Spring Framework example source code file (AbstractSimpleBeanDefinitionParser.java)

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Java - Spring Framework tags/keywords

abstractsimplebeandefinitionparser, abstractsinglebeandefinitionparser, attr, attr, beandefinitionbuilder, dom, element, illegal, illegal, namednodemap, namednodemap, string, string

The Spring Framework AbstractSimpleBeanDefinitionParser.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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 org.springframework.beans.factory.xml;

import org.w3c.dom.Attr;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.core.Conventions;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Convenient base class for when there exists a one-to-one mapping
 * between attribute names on the element that is to be parsed and
 * the property names on the {@link Class} being configured.
 *
 * <p>Extend this parser class when you want to create a single
 * bean definition from a relatively simple custom XML element. The
 * resulting <code>BeanDefinition will be automatically
 * registered with the relevant
 * {@link org.springframework.beans.factory.support.BeanDefinitionRegistry}.
 *
 * <p>An example will hopefully make the use of this particular parser
 * class immediately clear. Consider the following class definition:
 *
 * <pre class="code">public class SimpleCache implements Cache {
 * 
 *     public void setName(String name) {...}
 *     public void setTimeout(int timeout) {...}
 *     public void setEvictionPolicy(EvictionPolicy policy) {...}
 * 
 *     // remaining class definition elided for clarity...
 * }</pre>
 *
 * <p>Then let us assume the following XML tag has been defined to
 * permit the easy configuration of instances of the above class;
 *
 * <pre class="code"><caching:cache name="..." timeout="..." eviction-policy="..."/>

* * <p>All that is required of the Java developer tasked with writing * the parser to parse the above XML tag into an actual * <code>SimpleCache bean definition is the following: * * <pre class="code">public class SimpleCacheBeanDefinitionParser extends AbstractSimpleBeanDefinitionParser { * * protected Class getBeanClass(Element element) { * return SimpleCache.class; * } * }</pre> * * <p>Please note that the AbstractSimpleBeanDefinitionParser * is limited to populating the created bean definition with property values. * if you want to parse constructor arguments and nested elements from the * supplied XML element, then you will have to implement the * {@link #postProcess(org.springframework.beans.factory.support.BeanDefinitionBuilder, org.w3c.dom.Element)} * method and do such parsing yourself, or (more likely) subclass the * {@link AbstractSingleBeanDefinitionParser} or {@link AbstractBeanDefinitionParser} * classes directly. * * <p>The process of actually registering the * <code>SimpleCacheBeanDefinitionParser with the Spring XML parsing * infrastructure is described in the Spring Framework reference documentation * (in one of the appendices). * * <p>For an example of this parser in action (so to speak), do look at * the source code for the * {@link org.springframework.beans.factory.xml.UtilNamespaceHandler.PropertiesBeanDefinitionParser}; * the observant (and even not so observant) reader will immediately notice that * there is next to no code in the implementation. The * <code>PropertiesBeanDefinitionParser populates a * {@link org.springframework.beans.factory.config.PropertiesFactoryBean} * from an XML element that looks like this: * * <pre class="code"><util:properties location="jdbc.properties"/> * * <p>The observant reader will notice that the sole attribute on the * <code><util:properties/> element matches the * {@link org.springframework.beans.factory.config.PropertiesFactoryBean#setLocation(org.springframework.core.io.Resource)} * method name on the <code>PropertiesFactoryBean (the general * usage thus illustrated holds true for any number of attributes). * All that the <code>PropertiesBeanDefinitionParser needs * actually do is supply an implementation of the * {@link #getBeanClass(org.w3c.dom.Element)} method to return the * <code>PropertiesFactoryBean type. * * @author Rob Harrop * @author Rick Evans * @author Juergen Hoeller * @since 2.0 * @see Conventions#attributeNameToPropertyName(String) */ public abstract class AbstractSimpleBeanDefinitionParser extends AbstractSingleBeanDefinitionParser { /** * Parse the supplied {@link Element} and populate the supplied * {@link BeanDefinitionBuilder} as required. * <p>This implementation maps any attributes present on the * supplied element to {@link org.springframework.beans.PropertyValue} * instances, and * {@link BeanDefinitionBuilder#addPropertyValue(String, Object) adds them} * to the * {@link org.springframework.beans.factory.config.BeanDefinition builder}. * <p>The {@link #extractPropertyName(String)} method is used to * reconcile the name of an attribute with the name of a JavaBean * property. * @param element the XML element being parsed * @param builder used to define the <code>BeanDefinition * @see #extractPropertyName(String) */ protected final void doParse(Element element, BeanDefinitionBuilder builder) { NamedNodeMap attributes = element.getAttributes(); for (int x = 0; x < attributes.getLength(); x++) { Attr attribute = (Attr) attributes.item(x); if (isEligibleAttribute(attribute)) { String propertyName = extractPropertyName(attribute.getLocalName()); Assert.state(StringUtils.hasText(propertyName), "Illegal property name returned from 'extractPropertyName(String)': cannot be null or empty."); builder.addPropertyValue(propertyName, attribute.getValue()); } } postProcess(builder, element); } /** * Determine whether the given attribute is eligible for being * turned into a corresponding bean property value. * <p>The default implementation considers any attribute as eligible, * except for the "id" attribute and namespace declaration attributes. * @param attribute the XML attribute to check * @see #isEligibleAttribute(String) */ protected boolean isEligibleAttribute(Attr attribute) { String fullName = attribute.getName(); return (!fullName.equals("xmlns") && !fullName.startsWith("xmlns:") && isEligibleAttribute(attribute.getLocalName())); } /** * Determine whether the given attribute is eligible for being * turned into a corresponding bean property value. * <p>The default implementation considers any attribute as eligible, * except for the "id" attribute. * @param attributeName the attribute name taken straight from the * XML element being parsed (never <code>null) */ protected boolean isEligibleAttribute(String attributeName) { return !ID_ATTRIBUTE.equals(attributeName); } /** * Extract a JavaBean property name from the supplied attribute name. * <p>The default implementation uses the * {@link Conventions#attributeNameToPropertyName(String)} * method to perform the extraction. * <p>The name returned must obey the standard JavaBean property name * conventions. For example for a class with a setter method * '<code>setBingoHallFavourite(String)', the name returned had * better be '<code>bingoHallFavourite' (with that exact casing). * @param attributeName the attribute name taken straight from the * XML element being parsed (never <code>null) * @return the extracted JavaBean property name (must never be <code>null) */ protected String extractPropertyName(String attributeName) { return Conventions.attributeNameToPropertyName(attributeName); } /** * Hook method that derived classes can implement to inspect/change a * bean definition after parsing is complete. * <p>The default implementation does nothing. * @param beanDefinition the parsed (and probably totally defined) bean definition being built * @param element the XML element that was the source of the bean definition's metadata */ protected void postProcess(BeanDefinitionBuilder beanDefinition, Element element) { } }