解析xml有SAX，Stax,dom等方式，那么spring中是如何解析xml文件的呢？
Document doc = this.documentLoader.loadDocument(
inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());
spring中采用的DOM的方式，所要做的一切就是得到org.w3c.dom.Document对象
上面的documentLoader是DefaultDocumentLoader对象
/*
* 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 javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.xml.XmlValidationModeDetector;
import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource; /**
* Spring's default {@link DocumentLoader} implementation.
*
* <p>Simply loads {@link Document documents} using the standard JAXP-configured
* XML parser. If you want to change the {@link DocumentBuilder} that is used to
* load documents, then one strategy is to define a corresponding Java system property
* when starting your JVM. For example, to use the Oracle {@link DocumentBuilder},
* you might start your application like as follows:
*
* <pre code="class">java -Djavax.xml.parsers.DocumentBuilderFactory=oracle.xml.jaxp.JXDocumentBuilderFactory MyMainClass</pre>
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public class DefaultDocumentLoader implements DocumentLoader { /**
* JAXP attribute used to configure the schema language for validation.
*/
private static final String SCHEMA_LANGUAGE_ATTRIBUTE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage"; /**
* JAXP attribute value indicating the XSD schema language.
*/
private static final String XSD_SCHEMA_LANGUAGE = "http://www.w3.org/2001/XMLSchema"; private static final Log logger = LogFactory.getLog(DefaultDocumentLoader.class); /**
* Load the {@link Document} at the supplied {@link InputSource} using the standard JAXP-configured
* XML parser.
*/
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception { DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isDebugEnabled()) {
logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
}
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder.parse(inputSource);
} /**
* Create the {@link DocumentBuilderFactory} instance.
* @param validationMode the type of validation: {@link XmlValidationModeDetector#VALIDATION_DTD DTD}
* or {@link XmlValidationModeDetector#VALIDATION_XSD XSD})
* @param namespaceAware whether the returned factory is to provide support for XML namespaces
* @return the JAXP DocumentBuilderFactory
* @throws ParserConfigurationException if we failed to build a proper DocumentBuilderFactory
*/
protected DocumentBuilderFactory createDocumentBuilderFactory(int validationMode, boolean namespaceAware)
throws ParserConfigurationException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(namespaceAware); if (validationMode != XmlValidationModeDetector.VALIDATION_NONE) {
factory.setValidating(true); if (validationMode == XmlValidationModeDetector.VALIDATION_XSD) {
// Enforce namespace aware for XSD...
factory.setNamespaceAware(true);
try {
factory.setAttribute(SCHEMA_LANGUAGE_ATTRIBUTE, XSD_SCHEMA_LANGUAGE);
}
catch (IllegalArgumentException ex) {
ParserConfigurationException pcex = new ParserConfigurationException(
"Unable to validate using XSD: Your JAXP provider [" + factory +
"] does not support XML Schema. Are you running on Java 1.4 with Apache Crimson? " +
"Upgrade to Apache Xerces (or Java 1.5) for full XSD support.");
pcex.initCause(ex);
throw pcex;
}
}
} return factory;
} /**
* Create a JAXP DocumentBuilder that this bean definition reader
* will use for parsing XML documents. Can be overridden in subclasses,
* adding further initialization of the builder.
* @param factory the JAXP DocumentBuilderFactory that the DocumentBuilder
* should be created with
* @param entityResolver the SAX EntityResolver to use
* @param errorHandler the SAX ErrorHandler to use
* @return the JAXP DocumentBuilder
* @throws ParserConfigurationException if thrown by JAXP methods
*/
protected DocumentBuilder createDocumentBuilder(
DocumentBuilderFactory factory, EntityResolver entityResolver, ErrorHandler errorHandler)
throws ParserConfigurationException { DocumentBuilder docBuilder = factory.newDocumentBuilder();
if (entityResolver != null) {
docBuilder.setEntityResolver(entityResolver);
}
if (errorHandler != null) {
docBuilder.setErrorHandler(errorHandler);
}
return docBuilder;
} }
loadDocument中有一个参数entityResolver，类型是EntityResolver，这也没有什么，DocumentBuilder本来就可以设置setEntityResolver，那么现在这个entityResolver是什么对象呢？是
DelegatingEntityResolver ，
/*
* Copyright 2002-2012 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 java.io.IOException; import org.springframework.util.Assert;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException; /**
* {@link EntityResolver} implementation that delegates to a {@link BeansDtdResolver}
* and a {@link PluggableSchemaResolver} for DTDs and XML schemas, respectively.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Rick Evans
* @since 2.0
* @see BeansDtdResolver
* @see PluggableSchemaResolver
*/
public class DelegatingEntityResolver implements EntityResolver { /** Suffix for DTD files */
public static final String DTD_SUFFIX = ".dtd"; /** Suffix for schema definition files */
public static final String XSD_SUFFIX = ".xsd"; private final EntityResolver dtdResolver; private final EntityResolver schemaResolver; /**
* Create a new DelegatingEntityResolver that delegates to
* a default {@link BeansDtdResolver} and a default {@link PluggableSchemaResolver}.
