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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2014 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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package org.scijava.convert;

import org.scijava.Priority;
import org.scijava.plugin.Plugin;
import org.scijava.util.ConversionUtils;

/**
 * {@link Converter} implementation for handling {@code null} values. Performs
 * basic casting when given a {@code null} source and returns {@code} null
 * directly when given a {@code} null destination.
 * 
 * By running at {@link Priority#FIRST_PRIORITY}, other converters should
 * not need to worry about {@code null} source or destination parameters.
 * 
 * 
 * NB: if a {@link Class} source is queried for the {@link #canConvert},
 * this converter will always return false (as there is no way of knowing
 * if the source object will be null or not).
 * 
 *
 * @author Mark Hiner
 */
@Plugin(type = Converter.class, priority = Priority.FIRST_PRIORITY)
public class NullConverter extends AbstractConverter {

	@Override
	public boolean canConvert(final Object src, final Class dest) {
		return src == null;
	}

	@Override
	public  T convert(final Object src, final Class dest) {
		if (dest == null) return null;
		if (src == null) return ConversionUtils.getNullValue(dest);

		throw new IllegalArgumentException("Attempting non-null conversion: " +
			src + " > " + dest + " using NullConverter.");
	}

	@Override
	public Class