Applet Example 6
This example demonstrates
how to implement the applet so that the graph data is acquired
from a database. Here we set up the applet 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.
The configuration
data is acquired from the text file areaprops.txt
(click here to view)
and here
is the HTML code,
<applet code="AreaGraphApplet.class"
archive="AreaGraph.jar" width="460" height="440">
<!-- Start Up Parameters -->
<PARAM name="LOADINGMESSAGE" value="Area
Graph Loading - Please Wait."> <!-- Message to
be displayed on Startup -->
<PARAM name="STEXTCOLOR" value="0,0,100">
<!-- Message Text Color-->
<PARAM name="STARTUPCOLOR" value="255,255,255">
<!-- Applet Background color -->
<!-- Data files
-->
<PARAM
name="chartproperties" value="areaprops.txt">
<PARAM name="chartdata" value="http://www.jpowered.com/siriusjava/servlet/DatabaseServlet3">
</applet>
The DatabaseServlet2
is designed to retrieve product sales data from a MySQL database,
from a table with the following structure,
Table
Name : ProductSales |
|
|
ProductName |
Character |
Quarter1sales |
Integer |
Quarter2sales |
Integer |
Quarter2sales |
Integer |
Quarter2sales |
Integer |
Year |
Integer |
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 DatabaseServlet3.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 lineGraph.
Finally
the rsltStr is returned back to the calling process ( in this
case our Line Graph ) and the database connection is closed.
Note:
If you are using the evaluation version then in the applet
a pop-up window will appear upon the startup and an evaluation
message will be incorporated by the servlet. Both these features
have been removed from the licensed version. Licensing information
can be found at http://www.jpowered.com/graph_chart/index.htm
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