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/*
* JBoss, Home of Professional Open Source
* Copyright 2009, Red Hat, Inc. and/or its affiliates, and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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 javax.validation;

import java.lang.ref.SoftReference;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.WeakHashMap;
import javax.validation.bootstrap.GenericBootstrap;
import javax.validation.bootstrap.ProviderSpecificBootstrap;
import javax.validation.spi.BootstrapState;
import javax.validation.spi.ValidationProvider;

/**
 * This class is the entry point for Bean Validation. There are three ways
 * to bootstrap it:
 * 
    *
  • * The easiest approach is to build the default {@code ValidatorFactory}. *
    {@code ValidatorFactory factory = Validation.buildDefaultValidatorFactory();}
    * In this case, the default validation provider resolver * will be used to locate available providers. * The chosen provider is defined as followed: *
      *
    • if the XML configuration defines a provider, this provider is used
    • *
    • if the XML configuration does not define a provider or if no XML configuration * is present the first provider returned by the * {@code ValidationProviderResolver} instance is used.
    • *
    *
  • *
  • * The second bootstrap approach allows to choose a custom * {@code ValidationProviderResolver}. The chosen * {@code ValidationProvider} is then determined in the same way * as in the default bootstrapping case (see above). *
    {@code
     * Configuration configuration = Validation
     *    .byDefaultProvider()
     *    .providerResolver( new MyResolverStrategy() )
     *    .configure();
     * ValidatorFactory factory = configuration.buildValidatorFactory();}
     * 
    *
  • *
  • * The third approach allows you to specify explicitly and in * a type safe fashion the expected provider. *

    * Optionally you can choose a custom {@code ValidationProviderResolver}. *

    {@code
     * ACMEConfiguration configuration = Validation
     *    .byProvider(ACMEProvider.class)
     *    .providerResolver( new MyResolverStrategy() )  // optionally set the provider resolver
     *    .configure();
     * ValidatorFactory factory = configuration.buildValidatorFactory();}
     * 
    *
  • *
* Note:
*
    *
  • * The {@code ValidatorFactory} object built by the bootstrap process should be cached * and shared amongst {@code Validator} consumers. *
  • *
  • * This class is thread-safe. *
  • *
* * @author Emmanuel Bernard * @author Hardy Ferentschik */ public class Validation { /** * Build and return a {@code ValidatorFactory} instance based on the * default Bean Validation provider and following the XML configuration. *

* The provider list is resolved using the default validation provider resolver * logic. *

The code is semantically equivalent to * {@code Validation.byDefaultProvider().configure().buildValidatorFactory()} * * @return {@code ValidatorFactory} instance. * * @throws ValidationException if the ValidatorFactory cannot be built */ public static ValidatorFactory buildDefaultValidatorFactory() { return byDefaultProvider().configure().buildValidatorFactory(); } /** * Build a {@code Configuration}. The provider list is resolved * using the strategy provided to the bootstrap state. *

	 * Configuration<?> configuration = Validation
	 *    .byDefaultProvider()
	 *    .providerResolver( new MyResolverStrategy() )
	 *    .configure();
	 * ValidatorFactory factory = configuration.buildValidatorFactory();
	 * 
* The provider can be specified in the XML configuration. If the XML * configuration does not exist or if no provider is specified, * the first available provider will be returned. * * @return instance building a generic {@code Configuration} * compliant with the bootstrap state provided. */ public static GenericBootstrap byDefaultProvider() { return new GenericBootstrapImpl(); } /** * Build a {@code Configuration} for a particular provider implementation. * Optionally overrides the provider resolution strategy used to determine the provider. *

