I have 2 schemes in the database, and I want to create an application that uses data from the other schema.
My question , can I use many database schemes' connection in one application?
I know that each 'ear' file must have one connection.
so how could I create an application with 2 connections?!
You need to use composite persistence unit for this purpose. But this is slightly tough to handle, specially when anyone is a beginner. Please check these links for help:
http://docs.oracle.com/cd/E28280_01/doc.1111/e25034/usingmultipledbs.htm
http://wiki.eclipse.org/EclipseLink/Examples/JPA/Composite
Related
I'm trying to make a service architecture which includes two Node.js apps which shares the same database. The overall service architecture looks like below (simplified version)
I'm planning to use Sequelize as an ORM to access the database. As far as I know, if a service uses Sequelize, it needs model to get the structure of data tables. In my case, api and service will access the same database, which means they should share the same Sequelize model.
So here is the question: where should I locate the common Sequelize relevant files? It seems I have two choices:
put them on the upper common location (assuming the project structure is monorepo) so that each apps can use the single same files
maintain copies of files in each apps' project folders. In this case, each apps will be independent(Let's say I want to dockerize each apps) but in case the Sequelize files modified, the same action should be done for the other.
I'm not sure how I understood is correct. Is my question valid? If so, what is the better choice and practice? I appreciate for your answers in advance.
There is no correct answer, it depends on the specific situation, but sharing a database between multiple microservices is a bad design.
Sharing a database means tight coupling at the data level. The direct consequence is that when a service modifies the database table structure, such as deleting the name field of the user table, it may break the APIs of other services and all use the sequelize user model. All services need to update the model definition and modify the implementation code of the API.
If all of your services are maintained by a team, I suggest you choose the first solution, which costs less and is easier to maintain. If your services are maintained by different teams, the two solutions are actually similar, because as long as the table structure is modified, the application layer model needs to be modified or verified whether it still works well.
Therefore, I recommend following the best practices of microservice architecture, first splitting the database vertically according to the business model, and building application APIs on top of it.
Core principles of microservices:
loose coupling
high cohesion
Good day! I have created an application using nodejs + mongoose and now I want to make something like a superuser application. I need my admin panel application to connect to the same database. So, i have a question.
Should i store the same Schema file in both applications to have an ability to use my Schema methods? In other words, what is the best way to create one more API using the same db?
Thank you!
If I'm not mistaken, why not create another service that only interacts with the database? That way, the systems will refer to the same schema/DB regardless of which application you want to connect to it. So the superuser application and the normal application will just query the DB microservice that interacts the database.
Pro: source of truth for the schema for all applications and the DB queries will just be API calls
Con: additional overhead in creating your ecosystem
If you are using the same DB from two different applications, you will want to make sure those schemas are the same between the two. If one changes its inputs, the other might need to change its display (or risk not expecting all that information). Keep all this in mind during your release process.
I would suggest making the schemas an external library to both, or have the admin panel require the current app. You'll avoid getting two sets out of sync and know to look at one place for the schema definitions.
I started to use Jackrabbit in my project. As i found out there is no complex LoginModule and AccessManager given. I mean we can find SimpleLoginModule but it is just a mock.
What i need is a simple LoginModule which can be configured eg from a file with users, passwords and groups. I know that i can implement my own classes, but it is hard to believe that after so many years there is no ready solution...
there are a couple Jackrabbit based open source / closed source projects out there that use JCR as their reference implementation and have implementations. Most probably you're best of choosing one of them in order to not reinvent the wheel. For a complete list: http://en.wikipedia.org/wiki/Apache_Jackrabbit
Are you running inside an app server or web container? If so, you would usually expect the container to provide a JAAS implementation. For example, for instructions on how to set it up with Jetty, storing user information in a database, a properties file, or LDAP, see:
http://www.eclipse.org/jetty/documentation/current/jaas-support.html
I am new to subsonic and I'd like to know about the best practices regarding the following scenario:
Subsonic supports multiple database systems, e.g. SQLServer and MySQL. Our customers need to decide while deploying our application to their servers, which database system should be used. Long story short: the providerName, normally specified within the application configuration, should be configurable after the application is finished.
How can this be done? Do I have to generate seperate data libraries for each database system I want to support?
Thank you in advance
Marco
No you do not need to genarate seperate libraries.
How ever you can not use direct sql string as you understand but you need to go always using subsonic sql create code.
Also is good to make some tests on the diferent databases, because not all code have been 100% testes on every case.
I currently developed an app that connects to SQL Server 2005 database, so my DAL objects where generated using information from that DB.
It will also be possible to connect to an Oracle and MySQL db, all with the same table structures (aside from the normal differences in fields, such as varbinary(max) in SQL Server and BLOB in Oracle, and so on). For this purpose, I already defined multiple connection strings and multiple SubSonic providers for the different DB's the app will run on.
My question is, if I generated my objects using a SQL Server database, should the generated objects work transparently with the other DB's or do I need to generate a different DAL for each database engine I use? Should I be aware of any possible bugs I may encounter while performing these operations?
Thanks in advance for any advice on this issue.
I'm using SubSonic 2.2 by the way....
From what I've been able to test so far, I can't see an easy way to achieve what I'm trying to do.
The ideal situation for me would have been to generate SubSonic objects using SQL Server for example, and just be able to switch dynamically to MySQL by just creating at runtime the correct Provider for it along with its connection string. I got to a point where my app would correctly connect from SQL Server to a MySQL DB, but there's a point where the app fails since SubSonic internally generates queries of the form
SELECT * FROM dbo.MyTable
which MySQL doesn't support obviously. I also noticed queries that enclosed table names with brackets ([]), so it seems that there are a number of factors that would limit the use of one Provider along multiple DB engines.
I guess my only other option is to sort it out with multiple generated providers, although I must admit it does not make me comfortable knowing that I'll have N copies of basically the same classes along my project.
I would really love to hear from anyone else if they've had similar experiences. I'll be sure to post my results once I get everything sorted out and working for my project.
Has any of this changed in 3.0? This would definitely be a worthy reason for me to upgrade if life is any easier on this matter...