DefaultContainer


1   /*
2    * Copyright 2005 Joe Walker
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  package org.directwebremoting.impl;
17  
18  import java.lang.reflect.InvocationTargetException  ;
19  import java.lang.reflect.Method  ;
20  import java.util.Collection  ;
21  import java.util.Collections  ;
22  import java.util.Iterator  ;
23  import java.util.Map  ;
24  import java.util.TreeMap  ;
25  
26  import javax.servlet.Servlet  ;
27  
28  import org.directwebremoting.Container;
29  import org.directwebremoting.util.LocalUtil;
30  import org.directwebremoting.util.Logger;
31  
32  /**
33   * DefaultContainer is like a mini-IoC container for DWR.
34   * At least it is an IoC container by interface (check: no params that have
35   * anything to do with DWR), but it is hard coded specifically for DWR. If we
36   * want to make more of it we can later, but this is certainly not going to
37   * become a full blown IoC container.
38   * @author Joe Walker [joe at getahead dot ltd dot uk]
39   */
40  public class DefaultContainer extends AbstractContainer implements Container
41  {
42      /**
43       * Set the class that should be used to implement the given interface
44       * @param askFor The interface to implement
45       * @param valueParam The new implementation
46       * @throws IllegalAccessException If the specified beans could not be accessed
47       * @throws InstantiationException If the specified beans could not be created
48       */
49      public void addParameter(Object   askFor, Object   valueParam) throws InstantiationException  , IllegalAccessException  
50      {
51          Object   value = valueParam;
52  
53          // Maybe the value is a classname that needs instansiating
54          if (value instanceof String  )
55          {
56              try
57              {
58                  Class   impl = LocalUtil.classForName((String  ) value);
59                  value = impl.newInstance();
60              }
61              catch (ClassNotFoundException   ex)
62              {
63                  // it's not a classname, leave it
64              }
65          }
66  
67          // If we have an instansiated value object and askFor is an interface
68          // then we can check that one implements the other
69          if (!(value instanceof String  ) && askFor instanceof String  )
70          {
71              try
72              {
73                  Class   iface = LocalUtil.classForName((String  ) askFor);
74                  if (!iface.isAssignableFrom(value.getClass()))
75                  {
76                      log.error("Can't cast: " + value + " to " + askFor);
77                  }
78              }
79              catch (ClassNotFoundException   ex)
80              {
81                  // it's not a classname, leave it
82              }
83          }
84  
85          if (log.isDebugEnabled())
86          {
87              if (value instanceof String  )
88              {
89                  log.debug("Adding IoC setting: " + askFor + "=" + value);
90              }
91              else
92              {
93                  log.debug("Adding IoC implementation: " + askFor + "=" + value.getClass().getName());
94              }
95          }
96  
97          beans.put(askFor, value);
98      }
99  
100     /**
101      * Called to indicate that we finished adding parameters.
102      * The thread safety of a large part of DWR depends on this function only
103      * being called from {@link Servlet#init(javax.servlet.ServletConfig)},
104      * where all the setup is done, and where we depend on the undocumented
105      * feature of all servlet containers that they complete the init process
106      * of a Servlet before they begin servicing requests.
107      * @see DefaultContainer#addParameter(Object, Object)
108      * @noinspection UnnecessaryLabelOnContinueStatement
109      */
110     public void setupFinished()
111     {
112         // We try to autowire each bean in turn
113         for (Iterator   it = beans.entrySet().iterator(); it.hasNext();)
114         {
115             Map.Entry   entry = (Map.Entry  ) it.next();
116             // Class type = (Class) entry.getKey();
117             Object   ovalue = entry.getValue();
118 
119             if (!(ovalue instanceof String  ))
120             {
121                 log.debug("Trying to autowire: " + ovalue.getClass().getName());
122 
123                 Method  [] methods = ovalue.getClass().getMethods();
124                 methods:
125                 for (int i = 0; i < methods.length; i++)
126                 {
127                     Method   setter = methods[i];
128 
129                     if (setter.getName().startsWith("set") &&
130                         setter.getName().length() > 3 &&
131                         setter.getParameterTypes().length == 1)
132                     {
133                         String   name = Character.toLowerCase(setter.getName().charAt(3)) + setter.getName().substring(4);
134                         Class   propertyType = setter.getParameterTypes()[0];
135 
136                         // First we try auto-wire by name
137                         Object   setting = beans.get(name);
138                         if (setting != null)
139                         {
140                             if (propertyType.isAssignableFrom(setting.getClass()))
141                             {
142                                 log.debug("- autowire-by-name: " + name + "=" + setting);
143                                 invoke(setter, ovalue, setting);
144 
145                                 continue methods;
146                             }
147                             else if (setting.getClass() == String  .class)
148                             {
149                                 try
150                                 {
151                                     Object   value = LocalUtil.simpleConvert((String  ) setting, propertyType);
152 
153                                     log.debug("- autowire-by-name: " + name + "=" + value);
154                                     invoke(setter, ovalue, value);
155                                 }
156                                 catch (IllegalArgumentException   ex)
157                                 {
158                                     // Ignore - this was a specuative convert anyway
159                                 }
160 
161                                 continue methods;
162                             }
163                         }
164 
165                         // Next we try autowire-by-type
166                         Object   value = beans.get(propertyType.getName());
167                         if (value != null)
168                         {
169                             log.debug("- autowire-by-type: " + name + "=" + value.getClass().getName());
170                             invoke(setter, ovalue, value);
171 
172                             continue methods;
173                         }
174 
175                         log.debug("- skipped autowire: " + name);
176                     }
177                 }
178             }
179         }
180 
181         callInitializingBeans();
182     }
183 
184     /**
185      * A helper to do the reflection.
186      * This helper throws away all exceptions, prefering to log.
187      * @param setter The method to invoke
188      * @param bean The object to invoke the method on
189      * @param value The value to assign to the property using the setter method
190      */
191     private static void invoke(Method   setter, Object   bean, Object   value)
192     {
193         try
194         {
195             setter.invoke(bean, new Object  [] { value });
196         }
197         catch (IllegalArgumentException   ex)
198         {
199             log.error("- Internal error: " + ex.getMessage());
200         }
201         catch (IllegalAccessException   ex)
202         {
203             log.error("- Permission error: " + ex.getMessage());
204         }
205         catch (InvocationTargetException   ex)
206         {
207             log.error("- Exception during auto-wire: ", ex.getTargetException());
208         }
209     }
210 
211     /* (non-Javadoc)
212      * @see org.directwebremoting.Container#getBean(java.lang.String)
213      */
214     public Object   getBean(String   id)
215     {
216         Object   reply = beans.get(id);
217         if (reply == null)
218         {
219             log.debug("DefaultContainer: No bean with id=" + id);
220         }
221 
222         return reply;
223     }
224 
225     /* (non-Javadoc)
226      * @see org.directwebremoting.Container#getBeanNames()
227      */
228     public Collection   getBeanNames()
229     {
230         return Collections.unmodifiableCollection(beans.keySet());
231     }
232 
233     /**
234      * The beans that we know of indexed by type
235      */
236     protected Map   beans = new TreeMap  ();
237 
238     /**
239      * The log stream
240      */
241     private static final Logger log = Logger.getLogger(DefaultContainer.class);
242 }
243
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