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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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package org.scijava.command;
import java.util.Map;
import org.scijava.Cancelable;
import org.scijava.Context;
import org.scijava.Contextual;
import org.scijava.InstantiableException;
import org.scijava.NullContextException;
import org.scijava.module.AbstractModule;
import org.scijava.module.Module;
import org.scijava.module.ModuleException;
import org.scijava.module.ModuleInfo;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.PluginInfo;
import org.scijava.util.ClassUtils;
/**
* Module adapter class for working with a {@link Command} instance.
*
* The {@link Module} interface describes an encapsulated piece of functionality
* with inputs and outputs.
*
*
* Conceptually, a command is such a piece of functionality. However, the
* {@link Command} interface is intended to be as simple to implement as
* possible; the only required method is {@link Command#run()}, which is
* inherited from {@link Runnable}. The command's inputs and outputs are
* indicated using @{@link Parameter} annotations.
*
*
* To bridge the gap, this class adapts a {@link Command} instance into an
* object that fully implements the {@link Module} interface.
*
*
* @author Curtis Rueden
* @author Johannes Schindelin
* @author Grant Harris
* @see CommandInfo - An adapter class that bridges the gap between SciJava
* commands and the rich {@link ModuleInfo} interface.
* @see Module - The interface which provides many methods for interrogating an
* encapsulated piece of functionality with inputs and outputs.
*/
public class CommandModule extends AbstractModule implements Cancelable,
Contextual
{
/** The metadata describing the command. */
private final CommandInfo info;
/** The command instance handled by this module. */
@Parameter
private final Command command;
@Parameter
private Context context;
/**
* Reason for cancelation, or null if not canceled. Note that this field is
* only relevant if the delegate {@link Command} is not itself
* {@link Cancelable}.
*/
private String cancelReason;
/** Creates a command module for the given {@link PluginInfo}. */
public CommandModule(final CommandInfo info) throws ModuleException {
super();
this.info = info;
command = instantiateCommand();
assignPresets();
}
/**
* Creates a command module for the given {@link CommandInfo}, around the
* specified {@link Command} instance.
*/
public CommandModule(final CommandInfo info, final Command command) {
super();
this.info = info;
this.command = command;
assignPresets();
}
// -- CommandModule methods --
/** Gets the command instance handled by this module. */
public Command getCommand() {
return command;
}
// -- Module methods --
/**
* Computes a preview of the command's results. For this method to do
* anything, the command must implement the {@link Previewable} interface.
*/
@Override
public void preview() {
if (!(command instanceof Previewable)) return; // cannot preview
final Previewable previewPlugin = (Previewable) command;
previewPlugin.preview();
}
/**
* Cancels the command, undoing the effects of any {@link #preview()} calls.
* For this method to do anything, the command must implement the
* {@link Previewable} interface.
*/
@Override
public void cancel() {
if (!(command instanceof Previewable)) return; // nothing to cancel
final Previewable previewPlugin = (Previewable) command;
previewPlugin.cancel();
}
@Override
public CommandInfo getInfo() {
return info;
}
@Override
public Object getDelegateObject() {
return command;
}
@Override
public Object getInput(final String name) {
final CommandModuleItem item = info.getInput(name);
return item == null ? null : ClassUtils.getValue(item.getField(), command);
}
@Override
public Object getOutput(final String name) {
final CommandModuleItem item = info.getOutput(name);
return item == null ? null : ClassUtils.getValue(item.getField(), command);
}
@Override
public void setInput(final String name, final Object value) {
final CommandModuleItem item = info.getInput(name);
if (item == null) {
throw new IllegalArgumentException("No such input: " + name);
}
ClassUtils.setValue(item.getField(), command, value);
}
@Override
public void setOutput(final String name, final Object value) {
final CommandModuleItem item = info.getOutput(name);
if (item == null) {
throw new IllegalArgumentException("No such output: " + name);
}
ClassUtils.setValue(item.getField(), command, value);
}
// -- Object methods --
@Override
public String toString() {
return command.getClass().getName();
}
// -- Runnable methods --
@Override
public void run() {
command.run();
}
// -- Cancelable methods --
@Override
public boolean isCanceled() {
if (command instanceof Cancelable) {
return ((Cancelable) command).isCanceled();
}
return cancelReason != null;
}
@Override
public void cancel(final String reason) {
if (command instanceof Cancelable) {
((Cancelable) command).cancel(reason);
return;
}
cancelReason = reason == null ? "" : reason;
}
@Override
public String getCancelReason() {
if (command instanceof Cancelable) {
return ((Cancelable) command).getCancelReason();
}
return cancelReason;
}
// -- Contextual methods --
@Override
public Context context() {
if (context == null) throw new NullContextException();
return context;
}
@Override
public Context getContext() {
return context;
}
@Override
public void setContext(final Context context) {
context.inject(this);
}
// -- Helper methods --
private Command instantiateCommand() throws ModuleException {
try {
return info.createInstance();
}
catch (final InstantiableException exc) {
throw new ModuleException(exc);
}
}
private void assignPresets() {
final Map presets = info.getPresets();
for (final String name : presets.keySet()) {
final Object value = presets.get(name);
setInput(name, value);
resolveInput(name);
}
}
}