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1   /**
2    * Logback: the reliable, generic, fast and flexible logging framework.
3    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
4    *
5    * This program and the accompanying materials are dual-licensed under
6    * either the terms of the Eclipse Public License v1.0 as published by
7    * the Eclipse Foundation
8    *
9    *   or (per the licensee's choosing)
10   *
11   * under the terms of the GNU Lesser General Public License version 2.1
12   * as published by the Free Software Foundation.
13   */
14  package chapters.onJoran.calculator;
15  
16  import org.xml.sax.Attributes;
17  
18  import ch.qos.logback.core.joran.action.Action;
19  import ch.qos.logback.core.joran.spi.InterpretationContext;
20  
21  import java.util.EmptyStackException;
22  
23  /**
24   * 
25   * This action multiplies the two integers at the top of the stack (they are
26   * removed) and pushes the result on top the stack.
27   * 
28   * @author Ceki Gülcü
29   */
30  public class MultiplyAction extends Action {
31  
32      public void begin(InterpretationContext ic, String name, Attributes attributes) {
33          int first = fetchInteger(ic);
34          int second = fetchInteger(ic);
35          ic.pushObject(first * second);
36      }
37  
38      /**
39       * Pop the Integer object at the top of the stack. This code illustrates usage
40       * of Joran's error handling paradigm.
41       */
42      int fetchInteger(InterpretationContext ic) {
43          int result = 0;
44  
45          try {
46              Object o1 = ic.popObject();
47  
48              if (o1 instanceof Integer) {
49                  result = ((Integer) o1).intValue();
50              } else {
51                  String errMsg = "Object [" + o1 + "] currently at the top of the stack is not an integer.";
52                  ic.addError(errMsg);
53                  throw new IllegalArgumentException(errMsg);
54              }
55          } catch (EmptyStackException ese) {
56              ic.addError("Expecting an integer on the execution stack.");
57              throw ese;
58          }
59          return result;
60      }
61  
62      public void end(InterpretationContext ic, String name) {
63          // Nothing to do here.
64      }
65  }