https://github.com/seaswalker/Spring
使用版本spring4.2.2或者4.1.1
基本
本部分从最基本的Spring开始。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-3.0.xsd
">
<
bean
class
=
"
base.SimpleBean
"
></
bean
>
</
beans
>
###原作者没有写beans的命名空间及约束 导致xml验证失败，这里加上了
###bean部分就是类的引用地址
启动代码:
public
static
void
main(
String
[] args) {
ClassPathXmlApplicationContext
context
=
new
ClassPathXmlApplicationContext
(
"
config.xml
"
);
SimpleBean
bean
=
context
.
getBean(
SimpleBean
.
class);
bean
.
send();
context
.
close();
}
SimpleBean:
public
class
SimpleBean
{
public
void
send
() {
System
.
out
.
println(
"
I am send method from SimpleBean!
"
);
}
}
ClassPathXmlApplicationContext
整个继承体系如下:
ResourceLoader代表了 加载资源的一种方式，正是策略模式的实现 。
构造器源码:
public ClassPathXmlApplicationContext(
String
[] configLocations,
boolean
refresh,
ApplicationContext
parent) {
// null
super (parent);
setConfigLocations(configLocations);
// 默认true
if (refresh) {
refresh();
}
}
ClassPathXmlApplicationContext context = new
ClassPathXmlApplicationContext
(
"
config.xml
"
); 调用只会是上述两个方法其中一个，这里明显是
ClassPathXmlApplicationContext(String configLocation)
后面实际调用的都是本类的这个方法，如下图：
其实ClassPathXmlApplicationContext类里面的构造器（包括无参的共有9个在这个版本）。
构造器
AbstractApplicationContext
首先看父类构造器，沿着继承体系一直向上调用，直到AbstractApplicationContext:
public AbstractApplicationContext( ApplicationContext parent) {
this ();
setParent(parent);
}
public AbstractApplicationContext() {
this . resourcePatternResolver = getResourcePatternResolver();
}
PathMatchingResourcePatternResolver支持Ant风格的路径解析。下面简单概述下ant风格路径.
设置配置文件路径
即 AbstractRefreshableConfigApplicationContext. setConfigLocations:
public void setConfigLocations( 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 ;
}
}
resolvePath:
protected String resolvePath( String path) {
return getEnvironment() . resolveRequiredPlaceholders(path);
}
此方法的目的在于将占位符(placeholder)解析成实际的地址。比如可以这么写: new ClassPathXmlApplicationContext("classpath:config.xml"); 那么classpath:就是需要被解析的。
getEnvironment方法来自于ConfigurableApplicationContext接口，源码很简单，如果为空就调用createEnvironment创建一个。AbstractApplicationContext.createEnvironment:
protected ConfigurableEnvironment createEnvironment() {
return new StandardEnvironment ();//看下面的继承关系可以知道 StandardEnvironment是 ConfigurableEnvironment的实现类
}
Environment接口
继承体系:
Environmen接口**代表了当前应用所处的环境。**从此接口的方法可以看出，其主要和profile、Property相关。
Profile
Spring Profile特性是从3.1开始的，其主要是为了解决这样一种问题: 线上环境和测试环境使用不同的配置或是数据库或是其它。有了Profile便可以在 不同环境之间无缝切换。**Spring容器管理的所有bean都是和一个profile绑定在一起的。**使用了Profile的配置文件示例:
在启动代码中可以用如下代码设置活跃(当前使用的)Profile:
context . getEnvironment() . setActiveProfiles( " dev
"
);
当然使用的方式还有很多(比如注解)，参考:
spring3.1 profile 配置不同的环境 （打开失败）
Property
这里的Property指的是程序运行时的一些参数，引用注释:
properties files, JVM system properties, system environment variables, JNDI, servlet context parameters, ad-hoc Properties objects,Maps, and so on.
