Groovy example source code file (MethodRankHelper.java)

This example Groovy source code file (MethodRankHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

class, class, constructor, dl_delete, dl_delete, list, list, object, rankableconstructor, rankablefield, rankablemethod, reflection, string, stringbuffer, stringbuffer, util

The Groovy MethodRankHelper.java source code

/*
 * Copyright 2003-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.runtime;

import groovy.lang.MetaMethod;
import groovy.lang.MetaProperty;

import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import org.codehaus.groovy.reflection.CachedClass;
import org.codehaus.groovy.reflection.ClassInfo;

/**
 * Utility class for MissingMethodException, MissingPropertyException etc.
 * This class contains methods assisting in ranking and listing probable intended
 * methods/fields when a exception is thrown.
 *
 * @author Hjalmar Ekengren
 */
public class MethodRankHelper{
    //These are the costs for the various edit operations
    //they are used by the two DamerauLevenshtein implementations
    public static final int DL_SUBSTITUTION = 10;
    public static final int DL_DELETE = 10; //This is also the cost for a insert
    public static final int DL_TRANSPOSITION = 5;
    public static final int DL_CASE = 5;
    
    public static final int MAX_RECOMENDATIONS = 5;
    public static final int MAX_METHOD_SCORE = 50;
    public static final int MAX_CONSTRUCTOR_SCORE = 20;
    public static final int MAX_FIELD_SCORE = 30;
    
    private static final class Pair<U,V> {
        private U u;
        private V v;
        public Pair(U u, V v){
            this.u = u;
            this.v = v;
        }
    }
    
    /**
     * Returns a string detailing possible solutions to a missing method
     * if no good solutions can be found a empty string is returned.
     *
     * @param methodName the name of the method that doesn't exist
     * @param type the class on which the method is invoked
     * @param arguments the arguments passed to the method
     * @return a string with probable solutions to the exception
     */
    public static String getMethodSuggestionString(String methodName, Class type, Object[] arguments){
        ClassInfo ci = ClassInfo.getClassInfo(type);
        List<MetaMethod> methods = new ArrayList(ci.getMetaClass().getMethods());
        methods.addAll(ci.getMetaClass().getMetaMethods());
        List<MetaMethod> sugg = rankMethods(methodName,arguments,methods);
        StringBuffer sb = new StringBuffer();
        if (!sugg.isEmpty()){
            sb.append("\nPossible solutions: ");
            for(int i = 0; i < sugg.size(); i++) {
                if(i != 0) sb.append(", ");
                sb.append(sugg.get(i).getName()).append("(");
                sb.append(listParameterNames(sugg.get(i).getParameterTypes()));
                sb.append(")");
            }
        }
        Class[] argumentClasses = getArgumentClasses(arguments);
        List<Pair conflictClasses = getConflictClasses(sugg,argumentClasses);
        if (!conflictClasses.isEmpty()){
            sb.append("\nThe following classes appear as argument class and as parameter class, ");
            sb.append("but are defined by different class loader:\n");
            boolean first = true;
            for(Pair<Class,Class> pair: conflictClasses) {
                if (!first) {
                    sb.append(", ");
                } else {
                    first = false;
                }
                sb.append(pair.u.getName()).append(" (defined by '");
                sb.append(pair.u.getClassLoader());
                sb.append("' and '");
                sb.append(pair.v.getClassLoader());
                sb.append("')");
            }
            sb.append("\nIf one of the method suggestions matches the method you wanted to call, ");
            sb.append("\nthen check your class loader setup.");
        }
        return sb.toString();
    }
    
    private static List<Pair getConflictClasses(List sugg, Class[] argumentClasses) {
        List<Pair ret = new LinkedList>();
        Set<Class> recordedClasses = new HashSet();
        for (MetaMethod method : sugg) {
            Class[] para = method.getNativeParameterTypes();
            for (Class aPara : para) {
                if (recordedClasses.contains(aPara)) continue;
                for (Class argumentClass : argumentClasses) {
                    if (argumentClass == null) continue;
                    if (argumentClass == aPara) continue;
                    if (argumentClass.getName().equals(aPara.getName())) {
                        ret.add(new Pair<Class, Class>(argumentClass, aPara));
                    }
                }
                recordedClasses.add(aPara);
            }
        }
        return ret;
    }

    private static Class[] getArgumentClasses(Object[] arguments) {
        Class[] argumentClasses = new Class[arguments.length];
        for (int i=0; i<argumentClasses.length; i++) {
            Object arg = arguments[i];
            if (arg==null) continue;
            argumentClasses[i] = arg.getClass();
        }
        return argumentClasses;
    }

