JDBC-based bean definitions

[karsten]

Just wanted to verify my understanding of the following issue at
http://opensource.atlassian.com/proj.../browse/SPR-95
Addresses this a new feature where I can store my bean definitions in a DB table instead of an XML file?
is this correct?
Because this would come quite nice to play with the Timer functionality in Spring. I could specify the timertasks in a DB table then which I need for a project.
Is there any possibility to work on this and contribute it?
cheers.

[Colin Sampaleanu]

Karsten,

Yes, the existing JdbcBeanDefinitionReader can read bean definitions from a database, but it's not incredibly flexible. Additionally, there is the question of dynamic reconfiguration. One of the main reasons why somebody would put some data in a db (at least some of the time) is probably because they need to be able read that data dynamically, not just on program startup.

As for user contributions for this or any other area of Spring, sure, they are much appreciated. Any code can be submitted as a patch in Jira, and discussed in the dev list.

[karsten]

Colin,
thanks for the quick reply.
I will have a closer look at this subject and come back with more thoughts/code.
Keep your great work up!

[karsten]

I just wonder about some things with the functionality of retrieving bean definitions from a DB. Please correct me if I am wrong:
To retrieve bean configs from a DB, I need to store them as stated in the JdbcBeanDefinitionReader class (beanID, property name and value), then I need to instatiate a new JdbcBeanDefinitionReader, set a Datasource or JdbcTemplate on it. And I could do this with spring in the applicationContext.xml, or?
After that I have my own ServletContextListener implementation, which follows the spring ContextLoaderListener. In this class I retrieve the JdbcBeanDefinitionReader from the context and call the loadBeanDefinitions(String sql) method with the appropriate SQL.
The beans will get loaded into the same context as the others? or a new one?
Is this working at all, or am I missing something.
Thanx for clarifying.

[rstearns01]

Karsten,

Yes, the existing JdbcBeanDefinitionReader can read bean definitions from a database, but it's not incredibly flexible. Additionally, there is the question of dynamic reconfiguration. One of the main reasons why somebody would put some data in a db (at least some of the time) is probably because they need to be able read that data dynamically, not just on program startup.

I need to do something similar in that it is "policy" that if a configuration file changes, the application must go through a complete 30-day round of regression testing; yet there is no such rule for changing a value in the database. :roll:

[rstearns01]

Karsten,

Yes, the existing JdbcBeanDefinitionReader can read bean definitions from a database, but it's not incredibly flexible. Additionally, there is the question of dynamic reconfiguration. One of the main reasons why somebody would put some data in a db (at least some of the time) is probably because they need to be able read that data dynamically, not just on program startup.

I need to do something similar in that it is "policy" that if a configuration file changes, the application must go through a complete 30-day round of regression testing; yet there is no such rule for changing a value in the database. :roll:

[MHarhen]

Karsten,

Yes, the existing JdbcBeanDefinitionReader can read bean definitions from a database, but it's not incredibly flexible. Additionally, there is the question of dynamic reconfiguration. One of the main reasons why somebody would put some data in a db (at least some of the time) is probably because they need to be able read that data dynamically, not just on program startup.

As for user contributions for this or any other area of Spring, sure, they are much appreciated. Any code can be submitted as a patch in Jira, and discussed in the dev list.

I have written some code to initialize bean properties using initialization parameters stored in various locations e.g. database table, servlet context, servlet init parameters, Map, Properties, etc. It works both during application initialization and later during application execution. i.e. it supports dynamic reinitialization of bean properties,

I would be happy to submit the code to the Spring project. Let me know if you are interested.

See my posting from August 30 for additional information

[Colin Sampaleanu]

The best thing would be to put it on the wiki (Confluence) somewhere, so other people can get at it...

[irbouho]

MHarhen,

Your approach seems very interesting. I have two questions with regards to beans configurations using PropertyMapper:

1. Is it possible to configure PropertyMapper to call some initialization methods after properties were updated (to emulate Spring' init-method)?
2. How do you manage "dynamic reconfiguration": reconfigure a bean that is being used by other beans.

I am asking these questions because I will be using such "hot-configuration/reconfiguration" in a future project.

Thank you.

[MHarhen]

1. Is it possible to configure PropertyMapper to call some initialization methods after properties were updated (to emulate Spring' init-method)?
2. How do you manage "dynamic reconfiguration": reconfigure a bean that is being used by other beans.

Answers:
1. Yes - PropertyMapper has an initMethod property.
2. By dynamic reconfiguration, I mean changing the properties of a bean during execution. It is done by calling the PropertyMappers.refreshAll() method.