com.github.helenusdriver.persistence.SetStringTokenizer.java Source code

Introduction

Here is the source code for com.github.helenusdriver.persistence.SetStringTokenizer.java

Source

/*
 * Copyright (C) 2015-2015 The Helenus Driver Project 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 com.github.helenusdriver.persistence;

import java.lang.reflect.Field;

import java.io.IOException;

import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.commons.lang3.StringUtils;

/**
 * The <code>SetStringTokenizer</code> class provides an implementation for the
 * {@link Persister} interface that converts a set of strings into a string
 * where all elements of the set are separated by a separator string.
 * <p>
 * The <code>SetStringTokenizer</code> expects one argument configured on the
 * {@link Persisted} annotation. This argument is the separator string to be
 * used when joining and splitting strings.
 *
 * @copyright 2015-2015 The Helenus Driver Project Authors
 *
 * @author  The Helenus Driver Project Authors
 * @version 1 - Jan 15, 2015 - paouelle - Creation
 *
 * @since 1.0
 */
@SuppressWarnings("unchecked")
public class SetStringTokenizer implements Persister<Set<String>, String> {
    /**
     * Holds a dummy field of type Set<String>.
     *
     * @author paouelle
     */
    @SuppressWarnings("unused")
    private static final Set<String> SET = null;

    /**
     * Holds the the class for Set<String>.
     *
     * @author paouelle
     */
    private static final Class<Set<String>> SET_CLASS;

    static {
        // we use some magic to extract the class object for Set<String>
        try {
            final Field f = SetStringTokenizer.class.getDeclaredField("SET");

            SET_CLASS = (Class<Set<String>>) f.getType();
        } catch (Exception e) {
            throw new Error(e);
        }
    }

    /**
     * Holds the separator string.
     *
     * @author paouelle
     */
    private final String separator;

    /**
     * Instantiates a new <code>SetStringTokenizer</code> object.
     *
     * @author paouelle
     *
     * @param  args the list of arguments
     * @throws NullPointerException if <code>args</code> is <code>null</code>
     * @throws IllegalArgumentException if the arguments are not composed of a
     *         single argument
     */
    public SetStringTokenizer(String... args) {
        org.apache.commons.lang3.Validate.notNull(args, "invalid null args");
        org.apache.commons.lang3.Validate.isTrue(args.length == 1, "invalid number of arguments provided: %d",
                args.length);
        this.separator = args[0];
    }

    /**
     * {@inheritDoc}
     *
     * @author paouelle
     *
     * @see com.github.helenusdriver.persistence.Persister#getDecodedClass()
     */
    @Override
    public Class<Set<String>> getDecodedClass() {
        return SetStringTokenizer.SET_CLASS;

    }

    /**
     * {@inheritDoc}
     *
     * @author paouelle
     *
     * @see com.github.helenusdriver.persistence.Persister#getPersistedClass()
     */
    @Override
    public Class<String> getPersistedClass() {
        return String.class;
    }

    /**
     * {@inheritDoc}
     *
     * @author paouelle
     *
     * @see com.github.helenusdriver.persistence.Persister#encode(java.lang.Object)
     */
    @Override
    public String encode(Set<String> set) {
        return StringUtils.join(set, separator);
    }

    /**
     * {@inheritDoc}
     *
     * @author paouelle
     *
     * @see com.github.helenusdriver.persistence.Persister#decode(java.lang.Object)
     */
    @Override
    public Set<String> decode(String s) throws IOException {
        final String[] as = StringUtils.splitByWholeSeparator(s, separator);

        if (as == null) {
            return null;
        }
        final Set<String> set = new LinkedHashSet<>(as.length); // to maintain found order

        for (final String se : as) {
            set.add(se);
        }
        return set;
    }
}