SQL queries

[Sahil Sharma]

Hi All,

How to decide that it is good to keep all the SQL queries in the DAO class itself or keep it in the database or some text file.

Thanks.

[Oscar Costa]

Hi Sahil,

It depends what persistence framework you will use.

Examples:
- Hibernate, you can put the simple queries at NamedQueryes in Pojos...
- Ibatis, you can put the queries in xml files...
- DataBase you will need to use StoredProcedures or Function to use the queries...

[Sidd Kulk]

Sometimes I keep my queries in a Java Constants File as static final Strings. But may be this would cause JVM memory issues.

Cheers
Sid

[Sagar Rohankar]

Sidd Kulk wrote:Sometimes I keep my queries in a Java Constants File as static final Strings. But may be this would cause JVM memory issues.

[Sidd Kulk]

Sagar,

Like you keep your query strings in properties file and then fetch them at runtime, you can create a Constants class, and declare public static final Strings.

e.g.

public interface Constants
{
    String QUERY="SELECT * FROM TABLE_NAME";
}

My DAO class would be:

public class DataBaseImpl
{
    public List getData()
    {
          String query=Constants.QUERY;
          .
          .
          .
          . 
    }
}

In case of web applications, if there are too many queries, this would cause memory issues in JVM as the queries would remain loaded in memory all the time..

Hope this explains

Cheers!
Sid

[Sagar Rohankar]

I totally agree with your explanation and code, but I don't think declaring static string instance will cause any memory problems, after all they are not heavy resources like, IO streams or DB connections. And we know there is SCP (String Constant Pool), which takes care that there is only one such string exits in JVM memory, that means no duplication and I thought that ain't be the problem to memory