pl.allegro.tech.hermes.consumers.consumer.interpolation.MessageBodyInterpolator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of hermes-consumers Show documentation

Fast and reliable message broker built on top of Kafka.

There is a newer version: 2.8.0

package pl.allegro.tech.hermes.consumers.consumer.interpolation;

import com.damnhandy.uri.template.UriTemplate;
import com.damnhandy.uri.template.VariableExpansionException;
import com.google.common.base.Charsets;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.Maps;
import com.jayway.jsonpath.InvalidPathException;
import com.jayway.jsonpath.JsonPath;
import pl.allegro.tech.hermes.api.EndpointAddress;
import pl.allegro.tech.hermes.consumers.consumer.Message;

import java.net.URI;
import java.util.Map;

public class MessageBodyInterpolator implements UriInterpolator {

    private static final int MAX_CACHE_SIZE = 1000;

    private final LoadingCache templateCache = CacheBuilder
            .newBuilder()
            .maximumSize(MAX_CACHE_SIZE)
            .build(new TemplateLoader());

    private final LoadingCache variableCompiler = CacheBuilder
            .newBuilder()
            .maximumSize(MAX_CACHE_SIZE)
            .build(new JsonPathLoader());

    public URI interpolate(EndpointAddress endpoint, Message message) throws InterpolationException {
        UriTemplate template = templateCache.getUnchecked(endpoint.getEndpoint());
        String[] variables = template.getVariables();

        if (variables.length > 0) {
            Map values = Maps.newHashMap();
            String payload = new String(message.getData(), Charsets.UTF_8);

            for (String variable : variables) {

                JsonPath path = variableCompiler.getUnchecked(variable);

                try {
                    values.put(variable, path.read(payload));
                } catch (InvalidPathException e) {
                    throw new InterpolationException(String.format("Missing variable on path %s", path.getPath()), e);
                }
            }

            try {
                return URI.create(template.expand(values));
            } catch (VariableExpansionException e) {
                throw new InterpolationException("Cannot expand template", e);
            }
        }

        return endpoint.getUri();

    }

    private static class TemplateLoader extends CacheLoader {

        @Override
        public UriTemplate load(String url) throws Exception {
            return UriTemplate.fromTemplate(url);
        }
    }

    private static class JsonPathLoader extends CacheLoader {

        private static final String ROOT_PREFIX = "$.";

        @Override
        public JsonPath load(String key) throws Exception {
            return JsonPath.compile(ROOT_PREFIX + key);
        }
    }

}