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package tools.refinery.language.web;
import java.io.IOException;
import java.util.regex.Pattern;
import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.FilterConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
public class CacheControlFilter implements Filter {
private static final String CACHE_CONTROL_HEADER = "Cache-Control";
private static final String EXPIRES_HEADER = "Expires";
private static final Pattern CACHE_URI_PATTERN = Pattern.compile(".*\\.(css|gif|js|map|png|svg|woff2)");
private static final long EXPIRY = 31536000;
private static final String CACHE_CONTROL_CACHE_VALUE = "public, max-age: " + EXPIRY + ", immutable";
private static final String CACHE_CONTROL_NO_CACHE_VALUE = "no-cache, no-store, max-age: 0, must-revalidate";
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// Nothing to initialize.
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
if (request instanceof HttpServletRequest httpRequest && response instanceof HttpServletResponse httpResponse) {
if (CACHE_URI_PATTERN.matcher(httpRequest.getRequestURI()).matches()) {
httpResponse.setHeader(CACHE_CONTROL_HEADER, CACHE_CONTROL_CACHE_VALUE);
httpResponse.setDateHeader(EXPIRES_HEADER, System.currentTimeMillis() + EXPIRY * 1000L);
} else {
httpResponse.setHeader(CACHE_CONTROL_HEADER, CACHE_CONTROL_NO_CACHE_VALUE);
httpResponse.setDateHeader(EXPIRES_HEADER, 0);
}
}
chain.doFilter(request, response);
}
@Override
public void destroy() {
// Nothing to dispose.
}
}
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