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Super CSV is a fast, programmer-friendly, free CSV package for Java
There is a newer version: 2.4.0
/*
 * 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 org.supercsv.exception.SuperCsvReflectionException;

/**
 * This class cache's method lookups. Hence first time it introspects the instance's class, while subsequent method
 * lookups are super fast.
 */
public class MethodCache {
	
	/**
	 * A cache of setter methods. The three keys are the class the setter is being invoked on, the parameter type of the
	 * setter, and the variable name. The value is the setter method.
	 */
	private final ThreeDHashMap, Class, String, Method> setMethodsCache = new ThreeDHashMap, Class, String, Method>();
	
	/**
	 * A cache of getter methods. The two keys are the name of the class the getter is being invoked on, and the
	 * variable name. The value is the getter method.
	 */
	private final TwoDHashMap getCache = new TwoDHashMap();
	
	/**
	 * Returns the getter method for field on an object.
	 * 
	 * @param object
	 *            the object
	 * @param fieldName
	 *            the field name
	 * @return the getter associated with the field on the object
	 * @throws NullPointerException
	 *             if object or fieldName is null
	 * @throws SuperCsvReflectionException
	 *             if the getter doesn't exist or is not visible
	 */
	public Method getGetMethod(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");
		}
		
		Method method = getCache.get(object.getClass().getName(), fieldName);
		if( method == null ) {
			method = ReflectionUtils.findGetter(object, fieldName);
			getCache.set(object.getClass().getName(), fieldName, method);
		}
		return method;
	}
	
	/**
	 * Returns the setter method for the field on an object.
	 * 
	 * @param 
	 * @param object
	 *            the object
	 * @param fieldName
	 *            the field name
	 * @param argumentType
	 *            the type to be passed to the setter
	 * @return the setter method associated with the field on the object
	 * @throws NullPointerException
	 *             if object, fieldName or fieldType is null
	 * @throws SuperCsvReflectionException
	 *             if the setter doesn't exist or is not visible
	 */
	public  Method getSetMethod(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");
		}
		
		Method method = setMethodsCache.get(object.getClass(), argumentType, fieldName);
		if( method == null ) {
			method = ReflectionUtils.findSetter(object, fieldName, argumentType);
			setMethodsCache.set(object.getClass(), argumentType, fieldName, method);
		}
		return method;
	}
	
}