* Used by applications targeting a specific provider programmatically. *

*

	 * ACMEConfiguration configuration =
	 *     Validation.byProvider(ACMEProvider.class)
	 *             .providerResolver( new MyResolverStrategy() )
	 *             .configure();
	 * 
, * where {@code ACMEConfiguration} is the * {@code Configuration} sub interface uniquely identifying the * ACME Bean Validation provider. and {@code ACMEProvider} is the * {@code ValidationProvider} implementation of the ACME provider. * * @param providerType the {@code ValidationProvider} implementation type * * @return instance building a provider specific {@code Configuration} * sub interface implementation. */ public static , U extends ValidationProvider> ProviderSpecificBootstrap byProvider(Class providerType) { return new ProviderSpecificBootstrapImpl( providerType ); } //private class, not exposed private static class ProviderSpecificBootstrapImpl, U extends ValidationProvider> implements ProviderSpecificBootstrap { private final Class validationProviderClass; private ValidationProviderResolver resolver; public ProviderSpecificBootstrapImpl(Class validationProviderClass) { this.validationProviderClass = validationProviderClass; } /** * Optionally define the provider resolver implementation used. * If not defined, use the default ValidationProviderResolver * * @param resolver ValidationProviderResolver implementation used * * @return self */ public ProviderSpecificBootstrap providerResolver(ValidationProviderResolver resolver) { this.resolver = resolver; return this; } /** * Determine the provider implementation suitable for byProvider(Class) * and delegate the creation of this specific Configuration subclass to the provider. * * @return a Configuration sub interface implementation */ public T configure() { if ( validationProviderClass == null ) { throw new ValidationException( "builder is mandatory. Use Validation.byDefaultProvider() to use the generic provider discovery mechanism" ); } //used mostly as a BootstrapState GenericBootstrapImpl state = new GenericBootstrapImpl(); if ( resolver == null ) { resolver = state.getDefaultValidationProviderResolver(); } else { //stay null if no resolver is defined state.providerResolver( resolver ); } List> resolvers; try { resolvers = resolver.getValidationProviders(); } catch ( RuntimeException re ) { throw new ValidationException( "Unable to get available provider resolvers.", re ); } for ( ValidationProvider provider : resolvers ) { if ( validationProviderClass.isAssignableFrom( provider.getClass() ) ) { ValidationProvider specificProvider = validationProviderClass.cast( provider ); return specificProvider.createSpecializedConfiguration( state ); } } throw new ValidationException( "Unable to find provider: " + validationProviderClass ); } } //private class, not exposed private static class GenericBootstrapImpl implements GenericBootstrap, BootstrapState { private ValidationProviderResolver resolver; private ValidationProviderResolver defaultResolver; public GenericBootstrap providerResolver(ValidationProviderResolver resolver) { this.resolver = resolver; return this; } public ValidationProviderResolver getValidationProviderResolver() { return resolver; } public ValidationProviderResolver getDefaultValidationProviderResolver() { if ( defaultResolver == null ) { defaultResolver = new DefaultValidationProviderResolver(); } return defaultResolver; } public Configuration configure() { ValidationProviderResolver resolver = this.resolver == null ? getDefaultValidationProviderResolver() : this.resolver; List> validationProviders; try { validationProviders = resolver.getValidationProviders(); } // don't wrap existing ValidationExceptions in another ValidationException catch ( ValidationException e ) { throw e; } // if any other exception occurs wrap it in a ValidationException catch ( RuntimeException re ) { throw new ValidationException( "Unable to get available provider resolvers.", re ); } if ( validationProviders.size() == 0 ) { String msg = "Unable to create a Configuration, because no Bean Validation provider could be found." + " Add a provider like Hibernate Validator (RI) to your classpath."; throw new ValidationException( msg ); } Configuration config; try { config = resolver.getValidationProviders().get( 0 ).createGenericConfiguration( this ); } catch ( RuntimeException re ) { throw new ValidationException( "Unable to instantiate Configuration.", re ); } return config; } } /** * Find {@code ValidationProvider} according to the default {@code ValidationProviderResolver} defined in the * Bean Validation specification. This implementation first uses thread's context classloader to locate providers. * If no suitable provider is found using the aforementioned class loader, it uses current class loader. * If it still does not find any suitable provider, it tries to locate the built-in provider using the current * class loader. * * @author Emmanuel Bernard * @author Hardy Ferentschik */ private static class DefaultValidationProviderResolver implements ValidationProviderResolver { public List> getValidationProviders() { // class loading and ServiceLoader methods should happen in a PrivilegedAction return GetValidationProviderListAction.getValidationProviderList(); } } private static class GetValidationProviderListAction implements PrivilegedAction>> { //cache per classloader for an appropriate discovery //keep them in a weak hash map to avoid memory leaks and allow proper hot redeployment private static final WeakHashMap>>> providersPerClassloader = new WeakHashMap>>>(); public static List> getValidationProviderList() { final GetValidationProviderListAction action = new GetValidationProviderListAction(); if ( System.getSecurityManager() != null ) { return AccessController.doPrivileged( action ); } else { return action.run(); } } public List> run() { // Option #1: try first context class loader ClassLoader classloader = Thread.currentThread().getContextClassLoader(); List> cachedContextClassLoaderProviderList = getCachedValidationProviders( classloader ); if ( cachedContextClassLoaderProviderList != null ) { // if already processed return the cached provider list return cachedContextClassLoaderProviderList; } List> validationProviderList = loadProviders( classloader ); // Option #2: if we cannot find any service files with the context class loader use the current class loader if ( validationProviderList.isEmpty() ) { classloader = DefaultValidationProviderResolver.class.getClassLoader(); List> cachedCurrentClassLoaderProviderList = getCachedValidationProviders( classloader ); if ( cachedCurrentClassLoaderProviderList != null ) { // if already processed return the cached provider list return cachedCurrentClassLoaderProviderList; } validationProviderList = loadProviders( classloader ); } // cache the detected providers against the classloader in which they were found cacheValidationProviders( classloader, validationProviderList ); return validationProviderList; } private List> loadProviders(ClassLoader classloader) { ServiceLoader loader = ServiceLoader.load( ValidationProvider.class, classloader ); Iterator providerIterator = loader.iterator(); List> validationProviderList = new ArrayList>(); while ( providerIterator.hasNext() ) { try { validationProviderList.add( providerIterator.next() ); } catch ( ServiceConfigurationError e ) { // ignore, because it can happen when multiple // providers are present and some of them are not class loader // compatible with our API. } } return validationProviderList; } private synchronized List> getCachedValidationProviders(ClassLoader classLoader) { SoftReference>> ref = providersPerClassloader.get( classLoader ); return ref != null ? ref.get() : null; } private synchronized void cacheValidationProviders(ClassLoader classLoader, List> providers) { providersPerClassloader.put( classLoader, new SoftReference>>( providers ) ); } } }