前言
BeanNameUrlHandlerMapping处理容器中以/开头的bean
一、初始化
BeanNameUrlHandlerMapping间接继承了ApplicationContextAware，因此创建bean的过程中会回调
initApplicationContext( )
（1）initApplicationContext( )
public void initApplicationContext() throws ApplicationContextException {
super.initApplicationContext();
//找/开头的handler
detectHandlers();
}
（2）detectHandlers()
protected void detectHandlers() throws BeansException {
//获取ApplicationContext
ApplicationContext applicationContext = obtainApplicationContext();
//获取容器中所有的beanNames
String[] beanNames = (this.detectHandlersInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(applicationContext, Object.class) :
applicationContext.getBeanNamesForType(Object.class));
// Take any bean name that we can determine URLs for.
for (String beanName : beanNames) {
//找/开头的url或alials
String[] urls = determineUrlsForHandler(beanName);
if (!ObjectUtils.isEmpty(urls)) {
// URL paths found: Let's consider it a handler.
//注册到缓存中
registerHandler(urls, beanName);
}
}
if (mappingsLogger.isDebugEnabled()) {
mappingsLogger.debug(formatMappingName() + " " + getHandlerMap());
}
else if ((logger.isDebugEnabled() && !getHandlerMap().isEmpty()) || logger.isTraceEnabled()) {
logger.debug("Detected " + getHandlerMap().size() + " mappings in " + formatMappingName());
}
}
（3）determineUrlsForHandler( )
protected String[] determineUrlsForHandler(String beanName) {
List<String> urls = new ArrayList<>();
if (beanName.startsWith("/")) {
//beanName以/开头
urls.add(beanName);
}
String[] aliases = obtainApplicationContext().getAliases(beanName);
for (String alias : aliases) {
if (alias.startsWith("/")) {
//别名以/开头
urls.add(alias);
}
}
return StringUtils.toStringArray(urls);
}
（4）registerHandler( )
protected void registerHandler(String[] urlPaths, String beanName) throws BeansException, IllegalStateException {
Assert.notNull(urlPaths, "URL path array must not be null");
for (String urlPath : urlPaths) {
registerHandler(urlPath, beanName);
}
}
protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException {
Assert.notNull(urlPath, "URL path must not be null");
Assert.notNull(handler, "Handler object must not be null");
Object resolvedHandler = handler;
// Eagerly resolve handler if referencing singleton via name.
if (!this.lazyInitHandlers && handler instanceof String) {
String handlerName = (String) handler;
ApplicationContext applicationContext = obtainApplicationContext();
if (applicationContext.isSingleton(handlerName)) {
//初始化bean
resolvedHandler = applicationContext.getBean(handlerName);
}
}
Object mappedHandler = this.handlerMap.get(urlPath);
//校验是否已经存在
if (mappedHandler != null) {
if (mappedHandler != resolvedHandler) {
throw new IllegalStateException(
"Cannot map " + getHandlerDescription(handler) + " to URL path [" + urlPath +
"]: There is already " + getHandlerDescription(mappedHandler) + " mapped.");
}
}
else {
if (urlPath.equals("/")) {
if (logger.isTraceEnabled()) {
logger.trace("Root mapping to " + getHandlerDescription(handler));
}
//根请求处理器
setRootHandler(resolvedHandler);
}
else if (urlPath.equals("/*")) {
if (logger.isTraceEnabled()) {
logger.trace("Default mapping to " + getHandlerDescription(handler));
}
//默认请求处理器
setDefaultHandler(resolvedHandler);
}
else {
//存入缓存
this.handlerMap.put(urlPath, resolvedHandler);
if (getPatternParser() != null) {
this.pathPatternHandlerMap.put(getPatternParser().parse(urlPath), resolvedHandler);
}
if (logger.isTraceEnabled()) {
logger.trace("Mapped [" + urlPath + "] onto " + getHandlerDescription(handler));
}
}
}
}
二、使用
创建controller，继承springmvc的AbstractController ，重写handleRequestInternal( )方法，
当请求访问/beanName路径时，会回调handleRequestInternal( )
@Controller("/beanName")
public class BeanNameUrlController extends AbstractController {
@Override
protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception {
System.out.println("BeanNameUrlController");
return null;
}
}