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1   /**
2    * Copyright (c) 2004-2011 QOS.ch
3    * All rights reserved.
4    *
5    * Permission is hereby granted, free  of charge, to any person obtaining
6    * a  copy  of this  software  and  associated  documentation files  (the
7    * "Software"), to  deal in  the Software without  restriction, including
8    * without limitation  the rights to  use, copy, modify,  merge, publish,
9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
10   * permit persons to whom the Software  is furnished to do so, subject to
11   * the following conditions:
12   *
13   * The  above  copyright  notice  and  this permission  notice  shall  be
14   * included in all copies or substantial portions of the Software.
15   *
16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23   *
24   */
25  package org.slf4j.instrumentation;
26  
27  import javassist.CtBehavior;
28  import javassist.CtClass;
29  import javassist.CtMethod;
30  import javassist.Modifier;
31  import javassist.NotFoundException;
32  import javassist.bytecode.AttributeInfo;
33  import javassist.bytecode.CodeAttribute;
34  import javassist.bytecode.LocalVariableAttribute;
35  
36  /**
37   * Helper methods for Javassist functionality.
38   * 
39   */
40  public class JavassistHelper {
41  
42      /**
43       * Create a javassist source snippet which either is empty (for anything
44       * which does not return a value) or a explanatory text around the $_
45       * javassist return value variable.
46       * 
47       * @param method
48       *            descriptor of method
49       * @return source snippet
50       * @throws NotFoundException
51       */
52      public static String returnValue(CtBehavior method) throws NotFoundException {
53  
54          String returnValue = "";
55          if (methodReturnsValue(method)) {
56              returnValue = " returns: \" + $_ + \".";
57          }
58          return returnValue;
59      }
60  
61      /**
62       * determine if the given method returns a value, and return true if so.
63       * false otherwise.
64       * 
65       * @param method
66       * @return
67       * @throws NotFoundException
68       */
69      private static boolean methodReturnsValue(CtBehavior method) throws NotFoundException {
70  
71          if (method instanceof CtMethod == false) {
72              return false;
73          }
74  
75          CtClass returnType = ((CtMethod) method).getReturnType();
76          String returnTypeName = returnType.getName();
77  
78          boolean isVoidMethod = "void".equals(returnTypeName);
79  
80          boolean methodReturnsValue = isVoidMethod == false;
81          return methodReturnsValue;
82      }
83  
84      /**
85       * Return javassist source snippet which lists all the parameters and their
86       * values. If available the source names are extracted from the debug
87       * information and used, otherwise just a number is shown.
88       * 
89       * @param method
90       * @return
91       * @throws NotFoundException
92       */
93      public static String getSignature(CtBehavior method) throws NotFoundException {
94  
95          CtClass[] parameterTypes = method.getParameterTypes();
96  
97          CodeAttribute codeAttribute = method.getMethodInfo().getCodeAttribute();
98  
99          LocalVariableAttribute locals = null;
100 
101         if (codeAttribute != null) {
102             AttributeInfo attribute;
103             attribute = codeAttribute.getAttribute("LocalVariableTable");
104             locals = (LocalVariableAttribute) attribute;
105         }
106 
107         String methodName = method.getName();
108 
109         StringBuilder sb = new StringBuilder(methodName).append("(\" ");
110         for (int i = 0; i < parameterTypes.length; i++) {
111             if (i > 0) {
112                 // add a comma and a space between printed values
113                 sb.append(" + \", \" ");
114             }
115 
116             CtClass parameterType = parameterTypes[i];
117             boolean isArray = parameterType.isArray();
118             CtClass arrayType = parameterType.getComponentType();
119             if (isArray) {
120                 while (arrayType.isArray()) {
121                     arrayType = arrayType.getComponentType();
122                 }
123             }
124 
125             sb.append(" + \"");
126             try {
127                 sb.append(parameterNameFor(method, locals, i));
128             } catch (Exception e) {
129                 sb.append(i + 1);
130             }
131             sb.append("\" + \"=");
132 
133             if (parameterType.isPrimitive()) {
134                 // let the compiler handle primitive -> string
135                 sb.append("\"+ $").append(i + 1);
136             } else {
137                 String s = "org.slf4j.instrumentation.ToStringHelper.render";
138                 sb.append("\"+ ").append(s).append("($").append(i + 1).append(')');
139             }
140         }
141         sb.append("+\")");
142 
143         String signature = sb.toString();
144         return signature;
145     }
146 
147     /**
148      * Determine the name of parameter with index i in the given method. Use the
149      * locals attributes about local variables from the classfile. Note: This is
150      * still work in progress.
151      * 
152      * @param method
153      * @param locals
154      * @param i
155      * @return the name of the parameter if available or a number if not.
156      */
157     static String parameterNameFor(CtBehavior method, LocalVariableAttribute locals, int i) {
158 
159         if (locals == null) {
160             return Integer.toString(i + 1);
161         }
162 
163         int modifiers = method.getModifiers();
164 
165         int j = i;
166 
167         if (Modifier.isSynchronized(modifiers)) {
168             // skip object to synchronize upon.
169             j++;
170             // System.err.println("Synchronized");
171         }
172         if (Modifier.isStatic(modifiers) == false) {
173             // skip "this"
174             j++;
175             // System.err.println("Instance");
176         }
177         String variableName = locals.variableName(j);
178         // if (variableName.equals("this")) {
179         // System.err.println("'this' returned as a parameter name for "
180         // + method.getName() + " index " + j
181         // +
182         // ", names are probably shifted. Please submit source for class in slf4j bugreport");
183         // }
184         return variableName;
185     }
186 }