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Java example source code file (JpaPersistModule.java)

This example Java source code file (JpaPersistModule.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, dynamic, finder, invocationhandler, jpapersistmodule, map, method, methodinterceptor, object, override, proxy, reflection, throwable, unsupportedoperationexception, util

The JpaPersistModule.java Java example source code

/**
 * Copyright (C) 2010 Google, Inc.
 *
 * 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 com.google.inject.persist.jpa;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.inject.Inject;
import com.google.inject.Provides;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import com.google.inject.persist.PersistModule;
import com.google.inject.persist.PersistService;
import com.google.inject.persist.UnitOfWork;
import com.google.inject.persist.finder.DynamicFinder;
import com.google.inject.persist.finder.Finder;
import com.google.inject.util.Providers;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;
import java.util.Map;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

/**
 * JPA provider for guice persist.
 *
 * @author dhanji@gmail.com (Dhanji R. Prasanna)
 */
public final class JpaPersistModule extends PersistModule {
  private final String jpaUnit;

  public JpaPersistModule(String jpaUnit) {
    Preconditions.checkArgument(null != jpaUnit && jpaUnit.length() > 0,
        "JPA unit name must be a non-empty string.");
    this.jpaUnit = jpaUnit;
  }

  private Map<?,?> properties;
  private MethodInterceptor transactionInterceptor;

  @Override protected void configurePersistence() {
    bindConstant().annotatedWith(Jpa.class).to(jpaUnit);

    bind(JpaPersistService.class).in(Singleton.class);

    bind(PersistService.class).to(JpaPersistService.class);
    bind(UnitOfWork.class).to(JpaPersistService.class);
    bind(EntityManager.class).toProvider(JpaPersistService.class);
    bind(EntityManagerFactory.class)
        .toProvider(JpaPersistService.EntityManagerFactoryProvider.class);

    transactionInterceptor = new JpaLocalTxnInterceptor();
    requestInjection(transactionInterceptor);

    // Bind dynamic finders.
    for (Class<?> finder : dynamicFinders) {
      bindFinder(finder);
    }
  }

  @Override protected MethodInterceptor getTransactionInterceptor() {
    return transactionInterceptor;
  }

  @Provides @Jpa Map<?, ?> provideProperties() {
    return properties;
  }

  /**
   * Configures the JPA persistence provider with a set of properties.
   * 
   * @param properties A set of name value pairs that configure a JPA persistence
   *     provider as per the specification.
   * @since 4.0 (since 3.0 with a parameter type of {@code java.util.Properties})
   */
  public JpaPersistModule properties(Map<?,?> properties) {
    this.properties = properties;
    return this;
  }

  private final List<Class dynamicFinders = Lists.newArrayList();

  /**
   * Adds an interface to this module to use as a dynamic finder.
   *
   * @param iface Any interface type whose methods are all dynamic finders.
   */
  public <T> JpaPersistModule addFinder(Class iface) {
    dynamicFinders.add(iface);
    return this;
  }

  private <T> void bindFinder(Class iface) {
    if (!isDynamicFinderValid(iface)) {
      return;
    }

    InvocationHandler finderInvoker = new InvocationHandler() {
      @Inject JpaFinderProxy finderProxy;

      public Object invoke(final Object thisObject, final Method method, final Object[] args)
          throws Throwable {

        // Don't intercept non-finder methods like equals and hashcode.
        if (!method.isAnnotationPresent(Finder.class)) {
          // NOTE(dhanji): This is not ideal, we are using the invocation handler's equals
          // and hashcode as a proxy (!) for the proxy's equals and hashcode. 
          return method.invoke(this, args);
        }

        return finderProxy.invoke(new MethodInvocation() {
          public Method getMethod() {
            return method;
          }

          public Object[] getArguments() {
            return null == args ? new Object[0] : args; 
          }

          public Object proceed() throws Throwable {
            return method.invoke(thisObject, args);
          }

          public Object getThis() {
            throw new UnsupportedOperationException("Bottomless proxies don't expose a this.");
          }

          public AccessibleObject getStaticPart() {
            throw new UnsupportedOperationException();
          }
        });
      }
    };
    requestInjection(finderInvoker);

    @SuppressWarnings("unchecked") // Proxy must produce instance of type given.
    T proxy = (T) Proxy
        .newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class<?>[] { iface },
            finderInvoker);

    bind(iface).toInstance(proxy);
  }

  private boolean isDynamicFinderValid(Class<?> iface) {
    boolean valid = true;
    if (!iface.isInterface()) {
      addError(iface + " is not an interface. Dynamic Finders must be interfaces.");
      valid = false;
    }

    for (Method method : iface.getMethods()) {
      DynamicFinder finder = DynamicFinder.from(method);
      if (null == finder) {
        addError("Dynamic Finder methods must be annotated with @Finder, but " + iface
            + "." + method.getName() + " was not");
        valid = false;
      }
    }
    return valid;
  }
}

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