Spring源碼解析二：基於註解開發的Spring MVC配置原理
1、基於註解的方式使用Spring MVC
使用@RequestMapping,@Controller，@ResponseBodyjava
@RestController
public class HelloController {
@RequestMapping("hello")
public String hello (){
return "Hello Spring MVC";
}
}
2、如何進行註解開發的配置
基於XML進行配置
<?xml version="1.0" encoding="UTF-8"?>
<beans>
<mvc:annotation-driven/>
<beans>
基於@EnableWebMvc註解實現自動配置
-
基於SpringBoot中的自動配置
WebMvcAutoConfigurationweb
@Configuration
@EnableWebMvc
public class WebMvcConfig{
}
3、配置原理
-
<mvc:annotation-driven/>原理
添加此標籤後，Spring使用自定義的Bean定義解析器AnnotationDrivenBeanDefinitionParser加載了幾個比較幾個重要的Bean定義，主要是一些圍繞HandlerMethod進行處理的基礎組件對象spring
-
RequestHandlerMappingapi
根據請求映射找出對應的HandlerMethod進行處理
-
RequestMappingHandlerAdaptermvc
執行HandlerMethodChain進入到目標方法
-
AnnotationDrivenBeanDefinitionParser作了什麼？
public class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
Object source = parserContext.extractSource(element);
CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
parserContext.pushContainingComponent(compDefinition);
RuntimeBeanReference contentNegotiationManager = getContentNegotiationManager(element, source, parserContext);
// 註冊RequestMappingHandlerMapping，用於處理@RequestMaping註解的方法請求映射爲HandlerMethod
RootBeanDefinition handlerMappingDef = new RootBeanDefinition(RequestMappingHandlerMapping.class);
handlerMappingDef.setSource(source);
handlerMappingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
handlerMappingDef.getPropertyValues().add("order", 0);
handlerMappingDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
String methodMappingName = parserContext.getReaderContext().registerWithGeneratedName(handlerMappingDef);
if (element.hasAttribute("enable-matrix-variables")) {
Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enable-matrix-variables"));
handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
}
else if (element.hasAttribute("enableMatrixVariables")) {
Boolean enableMatrixVariables = Boolean.valueOf(element.getAttribute("enableMatrixVariables"));
handlerMappingDef.getPropertyValues().add("removeSemicolonContent", !enableMatrixVariables);
}
configurePathMatchingProperties(handlerMappingDef, element, parserContext);
RuntimeBeanReference conversionService = getConversionService(element, source, parserContext);
RuntimeBeanReference validator = getValidator(element, source, parserContext);
RuntimeBeanReference messageCodesResolver = getMessageCodesResolver(element);
RootBeanDefinition bindingDef = new RootBeanDefinition(ConfigurableWebBindingInitializer.class);
bindingDef.setSource(source);
bindingDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
bindingDef.getPropertyValues().add("conversionService", conversionService);
bindingDef.getPropertyValues().add("validator", validator);
bindingDef.getPropertyValues().add("messageCodesResolver", messageCodesResolver);
ManagedList<?> messageConverters = getMessageConverters(element, source, parserContext);
ManagedList<?> argumentResolvers = getArgumentResolvers(element, parserContext);
ManagedList<?> returnValueHandlers = getReturnValueHandlers(element, parserContext);
String asyncTimeout = getAsyncTimeout(element);
RuntimeBeanReference asyncExecutor = getAsyncExecutor(element);
ManagedList<?> callableInterceptors = getCallableInterceptors(element, source, parserContext);
ManagedList<?> deferredResultInterceptors = getDeferredResultInterceptors(element, source, parserContext);
// 註冊RequestMappingHandlerAdapter,用於適配處理HandlerMethod
RootBeanDefinition handlerAdapterDef = new RootBeanDefinition(RequestMappingHandlerAdapter.class);
handlerAdapterDef.setSource(source);
handlerAdapterDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
handlerAdapterDef.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
handlerAdapterDef.getPropertyValues().add("webBindingInitializer", bindingDef);
handlerAdapterDef.getPropertyValues().add("messageConverters", messageConverters);
addResponseBodyAdvice(handlerAdapterDef);
if (element.hasAttribute("ignore-default-model-on-redirect")) {
Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignore-default-model-on-redirect"));
handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
}
else if (element.hasAttribute("ignoreDefaultModelOnRedirect")) {
// "ignoreDefaultModelOnRedirect" spelling is deprecated
Boolean ignoreDefaultModel = Boolean.valueOf(element.getAttribute("ignoreDefaultModelOnRedirect"));
handlerAdapterDef.getPropertyValues().add("ignoreDefaultModelOnRedirect", ignoreDefaultModel);
}
if (argumentResolvers != null) {
handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
}
if (returnValueHandlers != null) {
handlerAdapterDef.getPropertyValues().add("customReturnValueHandlers", returnValueHandlers);
}
if (asyncTimeout != null) {
handlerAdapterDef.getPropertyValues().add("asyncRequestTimeout", asyncTimeout);
}
if (asyncExecutor != null) {
handlerAdapterDef.getPropertyValues().add("taskExecutor", asyncExecutor);
}
handlerAdapterDef.getPropertyValues().add("callableInterceptors", callableInterceptors);
handlerAdapterDef.getPropertyValues().add("deferredResultInterceptors", deferredResultInterceptors);
String handlerAdapterName = parserContext.getReaderContext().registerWithGeneratedName(handlerAdapterDef);
String uriCompContribName = MvcUriComponentsBuilder.MVC_URI_COMPONENTS_CONTRIBUTOR_BEAN_NAME;
RootBeanDefinition uriCompContribDef = new RootBeanDefinition(CompositeUriComponentsContributorFactoryBean.class);
uriCompContribDef.setSource(source);
uriCompContribDef.getPropertyValues().addPropertyValue("handlerAdapter", handlerAdapterDef);
uriCompContribDef.getPropertyValues().addPropertyValue("conversionService", conversionService);
parserContext.getReaderContext().getRegistry().registerBeanDefinition(uriCompContribName, uriCompContribDef);
RootBeanDefinition csInterceptorDef = new RootBeanDefinition(ConversionServiceExposingInterceptor.class);
csInterceptorDef.setSource(source);
csInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, conversionService);
RootBeanDefinition mappedCsInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
mappedCsInterceptorDef.setSource(source);
mappedCsInterceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
mappedCsInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, (Object) null);
mappedCsInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, csInterceptorDef);
String mappedInterceptorName = parserContext.getReaderContext().registerWithGeneratedName(mappedCsInterceptorDef);
RootBeanDefinition exceptionHandlerExceptionResolver = new RootBeanDefinition(ExceptionHandlerExceptionResolver.class);
exceptionHandlerExceptionResolver.setSource(source);
exceptionHandlerExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
exceptionHandlerExceptionResolver.getPropertyValues().add("contentNegotiationManager", contentNegotiationManager);
exceptionHandlerExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
exceptionHandlerExceptionResolver.getPropertyValues().add("order", 0);
addResponseBodyAdvice(exceptionHandlerExceptionResolver);
String methodExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(exceptionHandlerExceptionResolver);
RootBeanDefinition responseStatusExceptionResolver = new RootBeanDefinition(ResponseStatusExceptionResolver.class);
responseStatusExceptionResolver.setSource(source);
responseStatusExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
responseStatusExceptionResolver.getPropertyValues().add("order", 1);
String responseStatusExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(responseStatusExceptionResolver);
// 註冊默認的異常處理解析器
RootBeanDefinition defaultExceptionResolver = new RootBeanDefinition(DefaultHandlerExceptionResolver.class);
defaultExceptionResolver.setSource(source);
defaultExceptionResolver.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
defaultExceptionResolver.getPropertyValues().add("order", 2);
String defaultExceptionResolverName =
parserContext.getReaderContext().registerWithGeneratedName(defaultExceptionResolver);
parserContext.registerComponent(new BeanComponentDefinition(handlerMappingDef, methodMappingName));
parserContext.registerComponent(new BeanComponentDefinition(handlerAdapterDef, handlerAdapterName));
parserContext.registerComponent(new BeanComponentDefinition(uriCompContribDef, uriCompContribName));
parserContext.registerComponent(new BeanComponentDefinition(exceptionHandlerExceptionResolver, methodExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(responseStatusExceptionResolver, responseStatusExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(defaultExceptionResolver, defaultExceptionResolverName));
parserContext.registerComponent(new BeanComponentDefinition(mappedCsInterceptorDef, mappedInterceptorName));
// Ensure BeanNameUrlHandlerMapping (SPR-8289) and default HandlerAdapters are not "turned off"
MvcNamespaceUtils.registerDefaultComponents(parserContext, source);
parserContext.popAndRegisterContainingComponent();
return null;
}
}
AnnotationDrivenBeanDefinitionParser在哪裏被註冊？
public class MvcNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
......
