Http response wrapper for caching js, css and images for browsers.

ResourcesCachingWrapper.java

package eu.gruchala.web.wrapper;

import java.util.Arrays;
import java.util.Calendar;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * Caches requests for all CSS, JS and images.
 */
public class ResourcesCachingWrapper extends HttpServletResponseWrapper {

    public static final String[] CACHEABLE_CONTENT_TYPES = new String[]{
        "text/css", "text/javascript", "application/javascript",
        "image/png", "image/jpeg", "image/gif", "image/jpg"
    };

    private static long MONTH = 0l;

    static {
        Arrays.sort(CACHEABLE_CONTENT_TYPES);
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.MONTH, 1);
        MONTH = calendar.getTimeInMillis();
    }

    public ResourcesCachingWrapper(HttpServletResponse response) {
        super(response);
    }

    @Override
    public void setContentType(String contentType) {
        if (contentType != null && Arrays.binarySearch(CACHEABLE_CONTENT_TYPES, contentType) > -1) {
            super.setDateHeader("Expires", MONTH);
        } else {
            super.setHeader("Expires", "-1");
            super.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        }
        super.setContentType(contentType);
    }
}