86 Servlet to Database software communication Approach 1 | Adv java Servlet Programming Tutorial

#Servlet #to #Database software communication: #Advance #Java #Servlet #Programming #Tutorial: To make servlet program gathering inputs from Database table and storing results in database table we need to see/observe servlet program interacting with database software. For this we need to JDBC code in Servlet program.

Three important operations of JDBC persistence logic are:
---------------------------------------------------------
1) Create JDBC connection object.

2) Use JDBC connection object to create other JDBC objects (like Statement, ResultSet objects ...) and to develop JDBC persistence logic.

3) Close JDBC connection object.

- There are 3 approaches/Strategies to plan JDBC code in our servlet program.
-----------------------------------------------------------------------

1) Approach 1/Strategy 1:
-------------------------
- Create JDBC connection object in the init()method.

- Use this jdbc connection object in service(-,-) or doXxx(-,-) to create other jdbc objects and develop JDBC persistence logic.

- Close the JDBC connection object.

Here (Approach 1) JDBC connection object must be taken as instance variable in our servlet program

Sample Code:
pulic calss TestSrv extends HttpServlet{

Connection con=null; //here assigning null is optional, because each global object is by default null holds.

public void init(){
--------// logic to create the JDBC connection object
--------
}

public void service(-,-)/doXxx(-,-) throws SE,IOE{
----//logic to use jdbc connection object and to develop
----// JDBC persistence logic
}

public void destroy(){

-----//logic to close JDBC connection object (i.e. con.close())
}
}

Adavantages of Approach 1:
All the request coming to servlet program from different browsers , will use one JDBC conncetion object, to interact with Database software. so the performance is good.

Disadavantages of Approach 1:
- Here JDBC connection object is insance variable of servlet program, so its not threadsafe object by default, for this we need to work with SYNCHRONIZATION concept explicitly.