org.springsource.restbucks.training.core.MonetaryAmount.java Source code

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Here is the source code for org.springsource.restbucks.training.core.MonetaryAmount.java

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/*
 * Copyright 2012-2013 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.springsource.restbucks.training.core;

import java.math.BigDecimal;
import java.util.Currency;

import javax.persistence.Embeddable;

import lombok.Data;

import org.springframework.util.Assert;

/**
 * Value object to encapsulate a monetary amount consisting of a currency and a value. Provides basic mathematical
 * abstractions to allow adding up {@link MonetaryAmount}s.
 * 
 * @author Oliver Gierke
 */
@Data
@Embeddable
public class MonetaryAmount {

    public static Currency EURO = Currency.getInstance("EUR");
    public static MonetaryAmount ZERO = new MonetaryAmount();

    private final Currency currency;
    private final BigDecimal value;

    /**
     * Creates a new {@link MonetaryAmount} instance with the given value and {@link Currency}.
     * 
     * @param currency must not be {@literal null}.
     * @param value
     */
    public MonetaryAmount(Currency currency, double value) {
        this(currency, new BigDecimal(value));
    }

    /**
     * Creates a new {@link MonetaryAmount} of the given value and {@link Currency}.
     * 
     * @param currency must not be {@literal null}.
     * @param value must not be {@literal null}.
     */
    private MonetaryAmount(Currency currency, BigDecimal value) {

        Assert.notNull(currency);
        Assert.notNull(value);

        this.currency = currency;
        this.value = value;
    }

    /**
     * No-arg constructor to satisfy persistence mechanism.
     */
    protected MonetaryAmount() {
        this(EURO, BigDecimal.ZERO);
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return currency + value.toString();
    }

    /**
     * Adds the given {@link MonetaryAmount} to the current one. Treats {@literal null} values like
     * {@link MonetaryAmount#ZERO}.
     * 
     * @param other the {@link MonetaryAmount} to add.
     */
    public MonetaryAmount add(MonetaryAmount other) {

        if (other == null) {
            return this;
        }

        Assert.isTrue(this.currency.equals(other.currency));
        return new MonetaryAmount(this.currency, this.value.add(other.value));
    }
}