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Posted to user@struts.apache.org by "Jasvinder S. Bahra" <bb...@blueyonder.co.uk> on 2010/01/07 19:06:24 UTC
Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as Hibernate
Does anyone know of any techniques that would allow a Database Access Object
(DAO) to be used from the various actions that make up a Struts application?
I have a DAO which, when instantiated, acquires a data source from the
servlet container (in this case, Apache Tomcat). Thereafter, I can execute
the various methods provided by the object which use the data source to
execute SQL queries/statements, and return usable data in the form of
Strings, Maps, Vectors etc, as appropriate.
Instantiating the DAO in the execute() method of each of my action's
however, seems a little inefficient. Does Struts provide any way to
instantiate the object once and then make it available for the lifetime of
the container (in a way that my Actions can access it)?
Note please that i'm well aware that this is a somewhat non-standard
approach to database interaction. I am intending to investigate Hibernate
(and like) at some point, but for the time being I want to avoid such.
This is the skeleton of the DAO I have in mind...
----------------------------------------------------------------------
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
import javax.servlet.*;
public class MyDataAccessObject {
private DataSource dataSource;
private String SQL;
public MyDataAccessObject() throws Exception {
try {
Context init = new InitialContext();
Context ctx = (Context) init.lookup("java:comp/env");
dataSource = (DataSource) ctx.lookup("jdbc/mysqldb");
} catch (NamingException ne) {
throw new Exception("Cannot retrieve
java:comp/env/jdbc/mysqldb", ne);
}
SQL = null;
}
public String getValue(String name) {
Connection dbcon = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String value = null;
try {
dbcon = dataSource.getConnection();
SQL = "SELECT value FROM table WHERE name = ?";
pstmt = dbcon.prepareStatement(SQL);
pstmt.setString(1, name);
rs = pstmt.executeQuery();
while (rs.next()) {
value = rs.getString("value");
}
rs.close();
rs = null;
pstmt.close();
pstmt = null;
dbcon.close();
dbcon = null;
} catch (SQLException ex) {
log(ex);
} catch (Exception ex) {
log(ex);
} finally {
if (rs != null) {
try { rs.close(); } catch (Exception fe1) { log(fe1); }
rs = null;
}
if (pstmt != null) {
try { pstmt.close(); } catch (Exception fe2) { log(fe2); }
pstmt = null;
}
if (dbcon != null) {
try { dbcon.close(); } catch (Exception fe3) { log(fe3); }
dbcon = null;
}
}
SQL = null;
return value;
}
private void log(...) {
// Handle logging
}
}
----------------------------------------------------------------------
Thanks,
Jazz
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Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as Hibernate
Posted by "Jasvinder S. Bahra" <bb...@blueyonder.co.uk>.
> Jazz, here's a lightweight package that so far has met all of my needs:
> http://butterfly.jenkov.com/ ...
I'll be sure to take a look.
Thanks for the response.
Jazz
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Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as
Hibernate
Posted by Bill Bohnenberger <bi...@gmail.com>.
Jazz, here's a lightweight package that so far has met all of my needs:
http://butterfly.jenkov.com/ ...
Cheers, Bill*
*
On Thu, Jan 7, 2010 at 4:30 PM, Jasvinder S. Bahra <
bbdl21548@blueyonder.co.uk> wrote:
> I'll echo the Spring suggestion. It simplifies Action-level programming by
>> quite a bit.
>>
>> On the flip side, it requires some extra XML configuration, but IMO it's a
>> good tradeoff.
>>
>
> Spring seems to be quite popular here. I'm somewhat reluctant because
> Spring provides a lot more than just Database Injection - and for the time
> being, DI is all I really want.
>
> If I cant find what I want, I guess i'll have to bite the bullet and jump
> into it.
>
> Thanks for the response.
>
>
> Jazz
>
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> For additional commands, e-mail: user-help@struts.apache.org
>
>
Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as Hibernate
Posted by "Jasvinder S. Bahra" <bb...@blueyonder.co.uk>.
