com.strategicgains.restexpress.plugin.cache.CacheHeaderPostprocessor.java Source code

Introduction

Here is the source code for com.strategicgains.restexpress.plugin.cache.CacheHeaderPostprocessor.java

Source

/*
Copyright 2011, Strategic Gains, Inc.
    
   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
    
  http://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 com.strategicgains.restexpress.plugin.cache;

import static io.netty.handler.codec.http.HttpHeaders.Names.CACHE_CONTROL;
import static io.netty.handler.codec.http.HttpHeaders.Names.EXPIRES;
import static io.netty.handler.codec.http.HttpHeaders.Names.PRAGMA;

import java.util.Date;

import io.netty.handler.codec.http.HttpMethod;
import org.restexpress.Flags;
import org.restexpress.Parameters;
import org.restexpress.Request;
import org.restexpress.Response;
import org.restexpress.pipeline.Postprocessor;

import com.strategicgains.util.date.DateAdapter;
import com.strategicgains.util.date.HttpHeaderTimestampAdapter;

/**
 * For GET and HEAD requests, adds caching control headers.  May be used in conjunction
 * with DateHeaderPostprocessor to add Date header for GET and HEAD requests.
 * <p/>
 * If the route has a Parameters.Cache.MAX_AGE parameter, whose value is the
 * max-age in seconds then the following are added:
 * Cache-Control: max-age=<seconds><br/>
 * Expires: now + max-age
 * <p/>
 * If the route has a Flags.Cache.NO_CACHE flag, then the following
 * headers are set on the response:
 * Cache-Control: no-cache<br/>
 * Pragma: no-cache
 * <p/>
 * The MAX_AGE parameter takes precidence, in that, if present, the NO_CACHE flag
 * is ignored.
 * <p/>
 * To use: simply add server.addPostprocessor(new CacheHeaderPostprocessor()); in your main() method.
 * 
 * @author toddf
 * @since Oct 3, 2011
 */
public class CacheHeaderPostprocessor implements Postprocessor {
    private static final String NO_CACHE = "no-cache";

    DateAdapter fmt = new HttpHeaderTimestampAdapter();

    @Override
    public void process(Request request, Response response) {
        if (!request.isMethodGet() && !HttpMethod.HEAD.equals(request.getHttpMethod()))
            return;

        Object maxAge = request.getParameter(Parameters.Cache.MAX_AGE);

        if (maxAge != null) {
            response.addHeader(CACHE_CONTROL, String.format("max-age=%s", maxAge));
            response.addHeader(EXPIRES, fmt.format(computeExpiresDate((Integer) maxAge)));
        } else {
            if (request.isFlagged(Flags.Cache.DONT_CACHE)) {
                response.addHeader(CACHE_CONTROL, NO_CACHE);
                response.addHeader(PRAGMA, NO_CACHE);
            }
        }
    }

    /**
      * @param maxAge
      */
    private Date computeExpiresDate(Integer maxAge) {
        long millis = System.currentTimeMillis() + (((long) maxAge) * 1000l);
        return new Date(millis);
    }
}