Suppose I have a Employee class. It has got many fields like id, firstName, lastName, designaton, age, salary and other fields too. Now I am making a Get Query where I want to use all of these fields (required=false) to be passed as Request Params.
But the question is, there could be many combinations like (firstName,age) or (age,salary,lastName) or (designation,age,salary,lastName) and many more like this. So how should I handle all this filters. Shall I have to write each query for each case?
PS: I am using Spring Boot with Spring Data Jpa.
For this you will have to send Object from where you can get your combination. There may be many combination. So from this perspective you will send value as object and for database query you will select your combinations from that object.
If you want different combination, it won't be a good practice to write controller for every combination. So you can send a Object instead of RequestParam value where you can get your combinations from the Object
Example :
Class Employee{
// Your class instance variable
// Which is called your combinations
}
public Employee getEmployeeByName(Employee employee){
// now you send your desired combination from employee class for
// database query
}
Where you have too many fields, it's not a good practice to send all fields as RequestParam. Think of your class getting bigger day by day and you editing the controller method continously.
Better way is send as a object. No need to edit controller later. Only change the entity class
Related
I want to implement a filtering feature based on the properties of an entity that I have stored in my db.
I'm using a JPA query to do so. The problem that I'm facing is concerned with entity manager which requires the class of the object that is required to return.
public List<CountryEntity> getSortedCountries(String field, String type) {
return entityManager.createQuery(GET_ALL_SORTED.concat(field).concat(" " + type), CountryEntity.class).getResultList();
}
When I select only one field, let's say the name of the country, the query returns a String and not an object of type CountryEntity.
What is the best approach to handle this problem? Should I create classes for every single case or is there another way that I'm missing?
Because my project may be adapted to mysql or oracle,so I have a method that to produce id .When insert a new student record, the student record should call the method to produce the id. But what I'm curious about is when to call the method.Now my project is build by spring cloud. I should call the method in service module and pass the student object with id to the dao module. Or I pass the student object and the in the dao module,I call the id generator?
Which way is better?
Ok, i've decided to extend my comment.
In my opinion a better way would be to generate id inside dao, because you need id to save object in database, so you have to be sure that id is generated. For example if you have multiple clients and each client can save to database object student it would be difficult to make sure that each client uses id generator method in proper way. If you would use this method you don't need to take care about validation of id.
Moreover generating id inside dao follow low coupling principle.
Let's say if I have an Entity named person with lots of information including SSN. When other user query this person, I want to show a 'lite' version of person Entity. I could've done so by annotating SSN with #Transient, but that means the person himself would not get this field too. Is it possible to reuse the same Entity but return two different json to client? I'm using spring boot.
First of all #Transient just means that the value, the SSN in your case, won't be persisted to the database.
As for your problem annotations are static and cannot be applied dynamically.
You have 2 Options:
Define a new View class for your user.
Look at JacksonJsonViews
I need some help with MVC architecture. I use the following architecture for an object named User.
UserRepository -> IUserRepository -> UserService -> IUserService -> UserController
The User object comes from my database and I'm using EntityFramework. I have a function that returns a list of users Return_All_Users(). One of the fields that gets returned is "UserType". This comes out as a number, but when I show the list in my Index.aspx page, I would like it to show as a string. The number for "UserType" needs to look into a Dictionary to find the string that goes along with the number like "Administrator" and I would like this string to show in my Index page.
How would I go about doing this? I'm currently using this function:
public IEnumerable<User> Return_All_Users()
{
//my code here
}
I had another post for a similar question, and it was suggested that my IEnumerable should return a string, not the User object. I tried that, but then I'm working with a Dynamic model and I didn't want to do that. Nor do I know how to work with a Dynamic model, so I thought maybe there is a better way of doing this.
Should this happen in my UserService? Maybe I need to create a new class called NewUser, and define the UserType as a string, then instantiate a new NewUser and pass the value from User. Before the UserType is passed, I would look in the dictionary and get the correct value for the key.
Should I do that, or is there a better way?
After I posted this question, I just thought of doing this with a stored procedure. Maybe use a stored procedure in my database to return the data, as opposed to looking up my data straight from my database table.
I would create a View Model UserView that was formatted to the representation of how your view would best use that data. You could perform the mapping from User to UserView within your Repository or Controller depending on where you prefer doing this kind of mapping.
Suppose I have an automatically-generated Employee class based on the Employees table in my database.
Now suppose that I want to pass employee data to a ShowAges method that will print out name & age for a list of employees. I'll retrieve the data for a given set of employees via a linq query, which will return me a set of Employee instances. I can then pass the Employee instances to the ShowAges method, which can access the Name & Age fields to get the data it needs.
However, because my Employees table has relationships with various other tables in my database, my Employee class also has a Department field, a Manager field, etc. that provide access to related records in those other tables. If the ShowAges method were to invoke any of those methods, this would cause lots more data to be fetched from the database, on-demand.
I want to be sure that the ShowAges method only uses the data I have already fetched for it, but I really don't want to have to go to the trouble of defining a new class which replicates the Employee class but has fewer methods. (In my real-world scenario, the class would have to be considerably more complex than the Employee class described here; it would have several 'joined' classes that do need to be populated, and others that don't).
Is there a way to 'switch off' or 'disconnect' the Employees instances so that an attempt to access any property or related object that's not already populated will raise an exception?
If not, then I assume that since this must be a common requirement, there might be an already-established pattern for doing this sort of thing?
maybe not the answer you're looking for,but how about projecting the results of your query into a more light-weight POCO, eg:
var employeePOCOs = from e in l2sEmployees
select new EmployeePOCO
{
Id = e.Id,
Name = e.FirstName + " " + e.LastName
};
where EmployeePOCO is a predefined class
would that help? I've used this when returning Entity Framework objects back through an AJAX call where the output was going to JSON, and it seemed to do the trick.
One way to do this is to 'detach' the entity from its database context. Take a look at an answer I gave to a similar question. It shows you a couple ways of detaching entities.