wamblee.org Git - utils/blob - test/enterprise/src/main/java/org/wamblee/support/persistence/TransactionProxyFactory.java

   1 /*
   2  * Copyright 2005-2010 the original author or authors.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.wamblee.support.persistence;
  17
  18 import java.lang.reflect.InvocationHandler;
  19 import java.lang.reflect.InvocationTargetException;
  20 import java.lang.reflect.Method;
  21 import java.lang.reflect.Proxy;
  22
  23 import javax.persistence.EntityManager;
  24
  25 import org.wamblee.support.ThreadSpecificProxyFactory;
  26 import org.wamblee.support.persistence.JpaBuilder.JpaUnitOfWork;
  27
  28 /**
  29  * This utility makes sure that each invocation on a certain interface is
  30  * carried out within a JPA unit of work.
  31  *
  32  * Use {@link #getTransactionScopedEntityManager()} to get the transaction
  33  * scoped entity manager to pass to services.
  34  *
  35  * @param T
  36  *            Type of interface to proxy.
  37  *
  38  * @author Erik Brakkee
  39  */
  40 public class TransactionProxyFactory<T> {
  41
  42     private class UnitOfWorkInvocationHandler<T> implements InvocationHandler {
  43
  44         private T service;
  45
  46         public UnitOfWorkInvocationHandler(T aService) {
  47             service = aService;
  48         }
  49
  50         @Override
  51         public Object invoke(Object aProxy, final Method aMethod,
  52             final Object[] aArgs) throws Throwable {
  53             return TransactionProxyFactory.this.jpaBuilder
  54                 .execute(new JpaUnitOfWork<Object>() {
  55                     @Override
  56                     public Object execute(EntityManager aEm) throws Exception {
  57                         try {
  58                             ENTITY_MANAGER.set(aEm);
  59                             return aMethod.invoke(service, aArgs);
  60                         } catch (InvocationTargetException e) {
  61                             Throwable cause = e.getCause();
  62                             if (cause instanceof Exception) {
  63                                 throw (Exception) cause;
  64                             } else if (cause instanceof Error) {
  65                                 throw (Error) cause;
  66                             }
  67                             // last resort.
  68                             throw new RuntimeException(e);
  69                         } finally {
  70                             ENTITY_MANAGER.set(null);
  71                         }
  72                     }
  73                 });
  74         }
  75
  76     }
  77
  78     private static final ThreadSpecificProxyFactory<EntityManager> ENTITY_MANAGER = new ThreadSpecificProxyFactory<EntityManager>(
  79         EntityManager.class);
  80
  81     private JpaBuilder jpaBuilder;
  82     private Class<T> clazz;
  83
  84     /**
  85      * Constructs the transaction proxy.
  86      *
  87      * @param aJpaBuilder
  88      */
  89     public TransactionProxyFactory(JpaBuilder aJpaBuilder, Class<T> aClass) {
  90         jpaBuilder = aJpaBuilder;
  91         clazz = aClass;
  92     }
  93
  94     public EntityManager getTransactionScopedEntityManager() {
  95         return ENTITY_MANAGER.getProxy();
  96     }
  97
  98     public T getProxy(T aService) {
  99         InvocationHandler handler = new UnitOfWorkInvocationHandler<T>(aService);
 100         Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
 101             new Class[] { clazz });
 102         T proxy;
 103         try {
 104             proxy = (T) proxyClass.getConstructor(
 105                 new Class[] { InvocationHandler.class }).newInstance(
 106                 new Object[] { handler });
 107             return proxy;
 108         } catch (Exception e) {
 109             throw new RuntimeException("Could not create proxy for " +
 110                 clazz.getName(), e);
 111         }
 112     }
 113 }