}
}
MvcNamespaceHandler在哪裏被註冊？
做用： 簡單來講NamespaceHandler的做用就是處理自定義標籤的，例如<mvc:annotation-driven>，每個自定義標籤都必須隸屬於一個namespace下app
NamespaceHandler被定義META-INF/spring.handles文件，MvcNamespaceHandler也不例外。async
http\://www.springframework.org/schema/mvc=org.springframework.web.servlet.config.MvcNamespaceHandler
具體的解析過程
// 解析自定義標籤
public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
// 根據標籤拿到其namespaceUri
String namespaceUri = getNamespaceURI(ele);
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
// 使用Parser來解析標籤，上面咱們說過的AnnotationDrivenBeanDefinitionParser就是其一
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}
public static final String DEFAULT_HANDLER_MAPPINGS_LOCATION = "META-INF/spring.handlers";
private final String handlerMappingsLocation;
// 解析得到能處理該namespace下標籤的命名空間處理器
public NamespaceHandler resolve(String namespaceUri) {
Map<String, Object> handlerMappings = getHandlerMappings();
// 根據給定的namespaceUri找到對應的NamespaceHandler
Object handlerOrClassName = handlerMappings.get(namespaceUri);
if (handlerOrClassName == null) {
return null;
}
else if (handlerOrClassName instanceof NamespaceHandler) {
return (NamespaceHandler) handlerOrClassName;
}
else {
String className = (String) handlerOrClassName;
try {
Class<?> handlerClass = ClassUtils.forName(className, this.classLoader);
if (!NamespaceHandler.class.isAssignableFrom(handlerClass)) {
throw new FatalBeanException("Class [" + className + "] for namespace [" + namespaceUri +
"] does not implement the [" + NamespaceHandler.class.getName() + "] interface");
}
NamespaceHandler namespaceHandler = (NamespaceHandler) BeanUtils.instantiateClass(handlerClass);
namespaceHandler.init();
handlerMappings.put(namespaceUri, namespaceHandler);
return namespaceHandler;
}
catch (ClassNotFoundException ex) {
throw new FatalBeanException("NamespaceHandler class [" + className + "] for namespace [" +
namespaceUri + "] not found", ex);
}
catch (LinkageError err) {
throw new FatalBeanException("Invalid NamespaceHandler class [" + className + "] for namespace [" +
namespaceUri + "]: problem with handler class file or dependent class", err);
}
}
}
private Map<String, Object> getHandlerMappings() {
if (this.handlerMappings == null) {
synchronized (this) {
if (this.handlerMappings == null) {
try {
// 加載全部的spring.handlers文件內容爲Properties對象
Properties mappings =
PropertiesLoaderUtils.loadAllProperties(this.handlerMappingsLocation, this.classLoader);
if (logger.isDebugEnabled()) {
logger.debug("Loaded NamespaceHandler mappings: " + mappings);
}
Map<String, Object> handlerMappings = new ConcurrentHashMap<String, Object>(mappings.size());
CollectionUtils.mergePropertiesIntoMap(mappings, handlerMappings);
this.handlerMappings = handlerMappings;
}
catch (IOException ex) {
throw new IllegalStateException(
"Unable to load NamespaceHandler mappings from location [" + this.handlerMappingsLocation + "]", ex);
}
}
}
}
return this.handlerMappings;
}
at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.resolve(DefaultNamespaceHandlerResolver.java:114)
at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1419)
at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1414)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:189)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:143)
at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:110)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:508)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:335)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:303)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:216)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:187)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:129)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:537)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:452)
// 經過打印堆棧信息，咱們知道處理自定義標籤的步驟發生在spring容器的啓動過程當中，即refresh->obtainFreshBeanFactory->loadBeanDefinitions
// refresh()是構建IOC容器的最核心代碼，obtainFreshBeanFactory()加載xml中定義bean，轉換爲抽象世界中的BeanDefinition
Namespace在XML中的含義
<?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.w3school.com.cn" xmlns="http://www.w3school.com.cn" elementFormDefault="qualified"> ... ... </xs:schema>
(1)xmlns:xs="http://www.w3.org/2001/XMLSchema":代表schema中用到的元素和數據類型出自此命名空間,同時規定來自此命名空間的元素和數據都要使用前序xs.