    /**
     * Returns a string detailing possible solutions to a missing constructor
     * if no good solutions can be found a empty string is returned.
     *
     * @param arguments the arguments passed to the constructor
     * @param type the class on which the constructor is invoked
     * @return a string with probable solutions to the exception
     */
    public static String getConstructorSuggestionString(Class type, Object[] arguments){
        Constructor[] sugg = rankConstructors(arguments, type.getConstructors());
        if(sugg.length >0){
            StringBuffer sb = new StringBuffer();
            sb.append("\nPossible solutions: ");
            for(int i = 0; i < sugg.length; i++){
                if(i != 0) sb.append(", ");
                sb.append(type.getName()).append("(");
                sb.append(listParameterNames(sugg[i].getParameterTypes()));
                sb.append(")");
            }
            return sb.toString();
        } else{
            return "";
        }
    }
    
    /**
     * Returns a string detailing possible solutions to a missing field or property
     * if no good solutions can be found a empty string is returned.
     *
     * @param fieldName the missing field
     * @param type the class on which the field is sought
     * @return a string with probable solutions to the exception
     */
    public static String getPropertySuggestionString(String fieldName, Class type){
        ClassInfo ci = ClassInfo.getClassInfo(type);
        List<MetaProperty>  fi = ci.getMetaClass().getProperties();
        List<RankableField> rf = new ArrayList(fi.size());
        StringBuffer sb = new StringBuffer();
        sb.append("\nPossible solutions: ");
        
        for(MetaProperty mp : fi) rf.add(new RankableField(fieldName, mp));
        Collections.sort(rf);

        int i = 0;
        for (RankableField f : rf) {
            if (i > MAX_RECOMENDATIONS) break;
            if (f.score > MAX_FIELD_SCORE) break;
            if(i > 0) sb.append(", ");
            sb.append(f.f.getName());
            i++;
        }
        return i > 0? sb.toString(): "";
    }
    
    /**
     * creates a comma separated list of each of the class names.
     *
     * @param cachedClasses the array of Classes
     * @return the Class names
     */
    private static String listParameterNames(Class[] cachedClasses){
      StringBuffer sb = new StringBuffer();
      for(int i =0; i < cachedClasses.length;i++){
          if(i != 0) sb.append(", ");
          sb.append(cachedClasses[i].getName());
      }
      return sb.toString();
    }
    
    
    private static String listParameterNames(CachedClass[] cachedClasses){
        StringBuffer sb = new StringBuffer();
        for(int i =0; i < cachedClasses.length;i++){
            if(i != 0) sb.append(", ");
            sb.append(cachedClasses[i].getName());
        }
        return sb.toString();
      }
    
    /**
     * Returns a sorted(ranked) list of a selection of the methods among candidates which
     * most closely resembles original.
     *
     * @param name
     * @param original
     * @param methods
     * @return a sorted lists of Methods
     */
    private static List<MetaMethod> rankMethods(String name, Object[] original, List methods) {
        List<RankableMethod> rm = new ArrayList(methods.size());
        if (original==null) original = new Object[0];
        Class[] ta = new Class[original.length];
    
        Class nullC =  NullObject.class;
        for(int i = 0; i < original.length; i++){
            //All nulls have to be wrapped so that they can be compared
            ta[i] = original[i] == null?nullC: original[i].getClass();
        }

        for (MetaMethod m:methods) {
            rm.add(new RankableMethod(name, ta, m));
        }
        Collections.sort(rm);
        
        List<MetaMethod> l =  new ArrayList(rm.size());
        for (RankableMethod m : rm) {
            if (l.size() > MAX_RECOMENDATIONS) break;
            if (m.score > MAX_METHOD_SCORE) break;
            l.add(m.m);
        }
        return l;
    }

    /**
     * This class wraps a method object and a score variable so methods 
     * Can easily be ranked by their likeness to a another method
     *
     */
    private static final class RankableMethod implements Comparable {
        final MetaMethod m;
        final Integer score;

        public RankableMethod(String name, Class[] argumentTypes, MetaMethod m2) {
            this.m = m2;
            int nameDist = delDistance(name, m2.getName());

            //unbox primitives
            Class[] mArgs = new Class[m2.getParameterTypes().length];
            for(int i =0; i < mArgs.length; i++){
                //All args have to be boxed since argumentTypes is always boxed
                mArgs[i] = boxVar(m2.getParameterTypes()[i].getTheClass());
            }
            int argDist = damerauLevenshteinDistance(argumentTypes,mArgs);
            this.score = nameDist + argDist;
        }

        public int compareTo(Object o) {
            RankableMethod mo = (RankableMethod) o;
            return score.compareTo(mo.score);
        }
    }

