OptionsAcceptPatchHeaderFilter.java

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package org.glassfish.jersey.examples.httppatch;

import java.io.IOException;

import javax.ws.rs.HttpMethod;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerResponseContext;
import javax.ws.rs.container.ContainerResponseFilter;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;

/**
 * A JAX-RS container response filter that applies {@code Accept-Patch} header
 * to any response to an {@code OPTIONS} request.
 *
 * @author Gerard Davison (gerard.davison at oracle.com)
 * @author Marek Potociar (marek.potociar at oracle.com)
 */
public class OptionsAcceptPatchHeaderFilter implements ContainerResponseFilter {

    private static final String ACCEPT_PATCH_HEADER = "Accept-Patch";

    @Override
    public void filter(final ContainerRequestContext requestContext, final ContainerResponseContext responseContext)
            throws IOException {

        if (HttpMethod.OPTIONS.equals(requestContext.getMethod())) {
            final MultivaluedMap<String, Object> headers = responseContext.getHeaders();
            if (!headers.containsKey(ACCEPT_PATCH_HEADER)) {
                headers.putSingle(ACCEPT_PATCH_HEADER, MediaType.APPLICATION_JSON_PATCH_JSON);
            }
        }
    }
}