2009/05/20 - Apache Shale has been retired.

For more information, please explore the Attic.


1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to you under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  /*
19   * $Id: PluggableLookupCommand.java 473876 2006-11-12 04:50:13Z gvanmatre $
20   */
21  package org.apache.shale.clay.utils;
22  
23  import javax.faces.context.FacesContext;
24  import javax.faces.el.ValueBinding;
25  
26  import org.apache.commons.chain.Catalog;
27  import org.apache.commons.chain.CatalogFactory;
28  import org.apache.commons.chain.Command;
29  import org.apache.commons.chain.Context;
30  import org.apache.commons.chain.generic.LookupCommand;
31  
32  /***
33   * <p>This chains class performs a check to verify the catalog exists.
34   * If the catalog doesn't exist, it returns <code>true</code> if the
35   * <code>optional</code> property in the super class is <code>true</code>.
36   * If the catalog is not found and the command is not optional, it returns a
37   * <code>false</code> value.  Otherwise, if the catalog exists, the super
38   * implementation is invoked.  The name of the command can be a value
39   * binding expression.  The value is evaluated if it contains an expression
40   * and the resolved command is invoked.</p>
41   *
42   */
43  public class PluggableLookupCommand extends LookupCommand {
44  
45  
46      /***
47       * <p>Checks to see if the catalog exists.</p>
48       *
49       * @return <code>true</code> if the catalog exists
50       */
51      private boolean catalogExists() {
52          String catalogName = getCatalogName();
53          if (catalogName == null) {
54              return false;
55          }
56          CatalogFactory catalogFactory = CatalogFactory.getInstance();
57  
58          return (catalogFactory.getCatalog(catalogName) != null);
59      }
60  
61      /***
62       * @return <code>Catalog</code> for the <code>catalogName</code>
63       */
64      private Catalog getCatalog() {
65          CatalogFactory catalogFactory = CatalogFactory.getInstance();
66          return catalogFactory.getCatalog(getCatalogName());
67      }
68  
69      /***
70       * <p>Adds an additional check to determine if the catalog name is loaded.
71       * If loaded, the super implementation is invoked.  Otherwise, the chain
72       * continues if the command is optional.</p>
73       *
74       * @param context chains context
75       * @return <code>true</code> if the chain is done
76       * @exception Exception up the calling chain
77       */
78      public boolean execute(Context context) throws Exception {
79  
80          if (!catalogExists()) {
81             return !isOptional();
82          }
83  
84          if (isValueReference(getName())) {
85              // command is a binding expression; evaluate and the find the target command
86              FacesContext facesContext = FacesContext.getCurrentInstance();
87              ValueBinding vb = facesContext.getApplication().createValueBinding(getName());
88              String targetCommand = (String) vb.getValue(facesContext);
89  
90              if (targetCommand != null) {
91                 Command command = getCatalog().getCommand(targetCommand);
92                 if (command != null) {
93                     return command.execute(context);
94                 }
95              }
96          }
97          return super.execute(context);
98      }
99  
100     /***
101      * @param value the command name to test for a binding expression
102      * @return <code>true</code> if the <code>value</code> is a binding expression
103      */
104     private boolean isValueReference(String value) {
105         if (value == null) {
106             return false;
107         }
108 
109         if ((value.indexOf("#{") > -1)
110                 && (value.indexOf("}") > -1)) {
111             return true;
112         }
113 
114         return false;
115     }
116 
117 }