Spring Webflux --handler

提供包括抽象基類在內(nèi)的HandlerMapping實(shí)現(xiàn)。

先扔一張整體的diagram類圖：

simoleUrlHandlerMapping.jpg

AbstractHandlerMapping

HandlerMapping實(shí)現(xiàn)的抽象基類。

接口

• java.lang.Object
  • org.springframework.context.support.ApplicationObjectSupport
    • org.springframework.web.reactive.handler.AbstractHandlerMapping

實(shí)現(xiàn)了HandlerMapping, Ordered

    public abstract class AbstractHandlerMapping extends
    ApplicationObjectSupport implements HandlerMapping, Ordered {



private static final WebHandler REQUEST_HANDLED_HANDLER = exchange -> Mono.empty();


private int order = Integer.MAX_VALUE;  // default: same as non-Ordered

private final PathPatternParser patternParser;

private final UrlBasedCorsConfigurationSource globalCorsConfigSource;

private CorsProcessor corsProcessor = new DefaultCorsProcessor();


public AbstractHandlerMapping() {
      this.patternParser = new PathPatternParser();
      this.globalCorsConfigSource = new UrlBasedCorsConfigurationSource(this.patternParser);
}

查找給定請(qǐng)求的handler仰迁，如果找不到特定的請(qǐng)求，則返回一個(gè)空的Mono。這個(gè)方法被getHandler（org.springframework.web.server.ServerWebExchange）調(diào)用硬猫。

在CORS 預(yù)先請(qǐng)求中，該方法應(yīng)該返回一個(gè)匹配改执，而不是預(yù)先請(qǐng)求的請(qǐng)求啸蜜，而是基于URL路徑的預(yù)期實(shí)際請(qǐng)求，從“Access-Control-Request-Method”頭辈挂，以及“Access-Control-Request-Headers”頭的HTTP方法衬横，通過(guò) getcorsconfiguration獲得CORS配置來(lái)允許通過(guò)，

如果匹配到一個(gè)handler终蒂，就返回Mono

protected abstract Mono<?> getHandlerInternal(ServerWebExchange exchange);

檢索給定handle的CORS配置蜂林。

@Nullable
protected CorsConfiguration getCorsConfiguration(Object handler, ServerWebExchange exchange) {
    if (handler instanceof CorsConfigurationSource) {
        return ((CorsConfigurationSource) handler).getCorsConfiguration(exchange);
    }
    return null;
}

抽象類實(shí)現(xiàn)的主要的具體方法,來(lái)獲得具體的Handle，實(shí)現(xiàn)了HandlerMapping中的getHandler拇泣，Mono<Object> getHandler(ServerWebExchange exchange);

@Override
public Mono<Object> getHandler(ServerWebExchange exchange) {
    return getHandlerInternal(exchange).map(handler -> {
        if (CorsUtils.isCorsRequest(exchange.getRequest())) {
            CorsConfiguration configA = this.globalCorsConfigSource.getCorsConfiguration(exchange);
            CorsConfiguration configB = getCorsConfiguration(handler, exchange);
            CorsConfiguration config = (configA != null ? configA.combine(configB) : configB);
            if (!getCorsProcessor().process(config, exchange) ||
                    CorsUtils.isPreFlightRequest(exchange.getRequest())) {
                return REQUEST_HANDLED_HANDLER;
            }
        }
        return handler;
    });
}

AbstractUrlHandlerMapping

基于URL映射的HandlerMapping實(shí)現(xiàn)的抽象基類噪叙。

接口

• java.lang.Object
  • org.springframework.context.support.ApplicationObjectSupport
    • org.springframework.web.reactive.handler.AbstractHandlerMapping
      • org.springframework.web.reactive.handler.AbstractUrlHandlerMapping

支持直接匹配，例如注冊(cè)的“/ test”匹配“/ test”霉翔，以及各種ant樣式匹配睁蕾，例如， “/ test *”匹配“/ test”和“/ team”，“/ test / *”匹配“/ test”下的所有路徑子眶， 瀑凝。有關(guān)詳細(xì)信息，請(qǐng)參閱PathPattern javadoc臭杰。

