通过 Debug 运行 XmlBeanDefinitionReaderTests 类的 withFreshInputStream() 的方法，调试 Spring 解析 XML 配置文件，获得 Bean 的定义。
大体流程可根据序号查看，xml 配置文件随便看一眼，不用过多在意。
I have no properties and I'm happy without them. aliased aliased aliased Rod 31 Roderick Kerry 34 Kathy 28 typeMismatch 34x true true false listenerVeto 66 this is a ]]>
@Test
public void withFreshInputStream() {
// TODO 1.创建 SimpleBeanDefinitionRegistry 对象，提供注册BeanDefinition功能
SimpleBeanDefinitionRegistry registry = new SimpleBeanDefinitionRegistry();
// TODO 2.获取配置文件
Resource resource = new ClassPathResource("test.xml", getClass());
// TODO 3.创建 XmlBeanDefinitionReader 对象，提供读取 XMl 文件中的 Bean 的定义信息；
new XmlBeanDefinitionReader(registry).loadBeanDefinitions(resource);
// TODO 30.验证 BeanDefinitions 信息；
testBeanDefinitions(registry);
System.out.println("success");
}
private void testBeanDefinitions(BeanDefinitionRegistry registry) {
assertThat(registry.getBeanDefinitionCount()).isEqualTo(24);
assertThat(registry.getBeanDefinitionNames().length).isEqualTo(24);
assertThat(Arrays.asList(registry.getBeanDefinitionNames()).contains("rod")).isTrue();
assertThat(Arrays.asList(registry.getBeanDefinitionNames()).contains("aliased")).isTrue();
assertThat(registry.containsBeanDefinition("rod")).isTrue();
assertThat(registry.containsBeanDefinition("aliased")).isTrue();
assertThat(registry.getBeanDefinition("rod").getBeanClassName()).isEqualTo(TestBean.class.getName());
assertThat(registry.getBeanDefinition("aliased").getBeanClassName()).isEqualTo(TestBean.class.getName());
assertThat(registry.isAlias("youralias")).isTrue();
String[] aliases = registry.getAliases("aliased");
assertThat(aliases.length).isEqualTo(2);
assertThat(ObjectUtils.containsElement(aliases, "myalias")).isTrue();
assertThat(ObjectUtils.containsElement(aliases, "youralias")).isTrue();
}
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
// TODO 4.将读取的XML资源进行特殊的编码处理
return loadBeanDefinitions(new EncodedResource(resource));
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Loading XML bean definitions from " + encodedResource);
}
Set currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
// TODO 5. 将资源文件转为InputStream的I/O流
try (InputStream inputStream = encodedResource.getResource().getInputStream()) { // TODO 只有是Closeable的子类才能这样书写，有点是系统会自动帮助我们关闭
// TODO 从InputStream中得到XML的解析源
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// TODO 6.具体读取过程
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
// TODO 29.
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
// TODO 7. 加载Bean配置信息，并转换为文档对象
Document doc = doLoadDocument(inputSource, resource);
// TODO 8. 对Bean定义进行解析
int count = registerBeanDefinitions(doc, resource);
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + count + " bean definitions from " + resource);
}
return count;
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (SAXParseException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
}
catch (SAXException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"XML document from " + resource + " is invalid", ex);
}
catch (ParserConfigurationException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Parser configuration exception parsing XML from " + resource, ex);
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"IOException parsing XML document from " + resource, ex);
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Unexpected exception parsing XML document from " + resource, ex);
}
}
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
// TODO 9.得到BeanDefinitionDoucumentReader来对XML格式的BeanDefinition进行解析
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
// TODO 10.获得容器中注册的Bean数量
int countBefore = getRegistry().getBeanDefinitionCount();
// TODO 11. 解析过程的入口，这里使用了委派模式，BeanDefinitionDocumentReader只是一个接口
// TODO 具体的解析过程由实现类DefaultBeanDefinitionDocumentReader完成
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
// TODO 28. 统计解析的Bean数量
return getRegistry().getBeanDefinitionCount() - countBefore;
}
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
// TODO 获得XML描述符
this.readerContext = readerContext;
// TODO 12. doc.getDocumentElement() 获的Document根元素
doRegisterBeanDefinitions(doc.getDocumentElement());
}
@SuppressWarnings("deprecation") // for Environment.acceptsProfiles(String...)
protected void doRegisterBeanDefinitions(Element root) {
// Any nested elements will cause recursion in this method. In
// order to propagate and preserve default-* attributes correctly,
// keep track of the current (parent) delegate, which may be null. Create
// the new (child) delegate with a reference to the parent for fallback purposes,
// then ultimately reset this.delegate back to its original (parent) reference.
// this behavior emulates a stack of delegates without actually necessitating one.
// TODO 具体的解析过程由BeanDefinitionParserDelegate实现
// TODO BeanDefinitionParserDelegate中定义了Spring Bean定义XML文件的各元素
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = createDelegate(getReaderContext(), root, parent);
// TODO 校验是否引入 beans schemaLocation
if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
// We cannot use Profiles.of(...) since profile expressions are not supported
// in XML config. See SPR-12458 for details.
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (logger.isDebugEnabled()) {
logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}
// TODO 在解析Bean定义之前，进行自定义解析，增强解析过程的可扩展性
preProcessXml(root);
// TODO 12.从文档的根元素开始进行Bean定义的文档对象的解析
parseBeanDefinitions(root, this.delegate);
// TODO 27.在解析Bean定义之后，进行自定义解析，增强解析过程的可扩展性
postProcessXml(root);
this.delegate = parent;
}
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
// TODO 13. Bean定义的文档对象使用了Spring默认的XML命名空间
if (delegate.isDefaultNamespace(root)) {
// TODO 14. 获取Bean定义的文档对象根元素的所有子节点
NodeList nl = root.getChildNodes();
// TODO 此处是循环,忽略需要，需要是大体执行流程不是唯一
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
// TODO 15. 获得的文档节点是XML元素节点
if (node instanceof Element ele) {
// TODO 16. Bean定义的文档的元素节点使用的是Spring默认的XML命名空间
if (delegate.isDefaultNamespace(ele)) {
// TODO 17. 使用Spring的Bean规则解析元素节点
parseDefaultElement(ele, delegate);
}
else {
// TODO 如果没有使用Spring默认的XMl命名空间，则使用用户自定义的规则解析元素节点
delegate.parseCustomElement(ele);
}
}
}
}
else {
// TODO 如果没有使用Spring默认的XMl命名空间，则使用用户自定义的规则解析元素节点
delegate.parseCustomElement(root);
}
}
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
// TODO 18.如果节点是导入元素，进行导入元素解析
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
// TODO 19.如果节点是别名元素，进行别名解析
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
// TODO 20.如果节点是元素，则按照Spring的Bean规则解析元素
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
// TODO 如果节点是元素，则按照Spring的Bean规则解析元素
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
// TODO 21. BeanDefinitionHolder是对BeanDefinition的封装，即Bean定义的封装类
// TODO 对文档对象中元素的解析由BeanDefinitionParserDelegate实现
// TODO BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// 22.Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
// TODO 26.在完成向Spring Ioc容器注册解析得到的Bean定义之后，发送注册事件
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
// TODO 获取解析的beanDefinition的名称
String beanName = definitionHolder.getBeanName();
// TODO 23.向Spring Ioc容器注册BeanDefinition
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
// TODO 25.如果解析的BeanDefinition有别名，向Spring Ioc容器注册别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "'beanName' must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
// TODO 24.存储 BeanDefinition
this.beanDefinitionMap.put(beanName, beanDefinition);
}
