I have a postgres database and I want to generate the entity class of a table. I need this in order to connect to the database without using something like :
NpgsqlCommand cmd = new NpgsqlCommand("SELECT * FROM TABLE1", conn);
How can I obtain the class?
Can you provide some detailed steps? I can't seem to find this anywhere.
Thanks in advance!
Entity classes are usually hand-written, or are generated from a schema then hand-tweaked. In the Java world many tools like NetBeans and Eclipse can help, but things seem much less mature in the C#/.NET world if you're not using Microsoft databases and Microsoft query tools.
This answer refers to a few useful tools, and a quick search also found the NHibernate entity generator, which seems to be part of a tool with support for Entity Framework and LINQ too.
Depends on a language but yes - you can do something like this in Java or Python using Object Relational tools such as SQLAlchemy, Hybernate, iBatis, etc.
They can generate schema for you, can populate data based on the definitions of objects.
Related
I am using Telosys tools for code generation. It's very nice tool and help me a lot.
But there is one problem, that is, it provides database schema information and i can access in templates (templates are formerly velocity templates), which is good, but how can i get selected entity's data from database? There is no way i can find, by which i can get that selected table data.
Please provide solution if any, or provide alternate way to do it.
Thanking You!
Telosys Tools is designed to retrieve the model from the database,
not the data stored in the tables.
But it allows to create your own specific tooling classes usable
in the templates, so it's possible to create a specific Java Class to retrieve the data from the database.
There's an example of this kind of specific class in the "database-doc" bundle
https://github.com/telosys-tools/database-doc-bundle-TT210 ( in classes folder )
To simplify the loading the simplest way is to create the class in the "default package" (no java package)
NB:
The problem is that the jar containing the JDBC driver
is not accessible by the generator class-loader, so you will have to use a specific class-loader and to connect directly with the JDBC driver.
Here is an example : https://gist.github.com/l-gu/ed0c8726807e5e8dd83a
Don't use it as is (the connection is never closed) but it can be easily adapted.
How can I use the tools to generate DAOs?
In fact, instead of passing through the hbm files, I need to configure hibernate tools to generate the DAO and the annotations.
See Hibernate Tools - DAO generation and How generate DAO with Hibernate Tools in Eclipse?
First let me assume DAO as POJO/Entity beans. Basically you can accomplish your task either through forward or reverse engineering. In case of forward engineering, probably you can look into AndroMDA tool. In case If u wish to accomplish it through reverse engineering Click here ..
Hope this will be helpful.
Welcome. You got to write all your data access logic by your hand (if I’m not wrong). Hiberante let you interact with database in three ways.
Native SQL which is nothing but DDL/plain SQL query. This can be used very rarely in hibernate projects even though this is faster than below mentioned options. Reason is simple “One of the key advantage of hibernate or any other popular ORM framework over JDBC Is you can get rid of database specific queries from your application code!”
HQL stands for hibernate query language which is proprietary query language of hibernate. This looks similar to native SQL queries but the key difference is object/class name will be used instead of table name and public variable names will be used instead of column names. This is more Object oriented approach. Some interesting things will be happening in background and check if you are keen!
Criteria API is a more object oriented and elegant alternative to Hibernate Query Language (HQL). It’s always a good solution to an application which has many optional search criteria.
You can find lots of examples on internet. Please post your specific requirements for further clarification on your problem.
Cheers!
I want to know if there is a way to generate the class dynamically at runtime. I want to use it in Entity framework code first.
Consider if I have 100 tables(or connect to unknown database) I will have to create model/POCO for each table in EF Code First, instead of this I want to generate the POCO class and all its properties at runtime based on the database connected.
Probably not.
Consider this... If the classes aren't defined before compilation, then how is any other code going to use them? If no other code is going to use them, why do you need them?
You can generate objects based on the table schema at design time. Doesn't Entity Framework in fact do this already?
I realize that I've linked to something that is "database first" instead of "code first" but, well, that's what you're asking:
I want to use it in Entity framework code first.
[...]