將搜索所有路徑模式以查找當(dāng)前請(qǐng)求路徑的最具體匹配粤咪。最具體的模式定義為使用最少捕獲變量和通配符的最長(zhǎng)路徑模式。

private final Map<PathPattern, Object> handlerMap = new LinkedHashMap<>();

返回注冊(cè)路徑模式和handle的只讀視圖渴杆，這些注冊(cè)路徑模式和handle可能是一個(gè)實(shí)際的handle實(shí)例或延遲初始化handle的bean名稱寥枝。

public final Map<PathPattern, Object> getHandlerMap() {
    return Collections.unmodifiableMap(this.handlerMap);
}

我們可以再看到下面這兩個(gè)方法實(shí)現(xiàn)了handle的注冊(cè)，會(huì)把所有的路徑映射将塑，和handle實(shí)例放在handlerMap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);
    }
}


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;

    // Parse path pattern
    urlPath = prependLeadingSlash(urlPath);
    PathPattern pattern = getPathPatternParser().parse(urlPath);
    if (this.handlerMap.containsKey(pattern)) {
        Object existingHandler = this.handlerMap.get(pattern);
        if (existingHandler != null) {
            if (existingHandler != resolvedHandler) {
                throw new IllegalStateException(
                        "Cannot map " + getHandlerDescription(handler) + " to [" + urlPath + "]: " +
                        "there is already " + getHandlerDescription(existingHandler) + " mapped.");
            }
        }
    }

    // Eagerly resolve handler if referencing singleton via name.
    if (!this.lazyInitHandlers && handler instanceof String) {
        String handlerName = (String) handler;
        if (obtainApplicationContext().isSingleton(handlerName)) {
            resolvedHandler = obtainApplicationContext().getBean(handlerName);
        }
    }

    // Register resolved handler
    this.handlerMap.put(pattern, resolvedHandler);
    if (logger.isInfoEnabled()) {
        logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler));
    }
}

預(yù)處理映射的路徑脉顿，如果不以/開(kāi)頭就加上/

private static String prependLeadingSlash(String pattern) {
    if (StringUtils.hasLength(pattern) && !pattern.startsWith("/")) {
        return "/" + pattern;
    }
    else {
        return pattern;
    }
}

在這一步的時(shí)候開(kāi)始獲取內(nèi)部的handle蝌麸，查找給定請(qǐng)求的handle点寥，如果找不到特定的請(qǐng)求，則返回一個(gè)空的Mono来吩。

    @Override
public Mono<Object> getHandlerInternal(ServerWebExchange exchange) {
    PathContainer lookupPath = exchange.getRequest().getPath().pathWithinApplication();
    Object handler;
    try {
        handler = lookupHandler(lookupPath, exchange);
    }
    catch (Exception ex) {
        return Mono.error(ex);
    }

    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 Mono.justOrEmpty(handler);
}

獲取到handle的類敢辩，先獲取請(qǐng)求的url地址，調(diào)用lookupHandler(lookupPath, exchange)去找這個(gè)handle弟疆。

@Nullable
protected Object lookupHandler(PathContainer lookupPath, ServerWebExchange exchange)
        throws Exception {

    return this.handlerMap.entrySet().stream()
            .filter(entry -> entry.getKey().matches(lookupPath))
            .sorted((entry1, entry2) ->
                    PathPattern.SPECIFICITY_COMPARATOR.compare(entry1.getKey(), entry2.getKey()))
            .findFirst()
            .map(entry -> {
                PathPattern pattern = entry.getKey();
                if (logger.isDebugEnabled()) {
                    logger.debug("Matching pattern for request [" + lookupPath + "] is " + pattern);
                }
                PathContainer pathWithinMapping = pattern.extractPathWithinPattern(lookupPath);
                return handleMatch(entry.getValue(), pattern, pathWithinMapping, exchange);
            })
            .orElse(null);
}

在這里又調(diào)用了handleMatch(entry.getValue(), pattern, pathWithinMapping, exchange)來(lái)匹配handle戚长，驗(yàn)證過(guò)后，然后設(shè)置到ServerWebExchange中最后返回怠苔。

private Object handleMatch(Object handler, PathPattern bestMatch, PathContainer pathWithinMapping,
        ServerWebExchange exchange) {

