Configuring Jetty, Jersey, and Guice

Question

I'm refactoring a legacy Java codebase to provide Guice-powered dependency injection to Jersey resource classes.

Here is a stripped down application that uses the legacy Jetty/Jersey setup (see Main & Application ) along with my attempts to wire up Guice using their wiki article on servlets :

build.gradle

plugins {
    id 'java'
}

repositories {
    mavenCentral()
}

dependencies {
    compile 'org.projectlombok:lombok:1.16.18'
    compile 'com.google.inject:guice:4.1.0'
    compile 'com.google.inject.extensions:guice-servlet:4.1.0'
    compile 'com.fasterxml.jackson.jaxrs:jackson-jaxrs-json-provider:2.9.3'
    compile 'org.eclipse.jetty:jetty-server:9.4.8.v20171121'
    compile 'org.eclipse.jetty:jetty-servlet:9.4.8.v20171121'
    compile 'org.glassfish.jersey.media:jersey-media-sse:2.26'
    compile 'com.sun.jersey:jersey-servlet:1.19.4'
}

Main.java

package org.arabellan.sandbox;

import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.servlet.ServletModule;

import java.util.ArrayList;
import java.util.List;

public class Main {

    static Injector injector;

    public static void main(String[] args) throws Exception {
        List<AbstractModule> modules = new ArrayList<>();
        modules.add(new ExistingModule());
        modules.add(new ServletModule());
        injector = Guice.createInjector(modules);
        injector.getInstance(Application.class).run();
    }

}

Application.java

package org.arabellan.sandbox;

import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider;
import com.google.inject.servlet.GuiceFilter;
import com.sun.jersey.spi.container.servlet.ServletContainer;
import org.glassfish.jersey.message.DeflateEncoder;
import org.glassfish.jersey.message.GZipEncoder;
import org.glassfish.jersey.server.ResourceConfig;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.glassfish.jersey.server.filter.EncodingFilter;

class Application {

    void run() throws Exception {
        Server jettyServer = new Server(8080);
        ServletContextHandler httpContext = new ServletContextHandler(jettyServer, "/");
        httpContext.addEventListener(new GuiceServletConfig());
        httpContext.addFilter(GuiceFilter.class, "/*", null);
        httpContext.addServlet(new ServletHolder(new ServletContainer(buildResourceConfig())), "/*");
        jettyServer.setHandler(httpContext);
        jettyServer.start();
    }

    private ResourceConfig buildResourceConfig() {
        ResourceConfig config = new ResourceConfig();
        config.register(JacksonJsonProvider.class);
        config.registerClasses(EncodingFilter.class, GZipEncoder.class, DeflateEncoder.class);
        config.packages("org.arabellan.sandbox");
        return config;
    }

}

ExistingModule.java

package org.arabellan.sandbox;

import com.google.inject.AbstractModule;

public class ExistingModule extends AbstractModule {

    protected void configure() {
        bind(FooDao.class).to(DynamoDBFooDao.class);
    }

}

GuiceServletConfig.java

package org.arabellan.sandbox;

import com.google.inject.Injector;
import com.google.inject.servlet.GuiceServletContextListener;

public class GuiceServletConfig extends GuiceServletContextListener {

    @Override
    protected Injector getInjector() {
        return Main.injector;
    }

}

FooResource.java

package org.arabellan.sandbox;

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;

@Path("/foo")
public class FooResource {

    private final FooDao dao;

    @Inject
    public FooResource(FooDao dao) {
        this.dao = dao;
    }

    @GET
    @Path("/{id}")
    public Response getById(@PathParam("id") String id) {
        return Response.ok(dao.getById(id)).build();
    }

}

DynamoDBFooDao.java

package org.arabellan.sandbox;

import javax.inject.Singleton;

@Singleton
public class DynamoDBFooDao implements FooDao {

    public String getById(String id) {
        return id;
    }

}

FooDao.java

package org.arabellan.sandbox;

interface FooDao {

    String getById(String id);

}

I'm failing to understand the various components and how they work together. As such I keep getting the following error:

SEVERE: The following errors and warnings have been detected with resource and/or provider classes:
  SEVERE: Missing dependency for constructor public org.arabellan.sandbox.FooResource(org.arabellan.sandbox.FooDao) at parameter index 0

If I access the Guice injector directly in FooResource 's constructor then it works. This tells me the Jetty/Jersey stuff is setup properly to serve the resource and Guice is able to build it's dependency tree correctly. I believe this means the problem lies in getting Jersey to use Guice when constructing the resource.

Answer 1

As pointed out in the comments, I needed to settle on either version 1 or 2 of Jersey before trying to hook up Guice. I went with Jersey 2.

