Spring @RequestMapping 工作原理

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Spring @RequestMapping 工作原理

配置基础启动类及Controller类

@SpringBootApplication
public class DemoServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoServiceApplication.class, args);
    }
}
@RestController
public class HelloController {

    @PatchMapping("/hello")
    // above statement is a shortcut for below statement
    // @RequestMapping(value = "/hello", method = RequestMethod.PATCH)
    public ResponseData hello() {
        return ResponseData.success(null);
    }

    @PutMapping ("/hello")
	// above statement is a shortcut for below statement
	// @RequestMapping(value = "/hello", method = RequestMethod.PUT)
    public ResponseData hello2() {
        return ResponseData.success(null);
    }
}
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping(method = RequestMethod.PATCH)
public @interface PatchMapping {
	// ...
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping(method = RequestMethod.PUT)
public @interface PutMapping {
	// ...
}

请求验证

$ curl -X PUT http://localhost:8080/hello

Spring @RequestMapping 工作原理,spring,java,后端

package jakarta.servlet.http;

public abstract class HttpServlet extends GenericServlet {
	// ...
	
	/**
	 * Dispatches client requests to the protected service method. There's no need to override this method.
	 * ...
	 */
    @Override
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {

        HttpServletRequest request;
        HttpServletResponse response;

        try {
            request = (HttpServletRequest) req;
            response = (HttpServletResponse) res;
        } catch (ClassCastException e) {
            throw new ServletException(lStrings.getString("http.non_http"));
        }
        service(request, response);
    }
    
    // ...
    
	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String method = req.getMethod();

        if (method.equals(METHOD_GET)) {
        	// ..
	        doGet(req, resp);
            // ...
        } else if (method.equals(METHOD_HEAD)) {
        	// ..
	        doHead(req, resp);
        } else if (method.equals(METHOD_POST)) {
            doPost(req, resp);
        } else if (method.equals(METHOD_PUT)) {
            doPut(req, resp);
        } else if (method.equals(METHOD_DELETE)) {
            doDelete(req, resp);
        } else if (method.equals(METHOD_OPTIONS)) {
            doOptions(req, resp);
        } else if (method.equals(METHOD_TRACE)) {
            doTrace(req, resp);
        } else {
            // Note that this means NO servlet supports whatever
            // method was requested, anywhere on this server.
        }
    }
    // ...
}
package org.springframework.web.servlet;

public abstract class HttpServletBean extends HttpServlet implements EnvironmentCapable, EnvironmentAware {
	// ...
	// no override service(), subclass `FrameworkServlet` will implement this method
	// ...
}
package org.springframework.web.servlet;

public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware {

	// ...
	private static final Set<String> HTTP_SERVLET_METHODS =
			Set.of("DELETE", "HEAD", "GET", "OPTIONS", "POST", "PUT", "TRACE");
	// ...
	
	/**
	 * Override the parent class implementation in order to intercept requests
	 * using PATCH or non-standard HTTP methods (WebDAV).
	 */
	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		if (HTTP_SERVLET_METHODS.contains(request.getMethod())) {
			super.service(request, response);
		} // PATCH is missing, so process will go here
		else {
			processRequest(request, response);
		}
	}
	// ...

	@Override
	protected final void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate POST requests to {@link #processRequest}.
	 * @see #doService
	 */
	@Override
	protected final void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate PUT requests to {@link #processRequest}.
	 * @see #doService
	 */
	@Override
	protected final void doPut(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate DELETE requests to {@link #processRequest}.
	 * @see #doService
	 */
	@Override
	protected final void doDelete(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		processRequest(request, response);
	}

	/**
	 * Delegate OPTIONS requests to {@link #processRequest}, if desired.
	 * <p>Applies HttpServlet's standard OPTIONS processing otherwise,
	 * and also if there is still no 'Allow' header set after dispatching.
	 * @see #doService
	 */
	@Override
	protected void doOptions(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		if (this.dispatchOptionsRequest || CorsUtils.isPreFlightRequest(request)) {
			processRequest(request, response);
			if (response.containsHeader(HttpHeaders.ALLOW)) {
				// Proper OPTIONS response coming from a handler - we're done.
				return;
			}
		}

		// Use response wrapper in order to always add PATCH to the allowed methods
		super.doOptions(request, new HttpServletResponseWrapper(response) {
			@Override
			public void setHeader(String name, String value) {
				if (HttpHeaders.ALLOW.equals(name)) {
					value = (StringUtils.hasLength(value) ? value + ", " : "") + HttpMethod.PATCH.name();
				}
				super.setHeader(name, value);
			}
		});
	}

	/**
	 * Delegate TRACE requests to {@link #processRequest}, if desired.
	 * <p>Applies HttpServlet's standard TRACE processing otherwise.
	 * @see #doService
	 */
	@Override
	protected void doTrace(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		if (this.dispatchTraceRequest) {
			processRequest(request, response);
			if ("message/http".equals(response.getContentType())) {
				// Proper TRACE response coming from a handler - we're done.
				return;
			}
		}
		super.doTrace(request, response);
	}

