/*
* Copyright 2002-2017 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.springframework.beans;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
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.
*
* <p>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 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 s_i = s1.charAt(i - 1);
for (int j = 1; j <= s2.length(); j++) {
int cost;
char t_j = s2.charAt(j - 1);
if (s_i == t_j) {
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 propertyDescriptors the JavaBeans property descriptors to search
* @param maxDistance the maximum distance to accept
*/
private static String[] calculateMatches(String propertyName, PropertyDescriptor[] propertyDescriptors, int maxDistance) {
List<String> candidates = new ArrayList<>();
for (PropertyDescriptor pd : propertyDescriptors) {
if (pd.getWriteMethod() != null) {
String possibleAlternative = pd.getName();
if (calculateStringDistance(propertyName, possibleAlternative) <= maxDistance) {
candidates.add(possibleAlternative);
}
}
}
Collections.sort(candidates);
return StringUtils.toStringArray(candidates);
}
@Override
public String buildErrorMessage() {
String propertyName = getPropertyName();
String[] possibleMatches = getPossibleMatches();
StringBuilder msg = new StringBuilder();
msg.append("Bean property '");
msg.append(propertyName);
msg.append("' is not writable or has an invalid setter method. ");
if (ObjectUtils.isEmpty(possibleMatches)) {
msg.append("Does the parameter type of the setter match the return type of the getter?");
}
else {
appendHintMessage(msg);
}
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 propertyName, Class<?> beanClass, final int maxDistance) {
final List<String> candidates = new ArrayList<>();
ReflectionUtils.doWithFields(beanClass, new ReflectionUtils.FieldCallback() {
@Override
public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
String possibleAlternative = field.getName();
if (calculateStringDistance(propertyName, possibleAlternative) <= maxDistance) {
candidates.add(possibleAlternative);
}
}
});
Collections.sort(candidates);
return StringUtils.toStringArray(candidates);
}
@Override
public String buildErrorMessage() {
String propertyName = getPropertyName();
String[] possibleMatches = getPossibleMatches();
StringBuilder msg = new StringBuilder();
msg.append("Bean property '");
msg.append(propertyName);
msg.append("' has no matching field. ");
if (!ObjectUtils.isEmpty(possibleMatches)) {
appendHintMessage(msg);
}
return msg.toString();
}
}
}