    001/**
    002 * Copyright (c) 2004-2011 QOS.ch
    003 * All rights reserved.
    004 *
    005 * Permission is hereby granted, free  of charge, to any person obtaining
    006 * a  copy  of this  software  and  associated  documentation files  (the
    007 * "Software"), to  deal in  the Software without  restriction, including
    008 * without limitation  the rights to  use, copy, modify,  merge, publish,
    009 * distribute,  sublicense, and/or sell  copies of  the Software,  and to
    010 * permit persons to whom the Software  is furnished to do so, subject to
    011 * the following conditions:
    012 *
    013 * The  above  copyright  notice  and  this permission  notice  shall  be
    014 * included in all copies or substantial portions of the Software.
    015 *
    016 * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
    017 * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
    018 * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
    019 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
    020 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    021 * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
    022 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    023 *
    024 */
    025package org.slf4j.instrumentation;
    026
    027import javassist.CtBehavior;
    028import javassist.CtClass;
    029import javassist.CtMethod;
    030import javassist.Modifier;
    031import javassist.NotFoundException;
    032import javassist.bytecode.AttributeInfo;
    033import javassist.bytecode.CodeAttribute;
    034import javassist.bytecode.LocalVariableAttribute;
    035
    036/**
    037 * Helper methods for Javassist functionality.
    038 *
    039 */
    040public class JavassistHelper {
    041
    042    /**
    043     * Create a javassist source snippet which either is empty (for anything
    044     * which does not return a value) or a explanatory text around the $_
    045     * javassist return value variable.
    046     *
    047     * @param method
    048     *            descriptor of method
    049     * @return source snippet
    050     * @throws NotFoundException
    051     */
    052    public static String returnValue(CtBehavior method) throws NotFoundException {
    053
    054        String returnValue = "";
    055        if (methodReturnsValue(method)) {
    056            returnValue = " returns: \" + $_ + \".";
    057        }
    058        return returnValue;
    059    }
    060
    061    /**
    062     * determine if the given method returns a value, and return true if so.
    063     * false otherwise.
    064     *
    065     * @param method
    066     * @return
    067     * @throws NotFoundException
    068     */
    069    private static boolean methodReturnsValue(CtBehavior method) throws NotFoundException {
    070
    071        if (method instanceof CtMethod == false) {
    072            return false;
    073        }
    074
    075        CtClass returnType = ((CtMethod) method).getReturnType();
    076        String returnTypeName = returnType.getName();
    077
    078        boolean isVoidMethod = "void".equals(returnTypeName);
    079
    080        boolean methodReturnsValue = isVoidMethod == false;
    081        return methodReturnsValue;
    082    }
    083
    084    /**
    085     * Return javassist source snippet which lists all the parameters and their
    086     * values. If available the source names are extracted from the debug
    087     * information and used, otherwise just a number is shown.
    088     *
    089     * @param method
    090     * @return
    091     * @throws NotFoundException
    092     */
    093    public static String getSignature(CtBehavior method) throws NotFoundException {
    094
    095        CtClass[] parameterTypes = method.getParameterTypes();
    096
    097        CodeAttribute codeAttribute = method.getMethodInfo().getCodeAttribute();
    098
    099        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}