Environment实现类 AbstractEnvironment 构造器
private final MutablePropertySources propertySources = new MutablePropertySources ( this . logger);
public AbstractEnvironment() {
customizePropertySources( this . propertySources);
}
PropertySources接口
继承体系:
此接口实际上是PropertySource的容器，默认的MutablePropertySources实现内部含有一个CopyOnWriteArrayList作为存储载体。
StandardEnvironment.customizePropertySources:
/* * System environment property source name: {@value} */ public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = " systemEnvironment " ;
/* * JVM system properties property source name: {@value} */ public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = " systemProperties " ;
@Override protected void customizePropertySources( MutablePropertySources propertySources) {
propertySources . addLast( new MapPropertySource
( SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME , getSystemProperties()));
propertySources . addLast( new SystemEnvironmentPropertySource
( SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME , getSystemEnvironment()));
}
PropertySource接口
PropertySource接口代表了键值对的Property来源。继承体系：
AbstractEnvironment.getSystemProperties:（此方法在 org.springframework.core.env.AbstractEnvironment里面 ）
@Override public Map< String , Object >
try
return ( Map) System .getProperties();
}
catch ( AccessControlException
return ( Map) new ReadOnlySystemAttributesMap() {
@Override
protected String getSystemAttribute( String attributeName) {
try
return System .getProperty(attributeName);
}
catch ( AccessControlException
if (logger .isInfoEnabled()) {
.info(format( " Caught AccessControlException when accessing system " +
" property [%s]; its value will be returned [null]. Reason: %s ",
.getMessage()));
}
return null;
}
}
};
}
}
这里的实现很有意思，如果安全管理器阻止获取全部的系统属性，那么会尝试获取单个属性的可能性，如果还不行就抛异常了。
getSystemEnvironment方法也是一个套路，不过最终调用的是System.getenv，可以获取jvm和OS的一些版本信息。
路径Placeholder处理
AbstractEnvironment.resolveRequiredPlaceholders:
@Override public String resolveRequiredPlaceholders( String text) throws IllegalArgumentException
// text即配置文件路径，比如classpath:config.xml
return this .propertyResolver .resolveRequiredPlaceholders(text);
}
propertyResolver是一个PropertySourcesPropertyResolver对象:
private final ConfigurablePropertyResolver propertyResolver =
new PropertySourcesPropertyResolver ( this . propertySources);
PropertyResolver接口
PropertyResolver继承体系(排除Environment分支):
路径Placeholder处理
AbstractEnvironment.resolveRequiredPlaceholders:
@Override public String resolveRequiredPlaceholders( String text) throws IllegalArgumentException {
// text即配置文件路径，比如classpath:config.xml
return this . propertyResolver . resolveRequiredPlaceholders(text);
}
propertyResolver是一个PropertySourcesPropertyResolver对象:
private final ConfigurablePropertyResolver propertyResolver =
new PropertySourcesPropertyResolver ( this . propertySources);
PropertyResolver接口
PropertyResolver继承体系(排除Environment分支):
此接口正是用来解析PropertyResource。
解析
AbstractPropertyResolver.resolveRequiredPlaceholders:
@Override public String resolveRequiredPlaceholders( String text) throws IllegalArgumentException
if ( this .strictHelper == null) {
this .strictHelper = createPlaceholderHelper( false);
}
return doResolvePlaceholders(text, this .strictHelper);
}
private PropertyPlaceholderHelper createPlaceholderHelper( boolean ignoreUnresolvablePlaceholders) {
// 三个参数分别是${, }, :
return new PropertyPlaceholderHelper ( this . placeholderPrefix, this . placeholderSuffix,
this . valueSeparator, ignoreUnresolvablePlaceholders);
}
doResolvePlaceholders：
private String doResolvePlaceholders( String text, PropertyPlaceholderHelper helper) {
// PlaceholderResolver接口依然是策略模式的体现
return helper . replacePlaceholders(text, new PropertyPlaceholderHelper . PlaceholderResolver () {
@Override
public String resolvePlaceholder ( String placeholderName ) {
return getPropertyAsRawString(placeholderName);
}
});
}
其实代码执行到这里的时候还没有进行xml配置文件的解析，那么这里的解析placeHolder是什么意思呢，原因在于可以这么写:
System
.
