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你用剑????、我用刀????,好的代码都很烧????,望你不吝出招????!
往往简单的背后都有人为你承担着不简单,Spring 就是这样的家伙!而分析它的源码就像鬼吹灯,需要寻龙、点穴、分金、定位,最后往往受点伤(时间)、流点血(精力)、才能获得宝藏(成果)。
另外鉴于之前分析spring-mybatis、quartz,一篇写了将近2万字,内容过于又长又干,挖藏师好辛苦,看戏的也憋着肾,所以这次分析spring源码分块解读,便于理解、便于消化。
那么,这一篇就从 bean 的加载开始,从 xml 配置文件解析 bean 的定义,到注册到 Spring 的核心类 DefaultListableBeanFactory ,盗墓过程如下;
从上图可以看到从 xml 解析出 bean 到注册完成需要经历过8个核心类以及22个方法跳转流程,这也是本文后面需要重点分析的内容。好!那么就当为了你的钱程一起盗墓吧!
对于源码分析一定要单独列一个简单的工程,一针见血的搞你最需要的地方,模拟、验证、调试。现在这个案例工程还很简单,随着后面分析内容的增加,会不断的扩充。整体工程可以下载,可以关注公众号:bugstack虫洞栈 | 回复:源码分析
itstack-demo-code-spring └── src ├── main │ ├── java │ │ └── org.itstack.demo │ │ └── UserService.java │ └── resources │ └── spring-config.xml └── test └── java └── org.itstack.demo.test └── ApiTest.java
整个 bean 注册过程核心功能包括;配置文件加载、工厂创建、XML解析、Bean定义、Bean注册,执行流程如下;
从上图的注册 bean 流程看到,核心类包括;
好!摸金分金定穴完事,搬山的搬山、卸岭的卸岭,开始搞!
UserService.java & 定义一个 bean,Spring 万物皆可 bean
public class UserService { public String queryUserInfo(Long userId) { return "花花 id:" + userId; } }
spring-config.xml & 在 xml 配置 bean 内容
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd" default-autowire="byName"> <bean id="userService" class="org.itstack.demo.UserService" scope="singleton"/> </beans>
ApiTest.java & 单元测试类
@Test public void test_XmlBeanFactory() { BeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource("spring-config.xml")); UserService userService = beanFactory.getBean("userService", UserService.class); logger.info("测试结果:{}", userService.queryUserInfo(1000L)); } @Test public void test_ClassPathXmlApplicationContext() { BeanFactory beanFactory = new ClassPathXmlApplicationContext("spring-config.xml"); UserService userService = beanFactory.getBean("userService", UserService.class); logger.info("测试结果:{}", userService.queryUserInfo(1000L)); }
两个单测方法都可以做结果输出,但是 XmlBeanFactory 已经标记为 @Deprecated 就是告诉我们这个墓穴啥也没有了,被盗过了,别看了。好!我们也不看他了,我们看现在推荐的2号墓 ClassPathXmlApplicationContext
如上不出意外正确结果如下;
23:34:24.699 [main] INFO org.itstack.demo.test.ApiTest - 测试结果:花花 id:1000 Process finished with exit code 0
在整个 bean 的注册过程中,xml 解析是非常大的一块,也是非常重要的一块。如果顺着 bean 工厂初始化分析,那么一层层扒开,就像陈玉楼墓穴挖到一半,遇到大蜈蚣一样难缠。所以我们先把蜈蚣搞定!
@Test public void test_DocumentLoader() throws Exception { // 设置资源 EncodedResource encodedResource = new EncodedResource(new ClassPathResource("spring-config.xml")); // 加载解析 InputSource inputSource = new InputSource(encodedResource.getResource().getInputStream()); DocumentLoader documentLoader = new DefaultDocumentLoader(); Document doc = documentLoader.loadDocument(inputSource, new ResourceEntityResolver(new PathMatchingResourcePatternResolver()), new DefaultHandler(), 3, false); // 输出结果 Element root = doc.getDocumentElement(); NodeList nodeList = root.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (!(node instanceof Element)) continue; Element ele = (Element) node; if (!"bean".equals(ele.getNodeName())) continue; String id = ele.getAttribute("id"); String clazz = ele.getAttribute("class"); String scope = ele.getAttribute("scope"); logger.info("测试结果 beanName:{} beanClass:{} scope:{}", id, clazz, scope); } }
可能初次看这段代码还是有点晕的,但这样提炼出来单独解决,至少给你一种有抓手的感觉。在 spring 解析 xml 时候首先是将配置资源交给 ClassPathResource ,再通过构造函数传递给 EncodedResource;
private EncodedResource(Resource resource, String encoding, Charset charset) { super(); Assert.notNull(resource, "Resource must not be null"); this.resource = resource; this.encoding = encoding; this.charset = charset; }
以上这个过程还是比较简单的,只是一个初始化过程。接下来是通过 Document 解析处理 xml 文件。这个过程是仿照 spring 创建时候需要的参数信息进行组装,如下;
documentLoader.loadDocument(inputSource, new ResourceEntityResolver(new PathMatchingResourcePatternResolver()), new DefaultHandler(), 3, false); 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); }
通过上面的代码获取 org.w3c.dom.Document, Document 里面此时包含了所有 xml 的各个 Node 节点信息,最后输出节点内容,如下;
Element root = doc.getDocumentElement(); NodeList nodeList = root.getChildNodes();
好!测试一下,正常情况下,结果如下;
23:47:00.249 [main] INFO org.itstack.demo.test.ApiTest - 测试结果 beanName:userService beanClass:org.itstack.demo.UserService scope:singleton Process finished with exit code 0
可以看到的我们的 xml 配置内容已经完完整整的取出来了,接下来就交给 spring 进行处理了。红姑娘、鹧鸪哨、咱们出发!
