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Groovy Database Resource Handling

· Database Zone

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I am a big fan of using SQL in java and C# software. I typically dislike the usage of ORM frameworks like Hibernate. I feel that ORMs tend to hide a lot of of issues. They also tend to have a higher learning curve. I am not sure that the ROI on deeply learning an ORM is sufficient enough to use. However, there are a lot of pitfalls that come with being so close to the SQL. The largest of which is proper resource handling. If database connections are not closed properly, the application will soon become starved of available connections.

This post contains a simple example of using Groovy Categories to help manage the resource management of database connections. There are a lot more robust solutions (ie: GORM), but sometimes you only need a quick implementation.

To accomplish our goal, we will be using a static closure defined below. The OpenDatabase class is merely a container for the closure. I think the final implementation of the code reads nicely because of the name.
OpenDatabase.groovy

import groovy.sql.Sql
 
class OpenDatabase {
    def static with = { DbConnection conn, Closure closure ->
        Sql sql
        try {
            sql = conn.getConnection()
 
            if (closure) {
                closure(sql)
            }
        }
        finally {
            sql.close()
        }
    }
}

The DbConnection class is a simple interface for creating the groovy.sql.Sql object.

DbConnection.groovy

import groovy.sql.Sql;
 
public interface DbConnection {
  Sql getConnection();
}

Below is the sample usage of these two classes.

OpenDatabase.with(dbConnector) { sql ->
         sql.execute("insert into BLAH...")
}

The database connection will be closed after closure exits. Simple, easy resource handling. The groovy way.

The original article can be found at http://www.greenmoonsoftware.com/2014/04/groovy-database-resource-handling/ 

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