    /**
     * Returns a sorted(ranked) list of a selection of the constructors among candidates which
     * most closely resembles original.
     *
     * @param original
     * @param candidates
     * @return a sorted lists of Methods
     */
    private static Constructor[] rankConstructors(Object[] original, Constructor[] candidates) {
        RankableConstructor[] rc = new RankableConstructor[candidates.length];
        Class[] ta = new Class[original.length];

        Class nullC = NullObject.class;
        for (int i = 0; i < original.length; i++) {
            //All nulls have to be wrapped so that they can be compared
            ta[i] = original[i] == null ? nullC : original[i].getClass();
        }

        for (int i = 0; i < candidates.length; i++) {
            rc[i] = new RankableConstructor(ta, candidates[i]);
        }
        Arrays.sort(rc);
        List<Constructor> l = new ArrayList();
        int index = 0;
        while (l.size() < MAX_RECOMENDATIONS && index < rc.length && rc[index].score < MAX_CONSTRUCTOR_SCORE) {
            l.add(rc[index].c);
            index++;
        }
        return l.toArray(new Constructor[l.size()]);
    }

    /**
     * This class wraps a method object and a score variable so methods 
     * Can easily be ranked by their likeness to a another method
     *
     */
    private static final class RankableConstructor implements Comparable {
        final Constructor c;
        final Integer score;

        public RankableConstructor(Class[] argumentTypes, Constructor c) {
            this.c = c;
            //unbox primitives
            Class[] cArgs = new Class[c.getParameterTypes().length];
            for(int i =0; i < cArgs.length; i++){
                //All args have to be boxed since argumentTypes is always boxed
                cArgs[i] = boxVar(c.getParameterTypes()[i]);
            }

            this.score = damerauLevenshteinDistance(argumentTypes,cArgs);
        }

        public int compareTo(Object o) {
            RankableConstructor co = (RankableConstructor) o;
            return score.compareTo(co.score);
        }
    }
    
    /**
     * This class wraps a method object and a score variable so methods 
     * Can easily be ranked by their likeness to a another method
     *
     */
    private static final class RankableField implements Comparable {
        final MetaProperty f;
        final Integer score;

        public RankableField(String name, MetaProperty mp) {
            this.f = mp;
            this.score = delDistance(name,mp.getName());
        }

        public int compareTo(Object o) {
            RankableField co = (RankableField) o;
            return score.compareTo(co.score);
        }
    }
    
    /**
     * If c is a primitive class this method returns a boxed version
     * otherwise c is returned.
     * In java 1.5 this can be simplified thanks to the Type class.
     * @param c
     * @return a boxed version of c if c can be boxed, else c
     */
    protected static Class boxVar(Class c){
        if(Boolean.TYPE.equals(c)){
            return Boolean.class;
        }else if(Character.TYPE.equals(c)){
            return Character.class;
        }else if(Byte.TYPE.equals(c)){
            return Byte.class;
        }else if(Double.TYPE.equals(c)){
            return Double.class;
        }else if(Float.TYPE.equals(c)){
            return Float.class;
        }else if(Integer.TYPE.equals(c)){
            return Integer.class;
        }else if(Long.TYPE.equals(c)){
            return Long.class;
        }else if(Short.TYPE.equals(c)){
            return Short.class;
        }else{
            return c;
        }
    }
    
    /**
     * This is a small wrapper for nulls
     */
    private static class NullObject{
    }

    /**
     * This is a slightly modified version of the Damerau Levenshtein distance
     * algorithm. It has a additional test to see if a character has switched case,
     * in the original algorithm this counts as a substitution.
     * The "cost" for a substitution is given as 10 instead of 1 in this version,
     * this enables transpositions and case modifications to have a lower cost than
     * substitutions.
     *
     * Currently the lowercase versions of t_j and s_i isn't cached, its probable
     * that some speed could be gained from this.
     * 
     * This version is based on Chas Emerick's implementation of Levenshtein Distance
     * for jakarta commons.
     * @param s a CharSequence
     * @param t the CharSequence to be compared to s
     * @return a value representing the edit distance between s and t
     */
    public static int delDistance(CharSequence s, CharSequence t) {
        if (s == null || t == null) {
            throw new IllegalArgumentException("Strings must not be null");
        }

        int n = s.length(); // length of s
        int m = t.length(); // length of t

        if (n == 0) {
            return m;
        } else if (m == 0) {
            return n;
        }

