add simple cache filter

Author: karussell

src/main/java/com/graphhopper/converter/ConverterApplication.java

@@ -1,5 +1,6 @@
 package com.graphhopper.converter;
 
+import com.graphhopper.converter.api.CacheFilter;
 import com.graphhopper.converter.api.IPFilter;
 import com.graphhopper.converter.health.NominatimHealthCheck;
 import com.graphhopper.converter.resources.*;
@@ -53,6 +54,8 @@ public void run(ConverterConfiguration converterConfiguration, Environment envir
         final Client client = new JerseyClientBuilder(environment).using(cfg)
                 .build(getName());
 
+        environment.jersey().register(new CacheFilter());
+
         if (converterConfiguration.isNominatim()) {
             final ConverterResourceNominatim resource = new ConverterResourceNominatim(
                     converterConfiguration.getNominatimURL(),

src/main/java/com/graphhopper/converter/api/CacheFilter.java

@@ -0,0 +1,45 @@
+package com.graphhopper.converter.api;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+
+import javax.ws.rs.container.ContainerRequestContext;
+import javax.ws.rs.container.ContainerResponseContext;
+import javax.ws.rs.container.ContainerResponseFilter;
+import javax.ws.rs.container.PreMatching;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.Provider;
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+
+@Provider
+@PreMatching
+public class CacheFilter implements ContainerResponseFilter {
+
+    private static final Cache<String, Response> cache = CacheBuilder.newBuilder()
+            .maximumSize(1000)
+            .expireAfterWrite(10, TimeUnit.MINUTES)
+            .build();
+
+    @Override
+    public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) throws IOException {
+        if (!"GET".equalsIgnoreCase(requestContext.getMethod())) {
+            return; // Only cache GET requests
+        }
+
+        // TODO headers are ignored. shouldn't be a problem
+
+        String requestKey = requestContext.getUriInfo().getRequestUri().toString();
+        Response cachedResponse = cache.getIfPresent(requestKey);
+        if (cachedResponse != null) {
+            // LoggerFactory.getLogger(getClass()).info("now accessing cache");
+            responseContext.setStatus(cachedResponse.getStatus());
+            responseContext.setEntity(cachedResponse.getEntity());
+            return;
+        }
+
+        cache.put(requestKey, Response.status(responseContext.getStatus())
+                .entity(responseContext.getEntity())
+                .build());
+    }
+}