setProperty(
"
spring
"
, "
classpath
"
);
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext
(
"
${spring}:config.xml
"
);
SimpleBean bean = context
.
getBean(
SimpleBean
.
class);
这样就可以正确解析。placeholder的替换其实就是字符串操作，这里只说一下正确的属性是怎么来的。实现的关键在于PropertySourcesPropertyResolver.getProperty:
@Override protected String getPropertyAsRawString( String
return getProperty(key, String .class, false);
}
protected < T > T getProperty( String key, Class< T > targetValueType, boolean
if ( this .propertySources != null) {
for ( PropertySource<?> propertySource : this .propertySources) {
Object value = propertySource .getProperty(key);
return
}
}
return null;
}
很明显了，就是从System.getProperty和System.getenv获取，但是由于环境变量是无法自定义的，所以其实此处只能通过System.setProperty指定。
注意，classpath:XXX这种写法的classpath前缀到目前为止还没有被处理。
refresh
super(parent）和this.setConfigLocations(configLocations);说完 下面说是refresh这个方法
Spring bean解析就在此方法，所以单独提出来。
AbstractApplicationContext.refresh:
作者版本:
@Override public void refresh() throws BeansException , IllegalStateException {
synchronized ( this . startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh
();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
} catch ( BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
} finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
prepareRefresh
protected void
this .startupDate = System .currentTimeMillis();
this .closed .set( false);
this .active .set( true);
// Initialize any placeholder property sources in the context environment
// 空实现
initPropertySources();
// Validate that all properties marked as required are resolvable
// see ConfigurablePropertyResolver#setRequiredProperties
.validateRequiredProperties();
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this .earlyApplicationEvents = new LinkedHashSet< ApplicationEvent >();
}
属性校验
AbstractEnvironment.validateRequiredProperties:
@Override public void validateRequiredProperties() throws MissingRequiredPropertiesException {
this . propertyResolver . validateRequiredProperties();
}
AbstractPropertyResolver.validateRequiredProperties:
@Override public void validateRequiredProperties() {
MissingRequiredPropertiesException ex = new MissingRequiredPropertiesException ();
for ( String key : this . requiredProperties) {
if ( this . getProperty(key) == null ) {
ex . addMissingRequiredProperty(key);
}
}
if ( ! ex . getMissingRequiredProperties() . isEmpty()) {
throw ex;
}
}
requiredProperties是通过setRequiredProperties方法设置的，保存在一个set里面，默认是空的，也就是不需要校验任何属性。
作者说是list集合里，实际是错的，当然也许是版本不同而已。
BeanFactory创建
在refresh的这个方法里面
ConfigurableListableBeanFactory beanFactory = this. obtainFreshBeanFactory ();//下面会讲到这个
this.prepareBeanFactory(beanFactory);
由obtainFreshBeanFactory调用AbstractRefreshableApplicationContext.refreshBeanFactory:（见下图)
(这部分与作者源码一致）
BeanFactory接口
此接口实际上就是Bean容器，其继承体系:
BeanFactory定制
AbstractRefreshableApplicationContext.customizeBeanFactory方法用于给子类提供一个自由配置的机会，默认实现:
protected void customizeBeanFactory( DefaultListableBeanFactory beanFactory) {
if ( this . allowBeanDefinitionOverriding != null ) {
// 默认false，不允许覆盖
beanFactory . setAllowBeanDefinitionOverriding( this . allowBeanDefinitionOverriding);
}
if ( this . allowCircularReferences != null ) {
// 默认false，不允许循环引用
beanFactory . setAllowCircularReferences( this . allowCircularReferences);
}
}
Bean加载
AbstractXmlApplicationContext.loadBeanDefinitions，这个便是核心的bean加载了:
@Override protected void loadBeanDefinitions
