https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.context.request;

import org.springframework.lang.Nullable;
import org.springframework.ui.ModelMap;


Interface for general web request interception. Allows for being applied to Servlet request by building on the WebRequest abstraction. 
This interface assumes MVC-style request processing: A handler gets executed,
exposes a set of model objects, then a view gets rendered based on that model.
Alternatively, a handler may also process the request completely, with no
view to be rendered.

In an async processing scenario, the handler may be executed in a separate thread while the main thread exits without rendering or invoking the postHandle and afterCompletion callbacks. When concurrent handler execution completes, the request is dispatched back in order to proceed with rendering the model and all methods of this contract are invoked again. For further options and comments see org.springframework.web.context.request.async.AsyncWebRequestInterceptor 
This interface is deliberately minimalistic to keep the dependencies of
generic request interceptors as minimal as feasible.

Author:Juergen Hoeller
See Also:
Since:2.0
/**
 * Interface for general web request interception. Allows for being applied
 * to Servlet request by building on the {@link WebRequest} abstraction.
 *
 * <p>This interface assumes MVC-style request processing: A handler gets executed,
 * exposes a set of model objects, then a view gets rendered based on that model.
 * Alternatively, a handler may also process the request completely, with no
 * view to be rendered.
 *
 * <p>In an async processing scenario, the handler may be executed in a separate
 * thread while the main thread exits without rendering or invoking the
 * {@code postHandle} and {@code afterCompletion} callbacks. When concurrent
 * handler execution completes, the request is dispatched back in order to
 * proceed with rendering the model and all methods of this contract are invoked
 * again. For further options and comments see
 * {@code org.springframework.web.context.request.async.AsyncWebRequestInterceptor}
 *
 * <p>This interface is deliberately minimalistic to keep the dependencies of
 * generic request interceptors as minimal as feasible.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see ServletWebRequest
 * @see org.springframework.web.servlet.DispatcherServlet
 * @see org.springframework.web.servlet.handler.AbstractHandlerMapping#setInterceptors
 * @see org.springframework.web.servlet.HandlerInterceptor
 */
public interface WebRequestInterceptor {

	
Intercept the execution of a request handler before its invocation.

Allows for preparing context resources (such as a Hibernate Session)
and expose them as request attributes or as thread-local objects.

Params:
  • request – the current web request
Throws:
/**
	 * Intercept the execution of a request handler <i>before</i> its invocation.
	 * <p>Allows for preparing context resources (such as a Hibernate Session)
	 * and expose them as request attributes or as thread-local objects.
	 * @param request the current web request
	 * @throws Exception in case of errors
	 */
	void preHandle(WebRequest request) throws Exception;

	
Intercept the execution of a request handler after its successful
invocation, right before view rendering (if any).

Allows for modifying context resources after successful handler
execution (for example, flushing a Hibernate Session).

Params:
  • request – the current web request
  • model – the map of model objects that will be exposed to the view (may be null). Can be used to analyze the exposed model and/or to add further model attributes, if desired.
Throws:
/**
	 * Intercept the execution of a request handler <i>after</i> its successful
	 * invocation, right before view rendering (if any).
	 * <p>Allows for modifying context resources after successful handler
	 * execution (for example, flushing a Hibernate Session).
	 * @param request the current web request
	 * @param model the map of model objects that will be exposed to the view
	 * (may be {@code null}). Can be used to analyze the exposed model
	 * and/or to add further model attributes, if desired.
	 * @throws Exception in case of errors
	 */
	void postHandle(WebRequest request, @Nullable ModelMap model) throws Exception;

	
Callback after completion of request processing, that is, after rendering
the view. Will be called on any outcome of handler execution, thus allows
for proper resource cleanup.

Note: Will only be called if this interceptor's preHandle method has successfully completed! 
Params:
  • request – the current web request
  • ex – exception thrown on handler execution, if any
Throws:
/**
	 * Callback after completion of request processing, that is, after rendering
	 * the view. Will be called on any outcome of handler execution, thus allows
	 * for proper resource cleanup.
	 * <p>Note: Will only be called if this interceptor's {@code preHandle}
	 * method has successfully completed!
	 * @param request the current web request
	 * @param ex exception thrown on handler execution, if any
	 * @throws Exception in case of errors
	 */
	void afterCompletion(WebRequest request, @Nullable Exception ex) throws Exception;

}