    // Bean name or resolved handler?
    if (handler instanceof String) {
        String handlerName = (String) handler;
        handler = obtainApplicationContext().getBean(handlerName);
    }

    validateHandler(handler, exchange);

    exchange.getAttributes().put(BEST_MATCHING_HANDLER_ATTRIBUTE, handler);
    exchange.getAttributes().put(BEST_MATCHING_PATTERN_ATTRIBUTE, bestMatch);
    exchange.getAttributes().put(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);

    return handler;
}

SimpleUrlHandlerMapping

HandlerMapping的實(shí)現(xiàn)同廉，來(lái)把url請(qǐng)求映射到對(duì)應(yīng)的request handler的bean

支持映射到bean實(shí)例和映射到bean名稱;非單例的handler需要映射到bean名稱。

“urlMap”屬性適合用bean實(shí)例填充處理程序映射柑司∑刃ぃ可以通過(guò)java.util.Properties類接受的形式，通過(guò)“映射”屬性設(shè)置映射到bean名稱攒驰，如下所示：

/welcome.html=ticketController

/show.html=ticketController

語(yǔ)法是PATH = HANDLER_BEAN_NAME蟆湖。如果路徑不是以斜杠開(kāi)始的，則給它自動(dòng)補(bǔ)充一個(gè)斜杠玻粪。

支持直接匹配隅津，例如注冊(cè)的“/ test”匹配“/ test”，以及各種ant樣式匹配劲室，例如伦仍， “/ test *”匹配“/ test”和“/ team”，“/ test / *”匹配“/ test”下的所有路徑很洋， 充蓝。有關(guān)詳細(xì)信息，請(qǐng)參閱PathPattern javadoc蹲缠。

接口

• java.lang.Object
  • org.springframework.context.support.ApplicationObjectSupport
    • org.springframework.web.reactive.handler.AbstractHandlerMapping
      • org.springframework.web.reactive.handler.AbstractUrlHandlerMapping
        • org.springframework.web.reactive.handler.SimpleUrlHandlerMapping

private final Map<String, Object> urlMap = new LinkedHashMap<>();


程序啟動(dòng)遍歷的時(shí)候把加載到的所有映射路徑棺克，和handle設(shè)置到urlMap
public void setUrlMap(Map<String, ?> urlMap) {
    this.urlMap.putAll(urlMap);
}

獲得所有的urlMap悠垛，允許urlMap訪問(wèn)URL路徑映射，可以添加或覆蓋特定條目娜谊。
public Map<String, ?> getUrlMap() {
    return this.urlMap;
}


初始化程序上下文确买，除了父類的初始化，還調(diào)用了registerHandler
@Override
public void initApplicationContext() throws BeansException {
    super.initApplicationContext();
    registerHandlers(this.urlMap);
}

開(kāi)始注冊(cè)handler纱皆，注冊(cè)u(píng)rlMap中為相應(yīng)路徑指定的所有的handler湾趾。
如果handler不能注冊(cè)，拋出 BeansException
如果有注冊(cè)的handler有沖突派草，比如兩個(gè)相同的搀缠，拋出java.lang.IllegalStateException

protected void registerHandlers(Map<String, Object> urlMap) throws BeansException {
    if (urlMap.isEmpty()) {
        logger.warn("Neither 'urlMap' nor 'mappings' set on SimpleUrlHandlerMapping");
    }
    else {
        for (Map.Entry<String, Object> entry : urlMap.entrySet()) {
            String url = entry.getKey();
            Object handler = entry.getValue();
            // Prepend with slash if not already present.
            if (!url.startsWith("/")) {
                url = "/" + url;
            }
            // Remove whitespace from handler bean name.
            if (handler instanceof String) {
                handler = ((String) handler).trim();
            }
            registerHandler(url, handler);
        }
    }
}

這里調(diào)用的registerHandler(url, handler)就是剛剛抽象類AbstractUrlHandlerMapping中的registerHandler方法