What is orm tool? Give example and explain its architecture.
Answers
JDBC stands for Java Database Connectivity. It provides a set of Java API for accessing the relational databases from Java program. These Java APIs enables Java programs to execute SQL statements and interact with any SQL compliant database.
JDBC provides a flexible architecture to write a database independent application that can run on different platforms and interact with different DBMS without any modification.
Pros and Cons of JDBC
Pros of JDBC Cons of JDBC
Clean and simple SQL processing
Good performance with large data
Very good for small applications
Simple syntax so easy to learn
Complex if it is used in large projects
Large programming overhead
No encapsulation
Hard to implement MVC concept
Query is DBMS specific
Why Object Relational Mapping (ORM)?
When we work with an object-oriented system, there is a mismatch between the object model and the relational database. RDBMSs represent data in a tabular format whereas object-oriented languages, such as Java or C# represent it as an interconnected graph of objects.
Consider the following Java Class with proper constructors and associated public function.
public class Employee {
private int id;
private String first_name;
private String last_name;
private int salary;
public Employee() {}
public Employee(String fname, String lname, int salary) {
this.first_name = fname;
this.last_name = lname;
this.salary = salary;
}
public int getId() {
return id;
}
public String getFirstName() {
return first_name;
}
public String getLastName() {
return last_name;
}
public int getSalary() {
return salary;
}
}
What is ORM?
ORM stands for Object-Relational Mapping (ORM) is a programming technique for converting data between relational databases and object oriented programming languages such as Java, C#, etc.
An ORM system has the following advantages over plain JDBC −
Sr.No. Advantages
1 Let’s business code access objects rather than DB tables.
2 Hides details of SQL queries from OO logic.
3 Based on JDBC 'under the hood.'
4 No need to deal with the database implementation.
5 Entities based on business concepts rather than database structure.
6 Transaction management and automatic key generation.
7 Fast development of application.
An ORM solution consists of the following four entities −
Sr.No. Solutions
1 An API to perform basic CRUD operations on objects of persistent classes.
2 A language or API to specify queries that refer to classes and properties of classes.
3 A configurable facility for specifying mapping metadata.
4 A technique to interact with transactional objects to perform dirty checking, lazy association fetching, and other optimization functions.
Java ORM Frameworks
There are several persistent frameworks and ORM options in Java. A persistent framework is an ORM service that stores and retrieves objects into a relational database.
Enterprise JavaBeans Entity Beans
Java Data Objects
Castor
TopLink
Spring DAO
Hibernate
And many more