST_KEY";
45      private static final DataGridConfig DEFAULT_DATA_GRID_CONFIG = DataGridConfigFactory.getInstance();
46  
47      /**
48       * Get an instance of a DataGridStateFactory given a {@link JspContext}.
49       *
50       * @param jspContext the current {@link JspContext}
51       * @return an instance of the factory
52       */
53      public static final DataGridStateFactory getInstance(JspContext   jspContext) {
54          assert jspContext instanceof PageContext  ;
55          return getInstance(((PageContext  )jspContext).getRequest());
56      }
57  
58      /**
59       * Get an instance of a DataGridStateFactory given a {@link ServletRequest}.
60       *
61       * @param request the current {@link ServletRequest}
62       * @return an instance of the factory
63       */
64      public static final DataGridStateFactory getInstance(ServletRequest   request) {
65          Object   obj = request.getAttribute(KEY);
66          if(obj != null) {
67              assert obj instanceof DataGridStateFactory;
68              return (DataGridStateFactory)obj;
69          }
70          else {
71              DataGridStateFactory factory = new DataGridStateFactory(request);
72              request.setAttribute(KEY, factory);
73              return factory;
74          }
75      }
76  
77      private final ServletRequest   _request;
78      private final HashMap  /*<String, DataGridStateCodec>*/ _cache;
79  
80      private DataGridStateFactory(ServletRequest   request) {
81          _request = request;
82          _cache = new HashMap  /*<String, DataGridStateCodec>*/();
83      }
84  
85      /**
86       * <p>
87       * Lookup a {@link DataGridState} object given a data grid identifier.
88       * </p>
89       * <p>
90       * This method will use the default {@link DataGridConfig} object when returning a data grid specific
91       * implementation of the {@link DataGridState} object.  In order to specify a {@link DataGridConfig},
92       * the {@link DataGridStateFactory#getDataGridState(String, DataGridConfig)} can be supplied
93       * with a specific data grid configuration.
94       * </p>
95       *
96       * @param name the name of a data grid.
97       * @return the {@link DataGridState} for the data grid with the given name
98       */
99      public final DataGridState getDataGridState(String   name) {
100         return getDataGridState(name, DEFAULT_DATA_GRID_CONFIG);
101     }
102 
103     /**
104      * <p>
105      * Lookup a {@link DataGridState} object given a data grid identifier and a specific
106      * {@link DataGridConfig} object.
107      * </p>
108      *
109      * @param name the name of the data grid
110      * @param config the {@link DataGridConfig} object to use when creating the
111      * grid's {@link DataGridState} object.
112      * @return the data grid state object
113      */
114     public final DataGridState getDataGridState(String   name, DataGridConfig config) {
115         if(config == null)
116             throw new IllegalArgumentException  (Bundle.getErrorString("DataGridStateFactory_nullDataGridConfig"));
117 
118         DataGridStateCodec codec = lookupCodec(name, config);
119         DataGridState state = codec.getDataGridState();
120         return state;
121     }
122 
123     /**
124      * <p>
125      * Lookup a {@link DataGridURLBuilder} object given a data grid identifier.
126      * </p>
127      * <p>
128      * This method will use the default {@link DataGridConfig} object when returning a data grid specific
129      * implementation of the {@link DataGridURLBuilder} object.  In order to specify a {@link DataGridConfig},
130      * the {@link DataGridStateFactory#getDataGridURLBuilder(String, DataGridConfig)} can be supplied
131      * with a specific data grid configuration.
132      * </p>
133      *
134      * @param name the name of the data grid
135      * @return the {@link DataGridURLBuilder} for the data grid with the given name
136      */
137     public final DataGridURLBuilder getDataGridURLBuilder(String   name) {
138         return getDataGridURLBuilder(name, DEFAULT_DATA_GRID_CONFIG);
139     }
140 
141     /**
142      * <p>
143      * Lookup a {@link DataGridURLBuilder} object given a data grid identifier and a specific
144      * {@link DataGridConfig} object.
145      * </p>
146      *
147      * @param name the name of the data grid
148      * @param config the {@link DataGridConfig} object to use when creating the
149      * grid's {@link DataGridURLBuilder} object.
150      * @return the URL builder for a data grid's state object
151      */
152     public final DataGridURLBuilder getDataGridURLBuilder(String   name, DataGridConfig config) {
153         if(config == null)
154             throw new IllegalArgumentException  (Bundle.getErrorString("DataGridStateFactory_nullDataGridConfig"));
155 
156         DataGridStateCodec codec = lookupCodec(name, config);
157         DataGridURLBuilder builder = codec.getDataGridURLBuilder();
158         return builder;
159     }
160 
161     /**
162      * <p>
163      * Convenience method that allows a {@link DataGridState} object from a client to
164      * be attached to the factory.  This allows subsequent calls to retrieve this same {@link DataGridState}
165      * instance.
166      * </p>
167      *
168      * @param name the name of the data grid
169      * @param state the {@link DataGridState} object to attach
170      */
171     public final void attachDataGridState(String   name, DataGridState state) {
172         DataGridStateCodec codec = lookupCodec(name, DEFAULT_DATA_GRID_CONFIG);
173         codec.setDataGridState(state);
174     }
175 
176     private final DataGridStateCodec lookupCodec(String   name, DataGridConfig config) {
177         DataGridStateCodec codec = null;
178         if(_cache.containsKey(name))
179             codec = (DataGridStateCodec)_cache.get(name);
180         else {
181             assert config != null;
182             codec = config.createStateCodec(_request, name);
183             _cache.put(name, codec);
184         }
185 
186         return codec;
187     }
188 }
189
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