	/**
	 * Process this request, publishing an event regardless of the outcome.
	 * <p>The actual event handling is performed by the abstract
	 * {@link #doService} template method.
	 */
	protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		long startTime = System.currentTimeMillis();
		Throwable failureCause = null;

		LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
		LocaleContext localeContext = buildLocaleContext(request);

		RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
		ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);

		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
		asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());

		initContextHolders(request, localeContext, requestAttributes);

		try {
			doService(request, response);
		}
		catch (ServletException | IOException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (Throwable ex) {
			failureCause = ex;
			throw new ServletException("Request processing failed: " + ex, ex);
		}

		finally {
			resetContextHolders(request, previousLocaleContext, previousAttributes);
			if (requestAttributes != null) {
				requestAttributes.requestCompleted();
			}
			logResult(request, response, failureCause, asyncManager);
			publishRequestHandledEvent(request, response, startTime, failureCause);
		}
	}
	
	// ...
	protected abstract void doService(HttpServletRequest request, HttpServletResponse response) throws Exception;
	// ...
}
package org.springframework.web.servlet;

public class DispatcherServlet extends FrameworkServlet {
	// ...
	@Override
	protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
		// ...
		try {
			doDispatch(request, response);
		}
		finally {
			// ...
		}
		// ...
	}
	
	// ...
	
	/**
	 * Process the actual dispatching to the handler.
	 * The handler will be obtained by applying the servlet's HandlerMappings in order. 
	 * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters to find the first that supports the handler class. 
	 * All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers themselves to decide which methods are acceptable.
	 */	 
	@SuppressWarnings("deprecation")
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		// ...
		try {
		// ...
			try {
				// ...
				// Determine handler for the current request.
				// important here
				mappedHandler = getHandler(processedRequest);
				// ...
				// Determine handler adapter for the current request.
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
				// ...
				// Actually invoke the handler.
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

				if (asyncManager.isConcurrentHandlingStarted()) {
					return;
				}

				applyDefaultViewName(processedRequest, mv);
				mappedHandler.applyPostHandle(processedRequest, response, mv);
			}
			// catch()
		} 
		//catch()
	}
	
	// ...
	
	/**
	 * Return the HandlerExecutionChain for this request.
	 * <p>Tries all handler mappings in order.
	 */
	@Nullable
	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		if (this.handlerMappings != null) {
			for (HandlerMapping mapping : this.handlerMappings) {
				HandlerExecutionChain handler = mapping.getHandler(request);
				if (handler != null) {
					return handler;
				}
			}
		}
		return null;
	}

	// ...
}		
this.handlerMappings = {ArrayList@7649}  size = 5
	 0 = {RequestMappingHandlerMapping@6913} 
	 1 = {BeanNameUrlHandlerMapping@7828} 
	 2 = {RouterFunctionMapping@7829} 
	 3 = {SimpleUrlHandlerMapping@7830} 
	 4 = {WelcomePageHandlerMapping@7831} 

展开 0 = {RequestMappingHandlerMapping@6913}

 mappingRegistry = {AbstractHandlerMethodMapping$MappingRegistry@6921} 
	 registry = {HashMap@7840}  size = 5
		  {RequestMappingInfo@7864} "{GET [/api/tutorials]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7865} 
		  {RequestMappingInfo@7866} "{ [/error], produces [text/html]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7867} 
		  {RequestMappingInfo@7868} "{PATCH [/hello]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7869} 
		  {RequestMappingInfo@7870} "{ [/error]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7871} 
		  {RequestMappingInfo@7872} "{PUT [/hello]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7873} 
	 pathLookup = {LinkedMultiValueMap@7841}  size = 3
		  "/api/tutorials" -> {ArrayList@7852}  size = 1
		  "/hello" -> {ArrayList@7854}  size = 2
		  "/error" -> {ArrayList@7856}  size = 2

Spring @RequestMapping 工作原理,spring,java,后端文章来源地址https://www.toymoban.com/news/detail-595141.html

package org.springframework.web.servlet.handler;

public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
		implements HandlerMapping, Ordered, BeanNameAware {
	// ...
	
