SimpleDB Help
About the applet
Purpose
SimpleDB is a very basic data applet. It reads tab-delimited data
from a URL, and generates a form on the fly to read and edit the data.
Author
This applet was written by Andy Harris for the book "Java Fast and
Easy".
Setting up the database
The data file
The first row of the data file must contain field names seperated by
tab characters. Each row of the file must be the field values separated
by tabs. The last row must be blank. Most spreadsheets and database
packages allow you to save to a tab-delimited format. The data file
must be stored in the same directory as the HTML file which contains
the applet. The current version of the applet allows a maximum of
100 records, but this is easily changed in the java source code.
The HTML
Write an HTML file to use the applet with all the normal applet tag
information. Add a param tag with the appropriate datafile, like
this:
<applet code = SimpleDB
height = 400
width = 600>
<param name = "DataFile"
value = "grades.dat">
</applet>
If the file name is incorrect, the applet will pop up a warning
message.
The commands
Prev
Calls up the previous record in the database. If you are currently
on the first record, this command will 'wrap around' and show the
last element.
Next
Calls up the next record in the database. If you are currently
on the last record, this command will 'wrap around' and show the
first element.
Copy
Because of security restrictions, Java applets normally cannot save
information to a disk drive. SimpleDB allows you to copy the
current database to the system clipboard so you can paste it into a
text editor and change the data. This acts like a security feature,
as anyone who can access the data can modify their own copy of the
data, but only the person with access to the datafile can change it.
To use this feature, select the entire text area with the mouse, and
use the mouse menu (right click or click and hold on most systems)
to copy the data to the system clipboard. You can then paste the
data into a text editor, and save it to the data file. Don't forget
that the last line of your data file should be empty.
Search
This command requests a word or phrase to search for. It searches
through the data and displays each record that contains the data. The
search mechanism is case-sensitive.
Add
The add command adds a new record to the database. It then displays
the new record.
Remember that this applet cannot directly save the
data. You need to use the copy feature to copy the data to your
text editor if you want the changes to be permanent.
Editing Data
The user can edit the current record by just changing the values in
the fields.
Remember that this applet cannot directly save the
data. You need to use the copy feature to copy the data to your
text editor if you want the changes to be permanent.