前言
接着上次的spring上下文加载过程的源码解析
正文
上次主要介绍到刷新beanFactory，找到这个方法org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory的这行代码
@Override
protected final void refreshBeanFactory() throws BeansException {
// 如果存在beanFactory
if (hasBeanFactory()) {
// 销毁bean
destroyBeans();
// 关闭beanFactory
closeBeanFactory();
}
bean销毁介绍完了，找到这行代码
closeBeanFactory();
@Override
protected final void closeBeanFactory() {
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory != null) {
this.beanFactory.setSerializationId(null);
this.beanFactory = null;
}
}
}
操作beanFactory是同步的。
找到这行代码，创建banFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
protected DefaultListableBeanFactory createBeanFactory() {
return new DefaultListableBeanFactory(getInternalParentBeanFactory());
}
@Nullable
protected BeanFactory getInternalParentBeanFactory() {
// 如果父上下文是配置上下文
return (getParent() instanceof ConfigurableApplicationContext) ?
((ConfigurableApplicationContext) getParent()).getBeanFactory() : getParent();
}
返回到这个方法
org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory
customizeBeanFactory(beanFactory);
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
// 是否允许bean定义覆盖
if (this.allowBeanDefinitionOverriding != null) {
beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
// 是否允许bean之间循环引用
if (this.allowCircularReferences != null) {
beanFactory.setAllowCircularReferences(this.allowCircularReferences);
}
}
返回到这个方法
org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory
loadBeanDefinitions(beanFactory);
这一行代码，加载bean定义。
进入到这个方法
org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions(org.springframework.beans.factory.support.DefaultListableBeanFactory)通过XmlBeanDefinitionReader加载bean定义。
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.为给定的BeanFactory创建一个新的XmlBeanDefinitionReader。
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.使用该上下文的资源加载环境配置bean定义阅读器。
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.允许子类提供读取器的自定义初始化，然后继续加载bean定义。
initBeanDefinitionReader(beanDefinitionReader);
// 加载bean定义
loadBeanDefinitions(beanDefinitionReader);
}
// 加载资源 beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
public ResourceEntityResolver(ResourceLoader resourceLoader) {
super(resourceLoader.getClassLoader());
this.resourceLoader = resourceLoader;
}
进入调用了父类构造器的方法
public DelegatingEntityResolver(@Nullable ClassLoader classLoader) {
// 创建DTD解析器
this.dtdResolver = new BeansDtdResolver();
// 创建schema解析器
this.schemaResolver = new PluggableSchemaResolver(classLoader);
}
可以看到解析的是这个DTD
public class BeansDtdResolver implements EntityResolver {
// dtd解析
private static final String DTD_EXTENSION = ".dtd";
private static final String DTD_NAME = "spring-beans";
public PluggableSchemaResolver(@Nullable ClassLoader classLoader) {
this.classLoader = classLoader;
this.schemaMappingsLocation = DEFAULT_SCHEMA_MAPPINGS_LOCATION;
}
org.springframework.beans.factory.xml.PluggableSchemaResolver
// spring.schemas解析，这个路径下面的schemas都会被解析 META-INF/spring.schemas public static final String DEFAULT_SCHEMA_MAPPINGS_LOCATION = "META-INF/spring.schemas";
从这个地方加载的schema
找到这个方法
org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions(org.springframework.beans.factory.support.DefaultListableBeanFactory)的这行代码
// 初始化bean定义 initBeanDefinitionReader(beanDefinitionReader);
// 加载bean定义 loadBeanDefinitions(beanDefinitionReader);
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);
}
}
// 获取配置文件路径 String[] configLocations = getConfigLocations();
@Nullable
protected String[] getConfigLocations() {
return (this.configLocations != null ? this.configLocations : getDefaultConfigLocations());
}
我们看下configLocations变量在哪里赋值的
public void setConfigLocation(String location) {
setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS));
}
我们看下location变量在哪里赋值的
找到了这个方法org.springframework.web.context.ContextLoader#configureAndRefreshWebApplicationContext
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocationParam != null) {
wac.setConfigLocation(configLocationParam);
}
public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";
是从servlet容器启动时初始化的参数配置中获取的
返回到这个方法
org.springframework.context.support.AbstractRefreshableConfigApplicationContext#setConfigLocation
public void setConfigLocation(String location) {
setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS));
