Java Technical Architect interview @ Brillio

Hi Friends,

In this post, I am sharing interview questions and answers asked in Brillio.

Question 1:

What is the difference between @Autowired, @Inject and @resource annotations?

Answer:

Resource and Inject belong to java extension package: javax.annotation.Resource and javax.inject.Inject package.

@Autowired annotation belongs to org.springframework.beans.factory.annotation package.

Each of these annotations can resolve dependencies either by field injection or by setter injection.

@Inject and @Autowired have same execution paths:

• Match by Type
• Match by Qualifier
• Match by name

While @Resource has different execution path:

• Match by name
• Match by type
• Match by Qualifier

e.g.:

public class FieldResourceInjectionIntegrationTest{

    @Resource(name="namedFile")

    private File defaultFile;

    @Test

    public void givenResourceAnnotation(){

        assertNotNull(defaultFile);

        assertEquals("nameFile.txt", defaultFile.getName());

    }

}

This configuration will resolve dependencies using the match-by-name execution path. The bean namedFile must be defined in  the ApplicationContextTestResourceNameType application context.

@Configuration

public class ApplicationContextTestResourceNameType{

    @Bean(name="namedFile")

    public File namedFile(){

        File namedFile = new File("namedFile.txt");

        return namedFile;

    }

}

Failure to define the bean[with that name "namedFile"] in the application context will result in a org.springframework.beans.factory.NoSuchBeanDefinitionException being thrown.

Note: But if we use @Annotation or @Inject, in that case, it works, because execution path of @Annotation and @Inject contains "Match by Type" first.

Question 2:

What are Spring bean scopes?

Answer:

Spring bean scopes are:

• Singleton
• Prototype
• Request
• Session
• GlobalSession
• Application
• WebSocket

Singleton: Only one bean is created with same id per spring container.

But if, we have dependencies as prototype beans, then injection happens when the singleton object is instantiated, so injection just happens once.

Thus the prototype bean will always be the same instance even though it was defined with a prototype scope.

Prototype: Spring container will create a new instance of the object described by the bean each time it receives a request.  Prototype bean should be used in environment where there is session management(Stateful) and use singleton scope beans when working on environments without session management(Stateless).

Request: Spering container will create a new instance of the object defined by the bean each time it receives an HTTP request.

Session: Spring container will create a new instance for each HTTP session.

Global Session: It is same like Session , but it works for Portlet based applications.

 

Question 3:

How can we connect to multiple databases in hibernate?

Answer:

We need to use separate configuration file for connecting to a specific databases, so two configuration files are required to connect to two different databases.

To configure mysql database:

    hibernate-mysql.cfg.xml

To configure oracle database:

    hibernate-oracle.cfg.xml

In details, mysql configuration will be like this:

<?xml version="1.0" encoding="utf-8"?>

// DOCTYPE here......

<hibernate-configuration>

    <session-factory>

        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="hibernate.connection.password">PASSWORD</property>

        <property name="hibernate.connection.url">jdbc:mysql://locallhost:3306/db_name</property>

        <property name="hibernate.connection.username">USERNAME</property>

        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <mapping class="domain.EmployeeMySql"></mapping>

    </session-factory>

</hibernate-configuration>

In details, oracle configuration will be like this:

<?xml version="1.0" encoding="utf-8"?>

// DOCTYPE here......

<hibernate-configuration>

    <session-factory>

        <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

        <property name="hibernate.connection.password">PASSWORD</property>

        <property name="hibernate.connection.url">jdbc:oracle:thin:db_name</property>

        <property name="hibernate.connection.username">USERNAME</property>

        <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>

        <mapping class="domain.EmployeeOracleSql"></mapping>

    </session-factory>

</hibernate-configuration>

And code should be like this:

MySql configuration:

private static SessionFactory sessionAnnotationFactory;

sessionAnnotationFactory = new Configuration().configure("hibernate-mysql.cfg.xml");

Session session = sessionAnnotationFactory.openSession(); 

Oracle configuration:

private static SessionFactory sessionAnnotationFactory;

sessionAnnotationFactory = new Configuration().configure("hibernate-oracle.cfg.xml");

Session session = sessionAnnotationFactory.openSession(); 

Question 4:

What is the output of below code?

class A{

    void methodOne(Double d){

    }

    void methodTwo(Integer I){

    }

class B extends A{

    @Override

    void methodOne(double d){

    }

    @Override

    void methodTwo(Integer I){

    }

}

}

Answer:

Compile time error for not overriding proper method.

Question 5:

What is the effect when a transient mapped object is passed onto a session's save method?

Answer:

It will change its state from transient to persistent.

That's all for this post.

Thanks for reading!!