springMVC源码分析--AbstractHandlerMapping（二）

上一篇博客springMVC源码分析--HandlerMapping(一)中我们简单的介绍了HandlerMapping，接下来我们介绍一下它的抽象实现类AbstractHandlerMapping

HandlerMapping中定义了方法getHandler（HttpServletRequest request），AbstractHandlerMapping中的实现如下：

//获得一个HandlerExecutionChain
	@Override
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		//从实现类中获得HanlderMethod
		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);
		}
		//获得HandlerExecutionChain
		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
		if (CorsUtils.isCorsRequest(request)) {
			CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}
		return executionChain;
	}

在getHandler方法中又出现了两个方法getHandlerInternal（request），在子类中实现，目的就是获取要执行的Controller。

//模板方法，用于子类中实现，通过request去查找对应的执行方法HandlerMethod
	protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;

getHandlerExecutionChain就是创建一个HandlerExecutionChain实例，参数值就是handler和request。

//
	protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
		//如果没有获得则创建一个
		HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
				(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
		//获得IP地址及端口后的URL地址
		String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
		//在HandlerExecutionChain中添加拦截器
		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
			if (interceptor instanceof MappedInterceptor) {
				MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
				//根据lookupPath来获取Interceptor
				if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
					chain.addInterceptor(mappedInterceptor.getInterceptor());
				}
			}
			else {
				chain.addInterceptor(interceptor);
			}
		}
		return chain;
	}

AbstractHandlerMapping提供了设置不同HandlerMapping的执行顺序oder。

//设置不同HandlerMapping实现类的执行顺序
	public final void setOrder(int order) {
	  this.order = order;
	}

	@Override
	public final int getOrder() {
	  return this.order;
	}

除了以上几个重要的方法外，AbstractHandlerMapping还提供了进行拦截器初始化的一些操作。

//初始化时调用，初始化一些基本信息，这里主要是初始化一些拦截器
	@Override
	protected void initApplicationContext() throws BeansException {
		extendInterceptors(this.interceptors);//添加或修车intercept，现在并没有具体实现
		detectMappedInterceptors(this.adaptedInterceptors);//将springMVC容器或者父容器中的所有MappedInterceptor类型的Bean添加到mappedInterceptors属性中
		initInterceptors();
	}

	protected void extendInterceptors(List<Object> interceptors) {
	}

	//将springMVC容器或者父容器中的所有MappedInterceptor类型的Bean添加到mappedInterceptors属性中
	protected void detectMappedInterceptors(List<HandlerInterceptor> mappedInterceptors) {
		mappedInterceptors.addAll(
				BeanFactoryUtils.beansOfTypeIncludingAncestors(
						getApplicationContext(), MappedInterceptor.class, true, false).values());
	}

	//初始化Interceptor,将interceptors属性里所包含的对象按类型添加到mappedInterceptors或者adaptedInterceptors中。
	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");
				}
				this.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());
		}
	}

	protected final HandlerInterceptor[] getAdaptedInterceptors() {
		int count = this.adaptedInterceptors.size();
		return (count > 0 ? this.adaptedInterceptors.toArray(new HandlerInterceptor[count]) : null);
	}

	protected final MappedInterceptor[] getMappedInterceptors() {
		List<MappedInterceptor> mappedInterceptors = new ArrayList<MappedInterceptor>();
		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
			if (interceptor instanceof MappedInterceptor) {
				mappedInterceptors.add((MappedInterceptor) interceptor);
			}
		}
		int count = mappedInterceptors.size();
		return (count > 0 ? mappedInterceptors.toArray(new MappedInterceptor[count]) : null);
	}

总体来看AbstractHandlerMapping提供了抽象方法getHandlerInternal在子类中实现，根据获得的Handler及配置的拦截器Interceptor来生成HandlerExecutionChain。

完整的AbstractHandlerMapping源码如下：

public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
		implements HandlerMapping, Ordered {

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

	private Object defaultHandler;

	private UrlPathHelper urlPathHelper = new UrlPathHelper();

	private PathMatcher pathMatcher = new AntPathMatcher();

	private final List<Object> interceptors = new ArrayList<Object>();

	private final List<HandlerInterceptor> adaptedInterceptors = new ArrayList<HandlerInterceptor>();

	private CorsProcessor corsProcessor = new DefaultCorsProcessor();

	private final UrlBasedCorsConfigurationSource corsConfigSource = new UrlBasedCorsConfigurationSource();

	//设置不同HandlerMapping实现类的执行顺序
	public final void setOrder(int order) {
	  this.order = order;
	}

	@Override
	public final int getOrder() {
	  return this.order;
	}

	public void setDefaultHandler(Object defaultHandler) {
		this.defaultHandler = defaultHandler;
	}

	public Object getDefaultHandler() {
		return this.defaultHandler;
	}

	public void setAlwaysUseFullPath(boolean alwaysUseFullPath) {
		this.urlPathHelper.setAlwaysUseFullPath(alwaysUseFullPath);
		this.corsConfigSource.setAlwaysUseFullPath(alwaysUseFullPath);
	}

	public void setUrlDecode(boolean urlDecode) {
		this.urlPathHelper.setUrlDecode(urlDecode);
		this.corsConfigSource.setUrlDecode(urlDecode);
	}

	public void setRemoveSemicolonContent(boolean removeSemicolonContent) {
		this.urlPathHelper.setRemoveSemicolonContent(removeSemicolonContent);
		this.corsConfigSource.setRemoveSemicolonContent(removeSemicolonContent);
	}