(2)targetNamespace="http://www.w3school.com.cn":顯示 schema 中用到的元素和數據類型來自此命名空間.
(3)elementFormDefault="qualified":指出任何xml實例文檔所使用的且在此schema中聲明過的元素必須被命名空間限定.ide
@EnableWebMvc原理
使用@EnableWebMvc的做用大致上是與<annotation-driven>標籤的做用一致。具體能夠看WebMvcConfigurationSupport源碼ui
4、請求處理原理
-
重要對象含義
- HandlerMapping
做用是根據request請求找到對應的Handler處理器以及Interceptor攔截器，並將它們封裝在HandlerExecutionChain對象中 - RequestMappingInfo
存儲@RequestMapping註解中保存的信息，做用相似於TransactionInfo，存儲@Transactional註解信息
- HandlerMapping
初始化請求映射
映射存儲在this
// RequestMapping->HandlerMethod private final Map<T, HandlerMethod> handlerMethods = new LinkedHashMap<T, HandlerMethod>();
初始化映射的方法AbstractHandlerMethodMapping.initHandlerMethods()
@Override
public void afterPropertiesSet() {
initHandlerMethods();
}
protected void initHandlerMethods() {
if (logger.isDebugEnabled()) {
logger.debug("Looking for request mappings in application context: " + getApplicationContext());
}
// 得到IOC容器中的全部對象
String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
getApplicationContext().getBeanNamesForType(Object.class));
for (String beanName : beanNames) {
// 提取標註有@Controller或@RequestMapping的對象
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX) &&
isHandler(getApplicationContext().getType(beanName))){
// 提取全部標註有@RequestMapping的方法，並註冊到handlerMethods 中
detectHandlerMethods(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}
protected boolean isHandler(Class<?> beanType) {
return ((AnnotationUtils.findAnnotation(beanType, Controller.class) != null) ||
(AnnotationUtils.findAnnotation(beanType, RequestMapping.class) != null));
}
protected void detectHandlerMethods(final Object handler) {
Class<?> handlerType =
(handler instanceof String ? getApplicationContext().getType((String) handler) : handler.getClass());
// Avoid repeated calls to getMappingForMethod which would rebuild RequestMappingInfo instances
final Map<Method, T> mappings = new IdentityHashMap<Method, T>();
final Class<?> userType = ClassUtils.getUserClass(handlerType);
// 遍歷對象篩選標註有@RequestMaping註解的方法
Set<Method> methods = HandlerMethodSelector.selectMethods(userType, new MethodFilter() {
@Override
public boolean matches(Method method) {
// 將@RequestMapping註解標註的信息抽象爲@RequestMappingInfo對象
T mapping = getMappingForMethod(method, userType);
if (mapping != null) {
mappings.put(method, mapping);
return true;
}
else {
return false;
}
}
});
// 註冊請求映射
for (Method method : methods) {
registerHandlerMethod(handler, method, mappings.get(method));
}
}
請求原理
- 根據HttpRequest請求構建對應的RequestMappingInfo對象。
- 遍歷handlerMethods映射找到對應的處理器方法。
- 根據RequestMappingHandlerAdaptor執行目標方法。
上面三步只是簡化總結出了請求映射原理，更深一步的請求處理原理還請閱讀DispatcherServlet.doDispatch()方法源碼。
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