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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 - 2017 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
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 * 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 java.lang.reflect.Type;
import java.util.Collection;

import org.scijava.object.ObjectService;
import org.scijava.plugin.AbstractHandlerPlugin;
import org.scijava.plugin.Parameter;
import org.scijava.util.ConversionUtils;
import org.scijava.util.GenericUtils;

/**
 * Abstract superclass for {@link Converter} plugins. Performs appropriate
 * dispatching of {@link #canConvert(ConversionRequest)} and
 * {@link #convert(ConversionRequest)} calls based on the actual state of the
 * given {@link ConversionRequest}.
 * 
 * Note that the {@link #supports(ConversionRequest)} method is overridden as
 * well, to delegate to the appropriate {@link #canConvert}.
 * 
 * 
 * NB: by default, the {@link #populateInputCandidates(Collection)} method has a
 * dummy implementation. Effectively, this is opt-in behavior. If a converter
 * implementation would like to suggest candidates for conversion, this method
 * can be overridden.
 * 
 * 
 * NB: by default, the provied {@link #canConvert} methods will return
 * {@code false} if the input is {@code null}. This allows {@link Converter}
 * implementors to assume any input is non-{@code null} - but this behavior is
 * overridden. Casting {@code null Object} inputs is handled by the
 * {@link NullConverter}, while {@code null class} inputs are handled by the
 * {@link DefaultConverter}.
 * 
 *
 * @author Mark Hiner
 */
public abstract class AbstractConverter extends
	AbstractHandlerPlugin implements Converter
{

	// -- Parameters --

	@Parameter(required = false)
	private ObjectService objectService;

	// -- ConversionHandler methods --

	@Override
	public boolean canConvert(final ConversionRequest request) {
		Object src = request.sourceObject();
		if (src == null) {
			Class srcClass = request.sourceClass();
			if (request.destType() != null) return canConvert(srcClass, request.destType());
			return canConvert(srcClass, request.destClass());
		}

		if (request.destType() != null) return canConvert(src, request.destType());
		return canConvert(src, request.destClass());
	}

	@Override
	public boolean canConvert(final Object src, final Type dest) {
		if (src == null) return false;
		final Class srcClass = src.getClass();
		return canConvert(srcClass, dest);
	}

	@Override
	public boolean canConvert(final Object src, final Class dest) {
		if (src == null) return false;
		final Class srcClass = src.getClass();

		return canConvert(srcClass, dest);
	}

	@Override
	public boolean canConvert(final Class src, final Class dest) {
		if (src == null) return false;
		final Class saneSrc = ConversionUtils.getNonprimitiveType(src);
		final Class saneDest = ConversionUtils.getNonprimitiveType(dest);
		return ConversionUtils.canCast(saneSrc, getInputType()) &&
			ConversionUtils.canCast(getOutputType(), saneDest);
	}

	@Override
	public Object convert(final Object src, final Type dest) {
		final Class destClass = GenericUtils.getClass(dest);
		return convert(src, destClass);
	}

	@Override
	public Object convert(final ConversionRequest request) {
		if (request.destType() != null) {
			return convert(request.sourceObject(), request.destType());
		}
		
		return convert(request.sourceObject(), request.destClass());
	}

	@Override
	public void populateInputCandidates(final Collection