Passing variable to public/servlet

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Clive_ - 12 Nov 2007 16:15 GMT

Hi,

Does anyone know an example showing how to pass a database variable to
a public variable??

I would like to run a java file or JSP, passing <%= rs.getInt(1)%> to
a servlet???
The servlet would store the data, which could be retrieved using
getAttribute.

Thanks

Clive

<%
String connectionUrl =("jdbc:jtds:sqlserver://localhost:1032/");
String dbName="Calibration";
String driver="net.sourceforge.jtds.jdbc.Driver";
String user="aaaa";
String password="user";

// Establish the connection.
Class.forName(driver).newInstance();
con = DriverManager.getConnection(connectionUrl
+dbName,user,password);
stmt = con.createStatement() ;
rs = stmt.executeQuery(querySQL) ;

ResultSetMetaData rsmd = rs.getMetaData() ;

for(int i = 1 ; i <= rsmd.getColumnCount() ; i++) {
%>

<% } %>

</tr>

<% while(rs.next()) { %>
<tr>
<td> <%= rs.getInt(1)%> </td>
<td> <%= rs.getString(2) %> </td>
</tr>
<br>

<% }
con.close();
con = null;
%>

Reply to this Message

Lew - 12 Nov 2007 16:41 GMT

> Hi,
>
> Does anyone know an example showing how to pass a database variable to
> a public variable??

One question mark would suffice.

> I would like to run a java file or JSP, passing <%= rs.getInt(1)%> to
> a servlet???

A JSP is a servlet, so you've already done that. What do you need the value for?

> The servlet would store the data, which could be retrieved using
> getAttribute.

Do you mean in a request attribute? Where do you intend to store the data?

You can set request attributes with the request setAttribute() method. Check
out the Javadocs.

> <%

Do not put Java in JSPs. It's legal, but foolish.

> String connectionUrl =("jdbc:jtds:sqlserver://localhost:1032/");
> String dbName="Calibration";
[quoted text clipped - 4 lines]
> // Establish the connection.
> Class.forName(driver).newInstance();

You don't need to load the DB driver class again and again, and you certainly
don't need to create a throwaway instance of it.

> con = DriverManager.getConnection(connectionUrl
> +dbName,user,password);

What if this fails? You have no Exception handling at all.

> stmt = con.createStatement() ;
> rs = stmt.executeQuery(querySQL) ;

From where do you get the query?

> ResultSetMetaData rsmd = rs.getMetaData() ;

You assign the value then never refer to it again except to drive an empty
loop. Why?

> for(int i = 1 ; i <= rsmd.getColumnCount() ; i++) {
> %>

Empty loop.

> <% } %>
>
> </tr>

Where's the opening <tr> tag? The enclosing <table>?

> <% while(rs.next()) { %>
> <tr>
[quoted text clipped - 6 lines]
> con.close();
> con = null;

What in the world do you expect to accomplish with setting con to null? It
goes out of scope anyway, so it's a useless action.

> %>

There are tags in the JSTL for SQL access that likely would be much easier for
you. JSPs should do their action through separate server-side classes or tag
libs so that all this Java scriptlet doesn't cruft up your presentation artifacts.

You've already got the value in a servlet, so I am not clear what else you
need to accomplish.

Signature

Lew

Reply to this Message

Clive_ - 13 Nov 2007 09:50 GMT

Hi Lew,

All my web development, etc was done using VB, eVB & Javascript.

In VB
Private Sub Test_Click()

'Declare variables
Dim i As Integer
Dim X As Integer
Dim Y As Integer

Dim ColumnNames As String
Dim ColumnValues As String

'Code to Auto Increment the Primary Key
Dim AutoNumber As Integer
Dim Identity As ADOCE.Recordset
Set Identity = CreateObject("ADOCE.Recordset.3.0")
Identity.Open "SELECT SiteID FROM HealthInspForm ORDER BY SiteID
DESC", CN
AutoNumber = CInt(Identity(0)) + 1
Identity.Close

'check to see if there's any editing in progress
If RS.EditMode <> adEditNone Then
MsgBox "There's editing in progress. Try the operation again
later."
Exit Sub
End If

SiteName = Var2
X = Var19
Y = Var20

'Add the new record
RS.AddNew
RS("SiteName") = SiteName
RS("Easting") = X
RS("Northing") = Y

'Ask user if they want the record added
If MsgBox("Do you wish to add this record?", vbYesNoCancel) =
vbYes Then
RS.Update
Else
RS.CancelUpdate
MsgBox "No new record added."
End If

'Query the database again to refresh the grid
RS.Requery

'Remove existing data from grid
For i = 1 To GridCtrl1.Rows
GridCtrl1.RemoveItem 0
Next

'Set the Grid columns equal to the field count
GridCtrl1.Cols = RS.Fields.Count

'Get the column names
For i = 0 To RS.Fields.Count - 1
ColumnNames = ColumnNames & RS.Fields(i).name & vbTab
Next

'Add the column headers to the grid
GridCtrl1.AddItem ColumnNames

'Loop through the recordset
While Not RS.EOF

'Get the column values for this row
For i = 0 To RS.Fields.Count - 1
ColumnValues = ColumnValues & RS.Fields(i).Value & vbTab
Next

'Add the column values to the row
GridCtrl1.AddItem ColumnValues

'Set ColumnValues to a zero length string
'so it can be refilled with the next row
ColumnValues = ""

RS.MoveNext
Wend

End Sub

I am new to Java and would like to find a simple example that shows/
explains the process. There are hundreds of VB examples that explain
the basics. I have not found a simple working example for JSP +
servlets. Once I have a working example then it is easier to
understand the javadocs.

Thanks

clive

Reply to this Message

Lew - 13 Nov 2007 13:37 GMT

> All my web development, etc was done using VB, eVB & Javascript.
>
[quoted text clipped - 3 lines]
> servlets. Once I have a working example then it is easier to
> understand the javadocs.

<http://java.sun.com/javaee/5/docs/tutorial/doc/>

The Sun tutorials are usually first place to look.

Marty Hall's books on Web development with Java are worthwhile also.
<http://www.coreservlets.com/>

Signature

Lew

Reply to this Message

Chris ( Val ) - 13 Nov 2007 14:00 GMT

> > All my web development, etc was done using VB, eVB & Javascript.
>
[quoted text clipped - 7 lines]
>
> The Sun tutorials are usually first place to look.

Yes, it is a good place to start.

> Marty Hall's books on Web development with Java are worthwhile also.
> <http://www.coreservlets.com/>

Yes - I like his book a lot, as it is very good
for a beginner to intermediate level.

I have been slowly working my way through his
tutorials, and I'm waiting for volume 2 of his book.

--
Chris

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Passing variable to public/servlet

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