比如获取initializer时的排序:
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
// 排序
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
比如对runner排序:
private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<>();
// (1) 找到ApplicationRunner的实现类,加到list里面
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
// (2) 找到CommandLineRunner的实现类,加到list里面
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
// (3) 排序
AnnotationAwareOrderComparator.sort(runners);
// (4) 钩子回调
for (Object runner : new LinkedHashSet<>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
}
我们来分析一下这个排序AnnotationAwareOrderComparator.sort(list)的源码。
public static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator();
public static void sort(List<?> list) {
if (list.size() > 1) {
list.sort(INSTANCE);
}
}
default void sort(Comparator<? super E> c) {
Object[] a = this.toArray();
Arrays.sort(a, (Comparator) c);
ListIterator<E> i = this.listIterator();
for (Object e : a) {
i.next();
i.set((E) e);
}
}
public class AnnotationAwareOrderComparator extends OrderComparator {
...
}
public class OrderComparator implements Comparator<Object> {
...
}
compare方法在OrderComparator里面:
@Override
public int compare(@Nullable Object o1, @Nullable Object o2) {
return doCompare(o1, o2, null);
}
private int doCompare(@Nullable Object o1, @Nullable Object o2, @Nullable OrderSourceProvider sourceProvider) {
boolean p1 = (o1 instanceof PriorityOrdered);
boolean p2 = (o2 instanceof PriorityOrdered);
if (p1 && !p2) {
return -1;
}
else if (p2 && !p1) {
return 1;
}
int i1 = getOrder(o1, sourceProvider);
int i2 = getOrder(o2, sourceProvider);
return Integer.compare(i1, i2);
}
private int getOrder(@Nullable Object obj, @Nullable OrderSourceProvider sourceProvider) {
Integer order = null;
if (obj != null && sourceProvider != null) {
Object orderSource = sourceProvider.getOrderSource(obj);
if (orderSource != null) {
if (orderSource.getClass().isArray()) {
Object[] sources = ObjectUtils.toObjectArray(orderSource);
for (Object source : sources) {
order = findOrder(source);
if (order != null) {
break;
}
}
}
else {
order = findOrder(orderSource);
}
}
}
return (order != null ? order : getOrder(obj));
}
sourceProvider为空,我们可以直接看最后一行。
int LOWEST_PRECEDENCE = Integer.MAX_VALUE;
protected int getOrder(@Nullable Object obj) {
if (obj != null) {
Integer order = findOrder(obj);
if (order != null) {
return order;
}
}
return Ordered.LOWEST_PRECEDENCE;
}
protected Integer findOrder(Object obj) {
return (obj instanceof Ordered ? ((Ordered) obj).getOrder() : null);
}
@Override
@Nullable
protected Integer findOrder(Object obj) {
Integer order = super.findOrder(obj);
if (order != null) {
return order;
}
return findOrderFromAnnotation(obj);
}
@Nullable
private Integer findOrderFromAnnotation(Object obj) {
AnnotatedElement element = (obj instanceof AnnotatedElement ? (AnnotatedElement) obj : obj.getClass());
MergedAnnotations annotations = MergedAnnotations.from(element, SearchStrategy.TYPE_HIERARCHY);
Integer order = OrderUtils.getOrderFromAnnotations(element, annotations);
if (order == null && obj instanceof DecoratingProxy) {
return findOrderFromAnnotation(((DecoratingProxy) obj).getDecoratedClass());
}
return order;
}
@Nullable
static Integer getOrderFromAnnotations(AnnotatedElement element, MergedAnnotations annotations) {
if (!(element instanceof Class)) {
return findOrder(annotations);
}
Object cached = orderCache.get(element);
if (cached != null) {
return (cached instanceof Integer ? (Integer) cached : null);
}
Integer result = findOrder(annotations);
orderCache.put(element, result != null ? result : NOT_ANNOTATED);
return result;
}
@Nullable
private static Integer findOrder(MergedAnnotations annotations) {
MergedAnnotation<Order> orderAnnotation = annotations.get(Order.class);
if (orderAnnotation.isPresent()) {
return orderAnnotation.getInt(MergedAnnotation.VALUE);
}
MergedAnnotation<?> priorityAnnotation = annotations.get(JAVAX_PRIORITY_ANNOTATION);
if (priorityAnnotation.isPresent()) {
return priorityAnnotation.getInt(MergedAnnotation.VALUE);
}
return null;
}
private static final String JAVAX_PRIORITY_ANNOTATION = "javax.annotation.Priority";
回到最开始的方法,进行int值的排序
Integer.compare(i1, i2);
public static int compare(int x, int y) {
return (x < y) ? -1 : ((x == y) ? 0 : 1);
}
至此,我们的排序源码就分析完了,我们总结一下:
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