(
DefaultListableBeanFactory
beanFactory) {
// 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
));//
为Bean读取器设置SAX xml解析器，
下面会说到这个
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
// 默认空实现
initBeanDefinitionReader(beanDefinitionReader);
loadBeanDefinitions(beanDefinitionReader);
}
EntityResolver
此处只说明用到的部分继承体系:
EntityResolver 接口在org.xml.sax中定义。 DelegatingEntityResolver 用于schema和dtd的解析。
BeanDefinitionReader
继承体系:
路径解析(Ant)
protected void loadBeanDefinitions( XmlBeanDefinitionReader reader) {
Resource [] configResources = getConfigResources();
if (configResources != null ) {
reader . loadBeanDefinitions(configResources);
}
String [] configLocations = getConfigLocations();
// here
if (configLocations != null ) {
reader . loadBeanDefinitions(configLocations);
}
}
AbstractBeanDefinitionReader.loadBeanDefinitions:
下面作者这个肯定是不对的，因为调用了方法一样但参数列表不一样，实际是重载的 loadBeanDefinitions方法 ，上图两个是4.1.1的方法内容，与作者的版本不同。故贴出来。
4.1.1版本与这个稍微有些不同
@Override public int loadBeanDefinitions( String . .. locations) throws BeanDefinitionStoreException
Assert .notNull(locations, " Location array must not be null ");
int counter = 0;
for ( String location :
+=
}
return
}
之后调用:
//第二个参数为空
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = this.getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException("Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
} else {
int loadCount;
if (!(resourceLoader instanceof ResourcePatternResolver)) {
Resource resource = resourceLoader.getResource
(location);
loadCount = this.loadBeanDefinitions((Resource)resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
} else {
try {
Resource[] resources = ((ResourcePatternResolver)resourceLoader). getResources
(location);
loadCount = this.loadBeanDefinitions(resources);
if (actualResources != null) {
Resource[] var6 = resources;
int var7 = resources.length;
for(int var8 = 0; var8 < var7; ++var8) {
Resource resource = var6[var8];
actualResources.add(resource);
}
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
} catch (IOException var10) {
throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", var10);
}
}
}
}
getResources（作者写成 getResource,一字之差缪之千里 ）， 在AbstractApplicationContext. getResources ：
@Override
public Resource [] getResources( String locationPattern) throws IOException {
// 构造器中初始化，PathMatchingResourcePatternResolver对象
return this . resourcePatternResolver . getResources(locationPattern);
}
进入第二个方法，因为第一个是掉本类的方法。
public Resource[] getResources(String locationPattern) throws IOException {
//如果是ResourcePatternResolver
return this .resourceLoader instanceof ResourcePatternResolver ? ((ResourcePatternResolver) this .resourceLoader).getResources(locationPattern) : super .getResources(locationPattern) ;
}
PathMatchingResourcePatternResolver是ResourceLoader继承体系的一部分。
public Resource[] getResources(String locationPattern) throws IOException {
Assert.notNull(locationPattern , "Location pattern must not be null" ) ;
if (locationPattern.startsWith( "classpath*:" )) {
// matcher是一个AntPathMatcher对象
return this .getPathMatcher().isPattern(locationPattern.substring( "classpath*:" .length())) ? this .findPathMatchingResources(locationPattern) : this .findAllClassPathResources(locationPattern.substring( "classpath*:" .length())) ;
} else {
int prefixEnd = locationPattern.indexOf( ":" ) + 1 ;
return this .getPathMatcher(). isPattern
(locationPattern.substring(
prefixEnd
)) ?