> I'll echo the Spring suggestion. It simplifies Action-level programming
> by
> quite a bit.
>
> On the flip side, it requires some extra XML configuration, but IMO it's a
> good tradeoff.
Spring seems to be quite popular here. I'm somewhat reluctant because
Spring provides a lot more than just Database Injection - and for the time
being, DI is all I really want.
If I cant find what I want, I guess i'll have to bite the bullet and jump
into it.
Thanks for the response.
Jazz
---------------------------------------------------------------------
To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
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Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as
Hibernate
Posted by Brian Thompson <el...@gmail.com>.
I'll echo the Spring suggestion. It simplifies Action-level programming by
quite a bit.
On the flip side, it requires some extra XML configuration, but IMO it's a
good tradeoff.
-Brian
On Thu, Jan 7, 2010 at 12:18 PM, Chris Pratt <th...@gmail.com>wrote:
> We use Spring (and Spring-LDAP) for that layer. It works great, manages
> all
> our DAO's and their resources, and then injects them into the Actions as
> needed.
> (*Chris*)
>
> On Thu, Jan 7, 2010 at 10:06 AM, Jasvinder S. Bahra <
> bbdl21548@blueyonder.co.uk> wrote:
>
> > Does anyone know of any techniques that would allow a Database Access
> > Object (DAO) to be used from the various actions that make up a Struts
> > application?
> >
> > I have a DAO which, when instantiated, acquires a data source from the
> > servlet container (in this case, Apache Tomcat). Thereafter, I can
> execute
> > the various methods provided by the object which use the data source to
> > execute SQL queries/statements, and return usable data in the form of
> > Strings, Maps, Vectors etc, as appropriate.
> >
> > Instantiating the DAO in the execute() method of each of my action's
> > however, seems a little inefficient. Does Struts provide any way to
> > instantiate the object once and then make it available for the lifetime
> of
> > the container (in a way that my Actions can access it)?
> >
> > Note please that i'm well aware that this is a somewhat non-standard
> > approach to database interaction. I am intending to investigate
> Hibernate
> > (and like) at some point, but for the time being I want to avoid such.
> >
> > This is the skeleton of the DAO I have in mind...
> >
> > ----------------------------------------------------------------------
> > import java.sql.*;
> > import javax.sql.*;
> > import javax.naming.*;
> > import javax.servlet.*;
> >
> > public class MyDataAccessObject {
> >
> > private DataSource dataSource;
> > private String SQL;
> >
> > public MyDataAccessObject() throws Exception {
> >
> > try {
> > Context init = new InitialContext();
> > Context ctx = (Context) init.lookup("java:comp/env");
> > dataSource = (DataSource) ctx.lookup("jdbc/mysqldb");
> > } catch (NamingException ne) {
> > throw new Exception("Cannot retrieve
> java:comp/env/jdbc/mysqldb",
> > ne);
> > }
> >
> > SQL = null;
> > }
> >
> > public String getValue(String name) {
> >
> > Connection dbcon = null;
> > PreparedStatement pstmt = null;
> > ResultSet rs = null;
> >
> > String value = null;
> >
> > try {
> > dbcon = dataSource.getConnection();
> >
> > SQL = "SELECT value FROM table WHERE name = ?";
> >
> > pstmt = dbcon.prepareStatement(SQL);
> > pstmt.setString(1, name);
> >
> > rs = pstmt.executeQuery();
> > while (rs.next()) {
> > value = rs.getString("value");
> > }
> >
> > rs.close();
> > rs = null;
> >
> > pstmt.close();
> > pstmt = null;
> >
> > dbcon.close();
> > dbcon = null;
> > } catch (SQLException ex) {
> > log(ex);
> > } catch (Exception ex) {
> > log(ex);
> > } finally {
> > if (rs != null) {
> > try { rs.close(); } catch (Exception fe1) { log(fe1); }
> > rs = null;
> > }
> >
> > if (pstmt != null) {
> > try { pstmt.close(); } catch (Exception fe2) { log(fe2); }
> > pstmt = null;
> > }
> >
> > if (dbcon != null) {
> > try { dbcon.close(); } catch (Exception fe3) { log(fe3); }
> > dbcon = null;
> > }
> > }
> >
> > SQL = null;
> > return value;
> > }
> >
> > private void log(...) {
> > // Handle logging
> > }
> > }
> > ----------------------------------------------------------------------
> >
> > Thanks,
> >
> > Jazz
> >
> >
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> > For additional commands, e-mail: user-help@struts.apache.org
> >
> >
>
Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as
Hibernate
Posted by Chris Pratt <th...@gmail.com>.
