1 files changed, 92 insertions, 0 deletions
diff --git a/lib/java/src/org/apache/thrift/partial/EnumCache.java b/lib/java/src/org/apache/thrift/partial/EnumCache.java
new file mode 100644
index 000000000..22423f10c
--- /dev/null
+++ b/lib/java/src/org/apache/thrift/partial/EnumCache.java
@@ -0,0 +1,92 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.thrift.partial;
+
+import org.apache.thrift.partial.Validate;
+
+import org.apache.thrift.TEnum;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Provides a memoized way to lookup an enum by its value.
+ *
+ * This class is used internally by {@code TDeserializer}.
+ * It is not intended to be used separately on its own.
+ */
+public class EnumCache {
+  private static Logger LOG = LoggerFactory.getLogger(EnumCache.class);
+
+  private Map<Class<? extends TEnum>, Map<Integer, TEnum>> classMap;
+
+  public EnumCache() {
+    this.classMap = new HashMap<>();
+  }
+
+  /**
+   * Gets an instance of the enum type {@code enumClass}
+   * corresponding to the given {@code value}.
+   *
+   * @param enumClass class of the enum to be returned.
+   * @param value value returned by {@code getValue()}.
+   */
+  public TEnum get(Class<? extends TEnum> enumClass, int value) {
+    Validate.checkNotNull(enumClass, "enumClass");
+
+    Map<Integer, TEnum> valueMap = classMap.get(enumClass);
+    if (valueMap == null) {
+      valueMap = addClass(enumClass);
+      if (valueMap == null) {
+        return null;
+      }
+    }
+
+    return valueMap.get(value);
+  }
+
+  private Map<Integer, TEnum> addClass(Class<? extends TEnum> enumClass) {
+    try {
+      Method valuesMethod = enumClass.getMethod("values");
+      TEnum[] enumValues = (TEnum[]) valuesMethod.invoke(null);
+      Map<Integer, TEnum> valueMap = new HashMap<>();
+
+      for (TEnum enumValue : enumValues) {
+        valueMap.put(enumValue.getValue(), enumValue);
+      }
+
+      classMap.put(enumClass, valueMap);
+      return valueMap;
+    } catch (NoSuchMethodException e) {
+      LOG.error("enum class does not have values() method", e);
+      return null;
+    } catch (IllegalAccessException e) {
+      LOG.error("Enum.values() method should be public!", e);
+      return null;
+    } catch (InvocationTargetException e) {
+      LOG.error("Enum.values() threw exception", e);
+      return null;
+    }
+  }
+}