springMVC源码分析--AbstractUrlHandlerMapping（三）
上一篇博客springMVC源码分析--AbstractHandlerMapping（二）中我们介绍了AbstractHandlerMapping了，接下来我们介绍其子类AbstractUrlHandlerMapping。
在上一篇博客中我们了解到AbstractHandlerMapping提供了一个抽象类getHandlerInternal（HttpServletRequest request），我们首先看看AbstractUrlHandlerMapping中对抽象类getHandlerInternal（HttpServletRequest request）的实现。
//获取Handler，主要是通过url和method的对应关系来查找
@Override
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
//获取request中的请求链接
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
//根据链接查找handler
Object handler = lookupHandler(lookupPath, request);
if (handler == null) {
// We need to care for the default handler directly, since we need to
// expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
//定义一个变量，保存找到的原始Handler
Object rawHandler = null;
if ("/".equals(lookupPath)) {
rawHandler = getRootHandler();
}
if (rawHandler == null) {
rawHandler = getDefaultHandler();
}
if (rawHandler != null) {
// Bean name or resolved handler?
//如果是String类型则到容器中查找具体的Bean
if (rawHandler instanceof String) {
String handlerName = (String) rawHandler;
rawHandler = getApplicationContext().getBean(handlerName);
}
validateHandler(rawHandler, request);
handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
}
}
if (handler != null && logger.isDebugEnabled()) {
logger.debug("Mapping [" + lookupPath + "] to " + handler);
}
else if (handler == null && logger.isTraceEnabled()) {
logger.trace("No handler mapping found for [" + lookupPath + "]");
}
return handler;
}
从上面的实现方法getHandlerInternal来看，首先是通过lookupHandler方法来查找Handler，这里我们看到了之前说的Map对象，用来存储url和Handler之间的关系，当Handler获取为String时需要从Bean容器中获取注入的实现类，当然在查找过程中也会有模糊匹配等查找过程。
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
// Direct match?
//直接从map中获取
Object handler = this.handlerMap.get(urlPath);
if (handler != null) {
// Bean name or resolved handler?
//如果是String类型则从容器中获取
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
return buildPathExposingHandler(handler, urlPath, urlPath, null);
}
// Pattern match?
//通过模糊匹配来查找
List<String> matchingPatterns = new ArrayList<String>();
for (String registeredPattern : this.handlerMap.keySet()) {
if (getPathMatcher().match(registeredPattern, urlPath)) {
matchingPatterns.add(registeredPattern);
}
else if (useTrailingSlashMatch()) {
if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {
matchingPatterns.add(registeredPattern +"/");
}
}
}
String bestPatternMatch = null;
//匹配规则
Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);
if (!matchingPatterns.isEmpty()) {
Collections.sort(matchingPatterns, patternComparator);
if (logger.isDebugEnabled()) {
logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);
}
bestPatternMatch = matchingPatterns.get(0);
}
if (bestPatternMatch != null) {
handler = this.handlerMap.get(bestPatternMatch);
if (handler == null) {
Assert.isTrue(bestPatternMatch.endsWith("/"));
handler = this.handlerMap.get(bestPatternMatch.substring(0, bestPatternMatch.length() - 1));
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath);
// There might be multiple 'best patterns', let's make sure we have the correct URI template variables
// for all of them
Map<String, String> uriTemplateVariables = new LinkedHashMap<String, String>();
for (String matchingPattern : matchingPatterns) {
if (patternComparator.compare(bestPatternMatch, matchingPattern) == 0) {
Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
Map<String, String> decodedVars = getUrlPathHelper().decodePathVariables(request, vars);
uriTemplateVariables.putAll(decodedVars);
}
}
if (logger.isDebugEnabled()) {
logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);
}
return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables);
}
// No handler found...
return null;
}
上面两个方法介绍了通过url来查找handlerMap获取handler的操作，AbstractUrlHandlerMapping中也提供了注册url和handler到handlerMap中的操作，具体的调用则要到AbstractUrlHandlerMapping的子类中实现。
//注册url和Bean的map，注册多个string的url到一个处理器中
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);
}
}
////注册url和Bean的map,将具体的Handler注入到url对应的map中
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.
