ApiKeyHeaderFilter.java

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;

import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PRE_DECORATION_FILTER_ORDER;
import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PRE_TYPE;
import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PROXY_KEY;

/**
 * Adds an API key in the form of a request header to proxied requests.
 * You have to specify a prefix for the name of the Zuul proxy to match,
 * as we don't want to add these headers to requests made to other downstream services.
 */
public class ApiKeyHeaderFilter extends ZuulFilter {

    private String headerName = "Ocp-Apim-Subscription-Key";
    private String proxyPrefix;
    private String apiKey;

    public ApiKeyHeaderFilter(String proxyPrefix, String apiKey) {
        this.proxyPrefix = proxyPrefix;
        this.apiKey = apiKey;
    }

    /**
     * Default header name is {@code Ocp-Apim-Subscription-Key} as used by Microsoft Azure.
     *
     * @param headerName name of the header to contains the API key
     */
    public void setHeaderName(String headerName) {
        this.headerName = headerName;
    }

    @Override
    public String filterType() {
        return PRE_TYPE;
    }

    @Override
    public int filterOrder() {
        return PRE_DECORATION_FILTER_ORDER + 1;
    }

    @Override
    public boolean shouldFilter() {
        // only filter for the matching proxy, or we could accidentally expose secrets to other downstream services
        RequestContext currentContext = RequestContext.getCurrentContext();
        String currentProxy = (String) currentContext.get(PROXY_KEY);
        return currentProxy != null && currentProxy.startsWith(proxyPrefix);
    }

    @Override
    public Object run() throws ZuulException {
        RequestContext currentContext = RequestContext.getCurrentContext();
        currentContext.addZuulRequestHeader(headerName, apiKey);

        return null;
    }
}