CODEWITHSUNDEEP
javaspringspring-mvcspring-bootspring-data
Aman
Aman

Reputation: 3261

Could not initialize bean class in Spring

I am trying to develop rest code using spring.

@RestController
public class MongoController {

    @Autowired
    private MongoDAO mongoDAO ;

    @RequestMapping(value = "/mongotest", method = RequestMethod.GET)
    public String creatTest() {

        return " YO Mongo";
    }


}

And my MongoDAO class looks like below 

@Service("mongoDAO")
@Component
public class MongoDAO {


    @Resource
    private DBCollection user ;
    @Resource
    private MongoDatabase userDatabase;
    @Resource
    private MongoCollection<Document> usersCollection;
    @Resource
    private MongoClient mongoClient;

/*  public MongoDAO(final MongoDatabase userDatabase) {
        usersCollection = userDatabase.getCollection("user");
        MongoClient mongoClient = new MongoClient("localhost", 27017);
        DB db = mongoClient.getDB("ITAU");
        user = db.getCollection("user");
    }*/

    public MongoDAO(MongoDatabase userDatabase1) {
        usersCollection = userDatabase1.getCollection("user");

    }

    public MongoDAO() {
        usersCollection = userDatabase.getCollection("user");

    }

But the error I am getting is ..

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mongoDAO' defined in file [C:\Users\user\Desktop\ITAU\77\ABC-iCOE-WAL\ItauBankingTransac s\rest-client\target\classes\com\ABC\WAL\itaudemo\mongo\dao\MongoDAO.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could n nstantiate bean class [com.ABC.WAL.itaudemo.mongo.dao.MongoDAO]: Constructor threw exception; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1076)

Upvotes: 0

Views: 2699

Answers (2)

Dawid Wysakowicz
Dawid Wysakowicz

Reputation: 3422

The field userDatabase is autowired after creating MongoDao bean. If you want to perform some after constructing actions try this:

@Service("mongoDAO")
public class MongoDAO {


    @Resource
    private DBCollection user ;
    @Resource
    private MongoDatabase userDatabase;
    @Resource
    private MongoCollection<Document> usersCollection;
    @Resource
    private MongoClient mongoClient;

    public MongoDAO() {

    }

    @PostConstruct
    public postConstruct() {
        usersCollection = userDatabase.getCollection("user");

    }

The constructor might be omitted. Generally it is better not to have custom constructors for component classes.

Upvotes: 3

techPackets
techPackets

Reputation: 4506

Just use @Service("mongoDAO") no need of @Component

@Service("mongoDAO")
public class MongoDAO {

You can use either of the two annotations, @Service is used in service layer code for readability. @Component is more of a generic annotation.

Upvotes: 1

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