//如果Handler是String类型而且没有设置lazyInitHandlers则从springMVC容器中获取handler
if (!this.lazyInitHandlers && handler instanceof String) {
String handlerName = (String) handler;
if (getApplicationContext().isSingleton(handlerName)) {
resolvedHandler = getApplicationContext().getBean(handlerName);
}
}
Object mappedHandler = this.handlerMap.get(urlPath);
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.isInfoEnabled()) {
logger.info("Root mapping to " + getHandlerDescription(handler));
}
setRootHandler(resolvedHandler);
}
else if (urlPath.equals("/*")) {
if (logger.isInfoEnabled()) {
logger.info("Default mapping to " + getHandlerDescription(handler));
}
setDefaultHandler(resolvedHandler);
}
else {
this.handlerMap.put(urlPath, resolvedHandler);
if (logger.isInfoEnabled()) {
logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler));
}
}
}
}
通过上面介绍我们知道AbstractUrlHandlerMapping提供的功能就是根据url从handlerMap中获取handler和注册url和handler的对应关系到handlerMap中，当然这个过程中还包含很多其他的操作。
AbstractUrlHandlerMapping的完整源码如下：
public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
private Object rootHandler;
private boolean useTrailingSlashMatch = false;
private boolean lazyInitHandlers = false;
private final Map<String, Object> handlerMap = new LinkedHashMap<String, Object>();
public void setRootHandler(Object rootHandler) {
this.rootHandler = rootHandler;
}
public Object getRootHandler() {
return this.rootHandler;
}
public void setUseTrailingSlashMatch(boolean useTrailingSlashMatch) {
this.useTrailingSlashMatch = useTrailingSlashMatch;
}
public boolean useTrailingSlashMatch() {
return this.useTrailingSlashMatch;
}
public void setLazyInitHandlers(boolean lazyInitHandlers) {
this.lazyInitHandlers = lazyInitHandlers;
}
//获取Handler，主要是通过url和method的对应关系来查找
@Override
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
//获取request中的请求链接
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
//根据链接查找handler
Object handler = lookupHandler(lookupPath, request);
if (handler == null) {
// We need to care for the default handler directly, since we need to
// expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
//定义一个变量，保存找到的原始Handler
Object rawHandler = null;
if ("/".equals(lookupPath)) {
rawHandler = getRootHandler();
}
if (rawHandler == null) {
rawHandler = getDefaultHandler();
}
if (rawHandler != null) {
// Bean name or resolved handler?
//如果是String类型则到容器中查找具体的Bean
if (rawHandler instanceof String) {
String handlerName = (String) rawHandler;
rawHandler = getApplicationContext().getBean(handlerName);
}
validateHandler(rawHandler, request);
handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
}
}
if (handler != null && logger.isDebugEnabled()) {
logger.debug("Mapping [" + lookupPath + "] to " + handler);
}
else if (handler == null && logger.isTraceEnabled()) {
logger.trace("No handler mapping found for [" + lookupPath + "]");
}
return handler;
}
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
// Direct match?
//直接从map中获取
Object handler = this.handlerMap.get(urlPath);
if (handler != null) {
// Bean name or resolved handler?
//如果是String类型则从容器中获取
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
return buildPathExposingHandler(handler, urlPath, urlPath, null);
}
// Pattern match?
