SpringMVC在请求到handler处理器的分发这步是通过HandlerMapping模块解决的.handlerMapping 还处理拦截器.
先看看HandlerMapping的继承树吧
可以大致这样做个分类:
1. 一个接口HandlerMapping,定义一个api: HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
2. 一个基础抽象类:主要是准备上下文环境,提供getHandlerInternal钩子,封装拦截器到HandlerExecutionChain
3. 基于注解@Controller,@RequestMapping的使用
4. 配置文件中直接配置url到 handler的SimpleUrlHandlerMapping
5. 默认实现BeanNameUrlHandlerMapping
6. Controller子类的映射
看看HandlerMapping吧,就一个getHandler api 非常简单.
// HandlerMapping
package org.springframework.web.servlet;
public interface HandlerMapping {
HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception; }
AbstractHandlerMapping就没有这么简单了
先看AbstractHandlerMapping继承的类,实现的接口
package org.springframework.web.servlet.handler;
public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
implements HandlerMapping, Ordered {
// ...
}
WebApplicationObjectSupport用于提供上下文ApplicationContext和ServletContext.
还有这边的initApplicationContext方法,在后续经常会使用到.AbstractHandlerMapping就直接覆写了.
父类里还是实现了ApplicationContextAware和ServletContextAware接口,spring概念很统一.
Ordered用于集合排序.
再接着看AbstractHandlerMapping的属性吧
// AbstractHandlerMapping
// order赋了最大值,优先级是最小的
private int order = Integer.MAX_VALUE; // default: same as non-Ordered
// 默认的Handler,这边使用的Obejct,子类实现的时候,使用HandlerMethod,HandlerExecutionChain等
private Object defaultHandler;
// url计算的辅助类
private UrlPathHelper urlPathHelper = new UrlPathHelper();
// 基于ant进行path匹配,解决如/books/{id}场景
private PathMatcher pathMatcher = new AntPathMatcher();
// 拦截器配置:1,HandlerMapping属性设置;2,extendInterceptors设置
private final List<Object> interceptors = new ArrayList<Object>();
// 从interceptors中解析得到,直接添加给全部handler
private final List<HandlerInterceptor> adaptedInterceptors = new ArrayList<HandlerInterceptor>();
// 使用前需要跟url进行匹配,匹配通过才会使用
private final List<MappedInterceptor> mappedInterceptors = new ArrayList<MappedInterceptor>();
看下拦截器的初始化:
// AbstractHandlerMapping
@Override
protected void initApplicationContext() throws BeansException {
extendInterceptors(this.interceptors);
detectMappedInterceptors(this.mappedInterceptors);
initInterceptors();
} /**
* 提供给子类扩展拦截器,可惜都没有使用
*/
protected void extendInterceptors(List<Object> interceptors) {
} /**
* 扫描应用下的MappedInterceptor,并添加到mappedInterceptors
*/
protected void detectMappedInterceptors(List<MappedInterceptor> mappedInterceptors) {
mappedInterceptors.addAll(
BeanFactoryUtils.beansOfTypeIncludingAncestors(
getApplicationContext(),MappedInterceptor.class, true, false).values());
} /**
* 归集MappedInterceptor,并适配HandlerInterceptor和WebRequestInterceptor
*/
protected void initInterceptors() {
if (!this.interceptors.isEmpty()) {
for (int i = 0; i < this.interceptors.size(); i++) {
Object interceptor = this.interceptors.get(i);
if (interceptor == null) {
throw new IllegalArgumentException("Entry number " + i + " in interceptors array is null");
}
if (interceptor instanceof MappedInterceptor) {
mappedInterceptors.add((MappedInterceptor) interceptor);
}
else {
adaptedInterceptors.add(adaptInterceptor(interceptor));
}
}
}
} protected HandlerInterceptor adaptInterceptor(Object interceptor) {
if (interceptor instanceof HandlerInterceptor) {
return (HandlerInterceptor) interceptor;
}
else if (interceptor instanceof WebRequestInterceptor) {
return new WebRequestHandlerInterceptorAdapter((WebRequestInterceptor) interceptor);
}
else {
throw new IllegalArgumentException("Interceptor type not supported: " + interceptor.getClass().getName());
}
}
然后是getHandler(HttpServletRequest request)的实现,这边同时预留getHandlerInternal(HttpServletRequest request)给子类实现
// AbstractHandlerMapping
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
return getHandlerExecutionChain(handler, request);
}
protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;
最后是封装拦截器到HandlerExecutionChain
adaptedInterceptors直接添加
mappedInterceptors需要根据url匹配通过后添加
// AbstractHandlerMapping
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain =
(handler instanceof HandlerExecutionChain) ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler);
chain.addInterceptors(getAdaptedInterceptors());
String lookupPath = urlPathHelper.getLookupPathForRequest(request);
for (MappedInterceptor mappedInterceptor : mappedInterceptors) {
if (mappedInterceptor.matches(lookupPath, pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
return chain;
}
Controller子类的映射,这一分支先看类继承