* <p>Configures the {@link PluggableSchemaResolver} with the supplied
* {@link ClassLoader}.
* @param classLoader the ClassLoader to use for loading
* (can be {@code null}) to use the default ClassLoader)
*/
public DelegatingEntityResolver(ClassLoader classLoader) {
this.dtdResolver = new BeansDtdResolver();
this.schemaResolver = new PluggableSchemaResolver(classLoader);
} /**
* Create a new DelegatingEntityResolver that delegates to
* the given {@link EntityResolver EntityResolvers}.
* @param dtdResolver the EntityResolver to resolve DTDs with
* @param schemaResolver the EntityResolver to resolve XML schemas with
*/
public DelegatingEntityResolver(EntityResolver dtdResolver, EntityResolver schemaResolver) {
Assert.notNull(dtdResolver, "'dtdResolver' is required");
Assert.notNull(schemaResolver, "'schemaResolver' is required");
this.dtdResolver = dtdResolver;
this.schemaResolver = schemaResolver;
} public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
if (systemId != null) {
if (systemId.endsWith(DTD_SUFFIX)) {
return this.dtdResolver.resolveEntity(publicId, systemId);
}
else if (systemId.endsWith(XSD_SUFFIX)) {
return this.schemaResolver.resolveEntity(publicId, systemId);
}
}
return null;
} @Override
public String toString() {
return "EntityResolver delegating " + XSD_SUFFIX + " to " + this.schemaResolver +
" and " + DTD_SUFFIX + " to " + this.dtdResolver;
} }
在DocumentBuilder调用parse方法的时候会调用EntityResolver(这里是DelegatingEntityResolver)的resolveEntity方法：
public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
if (systemId != null) {
if (systemId.endsWith(DTD_SUFFIX)) {
return this.dtdResolver.resolveEntity(publicId, systemId);
}
else if (systemId.endsWith(XSD_SUFFIX)) {
return this.schemaResolver.resolveEntity(publicId, systemId);
}
}
return null;
}请注意resolveEntity方法会根据systemId来返回不同的对象，systemId即是xsi:schemaLocation种的值
/*
* Copyright 2002-2012 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 java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource; /**
* {@link EntityResolver} implementation that attempts to resolve schema URLs into
* local {@link ClassPathResource classpath resources} using a set of mappings files.
*
* <p>By default, this class will look for mapping files in the classpath using the pattern:
* {@code META-INF/spring.schemas} allowing for multiple files to exist on the
* classpath at any one time.
*
* The format of {@code META-INF/spring.schemas} is a properties
* file where each line should be of the form {@code systemId=schema-location}
* where {@code schema-location} should also be a schema file in the classpath.
* Since systemId is commonly a URL, one must be careful to escape any ':' characters
* which are treated as delimiters in properties files.
*
* <p>The pattern for the mapping files can be overidden using the
* {@link #PluggableSchemaResolver(ClassLoader, String)} constructor
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public class PluggableSchemaResolver implements EntityResolver { /**
* The location of the file that defines schema mappings.
* Can be present in multiple JAR files.
*/
public static final String DEFAULT_SCHEMA_MAPPINGS_LOCATION = "META-INF/spring.schemas"; private static final Log logger = LogFactory.getLog(PluggableSchemaResolver.class); private final ClassLoader classLoader; private final String schemaMappingsLocation; /** Stores the mapping of schema URL -> local schema path */
private volatile Map<String, String> schemaMappings; /**
* Loads the schema URL -> schema file location mappings using the default
* mapping file pattern "META-INF/spring.schemas".
