HttpRequestForwarder

Simple HttpServlet that can be used in a Jetty to forward requests

I needed a Resource, that can be used by a Jetty, that will forward the complete Reqest to a different target, that may use specific SSL configuration (that is why I could not use HttpServletResponse sendRedirect)

It was more complicated then anticipated, that's why I thought I'd share it.

import java.io.IOException;
import java.io.InputStream;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.client.Entity;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.MediaType;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.io.ByteStreams;

public class RequestForwarder extends HttpServlet {
    private static final Logger logger = LoggerFactory.getLogger(RequestForwarder.class);
    private static final String prefix = "relay";
    private final WebTarget webTarget;

    RequestForwarder(WebTarget webTarget) {
        this.webTarget = webTarget;
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String path = request.getPathInfo().replace("//", "/");

        WebTarget currentTarget = webTarget.path(prefix + path);
        Map<String, String[]> parameterMap = request.getParameterMap();
        for (var entry : parameterMap.entrySet()) {
            currentTarget = currentTarget.queryParam(entry.getKey(), (Object[]) entry.getValue());
        }

        InputStream relayResponse;
        if ("POST".equals(request.getMethod())) {
            relayResponse = currentTarget.request(MediaType.APPLICATION_JSON)
                                         .accept(MediaType.APPLICATION_OCTET_STREAM)
                                         .post(Entity.json(new ObjectMapper().readValue(request.getInputStream(), Object.class)))
                                         .readEntity(InputStream.class);
        } else if ("PUT".equals(request.getMethod())) {
            relayResponse = currentTarget.request(MediaType.APPLICATION_JSON)
                                         .accept(MediaType.APPLICATION_OCTET_STREAM)
                                         .put(Entity.json(new ObjectMapper().readValue(request.getInputStream(), Object.class)))
                                         .readEntity(InputStream.class);
        } else {
            relayResponse = currentTarget.request(MediaType.APPLICATION_JSON)
                                         .accept(MediaType.APPLICATION_OCTET_STREAM)
                                         .build(request.getMethod())
                                         .invoke()
                                         .readEntity(InputStream.class);
        }
        ByteStreams.copy(relayResponse, response.getOutputStream());
    }
}

The Webtarget can be set up for example like this and point anywhere

public static WebTarget createResource(String url, ObjectMapper objectMapper, SslContextFactory sslContextFactory) throws Exception {
    ClientBuilder builder = ClientBuilder.newBuilder();
    if (sslContextFactory != null) {
        logger.info("building with ssl");
        sslContextFactory.start();
        builder.sslContext(sslContextFactory.getSslContext());
    }

    JacksonJaxbJsonProvider jacksonProvider = new JacksonJaxbJsonProvider();
    jacksonProvider.setMapper(objectMapper);

    return builder.withConfig(new ClientConfig(jacksonProvider)).build().target(url);
}

Horus1337/HttpRequestForwarder

HttpRequestForwarder