package org.wamblee.general;
import java.lang.reflect.InvocationHandler;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* 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.
* 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.
+ *
+ * Care has been taken so that the invocation handler is serializable.
+ * However, it is only serializable within one virtual machine. It cannot be used in a distributed context
+ * where it can be sent to another JVM.
*
* @param T
* Interface to proxy.
*
*/
public class ThreadSpecificProxyFactory<T> {
- private class ThreadSpecificInvocationHandler implements InvocationHandler {
-
- @Override
- public Object invoke(Object aProxy, Method aMethod, Object[] aArgs)
- throws Throwable {
- try {
- return aMethod.invoke(svc.get(), 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.
throw new IllegalArgumentException("Class " + aClass.getName() +
" is not an interface");
}
+ svc = new ThreadLocal<T>();
clazz = aClass;
+ proxy = createProxy();
+
}
/**
}
/**
- * 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() {
* @return Proxy.
*/
public T getProxy() {
- InvocationHandler handler = new ThreadSpecificInvocationHandler();
+ return proxy;
+ }
+
+ private T createProxy() {
+ InvocationHandler handler = new ThreadSpecificInvocationHandler(svc, 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);