#32 - List<Instances> should return in order of @priority (from javax.annotations)

Author: rbygrave

src/main/java/io/dinject/BeanContext.java

@@ -133,6 +133,20 @@ public interface BeanContext extends Closeable {
    */
   <T> List<T> getBeans(Class<T> interfaceType);
 
+  /**
+   * Return the list of beans that implement the interface without
+   * sorting by priority (ignoring any Priority annotation).
+   */
+  <T> List<T> getBeansUnsorted(Class<T> interfaceType);
+
+  /**
+   * Sort the beans by javax.annotation.Priority annotation.
+   *
+   * @param list The beans to sort by priority
+   * @return A new list of beans sorted by priority
+   */
+  <T> List<T> sortByPriority(List<T> list);
+
   /**
    * Start the context firing any <code>@PostConstruct</code> methods.
    */

src/main/java/io/dinject/BootContext.java

@@ -465,6 +465,16 @@ public <T> List<T> getBeans(Class<T> interfaceType) {
       return context.getBeans(interfaceType);
     }
 
+    @Override
+    public <T> List<T> getBeansUnsorted(Class<T> interfaceType) {
+      return context.getBeansUnsorted(interfaceType);
+    }
+
+    @Override
+    public <T> List<T> sortByPriority(List<T> list) {
+      return context.sortByPriority(list);
+    }
+
     @Override
     public void start() {
       context.start();

src/main/java/io/dinject/SystemContext.java

@@ -120,4 +120,21 @@ public static <T> List<T> getBeans(Class<T> interfaceType) {
     return rootContext.getBeans(interfaceType);
   }
 
+  /**
+   * Return the list of beans that implement the interface without ordering based on <code>@Priority</code>.
+   *
+   * <pre>{@code
+   *
+   *   // e.g. register all web routes with web a framework
+   *
+   *   List<WebRoute> routes = SystemContext.getBeansUnsorted(WebRoute.class);
+   *
+   * }</pre>
+   *
+   * @param interfaceType An interface class.
+   */
+  public static <T> List<T> getBeansUnsorted(Class<T> interfaceType) {
+    return rootContext.getBeansUnsorted(interfaceType);
+  }
+
 }

src/main/java/io/dinject/core/DBeanContext.java

@@ -5,7 +5,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import javax.annotation.Priority;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -76,15 +78,45 @@ public <T> T getBean(Class<T> beanClass, String name) {
   }
 
   @Override
-  public <T> List<T> getBeans(Class<T> interfaceType) {
+  public <T> List<T> getBeansUnsorted(Class<T> interfaceType) {
     List<T> list = new ArrayList<>();
     beans.addAll(interfaceType, list);
     for (BeanContext childContext : children.values()) {
-      list.addAll(childContext.getBeans(interfaceType));
+      list.addAll(childContext.getBeansUnsorted(interfaceType));
     }
     return list;
   }
 
+  @Override
+  public <T> List<T> getBeans(Class<T> interfaceType) {
+    List<T> list = getBeansUnsorted(interfaceType);
+    return list.size() > 1 ? sortByPriority(list) : list;
+  }
+
+  @Override
+  public <T> List<T> sortByPriority(List<T> list) {
+    boolean priorityUsed = false;
+    List<SortBean<T>> tempList = new ArrayList<>(list.size());
+    for (T bean : list) {
+      SortBean<T> sortBean = new SortBean<>(bean);
+      tempList.add(sortBean);
+      if (!priorityUsed && sortBean.priorityDefined) {
+        priorityUsed = true;
+      }
+    }
+    if (!priorityUsed) {
+      // nothing with Priority annotation so return original order
+      return list;
+    }
+    Collections.sort(tempList);
+    // unpack into new sorted list
+    List<T> sorted = new ArrayList<>(tempList.size());
+    for (SortBean<T> sortBean : tempList) {
+      sorted.add(sortBean.bean);
+    }
+    return sorted;
+  }
+
   @Override
   public List<Object> getBeansWithAnnotation(Class<?> annotation) {
 
@@ -186,4 +218,34 @@ BeanEntry<T> get() {
       return secondary;
     }
   }
+
+  private static class SortBean<T> implements Comparable<SortBean<T>> {
+
+    private final T bean;
+
+    private boolean priorityDefined;
+
+    private final int priority;
+
+    SortBean(T bean) {
+      this.bean = bean;
+      this.priority = initPriority();
+    }
+
+    int initPriority() {
+      final Priority ann = bean.getClass().getAnnotation(Priority.class);
+      if (ann != null) {
+        priorityDefined = true;
+        return ann.value();
+      }
+      // Default priority as per javax.ws.rs.Priorities.USER
+      // User-level filter/interceptor priority
+      return 5000;
+    }
+
+    @Override
+    public int compareTo(SortBean<T> o) {
+      return Integer.compare(priority, o.priority);
+    }
+  }
 }

src/test/java/io/dinject/SystemContextTest.java

@@ -0,0 +1,33 @@
+package io.dinject;
+
+import org.example.coffee.list.ASomei;
+import org.example.coffee.list.BSomei;
+import org.example.coffee.list.Somei;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SystemContextTest {
+
+  @Test
+  public void getBeans_withPriority() {
+
+    final List<Somei> beans = SystemContext.getBeans(Somei.class);
+    assertThat(beans).hasSize(2);
+
+    assertThat(beans.get(0)).isInstanceOf(BSomei.class);
+    assertThat(beans.get(1)).isInstanceOf(ASomei.class);
+  }
+
+  @Test
+  public void getBeansUnsorted_withPriority() {
+
+    final List<Somei> beans = SystemContext.getBeansUnsorted(Somei.class);
+    assertThat(beans).hasSize(2);
+
+    assertThat(beans.get(0)).isInstanceOf(ASomei.class);
+    assertThat(beans.get(1)).isInstanceOf(BSomei.class);
+  }
+}

src/test/java/org/example/coffee/list/ASomei.java

@@ -1,8 +1,10 @@
 package org.example.coffee.list;
 
+import javax.annotation.Priority;
 import javax.inject.Singleton;
 
 @Singleton
+@Priority(2)
 public class ASomei implements Somei {
 
   @Override

src/test/java/org/example/coffee/list/BSomei.java

@@ -1,8 +1,10 @@
 package org.example.coffee.list;
 
+import javax.annotation.Priority;
 import javax.inject.Singleton;
 
 @Singleton
+@Priority(1)
 public class BSomei implements Somei {
 
   @Override