* @param classLoader the ClassLoader to use for loading
* (can be {@code null}) to use the default ClassLoader)
* @see PropertiesLoaderUtils#loadAllProperties(String, ClassLoader)
*/
public PluggableSchemaResolver(ClassLoader classLoader) {
this.classLoader = classLoader;
this.schemaMappingsLocation = DEFAULT_SCHEMA_MAPPINGS_LOCATION;
} /**
* Loads the schema URL -> schema file location mappings using the given
* mapping file pattern.
* @param classLoader the ClassLoader to use for loading
* (can be {@code null}) to use the default ClassLoader)
* @param schemaMappingsLocation the location of the file that defines schema mappings
* (must not be empty)
* @see PropertiesLoaderUtils#loadAllProperties(String, ClassLoader)
*/
public PluggableSchemaResolver(ClassLoader classLoader, String schemaMappingsLocation) {
Assert.hasText(schemaMappingsLocation, "'schemaMappingsLocation' must not be empty");
this.classLoader = classLoader;
this.schemaMappingsLocation = schemaMappingsLocation;
} public InputSource resolveEntity(String publicId, String systemId) throws IOException {
if (logger.isTraceEnabled()) {
logger.trace("Trying to resolve XML entity with public id [" + publicId +
"] and system id [" + systemId + "]");
} if (systemId != null) {
String resourceLocation = getSchemaMappings().get(systemId);
if (resourceLocation != null) {
Resource resource = new ClassPathResource(resourceLocation, this.classLoader);
try {
InputSource source = new InputSource(resource.getInputStream());
source.setPublicId(publicId);
source.setSystemId(systemId);
if (logger.isDebugEnabled()) {
logger.debug("Found XML schema [" + systemId + "] in classpath: " + resourceLocation);
}
return source;
}
catch (FileNotFoundException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Couldn't find XML schema [" + systemId + "]: " + resource, ex);
}
}
}
}
return null;
} /**
* Load the specified schema mappings lazily.
*/
private Map<String, String> getSchemaMappings() {
if (this.schemaMappings == null) {
synchronized (this) {
if (this.schemaMappings == null) {
if (logger.isDebugEnabled()) {
logger.debug("Loading schema mappings from [" + this.schemaMappingsLocation + "]");
}
try {
Properties mappings =
PropertiesLoaderUtils.loadAllProperties(this.schemaMappingsLocation, this.classLoader);
if (logger.isDebugEnabled()) {
logger.debug("Loaded schema mappings: " + mappings);
}
Map<String, String> schemaMappings = new ConcurrentHashMap<String, String>(mappings.size());
CollectionUtils.mergePropertiesIntoMap(mappings, schemaMappings);
this.schemaMappings = schemaMappings;
}
catch (IOException ex) {
throw new IllegalStateException(
"Unable to load schema mappings from location [" + this.schemaMappingsLocation + "]", ex);
}
}
}
}
return this.schemaMappings;
} @Override
public String toString() {
return "EntityResolver using mappings " + getSchemaMappings();
} }
/*
* Copyright 2002-2012 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 java.io.IOException;
import java.util.Arrays; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource; /**
* EntityResolver implementation for the Spring beans DTD,
* to load the DTD from the Spring class path (or JAR file).
*
* <p>Fetches "spring-beans-2.0.dtd" from the class path resource
* "/org/springframework/beans/factory/xml/spring-beans-2.0.dtd",
* no matter whether specified as some local URL that includes "spring-beans"
* in the DTD name or as "http://www.springframework.org/dtd/spring-beans-2.0.dtd".
*
* @author Juergen Hoeller
* @author Colin Sampaleanu
* @since 04.06.2003
* @see ResourceEntityResolver
*/
public class BeansDtdResolver implements EntityResolver { private static final String DTD_EXTENSION = ".dtd"; private static final String[] DTD_NAMES = {"spring-beans-2.0", "spring-beans"}; private static final Log logger = LogFactory.getLog(BeansDtdResolver.class); public InputSource resolveEntity(String publicId, String systemId) throws IOException {
if (logger.isTraceEnabled()) {
logger.trace("Trying to resolve XML entity with public ID [" + publicId +
"] and system ID [" + systemId + "]");
}
if (systemId != null && systemId.endsWith(DTD_EXTENSION)) {
int lastPathSeparator = systemId.lastIndexOf("/");
for (String DTD_NAME : DTD_NAMES) {
int dtdNameStart = systemId.indexOf(DTD_NAME);
if (dtdNameStart > lastPathSeparator) {
String dtdFile = systemId.substring(dtdNameStart);
if (logger.isTraceEnabled()) {
logger.trace("Trying to locate [" + dtdFile + "] in Spring jar");
}
try {
Resource resource = new ClassPathResource(dtdFile, getClass());
InputSource source = new InputSource(resource.getInputStream());
source.setPublicId(publicId);
source.setSystemId(systemId);
if (logger.isDebugEnabled()) {
logger.debug("Found beans DTD [" + systemId + "] in classpath: " + dtdFile);
}
return source;
}
catch (IOException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not resolve beans DTD [" + systemId + "]: not found in class path", ex);
}
} }
}
} // Use the default behavior -> download from website or wherever.
