Developer 21 Century: Java Interview Latest Questions

1) How hash map works internally.

Refer homeshop 18 post

2) Hbm cache – difference
First level cache is enabled by default and you can not disable it. When we query an entity first time, it is retrieved from database and stored in first level cache associated with hibernate session. If we query same object again with same session object, it will be loaded from cache and no sql query will be executed.

First-level cache - First-level cache always Associates with the Session object. Hibernate uses this cache by default. Here, it processes one transaction after another one, means wont process one transaction many times. Mainly it reduces the number of SQL queries it needs to generate within a given transaction. That is instead of updating after every modification done in the transaction, it updates the transaction only at the end of the transaction.1.2) Second-level cache

Second-level cache always associates with the Session Factory object. While running the transactions, in between it loads the objects at the Session Factory level, so that those objects will be available to the entire application, not bound to single user. Since the objects are already loaded in the cache, whenever an object is returned by the query, at that time no need to go for a database transaction. In this way the second level cache works. Here we can use query level cache also. Later we will discuss about it.

3) What is Connection pooling?

Ans:

import java.sql.*;
import javax.sql.*;

public class JDBCServlet extends HttpServlet {

private DataSource datasource;

public void init(ServletConfig config) throws ServletException {
    try {
      // Look up the JNDI data source only once at init time
      Context envCtx = (Context) new InitialContext().lookup("java:comp/env");
      datasource = (DataSource) envCtx.lookup("jdbc/MyDataSource");
    }
    catch (NamingException e) {
      e.printStackTrace();
    }
}

private Connection getConnection() throws SQLException {
    return datasource.getConnection();
}

public void doGet (HttpServletRequest req, HttpServletResponse res) throws ServletException {
    Connection connection=null;
    try {
      connection = getConnection();
      ..<do JDBC work>..
    }
    catch (SQLException sqlException) {
      sqlException.printStackTrace();
    }
    finally {
      if (connection != null)
        try {connection.close();} catch (SQLException e) {}
      }
    }
}
}

4) Explain Spring bean life cycle.

Here is the content of HelloWorld.java file:

package com.dev21century;

public class HelloWorld {

private String message;

public void setMessage(String message){

this.message = message;

}

public void getMessage(){

System.out.println("Your Message : " + message);

}

public void init(){

System.out.println("Bean is going through init.");

}

public void destroy(){

System.out.println("Bean will destroy now.");

}

Following is the content of the MainApp.java file. Here you need to register a shutdown hook registerShutdownHook() method that is declared on the AbstractApplicationContext class. This will ensures a graceful shutdown and calls the relevant destroy methods.

package com.dev21century;

import org.springframework.context.support.AbstractApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {

public static void main(String[] args) {

AbstractApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

HelloWorld obj = (HelloWorld) context.getBean("helloWorld");

obj.getMessage();

context.registerShutdownHook();

}

Following is the configuration file Beans.xml required for init and destroy methods:

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

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean id="helloWorld"

class="com.dev21century.HelloWorld"

init-method="init" destroy-method="destroy">

</bean>

</beans>

Once you are done with creating source and bean configuration files, let us run the application. If everything is fine with your application, this will print the following message:

Bean is going through init.

Your Message : Hello World!

Bean will destroy now.

Default initialization and destroy methods:

If you have too many beans having initialization and or destroy methods with the same name, you don't need to declare init-method and destroy-methodon each individual bean. Instead framework provides the flexibility to configure such situation using default-init-method and default-destroy-methodattributes on the <beans> element as follows:

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"

default-init-method="init"

default-destroy-method="destroy">

</bean>

</beans>

5) XmlBeanFactory uses

Ans: ApplicationContext is a sub-interface of BeanFactory.You can use this way

public class SpringHelloWorldTest {

    public static void main(String[] args) {

        ApplicationContext context= new ClassPathXmlApplicationContext("SpringHelloWorld.xml");

        Spring3HelloWorld myBean= (Spring3HelloWorld) context.getBean("Spring3HelloWorldBean");

        myBean.sayHello();

6) Data format used in restful. – json,text plain etc.
7) What is Db deadlock

Ans:

In a database, a deadlock is a situation in which two or more transactions are waiting for one another to give up locks. For example, Transaction A might hold a lock on some rows in the Accounts table and needs to update some rows in the Orders table to finish.

