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[utils] / test / enterprise / src / main / java / org / wamblee / test / jndi / LookupProxyFactory.java

diff --git a/test/enterprise/src/main/java/org/wamblee/test/jndi/LookupProxyFactory.java b/test/enterprise/src/main/java/org/wamblee/test/jndi/LookupProxyFactory.java
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+/*
+ * Copyright 2005-2010 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.wamblee.test.jndi;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+import javax.naming.InitialContext;
+import javax.naming.NamingException;
+
+/**
+ * Proxy factory that can provide contextual references to objects retrieved
+ * through a lookup mechanism.
+ * 
+ * @param T
+ *            Interface to proxy.
+ * @author Erik Brakkee
+ * 
+ */
+public class LookupProxyFactory<T> {
+    
+    /**
+     * Interface to lookup the object to delegate to. 
+     * 
+     * @author Erik Brakkee
+     */
+    public static interface Lookup { 
+         /**
+          * Looks up the object. 
+          * @return Object (non-null)
+          * @throws Any exception in case the object cannot be found. 
+          */
+         Object lookup() throws Exception; 
+    }
+    
+    /**
+     * Exception thrown in case an object cannot be retrieved from JNDI. 
+     * 
+     * @author Erik Brakkee
+     */
+    public static class LookupException extends RuntimeException {
+        public LookupException(String aMsg, Throwable aCause) {
+            super(aMsg, aCause);
+        }
+
+        public LookupException(String aMsg) {
+            super(aMsg);
+        }
+    }
+
+    /**
+     * Invocation handler that does a lookup in JNDI and invokes the method on the 
+     * object it found. 
+     * 
+     * @author Erik Brakkee
+     */
+    private class LookupInvocationHandler implements InvocationHandler {
+
+        @Override
+        /**
+         * @throws JndiWiringException in case the object could not be retrieved from JNDI. 
+         */
+        public Object invoke(Object aProxy, Method aMethod, Object[] aArgs)
+            throws Throwable {
+            Object svcObj = null;
+            try {
+                svcObj = lookup.lookup();
+            } catch (Exception e) {
+                throw new LookupException(
+                    "Error looking up object", e);
+            }
+            if (svcObj == null) {
+                throw new LookupException("Object at is null");
+            }
+            if (!clazz.isInstance(svcObj)) {
+                throw new LookupException("Object '" + svcObj + "' is not of type " + clazz.getName() +
+                    " but of type " + svcObj.getClass().getName());
+            }
+            T svc = (T) svcObj;
+            try {
+                return aMethod.invoke(svc, aArgs);
+            } catch (InvocationTargetException e) {
+                throw e.getCause();
+            }
+        }
+    }
+
+    private Lookup lookup;
+    private Class clazz;
+
+    /**
+     * Constructs the factory.
+     * 
+     * @param aClass
+     *            Interface class of the service to proxy.
+     * @param aJndi JNDI name of the object to lookup. 
+     * 
+     */
+    public LookupProxyFactory(Class<T> aClass, Lookup aLookup) {
+        if (!aClass.isInterface()) {
+            throw new IllegalArgumentException("Class " + aClass.getName() +
+                " is not an interface");
+        }
+        clazz = aClass;
+        lookup = aLookup; 
+    }
+
+    /**
+     * Gets the proxy that delegates to the thread-specific instance set by
+     * {@link #set(Object)}
+     * 
+     * When at runtime the proxy cannot find lookup the object in JNDI, it 
+     * throws {@link LookupException}. 
+     * 
+     * @return Proxy.
+     */
+    public T getProxy() {
+        InvocationHandler handler = new LookupInvocationHandler();
+        Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
+            new Class[] { clazz });
+        T proxy;
+        try {
+            proxy = (T) proxyClass.getConstructor(
+                new Class[] { InvocationHandler.class }).newInstance(
+                new Object[] { handler });
+            return proxy;
+        } catch (Exception e) {
+            throw new RuntimeException("Could not create proxy for " +
+                clazz.getName(), e);
+        }
+    }
+}