return null;
} @Override
public String toString() {
return "EntityResolver for DTDs " + Arrays.toString(DTD_NAMES);
} }
在PluggableSchemaResolver类中会去加载META-INF/spring.schemas
http\://www.springframework.org/schema/beans/spring-beans-2.0.xsd=org/springframework/beans/factory/xml/spring-beans-2.0.xsd
http\://www.springframework.org/schema/beans/spring-beans-2.5.xsd=org/springframework/beans/factory/xml/spring-beans-2.5.xsd
http\://www.springframework.org/schema/beans/spring-beans-3.0.xsd=org/springframework/beans/factory/xml/spring-beans-3.0.xsd
http\://www.springframework.org/schema/beans/spring-beans-3.1.xsd=org/springframework/beans/factory/xml/spring-beans-3.1.xsd
http\://www.springframework.org/schema/beans/spring-beans-3.2.xsd=org/springframework/beans/factory/xml/spring-beans-3.2.xsd
http\://www.springframework.org/schema/beans/spring-beans.xsd=org/springframework/beans/factory/xml/spring-beans-3.2.xsd
http\://www.springframework.org/schema/tool/spring-tool-2.0.xsd=org/springframework/beans/factory/xml/spring-tool-2.0.xsd
http\://www.springframework.org/schema/tool/spring-tool-2.5.xsd=org/springframework/beans/factory/xml/spring-tool-2.5.xsd
http\://www.springframework.org/schema/tool/spring-tool-3.0.xsd=org/springframework/beans/factory/xml/spring-tool-3.0.xsd
http\://www.springframework.org/schema/tool/spring-tool-3.1.xsd=org/springframework/beans/factory/xml/spring-tool-3.1.xsd
http\://www.springframework.org/schema/tool/spring-tool-3.2.xsd=org/springframework/beans/factory/xml/spring-tool-3.2.xsd
http\://www.springframework.org/schema/tool/spring-tool.xsd=org/springframework/beans/factory/xml/spring-tool-3.2.xsd
http\://www.springframework.org/schema/util/spring-util-2.0.xsd=org/springframework/beans/factory/xml/spring-util-2.0.xsd
http\://www.springframework.org/schema/util/spring-util-2.5.xsd=org/springframework/beans/factory/xml/spring-util-2.5.xsd
http\://www.springframework.org/schema/util/spring-util-3.0.xsd=org/springframework/beans/factory/xml/spring-util-3.0.xsd
http\://www.springframework.org/schema/util/spring-util-3.1.xsd=org/springframework/beans/factory/xml/spring-util-3.1.xsd
http\://www.springframework.org/schema/util/spring-util-3.2.xsd=org/springframework/beans/factory/xml/spring-util-3.2.xsd
http\://www.springframework.org/schema/util/spring-util.xsd=org/springframework/beans/factory/xml/spring-util-3.2.xsd
然后根据systemId去对象的位置获取对应xsd文件
为什么要设置EntityResolver呢？如果xml文件不符合xsd文件，则解析时候会报错，spring中对这种错误的情况只是报异常而已
/*
* Copyright 2002-2012 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.util.xml; import org.apache.commons.logging.Log;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException; /**
* Simple {@code org.xml.sax.ErrorHandler} implementation:
* logs warnings using the given Commons Logging logger instance,
* and rethrows errors to discontinue the XML transformation.
*
* @author Juergen Hoeller
* @since 1.2
*/
public class SimpleSaxErrorHandler implements ErrorHandler { private final Log logger; /**
* Create a new SimpleSaxErrorHandler for the given
* Commons Logging logger instance.
*/
public SimpleSaxErrorHandler(Log logger) {
this.logger = logger;
} public void warning(SAXParseException ex) throws SAXException {
logger.warn("Ignored XML validation warning", ex);
} public void error(SAXParseException ex) throws SAXException {
throw ex;
} public void fatalError(SAXParseException ex) throws SAXException {
throw ex;
} }