I know how to use BeanPropertyRowMapper and RowMapper as well.
But if I use BeanPropertyRowMapper,
i.e.
BeanPropertyRowMapper<MyClass> rowMapper = new BeanPropertyRowMapper<MyClass>(MyClass.class);
MyClass attributes becomes tightly coupled with tables column names and if I use RowMapper still MyClass attributes becomes tightly coupled and I have to write few more lines of code populate MyClass attribute with first GET and then SET operation extra.
Is there any way we can get rid of this dependency. Even after Table Columns names are changed, MyClass attributes should be populated as before and I do not need to change my code.
The Dozer mapping tool sounds like a good fit for what you're trying to do, and it's pretty simple to use. You'd still have to change something when changing column names, but it should be pretty easy. Check this out: http://dozer.sourceforge.net/
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I have an application which uses Parse to save objects on MongoDB. On my db, I have a class which has a column that should be a pointer to make my job easier. But I have a problem, this column should hold a pointer for differents classes. Parse doesn't allow me to do that because it takes the first pointer saved as the type of that column.
Does anyone have an idea about how I can work around this problem?
You can't have a pointer to two different classes in the same column. If you really need to do this, then you could create a new class that has fields for each of the possible pointer types.
So for example if you have a User and you need a pointer to either Car or Boat, then you could make a new class called Vehicle that has pointers to both Car and Boat. And then make the User just have one pointer to Vehicle.
That's a silly example, but it could technically work. How different are the classes that you need to point to from the same column? It's probably best practice if you consolidate them or find a different approach, but having a "holder" object that contains pointers to all possible values is one way you could essentially accomplish what you're trying to do.
I'd like to create a many-to-many relationship between two things: Notes and Labels. However, I'd like to define the labels themselves in code rather than having them in a database table.
Aside from a notes table to represent the Note model, I expect to have a "pivot" table (labels_notes) with two columns: note_id and label.
So, my question is: How would eager loading, getter, setter and "get notes by label" methods on the Note model work?
Background: The primary reason for wanting the Labels in code rather than as content of a table is that they are a small, fixed set of values; users will not be allowed to modify them. Further, there may need to be special logic in the code around certain labels. I considered storing them in a JSON column on notes, but am concerned about the performance impact when searching for Notes by Label.
The solution I opted for was to use a traditional Eloquent model for Labels (including a dedicated database table), but inject the desired values into it via the migration, and use a string primary key. That way we're able to use Eloquent in it's intended manner rather than fighting against it.
Using a string primary key means we can write logic based around specific Labels without worrying about arbitrary numeric IDs (i.e., "id=news" vs "id=12112"). Note that doing this also requires adding public $incrementing = false; in the Label model class.
Injecting the necessary Labels via migration lets us avoid having an additional setup task when deploying, and also avoids coupling our code with an external process.
I am working on a MVC3 code first web application and after I showed the first version to my bosses, they suggested they will need a 'spare' (spare like in something that's not yet defined and we will use it just in case we will need it) attribute in the Employee model.
My intention is to find a way to give them the ability to add as many attributes to the models as they will need. Obviously I don't want them to get their hands on the code and modify it, then deploy it again (I know I didn't mention about the database, that will be another problem). I want a solution that has the ability to add new attributes 'on the fly'.
Do any of you had similar requests and if you had what solution did you find/implement?
I haven't had such a request, but I can imagine a way to get what you want.
I assume you use the Entity Framework, because of your tag.
Let's say we have a class Employee that we want to be extendable. We can give this class a dictionary of strings where the key-type is string, too. Then you can easily add more properties to every employee.
For saving this structure to the database you would need two tables. One that holds the employees and one that holds the properties. Where the properties-table has a foreign-key targeting the employee-table.
Or as suggested in this Q&A (EF Code First - Map Dictionary or custom type as an nvarchar): you can save the contents of the dictionary as XML in one column of the employee table.
This is only one suggestion and it would be nice to know how you solved this.
I have a populated object from using the entity framework. Let's call it Order. The order has different properties such as Id, OrderDate, BillingAddress and so on. I need to let users update this data.
What's the best way to display this data in a form, while enforcing data annotations such as [Required]? I see MetadataType mentioned a lot, but I haven't seen how I can connect the dots with displaying the data as well.
One approach that I could take, but I'd like to avoid because of redundancy, is creating my own model object that has nearly identical properties. Then I would just need to basically just copy entity framework object A to new object B, where B has all my lovely data annotations. It just seems like there might be a better way.
Could anyone provide me with an example of a good way to accomplish this?
The "better way" is a big reason EF Code First is great. Otherwise, the only other way to do what you need is to do a mapping.
I have a table called Code in my LINQ to SQL datacontext. I also have a class called Codes in my Models folder. What I want to do is save the updated object Codes to my database table Code. Is this possible?
In my controller, I would pass the edited Object to my Model. My CodesRepository file contains this:
public Codes EditCode(Codes CodeToEdit)
{
private EventsDataContext _db = new EventsDataContext();
Codes C = new Codes();
C = CodeToEdit;
_db.Codes.InsertOnSubmit(C); //error here, something about invalid arguments
//InsertOnSubmit is for adding a new object, but I don't know the syntax
// for editing an existing object.
_db.SubmitChanges();
}
This is probably not the correct way of doing this so can someone point me in the right direction? Do I even need a class called Codes or do I need to somehow just use my database table? Thanks.
Solution: I decided to change from Linq to SQL to an Entity Framework and it works much better. This way, I don't have to define my Codes class since it comes straight from the database and I was able to delete the Codes class file.
You should use DataContext.Attach when you get an object back that corresponds to en existing row in the database. For Linq-to-sql's optimistic concurrency handling to work this requires that you either have the original, unsaved object available, or that you have a TimeStamp column in the database. The latter is preferred, as it only requires one extra field to be handled (probably through a hidden field in the web form).