Connecting Spring Boot Docker container to MongoDB docker container

Question

I am trying to connect a spring boot docker container to a mongodb docker container. While developing Spring Boot app, I used a MongoDB docker container with port 27017 mapped to the host machine's 27017 port with docker run -p 27017:27017 mongo:3.4. When development finished, I containerized the spring app, but containerized spring app could not connect to the mongodb container. I know the problem is spring app is looking for mongodb at localhost. My question is how should I modify the app so that instead of looking for mongodb at localhost, it uses mongodb containers's address?

My database connections are handled with class below:

public class DB {
private final Datastore datastore;
private Morphia morphia;

/**
 * Constructor for creating database instance
 */
public DB() {
    morphia = new Morphia();
    morphia.mapPackage("users");
    datastore =
            morphia.createDatastore(new MongoClient(), "test");
    datastore.ensureIndexes();
}

/**
 * Inserts given user to the database
 *
 * @param u a newly created user.
 */
public void addUser(User u) {
    datastore.save(u);
}

/**
 * Fetches and prints all documents in database
 *
 * @return json array of all documents in database
 */
public String getUsers() {
    final Query<User> query = datastore.createQuery(User.class);
    final List<User> employees = query.asList();

    return objToJson(employees);
}

/**
 * Returns the user with the specified ID.
 *
 * @param userID is the ID of the document in database
 * @return document in json format
 */
public String getUser(ObjectId userID) {
    final Query<User> query = datastore.createQuery(User.class)
            .field("id").equal(userID);

    final List<User> employees = query.asList();
    return objToJson(employees);
}

/**
 * Deletes the document with the given ID from database.
 *
 * @param userID is the ID of the document to be removed
 */
public void removeUser(ObjectId userID) {
    final Query<User> query = datastore.createQuery(User.class)
            .field("id").equal(userID);
    datastore.delete(query);
}

/**
 * Deletes all documents from database.
 */
public void removeUsers() {
    final Query<User> query = datastore.createQuery(User.class);
    datastore.delete(query);
}

/**
 * Updates the fields of the document with given ID.
 *
 * @param userID  is the ID of the document to be updated
 * @param newUser contains the new fields
 * @return results of the update in json format
 */
public String updateUser(ObjectId userID, User newUser) {
    final Query<User> query = datastore.createQuery(User.class)
            .field("id").equal(userID);
    final UpdateOperations<User> updateOperations = datastore.createUpdateOperations(User.class);

    if (newUser.getFirst_name() != null) {
        String newName = newUser.getFirst_name();
        updateOperations.set("first_name", newName);
    }

    if (newUser.getLast_name() != null) {
        String newLastName = newUser.getLast_name();
        updateOperations.set("last_name", newLastName);
    }

    if (newUser.getSalary() != 0) {
        int newSalary = newUser.getSalary();
        updateOperations.set("salary", newSalary);
    }

    final UpdateResults results = datastore.update(query, updateOperations);
    return results.toString();

}

/**
 * Translate object lists to the json array.
 *
 * @param query is the list of the user objects
 * @return json array of the given users
 */
private String objToJson(List<User> query) {
    List<String> attsToRemove = Arrays.asList(new String[]{"className"});

    List<DBObject> dbObjList = new ArrayList<>(query.size());
    DBObject dbObj;
    for (Object obj : query) {
        dbObj = morphia.toDBObject(obj);
        for (int i = 0; i < attsToRemove.size(); i++) {
            dbObj.removeField(attsToRemove.get(i));
        }
        dbObjList.add(dbObj);
    }
    String json = JSON.serialize(dbObjList);
    return json;
}

Here is my spring boot controller

@RestController
public class DemoController {

DB mongodb = new DB();

@RequestMapping(value = "/", method = RequestMethod.GET)
public String index() {
    return "Greetings from Spring Boot";
}

@RequestMapping(value = "/users/{user_id}", method = RequestMethod.GET)
public String getUser(@PathVariable("user_id") ObjectId userID) {
    return mongodb.getUser(userID);
}

@RequestMapping(value = "/users", method = RequestMethod.GET)
public String getUsers() {
    return mongodb.getUsers();
}

@RequestMapping(value = "/users", method = RequestMethod.POST)
public void createUser(@RequestBody User u) {
    try {
        mongodb.addUser(u);
    } catch (Exception e) {
        System.out.println(e.toString());
    }
}

@RequestMapping(value = "/users", method = RequestMethod.DELETE)
public void deleteUsers() {
    try {
        mongodb.removeUsers();
    } catch (Exception e) {
        System.out.println(e.toString());
    }
}

@RequestMapping(value = "/users/{user-id}", method = RequestMethod.DELETE)
public void deleteUser(@PathVariable("user-id") ObjectId userID) {
    try {
        mongodb.removeUser(userID);
    } catch (Exception e) {
        System.out.println(e.toString());
    }
}

@RequestMapping(value = "/users/{user-id}", method = RequestMethod.PUT)
public String updateUser(@PathVariable("user-id") ObjectId userID, @RequestBody User u) {
    return mongodb.updateUser(userID, u);
}

And here is my Dockerfile: FROM frolvlad/alpine-oraclejdk8:slim VOLUME /tmp ADD demo-0.0.1-SNAPSHOT.jar app.jar EXPOSE 27017 EXPOSE 8080 RUN sh -c 'touch /app.jar' ENV JAVA_OPTS="" ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar" ]

I read the solutions mentioned here and here. Also read through couple of tutorials but I couldn't fit any of these solutions to my code. In my code, where should I change?

Answer 1

The main issue is that your containers are not in the same network. I guess you can find a working example by this How to run Spring Boot and MongoDB in Docker containe. Here is a short extract:

1. docker network create spring_demo_net create a network
2. docker run --name spring-demo-mongo --network=spring_demo_net -v /home/ubuntu/mongo-data:/data/db -d mongo start a mongo container
3. Modify mongo host in application properties as following spring.data.mongodb.uri=mongodb://spring-demo-mongo/YOUR_DB here spring-demo-mongo is the name of container that you created on step 1.

Since you are not using SpringData repositories it will not work so you need to create a MongoClient by explicitly passing host and port:

MongoClient mongoClient2 = new MongoClient("spring-demo-mongo", 27017);

4. docker build --tag=spring-demo-1.0 build your docker image with tag
5. docker run -d --name spring-demo --network=spring_demo_net -p 8080:8080 spring-demo-1.0 start your docker image