DynamoDBBigDecimalItem.java

/**
 * Copyright (c) 2010-2016, openHAB.org and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.persistence.dynamodb.internal;

import java.math.BigDecimal;
import java.math.MathContext;
import java.util.Date;

import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAttribute;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBDocument;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBHashKey;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBRangeKey;

/**
 * DynamoDBItem for items that can be serialized as DynamoDB number
 *
 * @author Sami Salonen
 */
@DynamoDBDocument
public class DynamoDBBigDecimalItem extends AbstractDynamoDBItem<BigDecimal> {

    /**
     * We get the following error if the BigDecimal has too many digits
     * "Attempting to store more than 38 significant digits in a Number"
     *
     * See "Data types" section in
     * http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html
     */
    private static final int MAX_DIGITS_SUPPORTED_BY_AMAZON = 38;

    public DynamoDBBigDecimalItem() {
        this(null, null, null);
    }

    public DynamoDBBigDecimalItem(String name, BigDecimal state, Date time) {
        super(name, state, time);
    }

    @DynamoDBAttribute(attributeName = DynamoDBItem.ATTRIBUTE_NAME_ITEMSTATE)
    @Override
    public BigDecimal getState() {
        // When serializing this to the wire, we round the number in order to ensure
        // that it is within the dynamodb limits
        return loseDigits(state);
    }

    @DynamoDBHashKey(attributeName = DynamoDBItem.ATTRIBUTE_NAME_ITEMNAME)
    @Override
    public String getName() {
        return name;
    }

    @Override
    @DynamoDBRangeKey(attributeName = ATTRIBUTE_NAME_TIMEUTC)
    public Date getTime() {
        return time;
    }

    @Override
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void setState(BigDecimal state) {
        this.state = state;
    }

    @Override
    public void setTime(Date time) {
        this.time = time;
    }

    @Override
    public void accept(org.openhab.persistence.dynamodb.internal.DynamoDBItemVisitor visitor) {
        visitor.visit(this);
    }

    static BigDecimal loseDigits(BigDecimal number) {
        if (number == null) {
            return null;
        }
        return number.round(new MathContext(MAX_DIGITS_SUPPORTED_BY_AMAZON));
    }
}