com.tkmtwo.timex.convert.DurationConverter.java Source code

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Here is the source code for com.tkmtwo.timex.convert.DurationConverter.java

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/*
 *
 * Copyright 2014 Tom Mahaffey
 *
 * 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 com.tkmtwo.timex.convert;

import org.springframework.core.convert.converter.Converter;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Strings.isNullOrEmpty;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.joda.time.Duration;

/**
 * Coverts a <code>String</code> to a JodaTime <code>Duration</code>
 * consistent with Spring's <code>Converter</code> facility.
 *
 * <p>
 * Any expression which can be evaluated as a <code>long</code> value
 * is allowed.
 *
 * @author Tom Mahaffey
 * @see org.springframework.core.convert.converter.Converter
 * @see org.joda.time.format.ISODateTimeFormat#basicDateTimeNoMillis()
 */
public final class DurationConverter implements Converter<String, Duration> {

    private static final Logger logger = LoggerFactory.getLogger(DurationConverter.class);
    private static final ExpressionParser parser = new SpelExpressionParser();

    @Override
    public Duration convert(String s) {
        logger.debug("Converting '{}' to a Duration.", s);
        checkArgument(!isNullOrEmpty(s), "String may not be empty.");

        Long l = null;

        try {
            l = parser.parseExpression(s).getValue(Long.class);
        } catch (Exception ex) {
            throw new IllegalArgumentException("String '" + s + "' cannot be converted.", ex);
        }

        checkNotNull(l, "String '" + s + "' evaluated to null.");
        return new Duration(l.longValue());
    }

}