Spring-OrderComparator

docs/Spring/clazz/Spring-OrderComparator.md

@@ -0,0 +1,98 @@
+# Spring OrderComparator
+- Author: [HuiFer](https://github.com/huifer)
+- 源码阅读仓库: [huifer-spring](https://github.com/huifer/spring-framework-read)
+
+
+```java
+    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);
+        // 对比两个Order值得大小返回
+        return Integer.compare(i1, i2);
+    }
+
+```
+
+```java
+    private int getOrder(@Nullable Object obj, @Nullable OrderSourceProvider sourceProvider) {
+        Integer order = null;
+        if (obj != null && sourceProvider != null) {
+            // 获取Order
+            Object orderSource = sourceProvider.getOrderSource(obj);
+            if (orderSource != null) {
+                if (orderSource.getClass().isArray()) {
+                    // 获取 OrderSourceProvider 的值
+                    Object[] sources = ObjectUtils.toObjectArray(orderSource);
+                    for (Object source : sources) {
+                        // 找 order 返回
+                        order = findOrder(source);
+                        if (order != null) {
+                            break;
+                        }
+                    }
+                } else {
+                    // 寻找 order
+                    order = findOrder(orderSource);
+                }
+            }
+        }
+        return (order != null ? order : getOrder(obj));
+    }
+
+```
+
+- 测试用例
+```java
+    @Test
+    public void compareWithSourceProviderArray() {
+        Comparator<Object> customComparator = this.comparator.withSourceProvider(
+                new TestSourceProvider(5L, new Object[]{new StubOrdered(10), new StubOrdered(-25)}));
+        assertEquals(-1, customComparator.compare(5L, new Object()));
+    }
+
+```
+
+![image-20200116141838601](/images/spring/image-20200116141838601.png)
+
+
+
+```java
+    @Nullable
+    protected Integer findOrder(Object obj) {
+        // 获取Ordered实现类
+        return (obj instanceof Ordered ? ((Ordered) obj).getOrder() : null);
+    }
+
+```
+
+```java
+    private static final class StubOrdered implements Ordered {
+
+        private final int order;
+
+
+        public StubOrdered(int order) {
+            this.order = order;
+        }
+
+        @Override
+        public int getOrder() {
+            return this.order;
+        }
+    }
+
+```
+
+![image-20200116141932486](/images/spring/image-20200116141932486.png)
+
+
+
+最终`Integer.compare(i1, i2)`比较返回 OK !