org.supercsv.util.ReflectionUtils Maven / Gradle / Ivy
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/*
* Copyright 2007 Kasper B. Graversen
*
* 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.supercsv.util;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import org.supercsv.exception.SuperCsvReflectionException;
/**
* Provides useful utility methods for reflection.
*
* @author James Bassett
* @since 2.0.0
*/
public final class ReflectionUtils {
public static final String SET_PREFIX = "set";
public static final String GET_PREFIX = "get";
public static final String IS_PREFIX = "is";
/**
* A map of primitives and their associated wrapper classes, to cater for autoboxing.
*/
private static final Map, Class> AUTOBOXING_CONVERTER = new HashMap, Class>();
static {
AUTOBOXING_CONVERTER.put(long.class, Long.class);
AUTOBOXING_CONVERTER.put(Long.class, long.class);
AUTOBOXING_CONVERTER.put(int.class, Integer.class);
AUTOBOXING_CONVERTER.put(Integer.class, int.class);
AUTOBOXING_CONVERTER.put(char.class, Character.class);
AUTOBOXING_CONVERTER.put(Character.class, char.class);
AUTOBOXING_CONVERTER.put(byte.class, Byte.class);
AUTOBOXING_CONVERTER.put(Byte.class, byte.class);
AUTOBOXING_CONVERTER.put(short.class, Short.class);
AUTOBOXING_CONVERTER.put(Short.class, short.class);
AUTOBOXING_CONVERTER.put(boolean.class, Boolean.class);
AUTOBOXING_CONVERTER.put(Boolean.class, boolean.class);
AUTOBOXING_CONVERTER.put(double.class, Double.class);
AUTOBOXING_CONVERTER.put(Double.class, double.class);
AUTOBOXING_CONVERTER.put(float.class, Float.class);
AUTOBOXING_CONVERTER.put(Float.class, float.class);
}
// no instantiation
private ReflectionUtils() {
}
/**
* Returns the getter method associated with the object's field.
*
* @param object
* the object
* @param fieldName
* the name of the field
* @return the getter method
* @throws NullPointerException
* if object or fieldName is null
* @throws SuperCsvReflectionException
* if the getter doesn't exist or is not visible
*/
public static Method findGetter(final Object object, final String fieldName) {
if( object == null ) {
throw new NullPointerException("object should not be null");
} else if( fieldName == null ) {
throw new NullPointerException("fieldName should not be null");
}
final Class clazz = object.getClass();
// find a standard getter
final String standardGetterName = getMethodNameForField(GET_PREFIX, fieldName);
Method getter = findGetterWithCompatibleReturnType(standardGetterName, clazz, false);
// if that fails, try for an isX() style boolean getter
if( getter == null ) {
final String booleanGetterName = getMethodNameForField(IS_PREFIX, fieldName);
getter = findGetterWithCompatibleReturnType(booleanGetterName, clazz, true);
}
if( getter == null ) {
throw new SuperCsvReflectionException(
String
.format(
"unable to find getter for field %s in class %s - check that the corresponding nameMapping element matches the field name in the bean",
fieldName, clazz.getName()));
}
return getter;
}
/**
* Helper method for findGetter() that finds a getter with the supplied name, optionally enforcing that the method
* must have a Boolean/boolean return type. Developer note: this method could have accepted an actual return type to
* enforce, but it was more efficient to cater for only Booleans (as they're the only type that has differently
* named getters).
*
* @param getterName
* the getter name
* @param clazz
* the class
* @param enforceBooleanReturnType
* if true, the method must return a Boolean/boolean, otherwise it's return type doesn't matter
* @return the getter, or null if none is found
*/
private static Method findGetterWithCompatibleReturnType(final String getterName, final Class clazz,
final boolean enforceBooleanReturnType) {
for( final Method method : clazz.getMethods() ) {
if( !getterName.equalsIgnoreCase(method.getName()) || method.getParameterTypes().length != 0
|| method.getReturnType().equals(void.class) ) {
continue; // getter must have correct name, 0 parameters and a return type
}
if( !enforceBooleanReturnType || boolean.class.equals(method.getReturnType())
|| Boolean.class.equals(method.getReturnType()) ) {
return method;
}
}
return null;
}
/**
* Returns the setter method associated with the object's field.
*
* This method handles any autoboxing/unboxing of the argument passed to the setter (e.g. if the setter type is a
* primitive {@code int} but the argument passed to the setter is an {@code Integer}) by looking for a setter with
* the same type, and failing that checking for a setter with the corresponding primitive/wrapper type.
*
* It also allows for an argument type that is a subclass or implementation of the setter type (when the setter type
* is an {@code Object} or {@code interface} respectively).
*
* @param object
* the object
* @param fieldName
* the name of the field
* @param argumentType
* the type to be passed to the setter
* @return the setter method
* @throws NullPointerException
* if object, fieldName or fieldType is null
* @throws SuperCsvReflectionException
* if the setter doesn't exist or is not visible
*/
public static Method findSetter(final Object object, final String fieldName, final Class argumentType) {
if( object == null ) {
throw new NullPointerException("object should not be null");
} else if( fieldName == null ) {
throw new NullPointerException("fieldName should not be null");
} else if( argumentType == null ) {
throw new NullPointerException("argumentType should not be null");
}
final String setterName = getMethodNameForField(SET_PREFIX, fieldName);
final Class clazz = object.getClass();
// find a setter compatible with the supplied argument type
Method setter = findSetterWithCompatibleParamType(clazz, setterName, argumentType);
// if that failed, try the corresponding primitive/wrapper if it's a type that can be autoboxed/unboxed
if( setter == null && AUTOBOXING_CONVERTER.containsKey(argumentType) ) {
setter = findSetterWithCompatibleParamType(clazz, setterName, AUTOBOXING_CONVERTER.get(argumentType));
}
if( setter == null ) {
throw new SuperCsvReflectionException(
String
.format(
"unable to find method %s(%s) in class %s - check that the corresponding nameMapping element matches the field name in the bean, "
+ "and the cell processor returns a type compatible with the field", setterName,
argumentType.getName(), clazz.getName()));
}
return setter;
}
/**
* Helper method for findSetter() that returns the setter method of the supplied name, whose parameter type is
* compatible with the supplied argument type (will allow an object of that type to be used when invoking the
* setter), or returns null if no match is found. Preference is given to setters whose parameter type is an
* exact match, but if there is none, then the first compatible method found is returned.
*
* @param clazz
* the class containing the setter
* @param setterName
* the name of the setter
* @param argumentType
* the type to be passed to the setter
* @return the setter method, or null if none is found
*/
private static Method findSetterWithCompatibleParamType(final Class clazz, final String setterName,
final Class argumentType) {
Method compatibleSetter = null;
for( final Method method : clazz.getMethods() ) {
if( !setterName.equalsIgnoreCase(method.getName()) || method.getParameterTypes().length != 1 ) {
continue; // setter must have correct name and only 1 parameter
}
final Class parameterType = method.getParameterTypes()[0];
if( parameterType.equals(argumentType) ) {
compatibleSetter = method;
break; // exact match
} else if( parameterType.isAssignableFrom(argumentType) ) {
compatibleSetter = method; // potential match, but keep looking for exact match
}
}
return compatibleSetter;
}
/**
* Gets the camelcase getter/setter method name for a field.
*
* @param prefix
* the method prefix
* @param fieldName
* the field name
* @return the method name
*/
private static String getMethodNameForField(final String prefix, final String fieldName) {
return prefix + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);
}
}