我们来说说,这边每个类主要的职责
1. AbstractHandlerMapping 准备上下文环境;提供getHandlerInternal钩子;封装拦截器到HandlerExecutionChain
2. AbstractUrlHandlerMapping 实现注册handler的方法供子类使用;实现getHandlerInternal,根据子类初始化的配置信息,查找handler
3. AbstractDetectingUrlHandlerMapping 扫描应用下的Object,迭代后提供钩子方法determineUrlsForHandler由子类决定如何过滤
4. AbstractControllerUrlHandlerMapping 实现determineUrlsForHandler,添加过滤排除的handler操作(配置文件配置),预留钩子方法buildUrlsForHandler给子类实现;同时判断controller的子类
5. ControllerBeanNameHandlerMapping 根据bean name生成url
ControllerClassNameHandlerMapping根据class name生成url
从AbstractUrlHandlerMapping开始看吧,这边只是大致看下代码,如果需要仔细分析,请移步<SpringMVC源码解读 - HandlerMapping - AbstractUrlHandlerMapping系列request分发>
handler的注册
protected void registerHandler(String[] urlPaths, String beanName) throws BeansException, IllegalStateException { }
protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException { }
handler的查找
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {}
// 根据url查找handler
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {}
// 校验handler
protected void validateHandler(Object handler, HttpServletRequest request) throws Exception {}
// 封装拦截器到HandlerExecutionChain
protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,
String pathWithinMapping, Map<String, String> uriTemplateVariables) {}
AbstractDetectingUrlHandlerMapping,这边一样不展开,具体移步<SpringMVC源码解读 - HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化>
具体做的事情:
1. 通过覆写initApplicationContext,调用detectHandlers扫描Obejct
2. 提供钩子方法determineUrlsForHandler给子类根据handler生成url
3. 调用父类的registerHandler进行注册
@Override
public void initApplicationContext() throws ApplicationContextException {
super.initApplicationContext();
detectHandlers();
} protected void detectHandlers() throws BeansException {
// ...
} /**
* Determine the URLs for the given handler bean.
* 钩子而已
*/
protected abstract String[] determineUrlsForHandler(String beanName);
AbstractControllerUrlHandlerMapping,这边一样不展开,具体移步<SpringMVC源码解读 - HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化>
具体做的事情;
1. 覆写determineUrlsForHandler添加剔除部分类的逻辑,通过配置文件配置的excludedClasses和excludedPackages在这边使用
2. 判断是否controller的子类
3. 预留buildUrlsForHandler给子类生成url
@Override
protected String[] determineUrlsForHandler(String beanName) {
Class beanClass = getApplicationContext().getType(beanName);
if (isEligibleForMapping(beanName, beanClass)) {
return buildUrlsForHandler(beanName, beanClass);
}
else {
return null;
}
} protected boolean isEligibleForMapping(String beanName, Class beanClass) {} protected boolean isControllerType(Class beanClass) {} protected abstract String[] buildUrlsForHandler(String beanName, Class beanClass);
ControllerBeanNameHandlerMapping和ControllerClassNameHandlerMapping 直接看源码吧,或者移步<SpringMVC源码解读 - HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化>
配置文件中直接配置url到 handler的SimpleUrlHandlerMapping,就是使用registerHandlers注册配置文档中的handler,直接看代码或者移步<SpringMVC源码解读 - HandlerMapping - SimpleUrlHandlerMapping初始化>吧
BeanNameUrlHandlerMapping 实现determineUrlsForHandler生成url,直接看代码或者移步<SpringMVC源码解读 - HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化>吧
基于注解@Controller,@RequestMapping的使用
最难吭的骨头
先看类继承吧
说下各个类的职责吧,具体的分析还是移步下面的文章
<SpringMVC源码解读 - HandlerMapping - RequestMappingHandlerMapping初始化>
<SpringMVC源码解读 - HandlerMapping - RequestMappingHandlerMapping请求分发>
1. AbstractHandlerMethodMaping 定义初始化流程,请求时如何映射
初始化:
1.1.1 扫描应用下的Object
1.1.2 预留isHandler钩子方法给子类判断Object是否handler
1.1.3 迭代扫描每一个handler,找出符合要求的方法,这边判断依然是留给子类实现getMappingForMethod
1.1.4 注册查找到的处理器,需要确保一个匹配条件RequestMappingInfo只能映射到一个handler
1.1.5 根据匹配条件获取url,同样的只是定义流程,具体的算法留给子类实现getMappingPathPatterns
请求request分发处理:
1.2.1 直接字符串匹配的方式,查找handler
1.2.2 匹配条件查找,这边具体的算法交由子类处理getMatchingMapping
1.2.3 排序并获取最佳匹配handler,这边的排序方式还是子类处理getMappingConmparator
1.2.4 分别封装匹配到和未匹配到handler的情况
2. RequestMappingInfoHandlerMapping使用RequestMappingInfo实现匹配条件,RequestMappingInfo的初始化留给子类
2.1 根据RequestMappingInfo生成url ->getMappingPathPatterns
2.2 使用匹配条件查找Handler -> getMatchingMapping
2.3 完成比较器算法 -> getMappingComparator
2.4 覆写handleMatch,缓存n多信息到request
注册pattern,最佳匹配的pattern,url中解析出来的参数,url中解析出来的多值参数,mediaType
2.1.5 覆写handlerNoMatch,最后的挣扎,再尝试匹配一次
3. RequestMappingHandlerMapping 根据注解@Controller @RequestMapping生成RequestMappingInfo,并校验isHandler
3.1 覆写afterPropertiesSet,添加文件后缀判断
3.2 实现isHandler,类上有@Controller @RequestMapping其中一个注解就对
3.3 解析注解内容,生产RequestMappingInfo实例