ClassPathXmlApplicationContext.java & 截取部分代码
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } }
AbstractApplicationContext.java & 部分代码截取
@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // 设置容器初始化 prepareRefresh(); // 让子类进行 BeanFactory 初始化,并且将 Bean 信息 转换为 BeanFinition,最后注册到容器中 // 注意,此时 Bean 还没有初始化,只是配置信息都提取出来了 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); ... } }
AbstractApplicationContext.java & 部分代码截取
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); ConfigurableListableBeanFactory beanFactory = getBeanFactory(); if (logger.isDebugEnabled()) { logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory); } return beanFactory; }
AbstractRefreshableApplicationContext.java & 部分代码截取
protected final void refreshBeanFactory() throws BeansException { if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); } try { DefaultListableBeanFactory beanFactory = createBeanFactory(); beanFactory.setSerializationId(getId()); customizeBeanFactory(beanFactory); loadBeanDefinitions(beanFactory); synchronized (this.beanFactoryMonitor) { this.beanFactory = beanFactory; } } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } }
AbstractXmlApplicationContext.java & 部分代码截取
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { // Create a new XmlBeanDefinitionReader for the given BeanFactory. XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); // Configure the bean definition reader with this context's // resource loading environment. beanDefinitionReader.setEnvironment(this.getEnvironment()); beanDefinitionReader.setResourceLoader(this); beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this)); // Allow a subclass to provide custom initialization of the reader, // then proceed with actually loading the bean definitions. initBeanDefinitionReader(beanDefinitionReader); loadBeanDefinitions(beanDefinitionReader); }
AbstractXmlApplicationContext.java & 部分代码截取
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { Resource[] configResources = getConfigResources(); if (configResources != null) { reader.loadBeanDefinitions(configResources); } String[] configLocations = getConfigLocations(); if (configLocations != null) { reader.loadBeanDefinitions(configLocations); } }
AbstractBeanDefinitionReader.java & 部分代码截取
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException { Assert.notNull(locations, "Location array must not be null"); int counter = 0; for (String location : locations) { counter += loadBeanDefinitions(location); } return counter; }
AbstractBeanDefinitionReader.java & 部分代码截取
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException { return loadBeanDefinitions(location, null); }
AbstractBeanDefinitionReader.java & 部分代码截取
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException { ResourceLoader resourceLoader = getResourceLoader(); if (resourceLoader == null) { throw new BeanDefinitionStoreException( "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available"); } if (resourceLoader instanceof ResourcePatternResolver) { // Resource pattern matching available. try { Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location); int loadCount = loadBeanDefinitions(resources); if (actualResources != null) { for (Resource resource : resources) { actualResources.add(resource); } } if (logger.isDebugEnabled()) { logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]"); } return loadCount; } catch (IOException ex) { throw new BeanDefinitionStoreException( "Could not resolve bean definition resource pattern [" + location + "]", ex); } } else { // Can only load single resources by absolute URL. Resource resource = resourceLoader.getResource(location); int loadCount = loadBeanDefinitions(resource); if (actualResources != null) { actualResources.add(resource); } if (logger.isDebugEnabled()) { logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]"); } return loadCount; } }
XmlBeanDefinitionReader.java & 部分代码截取
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { // 判断验证 ... try { InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); if (encodedResource.getEncoding() != null) { inputSource.setEncoding(encodedResource.getEncoding()); } return doLoadBeanDefinitions(inputSource, encodedResource.getResource()); } finally { inputStream.close(); } } catch (IOException ex) { throw new BeanDefinitionStoreException( "IOException parsing XML document from " + encodedResource.getResource(), ex); } finally { currentResources.remove(encodedResource); if (currentResources.isEmpty()) { this.resourcesCurrentlyBeingLoaded.remove(); } } }
XmlBeanDefinitionReader.java & 部分代码截取
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException { try { Document doc = doLoadDocument(inputSource, resource); return registerBeanDefinitions(doc, resource); } catch(){} }
DefaultBeanDefinitionDocumentReader.java & 部分代码截取
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) { this.readerContext = readerContext; logger.debug("Loading bean definitions"); Element root = doc.getDocumentElement(); doRegisterBeanDefinitions(root); }
DefaultBeanDefinitionDocumentReader.java & 部分代码截取
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate deleg 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)) { parseDefaultElement(ele, delegate); } else { delegate.parseCustomElement(ele); } } } } else { delegate.parseCustomElement(root); } }
DefaultBeanDefinitionDocumentReader.java & 部分代码截取
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }
DefaultBeanDefinitionDocumentReader.java & 部分代码截取
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // 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)); } }
BeanDefinitionReaderUtils.java & 部分代码截取
public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } }
DefaultListableBeanFactory.java & 部分代码截取
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName); if (existingDefinition != null) { ... } else { ... else { // Still in startup registration phase this.beanDefinitionMap.put(beanName, beanDefinition); this.beanDefinitionNames.add(beanName); this.manualSingletonNames.remove(beanName); } this.frozenBeanDefinitionNames = null; } if (existingDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } }
源码853行: 这就是最终我们将 xml 中的配置信息注册到了配置中心,beanDefinitionMap,同时还会写入到 beanDefinitionNames
看下最终的注入结果,嗯!我们的盗墓挖到了一点宝物;