Good luck, and let us know how it goes.
(*Chris*)
On Thu, Jan 7, 2010 at 3:44 PM, Jasvinder S. Bahra <
bbdl21548@blueyonder.co.uk> wrote:
> We use Spring (and Spring-LDAP) for that layer. It works great, manages
>> all
>> our DAO's and their resources, and then injects them into the Actions as
>> needed.
>>
>
> Chris,
>
> At the moment, i'm trying to reaquaint myself with the ins and out of
> Struts (I haven't touched it for several years), so I dont (yet) want to
> introduce any additional libraries.
>
> I'm sure its possible to do what I need without them.
>
> Thanks for the suggestion anyway.
>
>
> Jazz
>
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> For additional commands, e-mail: user-help@struts.apache.org
>
>
Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as Hibernate
Posted by "Jasvinder S. Bahra" <bb...@blueyonder.co.uk>.
> We use Spring (and Spring-LDAP) for that layer. It works great, manages
> all
> our DAO's and their resources, and then injects them into the Actions as
> needed.
Chris,
At the moment, i'm trying to reaquaint myself with the ins and out of Struts
(I haven't touched it for several years), so I dont (yet) want to introduce
any additional libraries.
I'm sure its possible to do what I need without them.
Thanks for the suggestion anyway.
Jazz
---------------------------------------------------------------------
To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
For additional commands, e-mail: user-help@struts.apache.org
Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as
Hibernate
Posted by Chris Pratt <th...@gmail.com>.
We use Spring (and Spring-LDAP) for that layer. It works great, manages all
our DAO's and their resources, and then injects them into the Actions as
needed.
(*Chris*)
On Thu, Jan 7, 2010 at 10:06 AM, Jasvinder S. Bahra <
bbdl21548@blueyonder.co.uk> wrote:
> Does anyone know of any techniques that would allow a Database Access
> Object (DAO) to be used from the various actions that make up a Struts
> application?
>
> I have a DAO which, when instantiated, acquires a data source from the
> servlet container (in this case, Apache Tomcat). Thereafter, I can execute
> the various methods provided by the object which use the data source to
> execute SQL queries/statements, and return usable data in the form of
> Strings, Maps, Vectors etc, as appropriate.
>
> Instantiating the DAO in the execute() method of each of my action's
> however, seems a little inefficient. Does Struts provide any way to
> instantiate the object once and then make it available for the lifetime of
> the container (in a way that my Actions can access it)?
>
> Note please that i'm well aware that this is a somewhat non-standard
> approach to database interaction. I am intending to investigate Hibernate
> (and like) at some point, but for the time being I want to avoid such.
>
> This is the skeleton of the DAO I have in mind...
