Question

Conduct some research to find out how a Java-based application can be connected to a database. Provide some brief code snippets and annotate the code.

Answer 1

a Java-based application can be connected to a database using Java Database Connectivity(JDBC).

to establish a connection to database through jdbc first you will have to load jdbc driver using one of the two methods given below.
Class.forName() : Here we load the driver’s class file into memory at the runtime. to load oracle driver use

Class.forName(“oracle.jdbc.driver.OracleDriver”);

DriverManager.registerDriver(): DriverManager is a Java inbuilt class with a static member register. Here we call the constructor of the driver class at compile time

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver())
After loading the driver, establish connections using :
Connection con = DriverManager.getConnection(url,user,password)
url : Uniform Resource Locator. It can be created as follows:

String url = “ jdbc:oracle:thin:@localhost:1521:xe” where xe is sid ofthe oracle database you are trying to connect
once we have connection we can use sql queries to manipulate data in the database.
The JDBCStatement, CallableStatement, and PreparedStatement interfaces define the methods that enable you to send SQL commands and receive data from your database.

for example to insert a record use below code snippet. sql variable holds the query to actual insertion into a table

Statement st = con.createStatement();

String sql = "INSERT INTO Customers (CustomerName, ContactName)
VALUES ('Cardinal', 'Tom B. Erichsen')";
int m = st.executeUpdate(sql);
if (m==1)
System.out.println("inserted successfully : "+sql);
else
System.out.println("insertion failed");

finally when you are done talking to database you can close the connection
con.close();