I will have to create model/POCO for each table in EF
You have a database, and you want to generate models based on the schema of that database. That's database-first.
You can use the EF Power Tools (beta 3) for Visual Studio 2010 or 2012 to reverse engineer a database to POCOs. After installation, right click on a project and select Reverse Engineer Code First under the new Entity Framework menu group.
The Power tools: http://visualstudiogallery.msdn.microsoft.com/72a60b14-1581-4b9b-89f2-846072eff19d
Rowan Miller has a blog post about this, and some advanced uses: http://romiller.com/2012/05/09/customizing-reverse-engineer-code-first-in-the-ef-power-tools/
The method - Entity Framework Code-First - looks good. But its very difficult to create all the classes for a large database.
Is there any easy way to generate the Entity Framework Code-First classes?
You can use the recently released Entity Framework Power Tools CTP1. The tool gives you the ability to reverse engineer code first, meaning the Database will be mapped to Code.
Note that all tables in your large database will be mapped. There currently is no way to choose which tables will be mapped to code. Reading through the comments, this feature will most likely be implemented in a future release.
The point of EF Code-First is that you define your domain model in code, then your user-interface and database can be easily generated from that domain model. This has a number of advantages including reducing the amount of tedious code which needs to be written, and helping to ensure your database, your domain model, and your UI match each other.
However, at some point you are going to have to write your domain model - there's no way that can be "generated" (by which I assume you mean computer-generated) as it is personal to your application.
If I've misunderstood your question, please leave a comment and I'll update my answer.
If you want to use the code-first model, but already have an existing database, you can use the Entity Framework Power Tools to generate classes.
If you're reading this after May/2012, the above tool may be out of beta!
No there is no way to generate classes for you if you are using code-first. Code first means that there is no model and no database so you can't generate classes unless you have some upfront design in any case system (UML) which will autogenerate code for you. Simply generating classes without any input about how they should look like sounds like AI from Sci-fi, doesn't it?
If you already have databse you are not using code first but database first. In such case you can have your classes generated.
Check out the link below. It's a program that will generate POCO classes from your databases. I think that's what you're looking for.
http://msormcodegen.codeplex.com/
Generate the code from the database first using database first generation and then modify the resulting code to start your code first version
Is there an equivalence in Entity Framework to NHibernate SchemaExport?
Given I have a working Entity-Model, I would like to programmatically initialize a database.
I would like to use this functionality in the setup of my integration tests.
Creating the matching DDL for an Entity-Model would also suffice.
Yes - given that you're working with Entity Framework 4 (which is, confusingly enough, the second version...)
Edit: This is the way to do it with just EF4. In my original post below is described how to accomplish the same thing with the Code-Only approach in EF CTP3.
How to: Export model to database in EF4
To export a model to database, right-click anywhere in the designer (where you don't have an entity) and choose "Generate database from model..." and follow the steps described in the wizard. Voila!
Original post, targeting EF4 CTP3 and Code-Only: This is code I use in a little setup utility.
var builder = new ContextBuilder<ObjectContext>();
// Register all configurations you need here
builder.Configurations.Add(new EntryConfiguration());
builder.Configurations.Add(new TagConfiguration());
var conn = GetUnOpenedSqlConnection();
var db = builder.Create(conn);
if (db.DatabaseExists())
{ db.DeleteDatabase(); }
db.CreateDatabase();
It works on my machine (although here I've simplified a little bit for brevity...), so if something does not work it's because I over-simplified.
Note that, as TomTom stated, you will only get the basics. But it's pretty useful even if you have a more complicated schema - you only have to manually write DDL to add the complicated stuff onto the generated DB schema.
Nope, and seriously I do wonder why nhibernate bothers having this.
Problem is: an O/R mapper has LESS information about the database than needed for non-trivial setups.
Missing are:
Indices, fully configured
Information about server side constraints, triggers (yes, there may be some)
Information about object distribution over elements like table spaces
Information about permissions
I really love a test method (please check that database is good enough for all objects you know), but generation is VERY tricky - been there, done that. You need some serious additional annotations in the ORM to be able to even generate sensible indices.