- The fields of the physical file to be used
as an external Data Structure should define
only the variables which might be
in the input string sent by the client browser
- there is no need to define here
the output variables from your CGI programs
to the response html
- Field names must be the same as the names of the variables
in the input string (i.e. the names preceded by ? or &)
and must be different
from your data base field names
- to avoid mismatches inside your programs
- About fields that should be converted as numeric
- remember that no numeric field can be defined
in HTML, all fields there are in character format.
QtmhCvtDb API may convert them to numeric
if you define them as numeric in the external data structure.
However, read the following ...
- Fields defined with data type S
in the external data structure may not be converted
(the API may fail, your program bumps out
-you may need PTF's to fix the API-)
- Fields defined with data type P
in the external data structure are converted
by the API as long as their contents are really numeric
(if by chance the user enters alphabetics,
the API bumps out).
You have two ways to make sure that an input field
contains numeric data
- control the input data on the browser itself,
by means of a JavaScript routine
(see my Javascript tutorial);
this is my favorite approach
- writing in the CGI a routine that checks numeric fields
in the input string;
this routine should run before
the call to procedure CvtDb
- Fields defined with data type A
have no problems. If they are supposed to contain
numeric data, then your program should check them
before converting to numeric.
That is another way to differ numeric control after
the call to procedure CvtDb.
- How many external data structures do I need?
This is up to you to decide.
You may have:
- A separate data structure for each program
- Several data structures
shared among programs
- A single external data structure
for all programs in a given library
- ... etc.
- What then if I add, change, or delete fields
in an external data structure
shared by several programs?
- Any time you do this and recompile an external data structure
physical file, your existing CGI programs,
using that data structure,
though may not bump out, do not receive any longer
their input fields as expected.
You may tell this from the fact that they appear
as not receiving their inputs any longer.
- You should then
- endtcpsvr *http
- recompile all your RPG modules and
recreate
all the CGI programs using that external data structure
- strtcpsvr *http
This is why I recommend
you to maintain a CL program
to perform this job.
Worth doing it since the beginning of your developments,
in order to save a lot of your time.
- What is suggested if one decides to use a single
external data structure for all programs in a given
library?
- My suggestion is to create this data structure
independently from the need of the individual
programs.
- Field names could be just anonymous
(e.g.
CGIINP01, CGIINP02, CGIINP03, ...
- Field lengths should be great enough
to accomodate any program requirements
(e.g. 100 characters)
- There should be enough fields
for the most input-demanding programs
As an example, you may look at the
external
data structure used by command
crtcgisrc ... option(1)
- You should however be aware of some minor
performance problem when using large
external data structures,
expecially when running them in CGIDEBUG
mode.
Warning
In your HTML scripts you must make sure
that no input fields exceed their lengths
as specified in the corresponding fields
of the external data structure.
Should this happen, CvtDb would stop
parsing the input string.
- In the
input type=text
fields of your HTML
forms
you must always specify the
maxlength
attribute
- input type=textarea
fields
do not support the
maxlength
attribute.
In these cases you must use a Javascript
function to make sure that the length
of the input text does not exceed the
length of the target field in the
external data structure.
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