I want to implement data annotation on three tables Link, LinkRef and LinkMeta. Link is main table and other two have LinkId as primary key. Because the system is multi-lingual Link title will be in more than one language so as other details. No of languages will vary. I want to know can i use data annotation in this scenario and if yes then how? Im using Linq2SQL for creating model.
Can Data annotations be applied to class objects?
Related
I want to save data of a form into two tables simultaneously. The form contains multiple identical rows with some fields like
item, unit, unit_price, total.
1.) In the table1 I would like to save some data like id(auto generated, primary key), date, creator.
2.) In table2 I would like to save the id(auto generated, primary key), fid(id of the table1, foreign key), item, unit, unit price, total. Remember, in table2 multiple rows will be save from the form data.
I can't figure it out. Please help me with a valid step by step example, and please don't use static or pre-defined data, take the data from form only.
Is your form an HTML form on a web page, and are you writing a Spring MVC application? Have you setup Spring Security, or some other authentication mechanism such that you know who the user is? If so, here is one approach:
Define a plain old Java object (POJO) with fields id, unit, unit-price, total, creator, currentDate; perhaps you would name it Item.
Define another plain old Java object perhaps named "ItemHistory", with its own ID and a reference to an Item.
In the first POJO ("Item") include a reference to a list of ItemHistorys.
Annotate both classes with Hibernate/JPA annotations, such that the Item has a OneToMany relationship to ItemHistory.
Define a Spring MVC controller with a method annotated as a POST method, with an Item as one parameter, and an Authentication as another parameter (supposing you have configured Spring Security, the Authentication will automatically be populated with the identity of the currently-logged-in user. In this method, set the currentDate and author of the Item to the current date and the principal from the Authentication parameter. If it is a new Item (no id yet), add the first ItemHistory as a copy of the Item itself. If it is an existing item, add another ItemHistory if needed.
Define a Spring bean, perhaps named ItemService, with a method annotated as transactional, that takes an Item and saves it. Call this bean from the REST controller. Such a Spring bean is known as a DAO (data access object).
There are other strategies, but if you already have Spring MVC, Spring Security, and Hibernate/JPA configured to your needs, this one is pretty straight-forward.
I have two tables that have relationship like
tbl_department whose entities are dept_id and dept_name where dept_id is primary key and next table is tbl_employee whose entities are emp_id, emp_name and dept_id where dept_id is foreign key that references the dept_id of tbl_department. Now, in my jsp page i want to display the format like this:
Emp_id|Emp_name|dept_name.
I am doing above display in JSP page using the JSTL sql tag, and I know it violates the MVC architecture, so, how could I solve this problem i.e. how can I do this relationship mapping it in either Model or Controller in Spring instead in JSP page. Is there any examples or tutorial I can find for this kind of problem
Thank you
First, you have to decide whether it would be worth your while using Hibernate. You should research this yourself to decide whether the rest of your app would benefit from using it (too big a topic to address here).
Assuming you only want to do the use case you have outlined in the question, I'd suggest you use Spring's JDBC support and create a Service (or just a DAO) to perform the SQL that you are currently using in your JSP. I'd create a simple DTO class to hold the Emp_id|Emp_name|dept_name data and populate that in your Service/DAO and then pass it to the JSP via the Controller.
This Spring MVC Example (skeleton) app would be a good place to start, to see how those components are created and wired together.
I like the idea of using the data annotations to specify validation of fields within the Model. However in EF I notice that it wants to implement this at DB level ie [Required] becomes a "not null" field. Is it possible to just have the application apply this validation without changing the database?
Thanks,
Ed
What you can do is to use a separate view model for the views and separate entity classes for the database. And you can map those objects using a library like auto mapper.
I’m having a philosophical problem with understanding how to use Models on MVC3.
I believe the problem lies from the fact that I come from WebForms :--)
Let's say I have 10 tables on my DB and as expected when I get them into my EF4, I get those Entity classes that represent the tables (and all their FK integer values).
When I want to display data on the View, I cannot display a select * from table because those FK integers means nothing to my users …and also because some data lies on related tables.
So my understanding is that I can create a Stored Proc, create a Complex Type that represent the actual data to display, coming from separate tables via different SQL joins.
QUESTION 1:
On the view, id MVC compliant to use as #model ..that Complex Type?
or shall I always use Models that are created on the Models folder? And if so, does that mean that I have to replicate the Complex Type on a new model inside the Models folder?
Question 2:
Is this the right way …to create specific SP to collect data that will be displayed or ..is it better to use linq and lambda to be applied to the EF4 Types that come from importing the DB into the EMDX designer.
Thoughts ??
FP
The correct way is to always define view models. View models are classes which are specifically tailored to the needs of a given view and would be defined in the MVC application tier. Those classes would contain only the properties that would be needed to be displayed by the view. Then you need to map between your domain models (EF autogenerated classes?) and the view models.
So a controller action would query a repository in order to fetch a domain model, map it to a view model and pass this view model to the view. Top facilitate this mapping you could use AutoMapper. A view shouldn't be tied to a domain model and always work with a view model. This works also the other way around: a controller action receives a view model from the view as action argument, maps it to a domain model and passes this domain model to the repository in order to perform some action with it (CRUD).
So a view model could be a class that is mapped from multiple domain models or multiple view models could be mapped to a single domain model. It all depends on how your domain looks like and how do you want to represent the information to the user.
As far as validation is concerned, I distinguish two types: UI validation and business validation. As an example of UI validation is: a field is required, or a field must be entered in a given format. A business validation is : the username is already taken or insufficient funds to perform wire transfer. UI validation should be done on the view models and business validation on the domain models.
I'm not sure why you need to use a stored proc, LINQ to Entities is able to generate complex types without needing to create stored procs (in most cases). You select subsets of data, just like you would with regular SQL.
As Darin says, the use of a View Model is appropriate for situations where you have a lot of complex data that isn't represented by a single entity. This View Model would contain multiple entities, or even multiple collections of entities. It all depends on how your data needs to be consumed.
Have been trying out the new Dynamic Data site create tool that shipped with .NET 3.5. The tool uses LINQ Datasources to get the data from the database using a .dmbl context file for a reference. I am interseted in customizing a data grid but I need to show data from more than one table. Does anyone know how to do this using the LINQ Datasource object?
If the tables are connected by a foreign key, you can easily reference both tables as they will be joined by linq automatically (you can see easily if you look in your dbml and there is an arrow connecting the tables) - if not, see if you can add one.
To do that, you can just use something like this:
<%# Bind("unit1.unit_name") %>
Where in the table, 'unit' has a foreign key that references another table and you pull that 'unit's property of 'unit_name'
I hope that makes sense.
(EDIT misunderstood the question, revising my answer to the following)
Your LinqDataSource could point to a view, which allows you to overcome the problem of not being able to express a Join in the actual element. From "How to: Create LINQ to SQL Classes Mapped to Tables and Views (O/R Designer)":
The O/R Designer is a simple object relational mapper because it supports only 1:1 mapping relationships. In other words, an entity class can have only a 1:1 mapping relationship with a database table or view. Complex mapping, such as mapping an entity class to multiple tables, is not supported. However, you can map an entity class to a view that joins multiple related tables.
You cannot put more than one object/datasource on a datagrid. You will have to build a single ConceptObject that combines the exposed properties of the part Entities. Try to use DB -> L2S Entities -> ConceptObject. You must be very contrived if the DB model matches the ConceptObject field-for-field.
You are best using a ObjectDataSource when you wnt to do more complex Linq and bind your Grid to the ObjectDataSource.
You do however need to watch out for Anonymous types that could give you some trouble, but anything is posible...