Concerning JNDI Database Connection Pooling Sources, I
have read that if you fail to explicitely close Result
Sets, Statements, or Connections to the DataSource
from WITHIN the web application, a connection in the
pool will be "lost." (I read this at:
http://jakarta.apache.org/tomcat/tomcat-5.5-doc/jndi-datasource-examples-howto.html).
I understand that you can set an option to reclaim
"lost" connections. That's great.
But to avoid this in the first place, I have a
question.
I have a JSP which sends Statement objects to a Bean
(not a bean by exact definition) which accesses the
database and returns a ResultSet.
The jsp code is like this:
<% com.xxxxx.DatabaseInterface web = new
com.xxxxx.DatabaseInterface(); %>
<% web.connect(); %>
<% String selectSQL = "SELECT * FROM place;"; %>
<% ResultSet result = web.selectQuery(selectSQL); %>
<% while ( result.next() ) { %>
<%= result.getString("placename") %>
<% } %>
<% web.disconnect(); %>
Of course, there are statement objects and resultset
objects in the code above. Do I have to explicitely
close them IN JSP AND also the ones IN THE BEAN or
just the ones in the BEAN? I suppose this is a
fundamental principle of Java which I do not fully
understand as the objects . Can someone please
enlighten me?
The Bean looks like this:
package com.xxxx;
import java.sql.*;
import javax.sql.*;
import java.io.*;
import javax.naming.InitialContext;
import javax.naming.Context;
public class DatabaseInterface {
String error;
DataSource xxxx;
Connection database;
ResultSet result;
Statement select;
Statement update;
public DatabaseInterface() { }
public void connect() throws Exception {
try {
InitialContext initContext = new InitialContext();
xxxx = (DataSource)
initContext.lookup("java:comp/env/jdbc/xxxx");
database = xxxx.getConnection();
} catch (Exception e) {
error = "Data Source Opening Connection Error: " +
e;
throw new Exception(error);
}
}
public void disconnect() throws Exception {
try {
database.close();
} catch (Exception e) {
error = "Data Source Closing Connection Error: " +
e;
throw new Exception(error);
}
}
public ResultSet selectQuery(String webStatement)
throws SQLException, Exception {
try {
if ( database != null) {
select = database.createStatement();
result = select.executeQuery(webStatement);
}
} catch (SQLException sqle) {
error = "SQL Error Disconnecting: " + sqle;
throw new SQLException(error);
} catch (Exception e) {
error = "Error in selectQuery block:" + e;
throw new Exception(e);
}
return result;
}
public void insertQuery(String webStatement) throws
SQLException, Exception {
try {
if ( database != null) {
update = database.createStatement();
update.execute(webStatement);
}
} catch (SQLException sqle) {
error = "SQL Error: " + sqle;
throw new SQLException(error);
} catch (Exception e) {
error = "Error in insertQuery block:" + e;
throw new Exception(e);
}
}
}
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