AbstractDetectingUrlHandlerMapping是通过扫描方式注册Handler,收到请求时由AbstractUrlHandlerMapping的getHandlerInternal进行分发.
共有5个子类,一个抽象类.
与SimpleUrlHandlerMapping类似,通过覆写initApplicationContext,然后调用detectHandlers进行初始化.
detectHandlers通过BeanFactoryUtils扫描应用下的Object,然后预留determineUrlsForHandler给子类根据Handler生成对应的url.
注册使用的registerHandler依然由AbstractUrlHandlerMapping提供.
// AbstractDetectingUrlHandlerMapping
@Override
public void initApplicationContext() throws ApplicationContextException {
super.initApplicationContext();
detectHandlers();
}
这边一样是调用AbstractHandlerMapping的initApplicationContext初始化拦截器.
主角上场,detectHandlers,扫描Handlers
// AbstractDetectingUrlHandlerMapping
protected void detectHandlers() throws BeansException {
if (logger.isDebugEnabled()) {
logger.debug("Looking for URL mappings in application context: " + getApplicationContext());
}
String[] beanNames = (this.detectHandlersInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
getApplicationContext().getBeanNamesForType(Object.class));
// Take any bean name that we can determine URLs for.
for (String beanName : beanNames) {
String[] urls = determineUrlsForHandler(beanName);
if (!ObjectUtils.isEmpty(urls)) {
// URL paths found: Let's consider it a handler.
registerHandler(urls, beanName);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Rejected bean name '" + beanName + "': no URL paths identified");
}
}
}
}
这边预留的模板方法定义如下:
protected abstract String[] determineUrlsForHandler(String beanName);
我们再来看看模板方法在BeanNameUrlHandlerMapping和AbstractControllerUrlHandlerMapping中的实现吧.
BeanNameUrlHandlerMapping非常简单,就实现了determineUrlsForHandler.
其中的alias应该是应该就是通过beanName在配置文件中配置的.
// BeanNameUrlHandlerMapping
@Override
protected String[] determineUrlsForHandler(String beanName) {
List urls = new ArrayList();
if (beanName.startsWith("/")) {
urls.add(beanName);
}
String[] aliases = getApplicationContext().getAliases(beanName);
for (String alias : aliases) {
if (alias.startsWith("/")) {
urls.add(alias);
}
}
return StringUtils.toStringArray(urls);
}
再来看看AbstractControllerUrlHandlerMapping中的实现
isEligibleForMapping判断controller是否被排除在外(通过包package排除或类class排除).
buildUrlsForHandler由子类实现具体的url生成规则
isControllerType判断是否Controller的子类
buildUrlsForHandler预留给子类生产url的模板方法.
// AbstractControllerUrlHandlerMapping
@Override
protected String[] determineUrlsForHandler(String beanName) {
Class beanClass = getApplicationContext().getType(beanName);
if (isEligibleForMapping(beanName, beanClass)) {
return buildUrlsForHandler(beanName, beanClass);
}
else {
return null;
}
}
// AbstractControllerUrlHandlerMapping
protected boolean isEligibleForMapping(String beanName, Class beanClass) {
if (beanClass == null) {
if (logger.isDebugEnabled()) {
logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
"because its bean type could not be determined");
}
return false;
}
if (this.excludedClasses.contains(beanClass)) {
if (logger.isDebugEnabled()) {
logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
"because its bean class is explicitly excluded: " + beanClass.getName());
}
return false;
}
String beanClassName = beanClass.getName();
for (String packageName : this.excludedPackages) {
if (beanClassName.startsWith(packageName)) {
if (logger.isDebugEnabled()) {
logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
"because its bean class is defined in an excluded package: " + beanClass.getName());
}
return false;
}
}
return isControllerType(beanClass);
}
// AbstractControllerUrlHandlerMapping
protected boolean isControllerType(Class beanClass) {
return this.predicate.isControllerType(beanClass);
}
// ControllerTypePredicate
这边提供2个api,分别判断是Controller的子类还是MultiActionController的子类.
