Handling CORS with JAX-RS Using Jersey

Problem: You're encountering a CORS issue while handling requests with JAX-RS and Jersey. Specifically, the server is not setting the necessary CORS headers, leading to the error "No 'Access-Control-Allow-Origin' header is present on the requested resource."

Solution: To handle CORS in JAX-RS with Jersey, you need to implement a ContainerResponseFilter. The difference in implementation depends on whether you're using Jersey 1.x or 2.x.

Jersey 2.x:

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

@Provider
public class CORSFilter implements ContainerResponseFilter {

    @Override
    public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) {
        MultivaluedMap headers = responseContext.getHeaders();
        headers.add("Access-Control-Allow-Origin", "*");
        headers.add("Access-Control-Allow-Headers", "CSRF-Token, X-Requested-By, Authorization, Content-Type");
        headers.add("Access-Control-Allow-Credentials", "true");
        headers.add("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS, HEAD");
    }
}

Jersey 1.x:

import com.sun.jersey.spi.container.ContainerResponse;
import com.sun.jersey.spi.container.ContainerResponseFilter;

@Provider
public class CORSFilter implements ContainerResponseFilter {

    @Override
    public ContainerResponse filter(ContainerResponse response) {
        response.getHttpHeaders().add("Access-Control-Allow-Origin", "*");
        response.getHttpHeaders().add("Access-Control-Allow-Headers", "CSRF-Token, X-Requested-By, Authorization, Content-Type");
        response.getHttpHeaders().add("Access-Control-Allow-Credentials", "true");
        response.getHttpHeaders().add("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS, HEAD");

        return response;
    }
}

Additional Notes:

• Ensure that the CORS filter is registered with the ResourceConfig object.
• For better handling, consider using a more robust implementation that differentiates between simple and preflight CORS requests.
• Refer to the CORSFilter implementation in RESTeasy for a more comprehensive example.