CODEWITHSUNDEEP
javamongodbjersey
rrb_bbr
rrb_bbr

Reputation: 3056

Simple Logger API using Java, Jersey, MongoDB and Json

I'm learning the combo Java+Jersey+MongoDB and to do this, I'm trying to create a small Logger API. It's simple: you just POST to the server a Json file with the logged data.

Here is what I have so far.

My DBConnector:

public class DBConnector {
    private static DB db;
    private static MongoClient mongo = null;

    public static void init() {
        try {
            mongo = new MongoClient("localhost", 27017);
        } catch (final UnknownHostException e) {
            System.out.println("Erro!!!!");
        }
        db = mongo.getDB("log");
    }

    public static DB getDb() {
        return db;
    } 

    public static void close() { 
        mongo.close(); 
    }

My Resource:

@Path("/log")
public class LogResource {

    private static DBCollection LogCollection = DBConnector.getDb().getCollection("raw_data");


    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getIt() {
        return "OK you got it!"; // Just to Test

    }

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public String addLog() {

        String json = "{'parameter1' : 'banana','parameter2' : 'orange'}"; // I still don't know how to receive the json file

        DBObject dbObject = (DBObject)JSON.parse(json);

        LogCollection.insert(dbObject);    

        return "OK";
    }

My Main (Not mine, actually. Comes with the Jersey project ):

public class Main {
    // Base URI the Grizzly HTTP server will listen on
    public static final String BASE_URI = "http://localhost:8080/";


    /**
     * Starts Grizzly HTTP server exposing JAX-RS resources defined in this application.
     * @return Grizzly HTTP server.
     */
    public static HttpServer startServer() {
        // create a resource config that scans for JAX-RS resources and providers
        // in br.ufrj.cos.labia.scdp.ips_bs package
        final ResourceConfig rc = new ResourceConfig().packages("br.ufrj.cos.labia.scdp.ips_bs");

        // create and start a new instance of grizzly http server
        // exposing the Jersey application at BASE_URI
        return GrizzlyHttpServerFactory.createHttpServer(URI.create(BASE_URI), rc);
    }

    /**
     * Main method.
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        final HttpServer server = startServer();
        System.out.println(String.format("Jersey app started with WADL available at "
                + "%sapplication.wadl\nHit enter to stop it...", BASE_URI));
        System.in.read();
        server.stop();



    }
}

The problem so far is that I'm receiving a strange ExceptionInInitializerError that I'm not aware how to fix.

I should point it out that I'm still a rookie in Java.

Any help?

EDIT: 

Jersey app started with WADL available at http://localhost:8080/application.wadl
Hit enter to stop it...
Sep 16, 2015 7:14:20 PM org.glassfish.jersey.internal.Errors logErrors
WARNING: The following warnings have been detected: WARNING: Unknown HK2 failure detected:
MultiException stack 1 of 2
java.lang.ExceptionInInitializerError
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.glassfish.hk2.utilities.reflection.ReflectionHelper.makeMe(ReflectionHelper.java:1350)
    at org.jvnet.hk2.internal.ClazzCreator.createMe(ClazzCreator.java:271)
    at org.jvnet.hk2.internal.ClazzCreator.create(ClazzCreator.java:365)
    at org.jvnet.hk2.internal.SystemDescriptor.create(SystemDescriptor.java:471)
    at org.glassfish.jersey.process.internal.RequestScope.findOrCreate(RequestScope.java:162)
    at org.jvnet.hk2.internal.Utilities.createService(Utilities.java:2072)
    at org.jvnet.hk2.internal.ServiceLocatorImpl.internalGetService(ServiceLocatorImpl.java:767)
    at org.jvnet.hk2.internal.ServiceLocatorImpl.getService(ServiceLocatorImpl.java:706)
    at org.glassfish.jersey.internal.inject.Injections.getOrCreate(Injections.java:169)
    at org.glassfish.jersey.server.model.MethodHandler$ClassBasedMethodHandler.getInstance(MethodHandler.java:284)
    at org.glassfish.jersey.server.internal.routing.PushMethodHandlerRouter.apply(PushMethodHandlerRouter.java:74)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:109)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:92)
    at org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:61)
    at org.glassfish.jersey.process.internal.Stages.process(Stages.java:197)
    at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:301)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:292)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1139)
    at org.glassfish.jersey.grizzly2.httpserver.GrizzlyHttpContainer.service(GrizzlyHttpContainer.java:375)
    at org.glassfish.grizzly.http.server.HttpHandler$1.run(HttpHandler.java:224)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
    at com.test.LogResource<clinit>(LogResource.java:27) // <- Copy and Paste of the line: "private static DBCollection LogCollection = DBConnector.getDb().getCollection("raw_data");"
    ... 36 more
MultiException stack 2 of 2
java.lang.IllegalStateException: Unable to perform operation: create on com.test.LogResource
    at org.jvnet.hk2.internal.ClazzCreator.create(ClazzCreator.java:392)
    at org.jvnet.hk2.internal.SystemDescriptor.create(SystemDescriptor.java:471)
    at org.glassfish.jersey.process.internal.RequestScope.findOrCreate(RequestScope.java:162)
    at org.jvnet.hk2.internal.Utilities.createService(Utilities.java:2072)
    at org.jvnet.hk2.internal.ServiceLocatorImpl.internalGetService(ServiceLocatorImpl.java:767)
    at org.jvnet.hk2.internal.ServiceLocatorImpl.getService(ServiceLocatorImpl.java:706)
    at org.glassfish.jersey.internal.inject.Injections.getOrCreate(Injections.java:169)
    at org.glassfish.jersey.server.model.MethodHandler$ClassBasedMethodHandler.getInstance(MethodHandler.java:284)
    at org.glassfish.jersey.server.internal.routing.PushMethodHandlerRouter.apply(PushMethodHandlerRouter.java:74)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:109)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:112)
    at org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:92)
    at org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:61)
    at org.glassfish.jersey.process.internal.Stages.process(Stages.java:197)
    at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:301)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:292)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1139)
    at org.glassfish.jersey.grizzly2.httpserver.GrizzlyHttpContainer.service(GrizzlyHttpContainer.java:375)
    at org.glassfish.grizzly.http.server.HttpHandler$1.run(HttpHandler.java:224)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
    at java.lang.Thread.run(Thread.java:745)

Upvotes: 1

Views: 550

Answers (1)

Paul Samsotha
Paul Samsotha

Reputation: 209052

Look at this DBConnector.getDb(). Then look at the DBConnector. Unless init is called, db is never initialized, so it is always null. So calling getDb before inializing it will return null, and calling getCollection on null, will cause the NullPointerException, which is the problem you are facing now.

The easiest fix would be to just do something like

public static DB getDb() {
    if (db == null) {
        init();
    }
    return db;
}

Upvotes: 1

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