My original assumption however was correct, the linkage between Guice and Jersey (or rather HK2) needed to be setup. I facilitated this with the GuiceToHK2 class. I didn't want to define DI bindings in two places so this solution loops through all of the Guice bindings, filters them to a specific package (optional), and then binds them within HK2.

build.gradle

plugins {
    id 'java'
}

repositories {
    mavenCentral()
}

dependencies {
    compile 'org.projectlombok:lombok:1.16.18'
    compile 'com.google.inject:guice:4.1.0'
    compile 'com.google.inject.extensions:guice-servlet:4.1.0'
    compile 'com.fasterxml.jackson.jaxrs:jackson-jaxrs-json-provider:2.9.3'
    compile 'org.eclipse.jetty:jetty-server:9.4.8.v20171121'
    compile 'org.eclipse.jetty:jetty-servlet:9.4.8.v20171121'
    compile 'org.glassfish.jersey.containers:jersey-container-jetty-servlet:2.26'
    compile 'org.glassfish.jersey.media:jersey-media-sse:2.26'
    compile 'org.glassfish.jersey.inject:jersey-hk2:2.26'
}

Application.java

package org.arabellan.sandbox;

import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.HandlerCollection;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.glassfish.jersey.message.DeflateEncoder;
import org.glassfish.jersey.message.GZipEncoder;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.server.filter.EncodingFilter;
import org.glassfish.jersey.servlet.ServletContainer;

class Application {

    void run() throws Exception {
        ServletContextHandler httpContext = new ServletContextHandler(ServletContextHandler.NO_SESSIONS);
        ServletContainer container = new ServletContainer(buildResourceConfig());
        ServletHolder holder = new ServletHolder(container);
        httpContext.setContextPath("/");
        httpContext.addServlet(holder, "/*");

        Server jettyServer = new Server(8080);
        jettyServer.setHandler(httpContext);
        jettyServer.start();
    }

    private ResourceConfig buildResourceConfig() {
        ResourceConfig config = new ResourceConfig();
        config.register(new GuiceToHK2(Main.injector));
        config.register(JacksonJsonProvider.class);
        config.registerClasses(EncodingFilter.class, GZipEncoder.class, DeflateEncoder.class);
        config.packages("org.arabellan.sandbox");
        return config;
    }

}

GuiceToHK2.java

package com.flightstats.hub.app;

import com.google.inject.Injector;
import com.google.inject.Key;
import lombok.extern.slf4j.Slf4j;
import org.glassfish.hk2.api.Factory;
import org.glassfish.hk2.utilities.binding.AbstractBinder;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

@Slf4j
class GuiceToHK2 extends AbstractBinder {

    private final Injector injector;

    GuiceToHK2(Injector injector) {
        this.injector = injector;
    }

    @Override
    protected void configure() {
        injector.getBindings().forEach((key, value) -> {
            if (isNamedBinding(key)) {
                bindNamedClass(key);
            } else {
                bindClass(key);
            }
        });
    }

    private boolean isNamedBinding(Key<?> key) {
        return key.getAnnotationType() != null && key.getAnnotationType().getSimpleName().equals("Named");
    }

    private void bindClass(Key<?> key) {
        try {
            String typeName = key.getTypeLiteral().getType().getTypeName();
            log.info("mapping guice to hk2: {}", typeName);
            Class boundClass = Class.forName(typeName);
            bindFactory(new ServiceFactory<>(boundClass)).to(boundClass);
        } catch (ClassNotFoundException e) {
            log.warn("unable to bind {}", key);
        }
    }

    private void bindNamedClass(Key<?> key) {
        try {
            String typeName = key.getTypeLiteral().getType().getTypeName();
            Method value = key.getAnnotationType().getDeclaredMethod("value");
            String name = (String) value.invoke(key.getAnnotation());
            log.info("mapping guice to hk2: {} (named: {})", typeName, name);
            Class boundClass = Class.forName(typeName);
            bindFactory(new ServiceFactory<>(boundClass)).to(boundClass).named(name);
        } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
            log.warn("unable to bind {}", key);
        }
    }

    private class ServiceFactory<T> implements Factory<T> {

        private final Class<T> serviceClass;

        ServiceFactory(Class<T> serviceClass) {
            this.serviceClass = serviceClass;
        }

        public T provide() {
            return injector.getInstance(serviceClass);
        }

        public void dispose(T versionResource) {
            // do nothing
        }
    }

}

It's not a bulletproof solution but it solved my issue. It assumes that everything that needs to be injected into my resources is in the org.arabellan.sandbox package and isn't @Named .

UPDATE : Made the solution more generic by removing assumptions.

Answer 2

hmmn for me it looks like you execute one of the following URLs:

• http://localhost/foo
• http://localhost/foo/

so that the string-parameter "id" of this function: "public Response getById(@PathParam("id") String id)" is null. which results in your error.

It's just an assumption. Could you check it if i'm right, please