DWR and JdbcTemplate

[Charles Flynn]

Hello,
I just started with Spring and I'm trying get DWR working. Can I use a JdbcTemplate with DWR?
I set up a datasource in my applicationContext.xml but when I try and run the app it never finds the datasource. Let me know if I need to post any code, I thought maybe someone would know right away what my problem was.


Thanks

[Herman Schelti]

hi Buddy,

does your JDBCTemplate (or your class that uses it) work at all?

Herman

[Charles Flynn]

Hi Herman,
Yes, it will work if I set the datasource properties myself:

 
   DriverManagerDataSource dataSource = new DriverManagerDataSource();                     dataSource.setDriverClassName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
dataSource.setUrl("jdbc:sqlserver://mymachine:;DatabaseName=myDatabase");
dataSource.setUsername("myusername");
dataSource.setPassword("mypassword");
JdbcTemplate jt = new JdbcTemplate();
jt.setDataSource(dataSource);

Thanks for the help

[Herman Schelti]

hi Buddy/Enoch,

Did you look at http://getahead.org/dwr/server/spring

Just define the class that you made as a "Spring bean", and this site will tell you all that you need.
Most examples will call this file applicationContext.xml

Actually: you can also define dataSource, jdbctemplate etc as "Spring beans"
instead of coding it like you did

Herman

[Charles Flynn]

Hi Herman,
So I would define my JdbcTemplate and datasource in the dwr.xml instead of the applicationContext.xml? Would it look something like this?

  
   <create creator="spring" javascript="DWRFunction">
    <param name="beanName" value="JdbcTemplate"/>
    <param name="location" value="applicationContext.xml"/>
  </create>

Thanks again

[Herman Schelti]

hi Enoch,

First: define your Spring beans in some .xml file
(and make sure that they work without use if DWR).

Second: make them accessible to Javascript with by DWR

<create creator="spring" javascript="DWRFunction">
    <param name="beanName" value="JdbcTemplate"/>
    <param name="location" value="applicationContext.xml"/>
  </create>

Herman

I'm not sure though why you want to call "JdbcTemplate" from javascript.
It's just a helper class, it does not know which SQL to execute by itself.

[Charles Flynn]

Hi Herman,
Not sure what I'm doing wrong, it's still having a problem. I put a try-catch block to see what error it was throwing, the error gets caught but the error message is always null.

Thanks

[Herman Schelti]

Enoch,

probably NullPointerException then.

But where in your code, and how do you call that code.
Are all the Spring beans you defined created? (check your logs)

Herman
[ October 18, 2007: Message edited by: Herman Scheltinga ]

[Charles Flynn]

Herman,
I'll post part of my code, can you take a look and see what I've done wrong.

Thanks

  
   <!--DWR.xml-->
   <dwr>
   <allow> 
    <create creator="new" javascript="Demo">
      <param name="class" value="HomeController"/> 
     </create>   
     
    <!-- Reference to the config containing the JdbcTemplate -->
   <create creator="spring" javascript="Demo">
      <param name="beanName" value="HomeController" />
      <param name="location" value="classpath:Context.xml"/>
    </create> 
  </allow> 
</dwr>  

 
   <!--Context.xml-->
   <beans>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"
     destroy-method="close">
   <property name="driverClassName" value ="com.microsoft.sqlserver.jdbc.SQLServerDriver" />
   <property name="url" value="jdbc:sqlserver://localhost:1433;DatabaseName=NorthWind" />
   <property name="username" value="java" />
   <property name="password" value="java" />
 </bean>  
  <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
 <property name="dataSource" ref="dataSource"> 
 </property> 
 </bean> 
 <bean  id="HomeController" class="HomeController">
 <property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>
</beans>      

 
  //HomeController.java
   public class HomeController extends JdbcDaoSupport  {
   
public String showMessage(String name)
         {
//Just a small test to see if the JdbcTemplate is working
int x = getJdbcTemplate().queryForInt("SELECT COUNT(*) FROM            Employees");
return "Query complete";
    }

} 

[Herman Schelti]

hi,

Looks OK to me, it would be a little better if HomeController was in a package.
I'll try this at home later (probably tonight).

I still don't know which line of your code throws the NullPointerException, and don't know what program you ran that caused the exception.

And did you test this code without DWR (just with Spring)?

Herman

[Charles Flynn]

Hi Herman,
It fails when it calls

    
   int x = getJdbcTemplate().queryForInt("SELECT COUNT(*) FROM            Employees");

I have another class I tried in Spring and it works.

Thanks for taking the trouble to look at this

[Herman Schelti]

hi,

glad you got it working.

Can you tell us why it is working now: what's different in this other class?

Herman

[Charles Flynn]

Herman,
Sorry, I guess I didn't explain it clearly. It's working in the other class with Spring because it's not using DWR it's using MVC. For what ever reason it's not seeing the DataSource or the JdbcTemplate I have defined in the config files when I use DWR.
However I added this code im my class and I'm able to get the datasource and I can run the query. Do you think that the "Context.xml" is not being loaded and that's why the DataSource is null?

    
   ApplicationContext ctx = new ClassPathXmlApplicationContext("Context.xml");
   DriverManagerDataSource dataSource= (DriverManagerDataSource)  ctx.getBean("dataSource");

[Herman Schelti]

hi Enoch,

yes, I do think that Context.xml is not being loaded.

Default name for that file is applicationContext.xml, default location is in WEB-INF. If you want it differently, add to you web.xml:

<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>WEB-INF/Context.xml</param-value>
    </context-param>

Also: Spring needs commons-logging.jar (typically in WEB_INF/lib), if you want to see any logging. Without further configuration it will end-up in your console, which is fine for studying.

Like
INFO: Pre-instantiating singletons in factory [org.springframework.beans.factory.support.DefaultListableBeanFactory defining beans [dataSource,jdbcTemplate,HomeController]; root of BeanFactory hierarchy]

Herman

[Charles Flynn]

Hi Herman,
I'm just going in circles with this. I added the commons-logging.jar and you were right about the NullPointerException. I can post the log if that would be helpful, or do you have a working example that you would be willing to post.

Thanks