this
.findPathMatchingResources(locationPattern) :
new
Resource[]
{ this .getResourceLoader().getResource(locationPattern)} ;
}
}
isPattern:
注:本来以为是数字 ，后面才发现ASCII代表的数字：详情可查 https://baike.baidu.com/item/ASCII/309296?fr=aladdin
十进制指的是42
也经过测试发现是根据十进制的ASCII码参与运算的。
也就是可以这么写:
new ClassPathXmlApplicationContext ( " con*.xml " );
更多的例子
具体怎么解析ant风格的就不写了。
配置文件加载
入口方法在AbstractBeanDefinitionReader:
// 加载 Resource [] resources = (( ResourcePatternResolver ) resourceLoader) . getResources(location);
// 解析 int loadCount = loadBeanDefinitions(resources);
最终逐个调用XmlBeanDefinitionReader的loadBeanDefinitions方法:
Resource是代表一种资源的接口，其类图:
EncodedResource扮演的其实是一个装饰器的模式，为InputStreamSource添加了字符编码(虽然默认为null)。这样为我们自定义xml配置文件的编码方式提供了机会。
之后关键的源码只有两三行:(这个是4.1.1版本中的源码，关键部分为标红的地方)
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (this.logger.isInfoEnabled()) {
this.logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set<EncodedResource> currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!((Set)currentResources).add(encodedResource)) {
throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");
} else {
int var5;
try {
InputStream inputStream = encodedResource.getResource().getInputStream()
;
try {
InputSource inputSource = new InputSource(inputStream)
;
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
var5 = this
.doLoadBeanDefinitions(inputSource
, encodedResource.getResource())
;
} finally {
inputStream.close();
}
} catch (IOException var15) {
throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15);
} finally {
((Set)currentResources).remove(encodedResource);
if (((Set)currentResources).isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
return var5;
}
}
其实也差不多。
InputSource是org.xml.sax的类。
doLoadBeanDefinitions：
protected int doLoadBeanDefinitions( InputSource inputSource, Resource resource) {
Document doc = doLoadDocument(inputSource, resource);//下面先讲讲这部分 $ doLoadDocument $ 加载document
return registerBeanDefinitions(doc, resource);//在说说这部分$ registerBeanDefinitions $ 主要是注册bean
} （4.1.1版本有些不同，主要在抛出异常方面）
( $ doLoadDocument $ )doLoadDocument:
protected Document doLoadDocument( InputSource inputSource, Resource resource) {
return this . documentLoader . loadDocument
(inputSource,
getEntityResolver
(),
this
.
errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
//loadDocument方法实际调用的是DefaultDocumentLoader里面的loadDocument方法 #DefaultDocumentLoader.loadDocument
}
实际这个documentLoader就是 DefaultDocumentLoader . 此类是DocumentLoader接口的唯一实现。 getEntityResolver 方法返回ResourceEntityResolver，上面说过了。errorHandler是一个SimpleSaxErrorHandler对象。
校验模型 其实就是确定xml文件使用xsd方式还是dtd方式来校验，忘了的话左转度娘。Spring会通过读取xml文件的方式判断应该采用哪种。
NamespaceAware 默认false，因为默认配置了校验为true。(其实这个 默认校验 为true我还没找到）
DefaultDocumentLoader.loadDocument:
@Override public Document loadDocument( InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) {
// 这里就是老套路了，可以看出，Spring还是使用了dom的方式解析，即一次全部load到内存
DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder . parse(inputSource);
}
createDocumentBuilderFactory比较有意思:
如上图所示，4.1.1版本的是这样，我跟确信下面的版本更成熟，因为很多地方是常量控制，4.1.1都是写死的常量。
protected DocumentBuilderFactory createDocumentBuilderFactory( int validationMode, boolean namespaceAware{
DocumentBuilderFactory factory = DocumentBuilderFactory . newInstance();
factory . setNamespaceAware(namespaceAware);
if (validationMode != XmlValidationModeDetector . VALIDATION_NONE ) {
// 此方法设为true仅对dtd有效，xsd(schema)无效
factory . setValidating( true );
if (validationMode == XmlValidationModeDetector . VALIDATION_XSD ) {
// Enforce namespace aware for XSD...
// 开启xsd(schema)支持
factory . setNamespaceAware( true );
// 这个也是Java支持Schema的套路，可以问度娘
factory . setAttribute( SCHEMA_LANGUAGE_ATTRIBUTE , XSD_SCHEMA_LANGUAGE );
}
}
return factory;
}
Bean解析（这部分放在 spring源码解析---spring-core(二)）