Add AbstractSingleInputPreprocessor

Many of our InputPreprocessor plugins copy and paste the getSingleInput
method. Now we have an abstract superclass to provide it and any other
useful methods that come up.

Author: hinerm

src/main/java/org/scijava/module/process/AbstractSingleInputPreprocessor.java

@@ -0,0 +1,71 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2015 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
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.module.process;
+
+import org.scijava.module.Module;
+import org.scijava.module.ModuleItem;
+import org.scijava.module.ModuleService;
+import org.scijava.plugin.Parameter;
+
+/**
+ * Abstract superclass for {@link PreprocessorPlugin} implementations that
+ * populate singleton inputs (e.g. it is common to have modules that operate on
+ * a single {@link Dataset}). Contains helper methods to facilitate this
+ * functionality.
+ *
+ * @author Mark Hiner
+ */
+public abstract class AbstractSingleInputPreprocessor extends
+	AbstractPreprocessorPlugin
+{
+
+	@Parameter
+	private ModuleService moduleService;
+
+	/**
+	 * Helper method to look up the name of singleton module inputs of a given
+	 * type.
+	 *
+	 * @param module Module to check for single input
+	 * @param type Type of single input to look for
+	 * @return If the given module has exactly one input of the specified type,
+	 *         return that input's name. Otherwise null;
+	 */
+	protected String getSingleInput(final Module module, final Class<?> type) {
+		if (moduleService == null) return null;
+		final ModuleItem<?> item = moduleService.getSingleInput(module, type);
+		if (item == null || !item.isAutoFill()) return null;
+
+		return item.getName();
+	}
+
+}