Database Reference
In-Depth Information
In Python, to fetch the cow accessory information and present it using checkboxes or
a scrolling list, do this:
acc_info
=
get_enumorset_info
(
conn
,
'cookbook'
,
'cow_order'
,
'accessories'
)
if
acc_info
[
'default'
]
is
None
:
acc_def
=
""
else
:
acc_def
=
acc_info
[
'default'
]
.
split
(
','
)
print
(
make_checkbox_group
(
'accessories'
,
acc_info
[
'values'
],
acc_info
[
'values'
],
acc_def
,
True
))
# display items vertically
print
(
make_scrolling_list
(
'accessories'
,
acc_info
[
'values'
],
acc_info
[
'values'
],
acc_def
,
3
,
# display 3 items at a time
True
))
# create multiple-pick list
In JSP pages, the
getEnumOrSetValues()
function used earlier to get the value list for
the
size
column (an
ENUM
) can also be used for the
accessory
column (a
SET
). The
column definition and default value can be obtained from
INFORMATION_SCHEMA
. Query
the
COLUMNS
table, parse the type definition into a list of values named
values
, and put
the default value in
defList
like this:
<sql:query
dataSource=
"${conn}"
var=
"rs"
>
SELECT COLUMN_TYPE, COLUMN_DEFAULT
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'cookbook'
AND TABLE_NAME = 'cow_order'
AND COLUMN_NAME = 'accessories'
</sql:query>
<c:set
var=
"typeDef"
scope=
"page"
value=
"${rs.rowsByIndex[0][0]}"
/>
<%
getEnumOrSetValues
(
pageContext
,
"typeDef"
,
"values"
);
%>
<c:set
var=
"defList"
scope=
"page"
value=
"${rs.rowsByIndex[0][1]}"
/>
For a
SET
column, the
defList
value might contain multiple values, separated by com‐
mas. It needs no special treatment; the JSTL
<c:forEach>
tag can iterate over such a
string, so initialize the default values for a checkbox set as follows:
<c:forEach
items=
"${values}"
var=
"val"
>
<input
type=
"checkbox"
name=
"accessories"
value=
"<c:out value="
${val}"
/>
"
<c:forEach
items=
"${defList}"
var=
"defaultVal"
>
<c:if
test=
"${val == defaultVal}"
>
checked="checked"
</c:if>
</c:forEach>
/>
<c:out
value=
"${val}"
/><br
/>
</c:forEach>
