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/*
 * Copyright 2002-2018 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
 *
 *      https://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.springframework.beans;

import java.beans.PropertyDescriptor;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

/**
 * Helper class for calculating property matches, according to a configurable
 * distance. Provide the list of potential matches and an easy way to generate
 * an error message. Works for both java bean properties and fields.
 *
 * 

Mainly for use within the framework and in particular the binding facility. * * @author Alef Arendsen * @author Arjen Poutsma * @author Juergen Hoeller * @author Stephane Nicoll * @since 2.0 * @see #forProperty(String, Class) * @see #forField(String, Class) */ public abstract class PropertyMatches { /** Default maximum property distance: 2. */ public static final int DEFAULT_MAX_DISTANCE = 2; // Static factory methods /** * Create PropertyMatches for the given bean property. * @param propertyName the name of the property to find possible matches for * @param beanClass the bean class to search for matches */ public static PropertyMatches forProperty(String propertyName, Class beanClass) { return forProperty(propertyName, beanClass, DEFAULT_MAX_DISTANCE); } /** * Create PropertyMatches for the given bean property. * @param propertyName the name of the property to find possible matches for * @param beanClass the bean class to search for matches * @param maxDistance the maximum property distance allowed for matches */ public static PropertyMatches forProperty(String propertyName, Class beanClass, int maxDistance) { return new BeanPropertyMatches(propertyName, beanClass, maxDistance); } /** * Create PropertyMatches for the given field property. * @param propertyName the name of the field to find possible matches for * @param beanClass the bean class to search for matches */ public static PropertyMatches forField(String propertyName, Class beanClass) { return forField(propertyName, beanClass, DEFAULT_MAX_DISTANCE); } /** * Create PropertyMatches for the given field property. * @param propertyName the name of the field to find possible matches for * @param beanClass the bean class to search for matches * @param maxDistance the maximum property distance allowed for matches */ public static PropertyMatches forField(String propertyName, Class beanClass, int maxDistance) { return new FieldPropertyMatches(propertyName, beanClass, maxDistance); } // Instance state private final String propertyName; private final String[] possibleMatches; /** * Create a new PropertyMatches instance for the given property and possible matches. */ private PropertyMatches(String propertyName, String[] possibleMatches) { this.propertyName = propertyName; this.possibleMatches = possibleMatches; } /** * Return the name of the requested property. */ public String getPropertyName() { return this.propertyName; } /** * Return the calculated possible matches. */ public String[] getPossibleMatches() { return this.possibleMatches; } /** * Build an error message for the given invalid property name, * indicating the possible property matches. */ public abstract String buildErrorMessage(); // Implementation support for subclasses protected void appendHintMessage(StringBuilder msg) { msg.append("Did you mean "); for (int i = 0; i < this.possibleMatches.length; i++) { msg.append('\''); msg.append(this.possibleMatches[i]); if (i < this.possibleMatches.length - 2) { msg.append("', "); } else if (i == this.possibleMatches.length - 2) { msg.append("', or "); } } msg.append("'?"); } /** * Calculate the distance between the given two Strings * according to the Levenshtein algorithm. * @param s1 the first String * @param s2 the second String * @return the distance value */ private static int calculateStringDistance(String s1, String s2) { if (s1.isEmpty()) { return s2.length(); } if (s2.isEmpty()) { return s1.length(); } int[][] d = new int[s1.length() + 1][s2.length() + 1]; for (int i = 0; i <= s1.length(); i++) { d[i][0] = i; } for (int j = 0; j <= s2.length(); j++) { d[0][j] = j; } for (int i = 1; i <= s1.length(); i++) { char c1 = s1.charAt(i - 1); for (int j = 1; j <= s2.length(); j++) { int cost; char c2 = s2.charAt(j - 1); if (c1 == c2) { cost = 0; } else { cost = 1; } d[i][j] = Math.min(Math.min(d[i - 1][j] + 1, d[i][j - 1] + 1), d[i - 1][j - 1] + cost); } } return d[s1.length()][s2.length()]; } // Concrete subclasses private static class BeanPropertyMatches extends PropertyMatches { public BeanPropertyMatches(String propertyName, Class beanClass, int maxDistance) { super(propertyName, calculateMatches(propertyName, BeanUtils.getPropertyDescriptors(beanClass), maxDistance)); } /** * Generate possible property alternatives for the given property and class. * Internally uses the {@code getStringDistance} method, which in turn uses * the Levenshtein algorithm to determine the distance between two Strings. * @param descriptors the JavaBeans property descriptors to search * @param maxDistance the maximum distance to accept */ private static String[] calculateMatches(String name, PropertyDescriptor[] descriptors, int maxDistance) { List candidates = new ArrayList<>(); for (PropertyDescriptor pd : descriptors) { if (pd.getWriteMethod() != null) { String possibleAlternative = pd.getName(); if (calculateStringDistance(name, possibleAlternative) <= maxDistance) { candidates.add(possibleAlternative); } } } Collections.sort(candidates); return StringUtils.toStringArray(candidates); } @Override public String buildErrorMessage() { StringBuilder msg = new StringBuilder(160); msg.append("Bean property '").append(getPropertyName()).append( "' is not writable or has an invalid setter method. "); if (!ObjectUtils.isEmpty(getPossibleMatches())) { appendHintMessage(msg); } else { msg.append("Does the parameter type of the setter match the return type of the getter?"); } return msg.toString(); } } private static class FieldPropertyMatches extends PropertyMatches { public FieldPropertyMatches(String propertyName, Class beanClass, int maxDistance) { super(propertyName, calculateMatches(propertyName, beanClass, maxDistance)); } private static String[] calculateMatches(final String name, Class clazz, final int maxDistance) { final List candidates = new ArrayList<>(); ReflectionUtils.doWithFields(clazz, field -> { String possibleAlternative = field.getName(); if (calculateStringDistance(name, possibleAlternative) <= maxDistance) { candidates.add(possibleAlternative); } }); Collections.sort(candidates); return StringUtils.toStringArray(candidates); } @Override public String buildErrorMessage() { StringBuilder msg = new StringBuilder(80); msg.append("Bean property '").append(getPropertyName()).append("' has no matching field."); if (!ObjectUtils.isEmpty(getPossibleMatches())) { msg.append(' '); appendHintMessage(msg); } return msg.toString(); } } }





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