Is this an aptitude question or a program?
how can i download it any one help me please?
can anybody help me in person?
Why is it printing same hashcode inside each method?
What needs to be changed here?
with which object?
Hi, what is the best development platform to make a desktop application?
i have a paid udemy course on my account .how can i download it any one help me please?
Collation type should b same in db level . Try changing to utf8
Why is it printing same hashcode inside each method? Shouldn’t JUNIT create different instances for different different @Test methods?
What is the issue??
Why is it printing same hashcode inside each method? Shouldn’t JUNIT create different instances for different different @Test methods?
U r printing the hashcode of class but object . so it ll remain same.
anyone know how to consume this JSON response from external API become this one (sight side) ?
U r printing the hashcode of class but object . so it ll remain same.
I thought it was the same thing. What needs to be changed here?
I thought it was the same thing. What needs to be changed here?
Just call hashCode() directly
Just call hashCode() directly
with which object? As Junit internally creates the instance how will I get that instance?
anyone know how to consume this JSON response from external API become this one (sight side) ?
May be you are using another api for that one… Then call it
Is this an aptitude question or a program?
Program
Java Database Connectivity which is a specification for developing database applications with Java programming language.
The JDBC had several drawbacks
For example:
1. Boilerplate code (tedious code to work with data access Layer)
2. SQL exception-> Checked Exception so mandatorily needs to be handled.
3. Non portability because SQL codes are within the Java program; we can’t supply the SQL queries from outside the java program and also the SQL queries are database-specific.
4. Dialect issue in case of change of database
5. JDBC API can’t transfer the java objects directly
6. If the table structure is modified after the construction of Jdbc code then we must modify the sql queries again which is time consuming and burden for the java developer.
7. Manual resource clean up
8. Transactions must be handled manually
In order to overcome these problems spring JDBC was released.
It is an abstraction layer on top of jdbc technology.
Spring JDBC provides several methods to write the queries directly, so it saves a lot of work and time.
Spring JDBC however internally uses JDBC api only.
ORM:- (Object Relational Mapping) (To save the state of Java Objects into data base)
* It is a technique for converting/mapping data between java Objects and relational database
* Responsible for mapping the Domain Objects to Relational Model and vice versa
Why ORM?
Technical Differences between java Object and Relational Object
1. Granularity issue
2. Inheritance issue
3. Data Comparison issue
4. Data traversal difference
To overcome these technical problems, ORM was introduced.
They are several ORM tools available.
1. Hibernate
2. EclipseLink
3. OpenJPA
4. TopLink
5. Ibatis(MyBatis)
Which are all the implementations/JPA Providers/JPA vendors.
JPA (Java Persistence API) is a standard/specification/guidelines which are implemented/followed by all those ORM tools.
For easy understanding,
JPA is like an interface provided by the JCP( Java Community Process or Sun Microsystems (Oracle)) and ORM tools are the implementation classes
JPA facilities easy portability and migration.
With JPA, we can easily migrate from one JPA implementation to another JPA implementation.(Portability) (Loose Coupling)
Among all those JPA vendors, Hibernate (org.hibernate) is widely used because
1. It’s an Open source, publicly available without any cost and lightweight
2. Takes care of Auto Table Creation, Auto Primary Key generation
3. Provides Caching (Dual Layer caching) (first level and second level caching)
4. Supports Associations(mapping), inheritance, Joins
5. Provides Eager and lazy loading
6. Pagination support
7. Exception Handling is not mandatory.
8. Scalability
9. HQL (HIbernate Query Language) -> Database Independent Language
10. Transaction support
11. NativeSQL (we can write our SQL directly)
12. Locking -> Pessimistic and Optimistic Locking
13. Connection pooling mechanism for improving connection reusability
14. *Criteria API* which auto-generates *tuned Queries*
ORM tools however use the JDBC API internally
What is Optional in Java 8
A final class present in java.util package to help us
To avoid NullPointerException
To avoid too many Null Checks
To avoid abnormal termination or crash of the program
Using Optional, we can write neat code without too many null checks(isPresent())
Using Optional, we can specify the alternate value or code to execute (ifPresent(), orElse(),orElseGet(),orElseThrow())
It makes the program More readable