Advanced Line Graph by Sirius

Advanced Line Graph, version 3.2
by Sirius Computer Consultants Limited

 

Servlet Example 4

This example demonstrates how to implement the servlet so that the graph data is acquired from a database. Here we set up the servlet to acquire the configuration data from a text file and the graph data from a server side process which in turn acquires the data from a database.

and here is the HTML code,

<img src="http://localhost:8080/servlet/LineGraphServlet?
config=http://www.jpowered.com/line_graph/Examples/lineprops.txt&
data=http://www.jpowered.com/siriusjava/servlet/DatabaseServlet2"
width="500" height="420">

The graph servlet will pick up the configuration parameters from a text file lineprops2.txt and the graph data from our servlet DatabaseServlet2 ( click here to view java code ).

The DatabaseServlet is designed to retrieve product sales data from a MySQL database, from a table with the following structure,

Our servlet will pick out the sales figures for the year 2001 for three products ( ProductX, ProductY and ProductZ) and return the data in the correct format for the line graph.

The method is as follows,

• Set the output characteristics for the return data
  
• Establish the database connection
  
• Build the query statement and retrieve the database records
  
• Process the database records and return the Data
  
• All finished so close the database connection
  

The full servlet code is contained in the DatabaseServlet2.java file.
(Click here to view the code).

As you will see from the code the servlet connects to the database via JDBC and as such it is essential to have the correct JDBC drivers for your database. ( For further information on JDBC drivers please see http://industry.java.sun.com/products/jdbc/drivers )

The SQL statement used to retrieve the data from the database is simply,
SELECT * FROM ProductSales WHERE Year='2001'

The returned result set from this statement is then passed to a little routine, GraphData, which reads through the records picking out the relevant records for the three products. Also note in this routine how the "rsltStr" is constructed to provide the data in the correct format for the Line Graph.

Finally the rsltStr is returned back to the calling process ( in this case our Line Graph ) and the database connection is closed.

http://www.graph-chart.com/graph.htm