tested to push in some fixes for QA

utils/src/com/cloud/utils/Constant.java

@@ -0,0 +1,116 @@
+/**
+ *  Copyright (C) 2010 Cloud.com, Inc.  All rights reserved.
+ * 
+ * This software is licensed under the GNU General Public License v3 or later.
+ * 
+ * It is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or any later version.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ */
+package com.cloud.utils;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Constant is different from Enum in that it allows anyone who declares a
+ * class that extends from it to allow for more Constants to be added.  It does
+ * not all need to be declared in the same place like Enums are.  The class
+ * is really geared toward String as the underneath value.
+ * 
+ * However, the flexibility of Constant can lead to bad programming practices
+ * since you can dynamically add Constant values at any time.  The correct 
+ * thing to do is declare Constant like you would declare other constants, 
+ * as static variables.  Unfortunately, I have no way to enforce that so I
+ * leave it up to the developer to behave. .... So behave! 
+ */
+public abstract class Constant {
+    static Map<Class<?>, Map<String, Constant>> _values = new HashMap<Class<?>, Map<String, Constant>>();
+    
+    Serializable _value;
+    public Constant(Serializable value) {
+        Class<?> clazz = value.getClass();
+        synchronized(Constant.class) {
+            Map<String, Constant> map = alreadyContains(clazz, value);
+            if (map == null) {
+                map = new HashMap<String, Constant>();
+                _values.put(clazz, map);
+            }
+           _value = value; 
+           map.put(value.toString(), this);
+        }
+    }
+    
+    final private Map<String, Constant> alreadyContains(Class<?> clazz, Object value) {
+        Map<String, Constant> map = _values.get(clazz);
+        if (map == null) {
+            return null;
+        }
+
+        assert !map.containsKey(value.toString()) : "Unfortunately you can not declare this constant as it has been declared by someone else";
+        
+        return map;
+    }
+    
+    public final Serializable value() {
+        return _value;
+    }
+    
+    @Override
+    public boolean equals(Object obj) {
+        if (!(obj instanceof Constant)) {
+            return false;
+        }
+        Constant that = (Constant)obj;
+        return _value.equals(that._value);
+    }
+
+    @Override
+    public int hashCode() {
+        return _value.hashCode();
+    }
+    
+    @Override
+    public String toString() {
+        return _value.toString();
+    }
+    
+    @SuppressWarnings("unchecked")
+    public static <T extends Constant> Collection<T> constants(Class<T> clazz) {
+        // Note that this method is not synchronized for a reason.  We
+        // expect the developer to behave and use Constant as it is intended.
+        return (Collection<T>)_values.get(clazz).values();
+    }
+    
+    public static Collection<? extends Constant> values(Class<?> clazz) {
+        // Note that this method is not synchronized for a reason.  We
+        // expect the developer to behave and use Constant as it is intended.
+        return _values.get(clazz).values();
+    }
+    
+    public Collection<? extends Constant> values() {
+        return values(this.getClass());
+    }
+    
+    public static Constant constant(Class<?> clazz, Serializable value) {
+        // Note that this method is not synchronized for a reason.  We
+        // expect the developer to behave and use Constant as it is intended.
+        return _values.get(clazz).get(value.toString());
+    }
+    
+    public static Constant parseConstant(Class<?> clazz, String value) {
+        // Note that this method is not synchronized for a reason.  We
+        // expect the developer to behave and use Constant as it is intended.
+        return _values.get(clazz).get(value);
+    }
+}