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ServiceIndex: add getPrev, getNext API
Added convenience methods for accessing lower and higher priority services relative to a specified base service.
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2 files changed

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‎src/main/java/org/scijava/service/ServiceIndex.java‎

Lines changed: 68 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,6 @@
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package org.scijava.service;
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34-
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import java.util.List;
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import org.scijava.object.SortedObjectIndex;
@@ -51,10 +50,77 @@ public ServiceIndex() {
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/** Gets the first available service compatible with the given class. */
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public <S extends Service> S getService(final Class<S> c) {
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return getService(c, null, 0);
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}
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/**
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* Gets the highest priority service compatible with class {@code c}, which is
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* lower priority than the {@code ref} service.
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*/
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public <S extends Service> S getNextService(final Class<S> c,
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final Class<? extends S> ref)
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{
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return getService(c, ref, 1);
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}
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/**
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* Gets the lowest priority service compatible with class {@code c}, which is
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* higher priority than the {@code ref} service.
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*/
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public <S extends Service> S getPrevService(final Class<S> c,
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final Class<? extends S> ref)
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{
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return getService(c, ref, -1);
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}
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// -- Helper methods --
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/**
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* Gets the service compatible with the base class {@code c}, with the
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* modified priority relative to the given reference service, or the highest
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* priority service if no reference is given.
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*
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* @param c - Base class to find compatible services
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* @param ref - Reference service class for priority comparisons. If null,
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* highest priority service is returned.
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* @param priorityMod - Relative priority value. If {@code ref} is non-null,
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* this value is applied to the {@code ref} service's index in the
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* list of compatible services to determine the returned service. For
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* example, a value of +1 will return the next lowest priority
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* service, and a value of -1 will return the next highest priority
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* service - as the services are sorted from highest to lowest
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* priority.
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* @return Service matching the given criteria, or null if no applicable
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* service.
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*/
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private <S extends Service> S getService(final Class<S> c,
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final Class<? extends S> ref, final int priorityMod)
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{
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final List<Service> list = get(c);
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if (list.isEmpty()) return null;
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int index = 0;
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if (ref != null) {
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// find the ref class's index
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for (; index < list.size() && !list.get(index).getClass().equals(ref); index++)
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{}
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// ref class wasn't on the list
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if (index == list.size()) return null;
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// Update the index for the desired relative priority
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index += priorityMod;
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}
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// If the priorityMod took the index outside the list bounds, then there is
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// no appropriate
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// service to return.
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if (index < 0 || index >= list.size()) return null;
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@SuppressWarnings("unchecked")
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final S service = (S) list.get(0);
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final S service = (S) list.get(index);
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return service;
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}
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‎src/test/java/org/scijava/service/ServiceIndexTest.java‎

Lines changed: 79 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -32,6 +32,7 @@
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package org.scijava.service;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNull;
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import static org.junit.Assert.assertSame;
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import java.util.List;
@@ -40,6 +41,8 @@
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import org.scijava.Context;
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import org.scijava.event.DefaultEventService;
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import org.scijava.log.StderrLogService;
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import org.scijava.options.DefaultOptionsService;
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import org.scijava.options.OptionsService;
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import org.scijava.plugin.DefaultPluginService;
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import org.scijava.plugin.PluginService;
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import org.scijava.thread.DefaultThreadService;
@@ -63,4 +66,80 @@ public void testGetAll() {
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assertSame(StderrLogService.class, all.get(3).getClass());
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}
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/**
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* Test the {@link ServiceIndex#getPrevService(Class, Class)} operation.
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*/
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@Test
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public void testGetPrevService() {
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// Create a service index where the OptionsService hierarchy should be:
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// HigherOptionsService > DefaultOptionsService > LowerOptionsService
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final ServiceIndex serviceIndex = setUpPrivateServices();
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// DefaultOptionsService should be the previous service to LowerOptionsService
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assertEquals(DefaultOptionsService.class, serviceIndex.getPrevService(
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OptionsService.class, LowerOptionsService.class).getClass());
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// HigherOptionsService should be the previous service to
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// DefaultOptionsService
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assertEquals(HigherOptionsService.class, serviceIndex.getPrevService(
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OptionsService.class, DefaultOptionsService.class).getClass());
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// There should not be a previous service before HigherOptionsService
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assertNull(serviceIndex.getPrevService(OptionsService.class,
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HigherOptionsService.class));
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}
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/**
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* Test the {@link ServiceIndex#getNextService(Class, Class)} operation.
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*/
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@Test
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public void testGetNextService() {
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// Create a service index where the OptionsService hierarchy should be:
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// HigherOptionService > DefaultOptionService > LowerOptionService
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final ServiceIndex serviceIndex = setUpPrivateServices();
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// DefaultOptionsService should be the next service to HigherOptionsService
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assertEquals(DefaultOptionsService.class, serviceIndex.getNextService(
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OptionsService.class, HigherOptionsService.class).getClass());
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// HigherOptionsService should be the previous service to
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// DefaultOptionsService
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assertEquals(LowerOptionsService.class, serviceIndex.getNextService(
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OptionsService.class, DefaultOptionsService.class).getClass());
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// There should not be a next service after LowerOptionsService
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assertNull(serviceIndex.getNextService(OptionsService.class,
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LowerOptionsService.class));
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}
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// -- Helper methods --
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/**
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* @return A {@link ServiceIndex} with all private services manually added.
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*/
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private ServiceIndex setUpPrivateServices() {
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final Context context = new Context(SciJavaService.class);
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final ServiceIndex serviceIndex = context.getServiceIndex();
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serviceIndex.add(new HigherOptionsService());
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serviceIndex.add(new LowerOptionsService());
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return serviceIndex;
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}
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// -- Private services --
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private static class HigherOptionsService extends DefaultOptionsService {
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@Override
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public double getPriority() {
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return super.getPriority() + 25;
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}
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}
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private static class LowerOptionsService extends DefaultOptionsService {
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@Override
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public double getPriority() {
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return super.getPriority() - 30;
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}
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}
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}

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