>
> ----------------------------------------------------------------------
> import java.sql.*;
> import javax.sql.*;
> import javax.naming.*;
> import javax.servlet.*;
>
> public class MyDataAccessObject {
>
> private DataSource dataSource;
> private String SQL;
>
> public MyDataAccessObject() throws Exception {
>
> try {
> Context init = new InitialContext();
> Context ctx = (Context) init.lookup("java:comp/env");
> dataSource = (DataSource) ctx.lookup("jdbc/mysqldb");
> } catch (NamingException ne) {
> throw new Exception("Cannot retrieve java:comp/env/jdbc/mysqldb",
> ne);
> }
>
> SQL = null;
> }
>
> public String getValue(String name) {
>
> Connection dbcon = null;
> PreparedStatement pstmt = null;
> ResultSet rs = null;
>
> String value = null;
>
> try {
> dbcon = dataSource.getConnection();
>
> SQL = "SELECT value FROM table WHERE name = ?";
>
> pstmt = dbcon.prepareStatement(SQL);
> pstmt.setString(1, name);
>
> rs = pstmt.executeQuery();
> while (rs.next()) {
> value = rs.getString("value");
> }
>
> rs.close();
> rs = null;
>
> pstmt.close();
> pstmt = null;
>
> dbcon.close();
> dbcon = null;
> } catch (SQLException ex) {
> log(ex);
> } catch (Exception ex) {
> log(ex);
> } finally {
> if (rs != null) {
> try { rs.close(); } catch (Exception fe1) { log(fe1); }
> rs = null;
> }
>
> if (pstmt != null) {
> try { pstmt.close(); } catch (Exception fe2) { log(fe2); }
> pstmt = null;
> }
>
> if (dbcon != null) {
> try { dbcon.close(); } catch (Exception fe3) { log(fe3); }
> dbcon = null;
> }
> }
>
> SQL = null;
> return value;
> }
>
> private void log(...) {
> // Handle logging
> }
> }
> ----------------------------------------------------------------------
>
> Thanks,
>
> Jazz
>
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> For additional commands, e-mail: user-help@struts.apache.org
>
>
Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as Hibernate
Posted by "Jasvinder S. Bahra" <bb...@blueyonder.co.uk>.
> So want your DAO's to be singletons?
> You would have to make them Thread-safe (or synchronize and kill
> performance), beware that database connections are not thread-safe.
Please note that i'm using using the database connection pooling
facilities provided by the Servlet Container (Apache Tomcat). As long as
the DAO aquires the database connection through a JNDI datasource, the
Servlet Container will take care of the thread and connection management
issues.
> The preferred method is use a DI facility (like Guice or Spring) and
> instantiate a new DAO each time and inject the database connection
> into it and inject the DAO into the Struts action.
I'd prefer to avoid the use of additional libraries for the time being
which is why I haven't taken advantage of the libraries that you
mentioned.
I'm more than happy to remove the acquiring of the datasource code from
the DAO's constructor, and add a method to allow an instantiated version
of the class to be assigned a data source. However, I would need a way of
acquiring the datasource and assigning it to the DAO *without* using any
additional libraries.
Any ideas?
Thanks for the response.
Jazz
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Re: Struts, Tomcat, JNDI, JDBC without use of an ORM Library such as
Hibernate
Posted by Greg Lindholm <gr...@gmail.com>.
>
> Instantiating the DAO in the execute() method of each of my action's
> however, seems a little inefficient. Does Struts provide any way to
> instantiate the object once and then make it available for the lifetime of
> the container (in a way that my Actions can access it)?
>
So want your DAO's to be singletons?
You would have to make them Thread-safe (or synchronize and kill
performance), beware that database connections are not thread-safe.
Doesn't really sound like a good plan to me.
If you just have one DAO of each type (singletons) then you need to
ensure they are thread-safe and you need to either handle the
acquire/release of database connections within each method or pass in
the connection. Neither is a great design, the first make you
duplicate fragile difficult to test code in every DAO the second
exposes database connections in the DAO methods. It's hard to write
DAO's as singletons and get them right, much easier to use a new one
each time as if they have no state then instantiating them is cheap
(where writing thread safe code is hard, hard to write, hard to test).
The preferred method is use a DI facility (like Guice or Spring) and
instantiate a new DAO each time and inject the database connection
into it and inject the DAO into the Struts action. This make it easy
to write, easy to test and you don't have to expose database
connections and handling logic to the actions.
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