	/**
	 * Look up a handler for the given request, falling back to the default
	 * handler if no specific one is found.
	 * @param request current HTTP request
	 * @return the corresponding handler instance, or the default handler
	 * @see #getHandlerInternal
	 */
	@Override
	@Nullable
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		Object handler = getHandlerzInternal(request);
		if (handler == null) {
			handler = getDefaultHandler();
		}
		if (handler == null) {
			return null;
		}
		// Bean name or resolved handler?
		if (handler instanceof String handlerName) {
			handler = obtainApplicationContext().getBean(handlerName);
		}

		// Ensure presence of cached lookupPath for interceptors and others
		if (!ServletRequestPathUtils.hasCachedPath(request)) {
			initLookupPath(request);
		}

		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);

		if (logger.isTraceEnabled()) {
			logger.trace("Mapped to " + handler);
		}
		else if (logger.isDebugEnabled() && !DispatcherType.ASYNC.equals(request.getDispatcherType())) {
			logger.debug("Mapped to " + executionChain.getHandler());
		}

		if (hasCorsConfigurationSource(handler) || CorsUtils.isPreFlightRequest(request)) {
			CorsConfiguration config = getCorsConfiguration(handler, request);
			if (getCorsConfigurationSource() != null) {
				CorsConfiguration globalConfig = getCorsConfigurationSource().getCorsConfiguration(request);
				config = (globalConfig != null ? globalConfig.combine(config) : config);
			}
			if (config != null) {
				config.validateAllowCredentials();
			}
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}

		return executionChain;
	}

	// ...
}
package org.springframework.web.servlet.mvc.method;
public abstract class RequestMappingInfoHandlerMapping extends AbstractHandlerMethodMapping<RequestMappingInfo> {
	// ..
	
	@Override
	@Nullable
	protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
		// ...
		return super.getHandlerInternal(request);
		// ...
	}
	
	// ...	
}
package org.springframework.web.servlet.handler;

public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean {
	// ...
	
	@Override
	@Nullable
	protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
		String lookupPath = initLookupPath(request);
		this.mappingRegistry.acquireReadLock();
		try {
			HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
			return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
		}
		finally {
			this.mappingRegistry.releaseReadLock();
		}
	}
	// ...

	@Nullable
	protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
		List<Match> matches = new ArrayList<>();
		List<T> directPathMatches = this.mappingRegistry.getMappingsByDirectPath(lookupPath);
		if (directPathMatches != null) {
			addMatchingMappings(directPathMatches, matches, request);
		}
		if (matches.isEmpty()) {
			addMatchingMappings(this.mappingRegistry.getRegistrations().keySet(), matches, request);
		}
		if (!matches.isEmpty()) {
			Match bestMatch = matches.get(0);
			if (matches.size() > 1) {
				Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
				matches.sort(comparator);
				bestMatch = matches.get(0);
				if (logger.isTraceEnabled()) {
					logger.trace(matches.size() + " matching mappings: " + matches);
				}
				if (CorsUtils.isPreFlightRequest(request)) {
					for (Match match : matches) {
						if (match.hasCorsConfig()) {
							return PREFLIGHT_AMBIGUOUS_MATCH;
						}
					}
				}
				else {
					Match secondBestMatch = matches.get(1);
					if (comparator.compare(bestMatch, secondBestMatch) == 0) {
						Method m1 = bestMatch.getHandlerMethod().getMethod();
						Method m2 = secondBestMatch.getHandlerMethod().getMethod();
						String uri = request.getRequestURI();
						throw new IllegalStateException(
								"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
					}
				}
			}
			request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.getHandlerMethod());
			handleMatch(bestMatch.mapping, lookupPath, request);
			return bestMatch.getHandlerMethod();
		}
		else {
			return handleNoMatch(this.mappingRegistry.getRegistrations().keySet(), lookupPath, request);
		}
	}
	// ...
}

查看looupPath

lookupPath="/hello"
this.mappingRegistry = {AbstractHandlerMethodMapping$MappingRegistry@6921} 
	 registry = {HashMap@7840}  size = 5
		  {RequestMappingInfo@7864} "{GET [/api/tutorials]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7865} 
		  {RequestMappingInfo@7866} "{ [/error], produces [text/html]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7867} 
		  {RequestMappingInfo@7868} "{PATCH [/hello]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7869} 
		  {RequestMappingInfo@7870} "{ [/error]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7871} 
		  {RequestMappingInfo@7872} "{PUT [/hello]}" -> {AbstractHandlerMethodMapping$MappingRegistration@7873} 
	 pathLookup = {LinkedMultiValueMap@7841}  size = 3
		  "/api/tutorials" -> {ArrayList@7852}  size = 1
		  "/hello" -> {ArrayList@7854}  size = 2
		  "/error" -> {ArrayList@7856}  size = 2

directPathMatches

List<T> directPathMatches = this.mappingRegistry.getMappingsByDirectPath(lookupPath);
directPathMatches = {ArrayList@7854}  size = 2
	 0 = {RequestMappingInfo@7872} "{PUT [/hello]}"
	 1 = {RequestMappingInfo@7868} "{PATCH [/hello]}"
package org.springframework.web.method;

public class HandlerMethod {
	// ...
	public HandlerMethod createWithResolvedBean() {
		Object handler = this.bean;
		// default would go here
		if (this.bean instanceof String beanName) {
			Assert.state(this.beanFactory != null, "Cannot resolve bean name without BeanFactory");
			handler = this.beanFactory.getBean(beanName);
		}
		return new HandlerMethod(this, handler);
	}
	// ...
}

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