MongoDB Java Simple Example fails

Question

Mongo DB server is running on local machine. I can open mongo shell and query the database without any issue.

The java file compiles without any errors. However while executing I get error.

Exception in thread "main" java.lang.NoClassDefFoundError: com/mongodb/MongoClient
        at mongoTest.main(mongoTest.java:26)
Caused by: java.lang.ClassNotFoundException: com.mongodb.MongoClient
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 1 more

Sample Java code which I wrote is shown below. When I execute the file at command prompt

import com.mongodb.MongoClient;
import com.mongodb.MongoClientURI;
import com.mongodb.ServerAddress;

import com.mongodb.client.MongoDatabase;
import com.mongodb.client.MongoCollection;

import org.bson.Document;
import java.util.Arrays;
import com.mongodb.Block;

import com.mongodb.client.MongoCursor;
import static com.mongodb.client.model.Filters.*;
import com.mongodb.client.result.DeleteResult;
import static com.mongodb.client.model.Updates.*;
import com.mongodb.client.result.UpdateResult;
import java.util.ArrayList;
import java.util.List;

public class mongoTest {

    public static void main(String[] args) {

        MongoClient c = new MongoClient("localhost", 27017);
        MongoDatabase database = c.getDatabase("video");
        MongoCollection collection = database.getCollection("movieDetails");

        System.out.println(collection.count());

    }
}

Looks like a problems with your classpath. How are you executing the program? Through an IDE or via the command-line? — craigcaulfield
– craigcaulfield, Commented May 11, 2018 at 0:38
Compiled the java file at command line. No errors during compilaton. Tried to execute the same using command java mongoTest — ChanduS
– ChanduS, Commented May 11, 2018 at 0:51
And, when you compiled your class, did you you specify a classpath option pointing to your MongoDB JARs? — craigcaulfield
– craigcaulfield, Commented May 11, 2018 at 1:02
Yes... FYI MongoDB Server version is 3.6.2 and Java 8 update 171 Compile statement at command line is - javac -cp .;C:\Java\jdk1.8.0_171\jre\lib\mongo\bson-3.6.2.jar;C:\Java\jdk1.8.0_171\jre\lib\mongo\mongodb-driver-3.6.2.jar;C:\Java\jdk1.8.0_171\jre\lib\mongo\mongodb-driver-core-3.6.2.jar;C:\Java\jdk1.8.0_171\jre\lib\mongo\mongo-java-driver-3.6.2.jar mongoTest.java No errors during compilation — ChanduS
– ChanduS, Commented May 11, 2018 at 1:05

craigcaulfield · Accepted Answer · 2018-05-11 01:06:51Z

2

You'd just need to run the class with something like:

java -cp <path-to-your-mongodb-jars> mongoTest

It's also standard Java practice to capitalise the name of your class, so MongoTest rather than mongoTest

answered May 11, 2018 at 1:06

craigcaulfield

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3 Comments

ChanduS Over a year ago

Thank you.. that worked... Also regarding the java practices.. I will keep it in mind. Just started programming in java and mongo

craigcaulfield Over a year ago

If you haven't come across it already, check out the free online MongoDB course for Java developers at university.mongodb.com/courses/M101J/about. It's well worthwhile.

ChanduS Over a year ago

That was the first thing that I saw :) . I will be definitely doing that course when the next run starts on 29th of this month. Thank you

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