org.jbr.commons.rest.RestEndpointAspect.java Source code

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Here is the source code for org.jbr.commons.rest.RestEndpointAspect.java

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/**
 * Copyright (C) - 2013 jbrule
 * 
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>
 */
package org.jbr.commons.rest;

import java.net.URI;
import java.util.Date;
import java.util.UUID;

import org.apache.commons.lang3.time.DateFormatUtils;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.jbr.commons.service.uuid.UUIDService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.hateoas.ResourceSupport;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;

/**
 * TODO - type header
 * 
 * @author <a href="mailto:brulejr@gmail.com">Jon Brule</a>
 */
@Component
@Aspect
public class RestEndpointAspect {

    public static final String HEADER_ELAPSED_TIME = "x-rest-elapsed-time";
    public static final String HEADER_RESPONSE_ID = "x-rest-response-id";
    public static final String HEADER_START_TIME = "x-rest-start-time";

    private static final Logger LOG = LoggerFactory.getLogger(RestEndpointAspect.class);

    @Autowired(required = false)
    private UUIDService uuidService;

    /**
     * Aspect that surrounds a bound RESTful controller method to provide the
     * following enhanced functionality:
     * 
     * @param joinPoint
     *            Provides reflective access to both the state available at a
     *            join point and static information about it.
     * @param responseType
     *            the {@link ResponseType} annotation which is used to specify
     *            the response class for the bound controller method
     * @throws Throwable
     *             any encountered error is passed through
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Around(value = "@annotation(responseTimer)", argNames = "joinPoint, responseTimer")
    public Object around(final ProceedingJoinPoint joinPoint, final RestEndpoint responseTimer) throws Throwable {

        // start execution timer
        final Date startTime = startTimer();

        // execute wrapped method
        final Object returnValue = joinPoint.proceed();

        // halt and record execution timer
        final long elapsedTime = System.currentTimeMillis() - startTime.getTime();
        LOG.debug("elapsed time for {} is {}ms", joinPoint, elapsedTime);

        // handle response entity
        if (returnValue instanceof ResponseEntity<?>) {
            final ResponseEntity<?> entity = (ResponseEntity<?>) returnValue;
            final HttpHeaders headers = new HttpHeaders();

            // transfer any existing headers, if enabled
            if (responseTimer.transferHeaders()) {
                headers.putAll(entity.getHeaders());
            }

            // transfer self link as Location header, if CREATED reponse
            if (entity.getStatusCode().equals(HttpStatus.CREATED)) {
                if (entity.getBody() instanceof ResourceSupport) {
                    final ResourceSupport resource = (ResourceSupport) entity.getBody();
                    if (resource.getId() != null) {
                        headers.setLocation(new URI(resource.getId().getHref()));
                    }
                }
            }

            // save elapsed time header
            headers.add(HEADER_RESPONSE_ID, generatedResponseIdentifier());
            headers.add(HEADER_START_TIME, DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT.format(startTime));
            headers.add(HEADER_ELAPSED_TIME, String.valueOf(elapsedTime));

            // return new response entity
            return new ResponseEntity(entity.getBody(), headers, entity.getStatusCode());
        }

        // handle non-response entity
        else {
            return returnValue;
        }
    }

    private String generatedResponseIdentifier() {
        return (uuidService != null) ? uuidService.nextUUID().toString() : UUID.randomUUID().toString();
    }

    private Date startTimer() {
        final RequestAttributes attrs = RequestContextHolder.currentRequestAttributes();
        final int scope = RequestAttributes.SCOPE_REQUEST;
        Date startTime = (Date) attrs.getAttribute(HEADER_START_TIME, scope);
        if (startTime == null) {
            startTime = new Date();
            attrs.setAttribute(HEADER_START_TIME, startTime, scope);
        }
        return startTime;

    }

}