8) Restful and soap difference.

Ans:

No.	SOAP	REST
1)	SOAP is a protocol.	REST is an architectural style.
2)	SOAP stands for Simple Object Access Protocol.	REST stands for REpresentational State Transfer.
3)	SOAP can't use REST because it is a protocol.	REST can use SOAP web services because it is a concept and can use any protocol like HTTP, SOAP.
4)	SOAP uses services interfaces to expose the business logic.	REST uses URI to expose business logic.
5)	JAX-WS is the java API for SOAP web services.	JAX-RS is the java API for RESTful web services.
6)	SOAP defines standards to be strictly followed.	REST does not define too much standards like SOAP.
7)	SOAP requires more bandwidth and resource than REST.	REST requires less bandwidth and resource than SOAP.
8)	SOAP defines its own security.	RESTful web services inherits security measures from the underlying transport.
9)	SOAP permits XML data format only.	REST permits different data format such as Plain text, HTML, XML, JSON etc.
10)	SOAP is less preferred than REST.	REST more preferred than SOAP.

9) Explain Cookie and request data?
10)

Spring security implementation:

Web.xml entries:

Spring security implementation:

applicationContext.xml:

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:security="http://www.springframework.org/schema/security"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"

xmlns:mvc="http://www.springframework.org/schema/mvc"

xmlns:aop="http://www.springframework.org/schema/aop"

xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd

http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd

http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd

http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd

http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-3.0.3.xsd">

<context:component-scan base-package="com.ge.aviation.scit.supplier360.rest,com.ge.aviation.scit.supplier360.model,com.ge.aviation.scit.userservice.data,com.ge.aviation.scit.supplier360.util" />

<context:annotation-config />

<security:http use-expressions="true" auto-config="false" entry-point-ref="http403EntryPoint" >

<security:intercept-url pattern="/rest/supplier/search/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplier/details/**" access="hasRole('S_PROFILE_USER')"/>

<security:intercept-url pattern="/rest/supplier/update/**" access="hasRole('S_PROFILE_USER') and hasRole('PQE')" />

<security:intercept-url pattern="/rest/supplier/reCalculateRating/**" access="hasRole('S_PROFILE_USER') and hasRole('PQE')" />

<security:intercept-url pattern="/rest/supplier/finalSupplierRating/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplier/finalMetricRating/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplier/metricDetails/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplier/updateMetric/**" access="hasRole('S_PROFILE_USER') and hasRole('PQE')" />

<security:intercept-url pattern="/rest/supplierProfile/supplierInfo/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplierProfile/search/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/supplierProfile/yellowPage/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/sprofileUserAuth/userAuth/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/SupplierQMReport/GEAEPQEReport/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/SupplierQMReport/suppliersReportDetails/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/SupplierQMReport/suppliersNonQmReportDetails/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/SupplierQMReport/DSQRReportDetails/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedOrganizationData/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedProcessCodes/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedOthersCountryData/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedOthersStateData/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedOthersCityData/**" access="hasRole('S_PROFILE_USER')" />

<security:intercept-url pattern="/rest/preloadedDataAdvanceSearch/preloadedOthersZipData/**" access="hasRole('S_PROFILE_USER')" />

<security:custom-filter position="PRE_AUTH_FILTER" ref="siteminderFilter" />

</security:http>

</bean>

<security:authentication-manager alias="authenticationManager">

<security:authentication-provider ref="preauthAuthProvider" />

</security:authentication-manager>

</bean>

</property>

</bean>

</bean>

</bean>

</bean>

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