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.management.RuntimeErrorException;
  24 import javax.persistence.EntityManager;
  25
  26 import org.wamblee.support.ThreadSpecificProxyFactory;
  27 import org.wamblee.support.persistence.JpaBuilder.JpaUnitOfWork;
  28
  29 /**
  30  * This utility makes sure that each invocation on a certain interface is
  31  * carried out within a JPA unit of work.
  32  *
  33  * Use {@link #getTransactionScopedEntityManager()} to get the transaction
  34  * scoped entity manager to pass to services.
  35  *
  36  * @param T
  37  *            Type of interface to proxy.
  38  *
  39  * @author Erik Brakkee
  40  */
  41 public class TransactionProxyFactory<T> {
  42
  43     private class UnitOfWorkInvocationHandler<T> implements InvocationHandler {
  44
  45         private T service;
  46
  47         public UnitOfWorkInvocationHandler(T aService) {
  48             service = aService;
  49         }
  50
  51         @Override
  52         public Object invoke(Object aProxy, final Method aMethod,
  53             final Object[] aArgs) throws Throwable {
  54             return TransactionProxyFactory.this.jpaBuilder
  55                 .execute(new JpaUnitOfWork<Object>() {
  56                     @Override
  57                     public Object execute(EntityManager aEm) throws Exception {
  58                         try {
  59                             ENTITY_MANAGER.set(aEm);
  60                             return aMethod.invoke(service, aArgs);
  61                         } catch (InvocationTargetException e) {
  62                             Throwable cause = e.getCause();
  63                             if (cause instanceof Exception) {
  64                                 throw (Exception) cause;
  65                             } else if (cause instanceof Error) {
  66                                 throw (Error) cause;
  67                             }
  68                             // last resort.
  69                             throw new RuntimeException(e);
  70                         } finally {
  71                             ENTITY_MANAGER.set(null);
  72                         }
  73                     }
  74                 });
  75         }
  76
  77     }
  78
  79     private static final ThreadSpecificProxyFactory<EntityManager> ENTITY_MANAGER = new ThreadSpecificProxyFactory<EntityManager>(
  80         EntityManager.class);
  81
  82     private JpaBuilder jpaBuilder;
  83     private Class<T> clazz;
  84
  85     /**
  86      * Constructs the transaction proxy.
  87      *
  88      * @param aJpaBuilder
  89      */
  90     public TransactionProxyFactory(JpaBuilder aJpaBuilder, Class<T> aClass) {
  91         jpaBuilder = aJpaBuilder;
  92         clazz = aClass;
  93     }
  94
  95     public EntityManager getTransactionScopedEntityManager() {
  96         return ENTITY_MANAGER.getProxy();
  97     }
  98
  99     public T getProxy(T aService) {
 100         InvocationHandler handler = new UnitOfWorkInvocationHandler<T>(aService);
 101         Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
 102             new Class[] { clazz });
 103         T proxy;
 104         try {
 105             proxy = (T) proxyClass.getConstructor(
 106                 new Class[] { InvocationHandler.class }).newInstance(
 107                 new Object[] { handler });
 108             return proxy;
 109         } catch (Exception e) {
 110             throw new RuntimeException("Could not create proxy for " +
 111                 clazz.getName(), e);
 112         }
 113     }
 114 }