-------- Original Message --------
Subject: [MVC-Programmers] [Struts Tips] #6 - Use an array to capture
multiple parameters
Date: Tue, 09 Apr 2002 07:46:36 -0400
From: Ted Husted <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Organization: Apache Software Foundation / Jakarta
Newsgroups: MVC-Programmers
In a perfect universe, our users would happily subscribe to the One True
Workflow. in every case, we could list some records, select a record to
view or edit, and list some records again. But in real life, users often
want to do unreasonable things, like edit 17 records at once.
Usually, we'd already have a business procedure for saving one copy of
the record. Perhaps something like this
String key= form.getKey();
String category = form.getCategory();
db.updateCategory(new Integer(key),category);
A very simple way to convert this to multiple use would to do something
like this:
String[] key = form.getKey();
String[] category = form.getCategory();
for (int i=0; i<category.length; i++) {
db.updateCategory(new Integer(key),category);
}
Depending what the db object did behind the scenes, and the scale of the
application, this could too simple to efficient, but for many small
intranet applications, it could work just fine.
Of course, that still leaves the problem of where to get an array of
keys and a matching array of categories.
Happily, HTTP supports submitting multiple parameters of the same name,
and Struts will autopopulate a String array as easily as a single
String. So, to represent the "multi-use" business operation in an
ActionForm, we can just do this:
private String[] key= null;
public String[] getKey() {
return this.key;
}
public void setKey(String[] key) {
this.key = key;
}
private String[] category = null;
public String[] getCategory() {
return this.category;
}
public void setCategory(String[] category) {
this.category = category;
}
Which is just the single-record version but with String[] instead of
String.
In the JavaServer Page, the only real trick is to refer to the iterate
id in the html form tags.
<TABLE>
<html:form action="/item/StoreCategory">
<logic:iterate name="RESULT" property="iterator" id="row">
<TR>
<TH>name</TH>
<TH>category</TH>
</TR>
<TR>
<TD><bean:write name="row" property="name"/></TD>
<TD>
<%-- REMEMBER TO SPECIFY THE ITERATE ID AS THE NAME --%>
<html:select name="row" property="category">
<html:option value="ART">Art</html:option>
<html:option value="AUT">Automotive</html:option>
<%-- ... --%>
</html:select>
<%-- REMEMBER TO SPECIFY THE ITERATE ID AS THE NAME --%>
<html:hidden name="row" property="key"/>
</TD>
</TR>
</logic:iterate>
<TR>
<TD colspan="2">
<html:submit>SAVE CHANGES</html:submit>
</html:form>
</TD>
</TR>
</TABLE>
Now when they submit the form, it will include several
category=XYZ&key=123 tuples in the request. Struts will convert the
category and key entries to individual arrays, which your business logic
can then use to make the appropriate update.
HTH, Ted.
-----
About Ted. Ted Husted is an active Struts Committer and moderates the
Struts mailing list and the JGuru Struts FAQ.
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