JavassistHelper xref

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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 }