}
看下这个常量org.springframework.context.ConfigurableApplicationContext#CONFIG_LOCATION_DELIMITERS
String CONFIG_LOCATION_DELIMITERS = ",; \t\n";
bean定义配置文件可以是,或;或空格或换行符分开都可以。
进入到这个方法
org.springframework.context.support.AbstractRefreshableConfigApplicationContext#setConfigLocations
public void setConfigLocations(@Nullable String... locations) {
if (locations != null) {
Assert.noNullElements(locations, "Config locations must not be null");
this.configLocations = new String[locations.length];
for (int i = 0; i < locations.length; i++) {
this.configLocations[i] = resolvePath(locations[i]).trim();
}
}
else {
this.configLocations = null;
}
}
// 解析配置文件后把配置文件路径放到spring上下文中 this.configLocations[i] = resolvePath(locations[i]).trim();
bean定义配置文件中如果有占位符就替换占位符
protected String resolvePath(String path) {
return getEnvironment().resolveRequiredPlaceholders(path);
}
@Override
public String resolveRequiredPlaceholders(String text) throws IllegalArgumentException {
if (this.strictHelper == null) {
this.strictHelper = createPlaceholderHelper(false);
}
// 替换占位符
return doResolvePlaceholders(text, this.strictHelper);
}
返回到这个方法
org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions(org.springframework.beans.factory.xml.XmlBeanDefinitionReader)的这一行代码
// 加载bean定义 reader.loadBeanDefinitions(configLocations);
@Override
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;
}
org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions(java.lang.String)
@Override
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}
org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions(java.lang.String, java.util.Set<org.springframework.core.io.Resource>)
这段代码
// 从classpath下面加载
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);
}
}
找到这行代码
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
进入到这个方法
org.springframework.core.io.support.PathMatchingResourcePatternResolver#getResources
@Override
public Resource[] getResources(String locationPattern) throws IOException {
Assert.notNull(locationPattern, "Location pattern must not be null");
// 配置路径以classpath*:开头
if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
// a class path resource (multiple resources for same name possible)
if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
// a class path resource pattern 从classpath*路径下匹配的的jar，war包等文件中查找配置文件
return findPathMatchingResources(locationPattern);
}
else {
// all class path resources with the given name 从classpath下面加载jar、war文件中的配置文件
return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
}
}
else {
// Generally only look for a pattern after a prefix here,
// and on Tomcat only after the "*/" separator for its "war:" protocol.
int prefixEnd = (locationPattern.startsWith("war:") ? locationPattern.indexOf("*/") + 1 :
locationPattern.indexOf(':') + 1);
if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
// a file pattern
return findPathMatchingResources(locationPattern);
}
else {
// a single resource with the given name
return new Resource[] {getResourceLoader().getResource(locationPattern)};
}
}
}
返回到这个方法
org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions(java.lang.String, java.util.Set<org.springframework.core.io.Resource>)
递归调用 int loadCount = loadBeanDefinitions(resources);
@Override
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
for (Resource resource : resources) {
counter += loadBeanDefinitions(resource);
}
return counter;
}
org.springframework.beans.factory.xml.XmlBeanDefinitionReader#loadBeanDefinitions(org.springframework.core.io.Resource)
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
return loadBeanDefinitions(new EncodedResource(resource));
}
org.springframework.beans.factory.xml.XmlBeanDefinitionReader#loadBeanDefinitions(org.springframework.core.io.support.EncodedResource)
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
// resourcesCurrentlyBeingLoaded threadLocal保证线程安全
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()) {
// 防止内存泄漏
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
找到这行代码
// 加载bean定义 return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
内容太多，下篇文章接着解析。
最后
本次介绍到这里，以上内容仅供参考。大家从spring源码解析第一篇文章开始看，更容易点，否则可读性可能不台好，因为spring源码体系太庞大，不太好归类，按每篇文章的篇幅不太好拆分。
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