//通过模糊匹配来查找
List<String> matchingPatterns = new ArrayList<String>();
for (String registeredPattern : this.handlerMap.keySet()) {
if (getPathMatcher().match(registeredPattern, urlPath)) {
matchingPatterns.add(registeredPattern);
}
else if (useTrailingSlashMatch()) {
if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {
matchingPatterns.add(registeredPattern +"/");
}
}
}
String bestPatternMatch = null;
//匹配规则
Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);
if (!matchingPatterns.isEmpty()) {
Collections.sort(matchingPatterns, patternComparator);
if (logger.isDebugEnabled()) {
logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);
}
bestPatternMatch = matchingPatterns.get(0);
}
if (bestPatternMatch != null) {
handler = this.handlerMap.get(bestPatternMatch);
if (handler == null) {
Assert.isTrue(bestPatternMatch.endsWith("/"));
handler = this.handlerMap.get(bestPatternMatch.substring(0, bestPatternMatch.length() - 1));
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath);
// There might be multiple 'best patterns', let's make sure we have the correct URI template variables
// for all of them
Map<String, String> uriTemplateVariables = new LinkedHashMap<String, String>();
for (String matchingPattern : matchingPatterns) {
if (patternComparator.compare(bestPatternMatch, matchingPattern) == 0) {
Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
Map<String, String> decodedVars = getUrlPathHelper().decodePathVariables(request, vars);
uriTemplateVariables.putAll(decodedVars);
}
}
if (logger.isDebugEnabled()) {
logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);
}
return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables);
}
// No handler found...
return null;
}
protected void validateHandler(Object handler, HttpServletRequest request) throws Exception {
}
//用于给找到的Handler注册两个拦截器PathExposingHandlerInterceptor和UriTemplateVariablesHandlerInterceptor
//这两个拦截器的的作用是将与当前url实际匹配的Pattern、匹配条件和url模板参数设置到request的属性中
protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,
String pathWithinMapping, Map<String, String> uriTemplateVariables) {
HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);
chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));
if (!CollectionUtils.isEmpty(uriTemplateVariables)) {
chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));
}
return chain;
}
protected void exposePathWithinMapping(String bestMatchingPattern, String pathWithinMapping, HttpServletRequest request) {
request.setAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE, bestMatchingPattern);
request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);
}
protected void exposeUriTemplateVariables(Map<String, String> uriTemplateVariables, HttpServletRequest request) {
request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, uriTemplateVariables);
}
//注册url和Bean的map，注册多个string的url到一个处理器中
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);
}
}
////注册url和Bean的map,将具体的Handler注入到url对应的map中
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.
//如果Handler是String类型而且没有设置lazyInitHandlers则从springMVC容器中获取handler
if (!this.lazyInitHandlers && handler instanceof String) {
String handlerName = (String) handler;
if (getApplicationContext().isSingleton(handlerName)) {
resolvedHandler = getApplicationContext().getBean(handlerName);
}
}
Object mappedHandler = this.handlerMap.get(urlPath);
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.isInfoEnabled()) {
logger.info("Root mapping to " + getHandlerDescription(handler));
}
setRootHandler(resolvedHandler);
}
else if (urlPath.equals("/*")) {
if (logger.isInfoEnabled()) {
logger.info("Default mapping to " + getHandlerDescription(handler));
}
setDefaultHandler(resolvedHandler);
}
else {
this.handlerMap.put(urlPath, resolvedHandler);
if (logger.isInfoEnabled()) {
logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler));
}
}
}
}
private String getHandlerDescription(Object handler) {
return "handler " + (handler instanceof String ? "'" + handler + "'" : "of type [" + handler.getClass() + "]");
}
public final Map<String, Object> getHandlerMap() {
return Collections.unmodifiableMap(this.handlerMap);
}
protected boolean supportsTypeLevelMappings() {
return false;
}
private class PathExposingHandlerInterceptor extends HandlerInterceptorAdapter {
private final String bestMatchingPattern;
private final String pathWithinMapping;
public PathExposingHandlerInterceptor(String bestMatchingPattern, String pathWithinMapping) {
this.bestMatchingPattern = bestMatchingPattern;
this.pathWithinMapping = pathWithinMapping;
}
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
exposePathWithinMapping(this.bestMatchingPattern, this.pathWithinMapping, request);
request.setAttribute(HandlerMapping.INTROSPECT_TYPE_LEVEL_MAPPING, supportsTypeLevelMappings());
return true;
}
}
private class UriTemplateVariablesHandlerInterceptor extends HandlerInterceptorAdapter {
private final Map<String, String> uriTemplateVariables;
public UriTemplateVariablesHandlerInterceptor(Map<String, String> uriTemplateVariables) {
this.uriTemplateVariables = uriTemplateVariables;
}
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
exposeUriTemplateVariables(this.uriTemplateVariables, request);
return true;
}
}
}
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