Support the mechanism for initializing a cache after set all properties

fix gh-816

Author: kazuki43zoo

src/main/java/org/apache/ibatis/builder/InitializingObject.java

@@ -0,0 +1,35 @@
+/**
+ *    Copyright 2009-2016 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.builder;
+
+/**
+ * Interface that indicate to provide a initialization method.
+ *
+ * @since 3.4.2
+ * @author Kazuki Shimizu
+ */
+public interface InitializingObject {
+
+  /**
+   * Initialize a instance.
+   * <p>
+   * This method will be invoked after it has set all properties.
+   * </p>
+   * @throws Exception in the event of misconfiguration (such as failure to set an essential property) or if initialization fails
+   */
+  void initialize() throws Exception;
+
+}

src/main/java/org/apache/ibatis/mapping/CacheBuilder.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2015 the original author or authors.
+ *    Copyright 2009-2016 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@
 
 import org.apache.ibatis.cache.Cache;
 import org.apache.ibatis.cache.CacheException;
+import org.apache.ibatis.builder.InitializingObject;
 import org.apache.ibatis.cache.decorators.BlockingCache;
 import org.apache.ibatis.cache.decorators.LoggingCache;
 import org.apache.ibatis.cache.decorators.LruCache;
@@ -175,6 +176,14 @@ private void setCacheProperties(Cache cache) {
         }
       }
     }
+    if (InitializingObject.class.isAssignableFrom(cache.getClass())){
+      try {
+        ((InitializingObject) cache).initialize();
+      } catch (Exception e) {
+        throw new CacheException("Failed cache initialization for '" +
+            cache.getId() + "' on '" + cache.getClass().getName() + "'", e);
+      }
+    }
   }
 
   private Cache newBaseCacheInstance(Class<? extends Cache> cacheClass, String id) {

src/test/java/org/apache/ibatis/mapping/CacheBuilderTest.java

@@ -0,0 +1,97 @@
+/**
+ *    Copyright 2009-2016 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.mapping;
+
+import org.apache.ibatis.builder.InitializingObject;
+import org.apache.ibatis.cache.Cache;
+import org.apache.ibatis.cache.CacheException;
+import org.apache.ibatis.cache.impl.PerpetualCache;
+import org.hamcrest.core.Is;
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import java.lang.reflect.Field;
+
+public class CacheBuilderTest {
+
+  @Rule
+  public ExpectedException expectedException = ExpectedException.none();
+
+  @Test
+  public void testInitializing() throws Exception {
+    InitializingCache cache = unwrap(new CacheBuilder("test").implementation(InitializingCache.class).build());
+
+    Assert.assertThat(cache.initialized, Is.is(true));
+  }
+
+  @Test
+  public void testInitializingFailure() throws Exception {
+    expectedException.expect(CacheException.class);
+    expectedException.expectMessage("Failed cache initialization for 'test' on 'org.apache.ibatis.mapping.CacheBuilderTest$InitializingFailureCache'");
+
+    new CacheBuilder("test").implementation(InitializingFailureCache.class).build();
+  }
+
+  @SuppressWarnings("unchecked")
+  private <T> T unwrap(Cache cache){
+    Field field;
+    try {
+      field = cache.getClass().getDeclaredField("delegate");
+    } catch (NoSuchFieldException e) {
+      throw new IllegalStateException(e);
+    }
+    try {
+      field.setAccessible(true);
+      return (T)field.get(cache);
+    } catch (IllegalAccessException e) {
+      throw new IllegalStateException(e);
+    } finally {
+      field.setAccessible(false);
+    }
+  }
+
+
+  private static class InitializingCache extends PerpetualCache implements InitializingObject {
+
+    private boolean initialized;
+
+    public InitializingCache(String id) {
+      super(id);
+    }
+
+    @Override
+    public void initialize() {
+      this.initialized = true;
+    }
+
+  }
+
+  private static class InitializingFailureCache extends PerpetualCache implements InitializingObject {
+
+    public InitializingFailureCache(String id) {
+      super(id);
+    }
+
+    @Override
+    public void initialize() throws Exception {
+      throw new IllegalStateException("error");
+    }
+
+  }
+
+}