How to implement abstract Java class in Groovy?

Question

I am trying to write some Spring code in Groovy from one of Spring's tutorials . When I write the following code in Groovy:

Java

@Component
public class SimpleCORSFilter implements Filter {

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, PUT, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
        chain.doFilter(req, res);
    }

    public void init(FilterConfig filterConfig) {}

    public void destroy() {}

}

Groovy

@Component
class SimpleCORSFilter implements Filter {

    void doFilter(ServletRequest req, ServletResponse, FilterChain chain)
            throws IOException, ServletException {
        HttpServletResponse response = res as HttpServletResponse
        response.setHeader("Access-Control-Allow-Origin", "*")
        chain.doFilter(req, res)
    }

    void init (FilterConfig filterConfig) {}
    void destroy() {}
}

I get the following error

Can't have an abstract method in a non-abstract class. The class 'com.myproject.main.SimpleCORSFilter' must be declared abstract or the method 'void doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)' must be implemented.
 @ line X, column Y.
   @Component
   ^

Question

I have implemented the abstract doFilter method. Why is it not valid?

How can I fix this?

Answer 1

You have a syntax error here

void doFilter(ServletRequest req, ServletResponse, FilterChain chain)

Should be

void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)