什么是Handler

能够处理请求的方法或类

四种Handler

1. 标有@RequestMapping注解的方法

@RestController
public class HelloController {
    @RequestMapping("/hello")
    public Object hello(){
        return "success";
    }
}

2. 实现了Controller的类

@Component("/helloHandler")
public class HelloHandler implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        System.out.println("Controller handleRequest...");
        return null;
    }
}

3. 实现了HttpRequestHandler接口的类

@Component("/helloHttpRequestHandler")
public class HelloHttpRequestHandler implements HttpRequestHandler {
    @Override
    public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("HelloHttpRequestHandler");
    }
}

4. HandlerFunction的对象

@Configuration
public class HandlerConfig {
    @Bean
    public  RouterFunction<ServerResponse> routerFunction(){
        RouterFunction<ServerResponse> route = route()
                .GET("/app/person", accept(APPLICATION_JSON), request->ServerResponse.ok().body("get hello router function"))
                .POST("/app/person", request->ServerResponse.ok().body("post hello router function"))
                .build();
        return route;
    }
}

Builder GET(String pattern, RequestPredicate predicate, HandlerFunction<ServerResponse> handlerFunction);

@FunctionalInterface
public interface HandlerFunction<T extends ServerResponse> {

	T handle(ServerRequest request) throws Exception;

}

HandlerMapping

public interface HandlerMapping {
    // ...
    @Nullable
	HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

三种HandlerMapping

在DispatcherServlet.properties中定义

org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\
	org.springframework.web.servlet.function.support.RouterFunctionMapping

其中BeanNameUrlHandlerMapping内部存有实现了Controller的类和实现了HttpRequestHandler接口的类的映射规则,RequestMappingHandlerMapping内存存储了标有@RequestMapping注解的方法相关的映射,RouterFunctionMapping内部存储了HandlerFunction相关的映射规则

HandlerAdapter

public interface HandlerAdapter {

	// 支不支持传入的handler
	boolean supports(Object handler);

	// 处理传入的handler
	@Nullable
	ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;

	
	long getLastModified(HttpServletRequest request, Object handler);

}

四种HandlerAdapter

1. RequestMappingHandlerAdapter 对应@RequestMapping的方法

   public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
   		implements BeanFactoryAware, InitializingBean {
       
   }
   

   public abstract class AbstractHandlerMethodAdapter extends WebContentGenerator implements HandlerAdapter, Ordered {
       // ...
       @Override
   	public final boolean supports(Object handler) {
           // HandlerMethod 对@RequestMapping标注的方法的封装
   		return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
   	}
       // ...
   }
   

2. SimpleControllerHandlerAdapter 对应实现了Controller的类

   public class SimpleControllerHandlerAdapter implements HandlerAdapter {
   
   	@Override
   	public boolean supports(Object handler) {
   		return (handler instanceof Controller);
   	}
   
   	@Override
   	@Nullable
   	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
   			throws Exception {
   
   		return ((Controller) handler).handleRequest(request, response);
   	}
   
   	// ... 
   }
   

3. HttpRequestHandlerAdapter 对应实现了HttpRequestHandler接口的类

   public class HttpRequestHandlerAdapter implements HandlerAdapter {
   
   	@Override
   	public boolean supports(Object handler) {
   		return (handler instanceof HttpRequestHandler);
   	}
   
   	@Override
   	@Nullable
   	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
   			throws Exception {
   
   		((HttpRequestHandler) handler).handleRequest(request, response);
   		return null;
   	}
   
   	@Override
   	public long getLastModified(HttpServletRequest request, Object handler) {
   		if (handler instanceof LastModified) {
   			return ((LastModified) handler).getLastModified(request);
   		}
   		return -1L;
   	}
   
   }
   

4. HandlerFunctionAdapter 对应HandlerFunction的对象

   public class HandlerFunctionAdapter implements HandlerAdapter, Ordered {
   
   	//...
       
   	@Override
   	public boolean supports(Object handler) {
           // HandlerFunction对象
   		return handler instanceof HandlerFunction;
   	}
   
   	@Nullable
   	@Override
   	public ModelAndView handle(HttpServletRequest servletRequest,
   			HttpServletResponse servletResponse,
   			Object handler) throws Exception {
   
   
   		HandlerFunction<?> handlerFunction = (HandlerFunction<?>) handler;
   
   		ServerRequest serverRequest = getServerRequest(servletRequest);
   		ServerResponse serverResponse = handlerFunction.handle(serverRequest);
   
   		return serverResponse.writeTo(servletRequest, servletResponse,
   				new ServerRequestContext(serverRequest));
   	}
   
   	// ...
   }