	public void setUrlPathHelper(UrlPathHelper urlPathHelper) {
		Assert.notNull(urlPathHelper, "UrlPathHelper must not be null");
		this.urlPathHelper = urlPathHelper;
		this.corsConfigSource.setUrlPathHelper(urlPathHelper);
	}

	public UrlPathHelper getUrlPathHelper() {
		return urlPathHelper;
	}

	public void setPathMatcher(PathMatcher pathMatcher) {
		Assert.notNull(pathMatcher, "PathMatcher must not be null");
		this.pathMatcher = pathMatcher;
		this.corsConfigSource.setPathMatcher(pathMatcher);
	}

	public PathMatcher getPathMatcher() {
		return this.pathMatcher;
	}

	public void setInterceptors(Object[] interceptors) {
		this.interceptors.addAll(Arrays.asList(interceptors));
	}

	public void setCorsProcessor(CorsProcessor corsProcessor) {
		Assert.notNull(corsProcessor, "CorsProcessor must not be null");
		this.corsProcessor = corsProcessor;
	}

	/**
	 * Return the configured {@link CorsProcessor}.
	 */
	public CorsProcessor getCorsProcessor() {
		return this.corsProcessor;
	}

	public void setCorsConfigurations(Map<String, CorsConfiguration> corsConfigurations) {
		this.corsConfigSource.setCorsConfigurations(corsConfigurations);
	}

	/**
	 * Get the CORS configuration.
	 */
	public Map<String, CorsConfiguration> getCorsConfigurations() {
		return this.corsConfigSource.getCorsConfigurations();
	}

	//初始化时调用，初始化一些基本信息，这里主要是初始化一些拦截器
	@Override
	protected void initApplicationContext() throws BeansException {
		extendInterceptors(this.interceptors);//添加或修车intercept，现在并没有具体实现
		detectMappedInterceptors(this.adaptedInterceptors);//将springMVC容器或者父容器中的所有MappedInterceptor类型的Bean添加到mappedInterceptors属性中
		initInterceptors();
	}

	protected void extendInterceptors(List<Object> interceptors) {
	}

	//将springMVC容器或者父容器中的所有MappedInterceptor类型的Bean添加到mappedInterceptors属性中
	protected void detectMappedInterceptors(List<HandlerInterceptor> mappedInterceptors) {
		mappedInterceptors.addAll(
				BeanFactoryUtils.beansOfTypeIncludingAncestors(
						getApplicationContext(), MappedInterceptor.class, true, false).values());
	}

	//初始化Interceptor,将interceptors属性里所包含的对象按类型添加到mappedInterceptors或者adaptedInterceptors中。
	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");
				}
				this.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());
		}
	}

	protected final HandlerInterceptor[] getAdaptedInterceptors() {
		int count = this.adaptedInterceptors.size();
		return (count > 0 ? this.adaptedInterceptors.toArray(new HandlerInterceptor[count]) : null);
	}

	protected final MappedInterceptor[] getMappedInterceptors() {
		List<MappedInterceptor> mappedInterceptors = new ArrayList<MappedInterceptor>();
		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
			if (interceptor instanceof MappedInterceptor) {
				mappedInterceptors.add((MappedInterceptor) interceptor);
			}
		}
		int count = mappedInterceptors.size();
		return (count > 0 ? mappedInterceptors.toArray(new MappedInterceptor[count]) : null);
	}

	//获得一个HandlerExecutionChain
	@Override
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		//从实现类中获得HanlderMethod
		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);
		}
		//获得HandlerExecutionChain
		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
		if (CorsUtils.isCorsRequest(request)) {
			CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}
		return executionChain;
	}

	//模板方法，用于子类中实现，通过request去查找对应的执行方法HandlerMethod
	protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;

	//
	protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
		//如果没有获得则创建一个
		HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
				(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
		//获得IP地址及端口后的URL地址
		String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
		//在HandlerExecutionChain中添加拦截器
		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
			if (interceptor instanceof MappedInterceptor) {
				MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
				//根据lookupPath来获取Interceptor
				if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
					chain.addInterceptor(mappedInterceptor.getInterceptor());
				}
			}
			else {
				chain.addInterceptor(interceptor);
			}
		}
		return chain;
	}

	protected CorsConfiguration getCorsConfiguration(Object handler, HttpServletRequest request) {
		if (handler instanceof HandlerExecutionChain) {
			handler = ((HandlerExecutionChain) handler).getHandler();
		}
		if (handler instanceof CorsConfigurationSource) {
			return ((CorsConfigurationSource) handler).getCorsConfiguration(request);
		}
		return null;
	}
	protected HandlerExecutionChain getCorsHandlerExecutionChain(HttpServletRequest request,
			HandlerExecutionChain chain, CorsConfiguration config) {
		if (CorsUtils.isPreFlightRequest(request)) {
			HandlerInterceptor[] interceptors = chain.getInterceptors();
			chain = new HandlerExecutionChain(new PreFlightHandler(config), interceptors);
		}
		else {
			chain.addInterceptor(new CorsInterceptor(config));
		}
		return chain;
	}

	private class PreFlightHandler implements HttpRequestHandler {
		private final CorsConfiguration config;
		public PreFlightHandler(CorsConfiguration config) {
			this.config = config;
		}
		@Override
		public void handleRequest(HttpServletRequest request, HttpServletResponse response)
				throws IOException {
			corsProcessor.processRequest(this.config, request, response);
		}
	}

	private class CorsInterceptor extends HandlerInterceptorAdapter {

		private final CorsConfiguration config;
		public CorsInterceptor(CorsConfiguration config) {
			this.config = config;
		}
		@Override
		public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
				Object handler) throws Exception {
			return corsProcessor.processRequest(this.config, request, response);
		}
	}

}