rdonkin 2003/08/21 15:39:00 Added: betwixt/src/java/org/apache/commons/betwixt/io/read ChainedBeanCreatorFactory.java Log: Reafactored read bean creation into chain of independet creators. It can now be extended by users. Revision Changes Path 1.1 jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/io/read/ChainedBeanCreatorFactory.java Index: ChainedBeanCreatorFactory.java =================================================================== /* * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/io/read/ChainedBeanCreatorFactory.java,v 1.1 2003/08/21 22:39:00 rdonkin Exp $ * $Revision: 1.1 $ * $Date: 2003/08/21 22:39:00 $ * * ==================================================================== * * The Apache Software License, Version 1.1 * * Copyright (c) 1999-2002 The Apache Software Foundation. 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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * * $Id: ChainedBeanCreatorFactory.java,v 1.1 2003/08/21 22:39:00 rdonkin Exp $ */ package org.apache.commons.betwixt.io.read; /** * Group of factory methods for <code>ChainedBeanCreator</code>'s. * The standard implementations used by Betwixt are present here. * * @author Robert Burrell Donkin * @version $Revision: 1.1 $ */ public class ChainedBeanCreatorFactory { /** Singleton instance for creating derived beans */ private static final ChainedBeanCreator derivedBeanCreator = new ChainedBeanCreator() { public Object create( ElementMapping elementMapping, ReadContext context, BeanCreationChain chain) { String className = elementMapping.getAttributes().getValue( context.getClassNameAttribute() ); if ( className != null ) { try { // load the class we should instantiate ClassLoader classLoader = context.getClassLoader(); if ( classLoader == null ) { context.getLog().warn( "Could not create derived instance: read context classloader not set." ); } Class clazz = classLoader.loadClass( className ); return clazz.newInstance(); } catch (Exception e) { // it would be nice to have a pluggable strategy for exception management context.getLog().warn( "Could not create instance of type: " + className ); context.getLog().debug( "Create new instance failed: ", e ); return null; } } else { // pass responsibility down the chain return chain.create( elementMapping, context ); } } }; /** * Creates a <code>ChainedBeanCreator</code> that constructs derived beans. * These have their classname set by an xml attribute. * @return <code>ChainedBeanCreator</code> that implements Derived beans logic, not null */ public static final ChainedBeanCreator createDerivedBeanCreator() { return derivedBeanCreator; } /** Singleton instance that creates beans based on type */ private static final ChainedBeanCreator elementTypeBeanCreator = new ChainedBeanCreator() { public Object create( ElementMapping element, ReadContext context, BeanCreationChain chain) { // create based on type Class theClass = element.getType(); try { return theClass.newInstance(); } catch (Exception e) { // it would be nice to have a pluggable strategy for exception management context.getLog().warn( "Could not create instance of type: " + theClass.getName() ); context.getLog().debug( "Create new instance failed: ", e ); return null; } } }; /** * Creates a <code>ChainedBeanCreator</code> that constructs beans based on element type. * @return <code>ChainedBeanCreator</code> that implements load by type beans logic, not null */ public static final ChainedBeanCreator createElementTypeBeanCreator() { return elementTypeBeanCreator; } /** Singleton instance that creates beans based on IDREF */ private static final ChainedBeanCreator idRefBeanCreator = new ChainedBeanCreator() { public Object create( ElementMapping elementMapping, ReadContext context, BeanCreationChain chain) { if ( context.getMapIDs() ) { String idref = elementMapping.getAttributes().getValue( "idref" ); if ( idref != null ) { // XXX need to check up about ordering // XXX this is a very simple system that assumes that // XXX id occurs before idrefs // XXX would need some thought about how to implement a fuller system context.getLog().trace( "Found IDREF" ); Object bean = context.getBean( idref ); if ( bean != null ) { if ( context.getLog().isTraceEnabled() ) { context.getLog().trace( "Matched bean " + bean ); } return bean; } context.getLog().trace( "No match found" ); } } return chain.create( elementMapping, context ); } }; /** * Creates a <code>ChainedBeanCreator</code> that finds existing beans based on their IDREF. * @return <code>ChainedBeanCreator</code> that implements IDREF beans logic, not null */ public static final ChainedBeanCreator createIDREFBeanCreator() { return idRefBeanCreator; } }
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