class ControllerTypePredicate {
public boolean isControllerType(Class beanClass) {
return Controller.class.isAssignableFrom(beanClass);
}
public boolean isMultiActionControllerType(Class beanClass) {
return MultiActionController.class.isAssignableFrom(beanClass);
}
}
预留生成url的模板方法
// AbstractControllerUrlHandlerMapping protected abstract String[] buildUrlsForHandler(String beanName, Class beanClass);
再来看看AbstractControllerUrlHandlerMapping的2个实现ControllerBeanNameUrlHandlerMapping和ControllerClassNameUrlHandlerMapping.
其实这两个,很简单,一个是根据beanName来生产url,一个是根据className来生产url.
// ControllerBeanNameUrlHandlerMapping
@Override
protected String[] buildUrlsForHandler(String beanName, Class beanClass) {
List urls = new ArrayList();
urls.add(generatePathMapping(beanName));
String[] aliases = getApplicationContext().getAliases(beanName);// 也获取配置的别名
for (String alias : aliases) {
urls.add(generatePathMapping(alias));
}
return StringUtils.toStringArray(urls);
}
// ControllerBeanNameUrlHandlerMapping
protected String generatePathMapping(String beanName) {
String name = (beanName.startsWith("/") ? beanName : "/" + beanName);
StringBuilder path = new StringBuilder();
if (!name.startsWith(this.urlPrefix)) {
path.append(this.urlPrefix);
}
path.append(name);
if (!name.endsWith(this.urlSuffix)) {
path.append(this.urlSuffix);
}
return path.toString();
}
// ControllerClassNameUrlHandlerMapping
直接委托给generatePathMappings实现
@Override
protected String[] buildUrlsForHandler(String beanName, Class beanClass) {
return generatePathMappings(beanClass);
}
// ControllerClassNameUrlHandlerMapping
通过buildPathPrefix获取path的前缀
通过ClassUtils获取className,如BookController(不带包名),同时使用cglib代理的问题一并解决
根据大小写是否敏感,转换className(默认caseSensitive = false;)
isMultiActionControllerType判断Controller是否MultiActionController的子类,就是controller是否包含多个handler
protected String[] generatePathMappings(Class beanClass) {
StringBuilder pathMapping = buildPathPrefix(beanClass);
String className = ClassUtils.getShortName(beanClass);
String path = (className.endsWith(CONTROLLER_SUFFIX) ?
className.substring(, className.lastIndexOf(CONTROLLER_SUFFIX)) : className);
if (path.length() > ) {
if (this.caseSensitive) {
pathMapping.append(path.substring(, ).toLowerCase()).append(path.substring());
}
else {
pathMapping.append(path.toLowerCase());
}
}
if (isMultiActionControllerType(beanClass)) {
return new String[] {pathMapping.toString(), pathMapping.toString() + "
private StringBuilder buildPathPrefix(Class beanClass) {
StringBuilder pathMapping = new StringBuilder();
if (this.pathPrefix != null) {
pathMapping.append(this.pathPrefix);
pathMapping.append("/");
}
else {
pathMapping.append("/");
}
if (this.basePackage != null) {
String packageName = ClassUtils.getPackageName(beanClass);
if (packageName.startsWith(this.basePackage)) {
String subPackage = packageName.substring(this.basePackage.length()).replace('.', '/');
pathMapping.append(this.caseSensitive ? subPackage : subPackage.toLowerCase());
pathMapping.append("/");
}
}
return pathMapping;
}
// AbstractControllerUrlHandlerMapping
predicate.isMultiActionControllerType具体实现看上面的ControllerTypePredicate
protected boolean isMultiActionControllerType(Class beanClass) {
return this.predicate.isMultiActionControllerType(beanClass);
}
以上所述是小编给大家介绍的SpringMVC源码解读之 HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化的相关知识，希望对大家有所帮助！
