spring 源码解析
BeanFactory 的创建阶段
示例代码
main 函数
public static void main(String[] args) {
@SuppressWarnings("resource")
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
App app = (App) applicationContext.getBean("app");
app.say();
}
App.java 示例类代码
public class App {
public void say() {
System.out.println("App.app()");
}
}
applicationContext.xml 示例配置文件
<?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.xsd">
<bean id="app" class="com.mycompany.app.App"></bean>
</beans>
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.app</groupId>
<artifactId>myapp</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>myapp</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>5.0.0.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
</project>
开始
14行创建 ClassPathXmlApplicationContext 实例打断点。
调用顺序
1.new ClassPathXmlApplicationContext(String configLocation)调用内部构造器
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
--->this(new String[] {configLocation}, true, null);
}
2.this(new String[] {configLocation}, true, null)
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
// 替换配置文件路径中的占位符,并将其保存
setConfigLocations(configLocations);
if (refresh) {
// 重点分析 refresh 方法
----->refresh();
}
}
3.refresh()
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 准备上下文进行刷新,准备工作包括设置启动时间,是否激活标识位,初始化属性源(property source)配置
prepareRefresh();
// 本次分析的重点 创建beanFactory
//(过程是根据 xml 为每个 bean 生成 BeanDefinition 并注册到生成的 beanFactory 的 beanDefinitionMap 中)
----------->ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 其他代码.....
}
4.obtainFreshBeanFactory()
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 刷新 beanFactory
--->refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
5.refreshBeanFactory()
/**
*官方注释 subclasses must implement this method to perform the actual configuration load.
* 子类必须实现这个方法才能进行配置的加载
*/
protected final void refreshBeanFactory() throws BeansException {
//如果已经存在 beanFactory ,销毁所有的 bean ,然后将该 beanFactory 关闭
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
// 创建一个 beanfactory ,并进行初始化
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
// 加载 beanDefinitions bean定义
---------->loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
6.loadBeanDefinitions(DefaultListableBeanFactory beanFactory)
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 使用 beanFactory 创建一个 xml 的 bean 定义读取器 , 因为 beanfactory 实现了BeanDefinitionRegistry 接口,所以此处可以使用它来new
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// 读取器的配置及初始化
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
initBeanDefinitionReader(beanDefinitionReader);
// 使用创建的 reader 加载 bean定义
--->loadBeanDefinitions(beanDefinitionReader);
}
7.loadBeanDefinitions(XmlBeanDefinitionReader reader)
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
// 此处 getConfigLocations() 返回的就是
// 在步骤二 setConfigLocations(configLocations)中保存的 configLocations
// 也就是在 main() 函数中 传入的配置文件路径参数
String[] configLocations = getConfigLocations();
if (configLocations != null) {
// 使用 configLocations 加载beanDefinions
-------->reader.loadBeanDefinitions(configLocations);
}
}
8.loadBeanDefinitions(String… locations)
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
for (String location : locations) {
// 从指定的位置加载 bean 定义 ,并计数
------>counter += loadBeanDefinitions(location);
}
return counter;
}
9.loadBeanDefinitions(String location)
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
------->return loadBeanDefinitions(location, null);
}
10.loadBeanDefinitions(String location, @Nullable Set actualResources)
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
// 从指定路径加载 bean 定义
--------------->int count = loadBeanDefinitions(resources);
if (actualResources != null) {
Collections.addAll(actualResources, resources);
}
if (logger.isTraceEnabled()) {
logger.trace("Loaded " + count + " bean definitions from location pattern [" + location + "]");
}
return count;
}
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 count = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isTraceEnabled()) {
logger.trace("Loaded " + count + " bean definitions from location [" + location + "]");
}
return count;
}
}
11.loadBeanDefinitions(Resource… resources)
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int count = 0;
for (Resource resource : resources) {
// 从指定路径加载 bean 定义
------->count += loadBeanDefinitions(resource);
}
return count;
}
12.loadBeanDefinitions(Resource resource)
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//使用指定编码加载 bean 定义
--->return loadBeanDefinitions(new EncodedResource(resource));
}
13.loadBeanDefinitions(EncodedResource encodedResource)
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<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 加载 bean 定义
------->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();
}
}
}
14.doLoadBeanDefinitions(InputSource inputSource, Resource resource)
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
// 加载文档
Document doc = doLoadDocument(inputSource, resource);.
// 注册 bean 定义
----------->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);
}
}
15.registerBeanDefinitions(Document doc, Resource resource)
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
// 注册 bean 定义
--->documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
16.registerBeanDefinitions(Document doc, XmlReaderContext readerContext)
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
// 使用文档注册bean
--->doRegisterBeanDefinitions(doc.getDocumentElement());
}
17.doRegisterBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate)
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)) {
//循环bean.xml中定义的每一个元素
------------------>parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
18.parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate)
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
// 对标签<bean><import>等等,分别解析
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
// 解析 bean 标签
------->processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
19.processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate)
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// 注册最终修饰的实例。
----------->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));
}
}
20.registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// 在主名称(真实名字,区别于别名)下注册bean定义
String beanName = definitionHolder.getBeanName();
--->registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// 如果有别名,注册别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
21.registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
@Override
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);
}
}
// 判断系统中是否存在该 name 的 bean
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
// 如果存在,检测是否允许覆盖
if (existingDefinition != null) {
// 不允许覆盖,抛异常
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
// 覆盖之前的 bean
---------->this.beanDefinitionMap.put(beanName, beanDefinition);
}
// 如果 容器中 不存在该 bean ,放入容器中
else {
// 如果注册已经开始
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
//因为beanDefinitionMap是全局变量,这里定会存在并发访问的情况
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
removeManualSingletonName(beanName);
}
}
else {
// Still in startup registration phase
-------------->this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
// 重置所有beanName对应的缓存
resetBeanDefinition(beanName);
}
}
过程总结
Spring BeanFactory 创建 基本流程就三步
- 创建 beanFactory
- 解析文档生成 beanDefinition
- 将解析生成的 beanDefinition 放入 map 中保存起来为 bean 的实例化做准备