Now the thread-specific proxies are serializable.

[utils] / support / general / src / main / java / org / wamblee / general / ThreadSpecificProxyFactory.java

diff --git a/support/general/src/main/java/org/wamblee/general/ThreadSpecificProxyFactory.java b/support/general/src/main/java/org/wamblee/general/ThreadSpecificProxyFactory.java
index f7087296796d8a60ae14fc83139aed7603c5ef2e..036a6828648b2cd25153d8ecb6edcd8c517b7e73 100644 (file)
--- a/support/general/src/main/java/org/wamblee/general/ThreadSpecificProxyFactory.java
+++ b/support/general/src/main/java/org/wamblee/general/ThreadSpecificProxyFactory.java
@@ -15,16 +15,21 @@
  */
 package org.wamblee.general;
 
+import java.io.Serializable;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
 
 /**
  * Thread-specific proxy is used to create implementations of interfaces that
  * delegate to a thread-specific implementation of the service.
  * 
- * It is used for instance to pass a transaction scoped entity manager around.
+ * It can be used for instance to create a contextual reference to an entity manager 
+ * that delegates to a thread-specific instance. 
  * 
  * The {@link #set(Object)} method sets the current service instance for the current thread. 
  * The {@link #get()} method gets the current service instance for the current thread. 
@@ -32,7 +37,7 @@ import java.lang.reflect.Proxy;
  * instance. The result from this method can be passed at construction of an object that will be used
  * by multiple threads. 
  * 
- * This class is mostly used by other test tools. 
+ * This class is mostly used by infrastructure code (utilities) and test tools.
  * 
  * @param T
  *            Interface to proxy.
@@ -40,21 +45,45 @@ import java.lang.reflect.Proxy;
  * 
  */
 public class ThreadSpecificProxyFactory<T> {
-    private class ThreadSpecificInvocationHandler implements InvocationHandler {
+    
+    /**
+     * We store a map of unique ids of invocation handlers to thread local storage of the 
+     * service. In this way, serialiability of the generated proxy is obtained (required by 
+     * framweorks such as wicket). Also, different factories will still be separate and never
+     * use the same threadlocal storage. 
+     */
+    private static Map<String,ThreadLocal> STORAGE = 
+        initializeThreadLocal();
+    
+    private static class ThreadSpecificInvocationHandler<T> implements InvocationHandler, Serializable {
+        
+        private String id; 
+        private Class clazz; 
+        
+        public ThreadSpecificInvocationHandler(String aId, Class aClass) { 
+            id = aId; 
+            clazz = aClass;
+        }
 
         @Override
         public Object invoke(Object aProxy, Method aMethod, Object[] aArgs)
             throws Throwable {
+            ThreadLocal<T> local = STORAGE.get(id);
+            T actualSvc = local.get();
+            if ( aMethod.getName().equals("toString") && actualSvc == null) { 
+                return "Thread-specific proxy for '" + clazz.getName() + "'";
+            }
             try {
-                return aMethod.invoke(svc.get(), aArgs);
+                return aMethod.invoke(actualSvc, aArgs);
             } catch (InvocationTargetException e) {
                 throw e.getCause();
             }
         }
     }
 
-    private ThreadLocal<T> svc = new ThreadLocal<T>();
+    private ThreadLocal<T> svc;
     private Class clazz;
+    private T proxy; 
 
     /**
      * Constructs the factory.
@@ -67,7 +96,14 @@ public class ThreadSpecificProxyFactory<T> {
             throw new IllegalArgumentException("Class " + aClass.getName() +
                 " is not an interface");
         }
+        svc = new ThreadLocal<T>();
         clazz = aClass;
+        proxy = createProxy(); 
+    }
+
+    private static Map<String, ThreadLocal> initializeThreadLocal() {
+        Map<String,ThreadLocal> map = new HashMap<String,ThreadLocal>();
+        return map;
     }
 
     /**
@@ -81,7 +117,9 @@ public class ThreadSpecificProxyFactory<T> {
     }
     
     /**
-     * Gets the current thread-specific service. 
+     * Gets the current thread-specific service.
+     * To get a contextual reference that can be used by any thread but delegates to a thread-specific
+     * instance, use {@link #getProxy()}.  
      * @return Service. 
      */
     public T get() { 
@@ -95,15 +133,21 @@ public class ThreadSpecificProxyFactory<T> {
      * @return Proxy.
      */
     public T getProxy() {
-        InvocationHandler handler = new ThreadSpecificInvocationHandler();
+        return proxy;
+    }
+
+    private T createProxy() {
+        String id = UUID.randomUUID().toString();
+        STORAGE.put(id, svc);
+        InvocationHandler handler = new ThreadSpecificInvocationHandler(id, clazz);
         Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
             new Class[] { clazz });
-        T proxy;
+        T proxyObj;
         try {
-            proxy = (T) proxyClass.getConstructor(
+            proxyObj = (T) proxyClass.getConstructor(
                 new Class[] { InvocationHandler.class }).newInstance(
                 new Object[] { handler });
-            return proxy;
+            return proxyObj;
         } catch (Exception e) {
             throw new RuntimeException("Could not create proxy for " +
                 clazz.getName(), e);