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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  package org.apache.mina.integration.ognl;
18  
19  import java.util.LinkedHashSet;
20  import java.util.Set;
21  
22  import ognl.Ognl;
23  import ognl.OgnlContext;
24  import ognl.OgnlException;
25  import ognl.TypeConverter;
26  
27  import org.apache.mina.core.session.IoSession;
28  
29  /**
30   * Finds {@link IoSession}s that match a boolean OGNL expression.
31   * 
32   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
33   */
34  public class IoSessionFinder {
35  
36      private final String query;
37  
38      private final TypeConverter typeConverter = new PropertyTypeConverter();
39  
40      private final Object expression;
41  
42      /**
43       * Creates a new instance with the specified OGNL expression that returns
44       * a boolean value (e.g. <tt>"id == 0x12345678"</tt>).
45       * 
46       * @param query The OGNL expression 
47       */
48      public IoSessionFinder(String query) {
49          if (query == null) {
50              throw new IllegalArgumentException("query");
51          }
52  
53          query = query.trim();
54          
55          if (query.length() == 0) {
56              throw new IllegalArgumentException("query is empty.");
57          }
58  
59          this.query = query;
60          
61          try {
62              expression = Ognl.parseExpression(query);
63          } catch (OgnlException e) {
64              throw new IllegalArgumentException("query: " + query);
65          }
66      }
67  
68      /**
69       * Finds a {@link Set} of {@link IoSession}s that matches the query
70       * from the specified sessions and returns the matches.
71       * @throws OgnlException if failed to evaluate the OGNL expression
72       * 
73       * @param sessions The list of sessions to check
74       * @return A set of the session that matches the query
75       * @throws OgnlException If we can't find a boolean value in a session's context
76       */
77      public Set<IoSession> find(Iterable<IoSession> sessions) throws OgnlException {
78          if (sessions == null) {
79              throw new IllegalArgumentException("sessions");
80          }
81  
82          Set<IoSession> answer = new LinkedHashSet<IoSession>();
83          
84          for (IoSession s : sessions) {
85              OgnlContext context = (OgnlContext) Ognl.createDefaultContext(s);
86              context.setTypeConverter(typeConverter);
87              context.put(AbstractPropertyAccessor.READ_ONLY_MODE, true);
88              context.put(AbstractPropertyAccessor.QUERY, query);
89              Object result = Ognl.getValue(expression, context, s);
90              
91              if (result instanceof Boolean) {
92                  if (((Boolean) result).booleanValue()) {
93                      answer.add(s);
94                  }
95              } else {
96                  throw new OgnlException("Query didn't return a boolean value: " + query);
97              }
98          }
99  
100         return answer;
101     }
102 }