Spring实现默认标签解析流程
作者：大大明001
这篇文章主要为大家详细介绍了Spring实现默认标签解析流程，文中示例代码介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
本文实例为大家分享了Spring实现默认标签解析流程的具体代码，供大家参考，具体内容如下
承接上文，进入parseBeanDefinitions（）方法
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
//默认标签解析，此次着重分析这个方法
parseDefaultElement(ele, delegate);
}
else {
//自定义标签解析
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}-进入parseDefaultElement（）方法,此方法在parseBeanDefinitions的下方
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//import标签解析 ，可看可不看
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//alias标签解析 别名标签 可看可不看
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//bean标签，重要（看这个方法）
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
//beans标签，不重要
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}-进入到bean标签解析方法
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//重点看这个方法 ，解析document，封装成BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//完成document到BeanDefinition对象转换后，对BeanDefinition对象进行缓存注册
// 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.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}进入
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
//思考一下这个的第二个参数为啥要传入null（BeanDefinition类型），进入方法
return parseBeanDefinitionElement(ele, null);
}打开parseBeanDefinitionElement方法
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
//获取id
String id = ele.getAttribute(ID_ATTRIBUTE);
//获取别名
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
//将别名添加到aliases内
List<String> aliases = new ArrayList<>();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}
String beanName = id;
if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
beanName = aliases.remove(0);
if (logger.isTraceEnabled()) {
logger.trace("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}
//检查beanName是否重复
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
//<bean>标签解析的核心方法
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
......不重要的就不要看了，浪费时间
}
return null;
}看核心方法parseBeanDefinitionElement
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, @Nullable BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
try {
//创建GenericBeanDefinition对象
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
//解析bean标签的属性，并把解析出来的属性设置到BeanDefinition对象中
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
//解析bean中的meta标签
parseMetaElements(ele, bd);
//解析bean中的lookup-method标签 ，可看可不看
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
//解析bean中的replaced-method标签 ，可看可不看
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//解析bean中的constructor-arg标签 ，可看可不看
parseConstructorArgElements(ele, bd);
//解析bean中的property标签 可看可不看
parsePropertyElements(ele, bd);
//可以不看，用不到
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
}
......有兴趣自己看
return null;
}打开这个方法parseBeanDefinitionAttributes（），对BeanDefinition属性进行默认的封装，然后返回BeanDefinition对象
public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName,
@Nullable BeanDefinition containingBean, AbstractBeanDefinition bd) {
//
if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
error("Old 1.x 'singleton' attribute in use - upgrade to 'scope' declaration", ele);
}
else if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE));
}
else if (containingBean != null) {
// Take default from containing bean in case of an inner bean definition.
bd.setScope(containingBean.getScope());
}
if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
}
String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
if (isDefaultValue(lazyInit)) {
lazyInit = this.defaults.getLazyInit();
}
bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
bd.setAutowireMode(getAutowireMode(autowire));
if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) {
String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE);
bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, MULTI_VALUE_ATTRIBUTE_DELIMITERS));
}
String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE);
if (isDefaultValue(autowireCandidate)) {
String candidatePattern = this.defaults.getAutowireCandidates();
if (candidatePattern != null) {
String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern);
bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName));
}
}
else {
bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate));
}
if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
}
if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) {
String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE);
bd.setInitMethodName(initMethodName);
}
else if (this.defaults.getInitMethod() != null) {
bd.setInitMethodName(this.defaults.getInitMethod());
bd.setEnforceInitMethod(false);
}
if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) {
String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE);
bd.setDestroyMethodName(destroyMethodName);
}
else if (this.defaults.getDestroyMethod() != null) {
bd.setDestroyMethodName(this.defaults.getDestroyMethod());
bd.setEnforceDestroyMethod(false);
}
if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
}
if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
}
return bd;
}然后回到processBeanDefinition方法，将BeanDefinition注册到缓存中，此时看
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//重点看这个方法，重要程度 5 ，解析document，封装成BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
//该方法功能不重要，设计模式重点看一下，装饰者设计模式，加上SPI设计思想
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//完成document到BeanDefinition对象转换后，对BeanDefinition对象进行缓存注册
// 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.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}打开registerBeanDefinition方法
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
//完成BeanDefinition的注册，重点看
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
//建立别名和 id的映射，这样就可以根据别名获取到id
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}打开registerBeanDefinition方法，将创建好的beanDefinition存入map。默认标签解析就此完毕
@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");
this.beanDefinitionMap.put(beanName, beanDefinition);
}以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。