        //we have to keep 3 rows instead of the 2 used in Levenshtein
        int[][] vals = new int[3][n + 1];


        int _d[]; //placeholder to assist in rotating vals

        // indexes into strings s and t
        int i; // iterates through s
        int j; // iterates through t

        char t_j; // jth character of t
        char s_i; // ith character of s
        int cost; // cost

        for (i = 0; i <= n; i++) {
            vals[1][i] = i * DL_DELETE;
        }

        for (j = 1; j <= m; j++) {
            t_j = t.charAt(j - 1);
            vals[0][0] = j * DL_DELETE;

            for (i = 1; i <= n; i++) {
                s_i = s.charAt(i - 1);
                if (Character.isLowerCase(s_i) ^ Character.isLowerCase(t_j)) {
                    //if s_i and t_i don't have have the same case
                    cost = caselessCompare(s_i, t_j) ? DL_CASE : DL_SUBSTITUTION;
                } else {
                    //if they share case check for substitution
                    cost = s_i == t_j ? 0 : DL_SUBSTITUTION;
                }

                // minimum of cell to the left+1, to the top+1, diagonally left and up +cost
                vals[0][i] = Math.min(Math.min(vals[0][i - 1] + DL_DELETE, vals[1][i] + DL_DELETE), vals[1][i - 1] + cost);

                //Check for transposition, somewhat more complex now since we have to check for case
                if (i > 1 && j > 1) {
                    cost = Character.isLowerCase(s_i) ^ Character.isLowerCase(t.charAt(j - 2)) ? DL_CASE : 0;
                    cost = Character.isLowerCase(s.charAt(i - 2)) ^ Character.isLowerCase(t_j) ? cost + DL_CASE : cost;

                    if (caselessCompare(s_i, t.charAt(j - 2)) && caselessCompare(s.charAt(i - 2), t_j)) {
                        vals[0][i] = Math.min(vals[0][i], vals[2][i - 2] + DL_TRANSPOSITION + cost);
                    }
                }
            }

            // rotate all value arrays upwards(older rows get a higher index)
            _d = vals[2];
            vals[2] = vals[1];
            vals[1] = vals[0];
            vals[0] = _d;
        }

        // our last action in the above loop was to rotate vals, so vals[1] now
        // actually has the most recent cost counts
        return vals[1][n];
    }

    /**
     * Compares two characters whilst ignoring case.
     * @param a the first character
     * @param b the second character
     * @return true if the characters are equal
     */
    private static boolean caselessCompare(char a, char b){
        return Character.toLowerCase(a) == Character.toLowerCase(b);
    }
    
    /**
     * This is a implementation of DL distance between two Object arrays instead
     * of character streams. The objects are compared using their equals method.
     * No objects may be null.
     * This implementation is based on Chas Emerick's implementation of Levenshtein Distance
     * for jakarta commons.
     * @param s a Object array
     * @param t this array is compared to s
     * @return the edit distance between the two arrays
     */
    public static int damerauLevenshteinDistance(Object[] s, Object[] t) {
        if (s == null || t == null) {
            throw new IllegalArgumentException("Arrays must not be null");
        }

        int n = s.length; // length of s
        int m = t.length; // length of t

        if (n == 0) {
            return m;
        } else if (m == 0) {
            return n;
        }

        int[][] vals = new int[3][n + 1];


        int _d[]; //placeholder to assist in rotating vals

        // indexes into arrays s and t
        int i; // iterates through s
        int j; // iterates through t

        Object t_j; // jth object of t

        int cost; // cost

        for (i = 0; i <= n; i++) {
            vals[1][i] = i * DL_DELETE ;
        }

        for (j = 1; j <= m; j++) {
            t_j = t[j - 1];
            vals[0][0] = j * DL_DELETE ;

            for (i = 1; i <= n; i++) {
                cost = s[i - 1].equals(t_j)? 0 : DL_SUBSTITUTION;
                // minimum of cell to the left+1, to the top+1, diagonally left and up +cost
                vals[0][i] = Math.min(Math.min(vals[0][i - 1] + DL_DELETE, vals[1][i] + DL_DELETE), vals[1][i - 1] + cost);

                //Check for transposition
                if(i > 1 && j > 1 && s[i -1].equals(t[j -2]) && s[i- 2].equals(t_j)){
                    vals[0][i] = Math.min(vals[0][i], vals[2][i-2] + DL_TRANSPOSITION);
                }
            }

            // rotate all value arrays upwards(older rows get a higher index)
            _d = vals[2];
            vals[2] = vals[1];
            vals[1] = vals[0];
            vals[0] = _d;
        }

        return vals[1][n];
    }
}