Is it possible to call method from Entity in Spring Data Specification or QueryDSL?
I have collection of shapes (few types with different parameters) and every shape has method countArea() in entity class. Is it possible to add parameter to search like "area" and use it as filter?
If not, is there any other solution for this?
Related
I have a query in Spring boot:
I am using CrudRepository where i need to declare method names for all possible combination of where conditions being used in project. Can we declare a method in CrudRepository which can accept dynamic where condition?
Suppose i have a table named "Student" which is having 20 columns. I don't want to define all possible combination of methods names in CrudRepository for those 20 fields. I need a generic method which can accept a json object as parameter and return records based on the where condition passed as json object. Is there any solution or workaround for this?
I think what you are looking for are called Specifications.
These allow for more precise queries.
It is nicely expained here (take a look at 5. Using JPA Specifications).
I know Spring Data JPA has offered some query methods which can accept a list as its parameter like List<T> findAllById(Iterable<ID> ids).So how can I customize such methods? Can anyone help?
You can use IN. This accepts a collection of attributes.
List<T> findByIdIn(Collection<ID> ids)
How to write JPA query in Spring Data that uses at least one of three parameters?
I have these three parameters:
Id (PK)
Name
Surname
Client must supply at least one of these three parameters and I want to find user by these not-empty parameters.
Is it possible to create such custom query to my repository or do I have to create custom queries for all possible combination of WHERE conditions?
You can have your repository extend org.springframework.data.querydsl.QueryDslPredicateExecutor and use the inherited findAll(Predicate predicate) method to query using any combination of parameters.
You would not then have to write any query methods:
http://docs.spring.io/spring-data/jpa/docs/1.10.5.RELEASE/reference/html/#core.extensions.querydsl
You can also have the Predicate automatically bound in a Spring MVC Controller as detailed here:
https://spring.io/blog/2015/09/04/what-s-new-in-spring-data-release-gosling#querydsl-web-support
and here:
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#core.web.type-safe
So your controller can then automatically handle a search with 1,2 or all 3 parameters passed as request parameters without your having to write any code at all.
This is where you need the ability to create dynamic queries at runtime.
In your application code, you should have logic to build the predicate based on whether each of the above properties from the input DTO is empty or not.
One way to do it is to use QueryDSL.
To use QueryDSL, you should include the relevant dependency in your pom/gradle file and then your repository should extend the QueryDslPredicateExecutor interface. This will give you two additional generic finder methods.
T findAll(Predicate) or
Page<T> findAll(Predicate, Pageable)
One thing to keep in mind is that the above two methods are appropriate where this is no need to do a join
Your requirement here seems to be a single table query, so either one of the finder methods should suffice.
If you do need to do a join with other tables and need fine grained control over how the JOIN happens (INNER JOIN vs LEFT OUTER JOIN vs CROSS JOIN) etc, then you should consider creating a Custom repository that your repository can extend.
And then provide your own customImpl that you can now access from the repository.
thanks a lot for the reply ... as i read Spring is not easy flexible as other framework... for i.e i tried some node js api framework and it is easier and more flexible .. what do you think about this ?
I want to use projections in order to return less elements for the same queries.
Page<Network> findByIdIn(List<Long> ids);
Page<NetworkSimple> findByIdIn(List<Long> ids);
Since the queries are created using the name of the method, what options do I have to do the same query but with different name ?
I ran into this today, and the accepted answer is actually incorrect; you can change the method name without altering the behavior. According to the Spring Data documentation:
Any text between find (or other introducing keywords) and By is considered to be descriptive unless using one of the result-limiting keywords such as a Distinct to set a distinct flag on the query to be created or Top/First to limit query results.
Thus you can have a method named findByIdIn and another named findNetworkSimpleByIdIn and the two will return the same data (optionally converted to a different form depending on the defined return type).
Spring Data query via method is constructed by convention and you can't change the name and yet expecting a same behavior.
You can try to use #Query annotations which doesn't depend on the method name, or possibly implementing custom DAO using JPAQuery plus FactoryExpression which has the same effect as projections.
If I want to select only few columns when retrieving data for an EF entity and cast them to the Entity type, I am not able to do that because it throws an error as mentioned in this post
The entity cannot be constructed in a LINQ to Entities query. I don't want to select all the columns, because I need only few of them. I can use anonymous types, but if I am using repository pattern and want to encapsulate all data access code in repository object and pass strongly typed object collection to the controller (not an anonymous object collection), how can I achieve that? Is the only option to define a DTO object for every subset of the properties for the EF entity? I know there is a risk of losing data with partial loaded entities, but if I am ready to take the risk and want full control over data updates, is that not possible?
for example I would like the "ProductRepository" method signature to be like this
public IEnumerable<Product> GetProducts(int categoryID) //selection of subset of data
and I want to pass this product collection from the controller to the view (in ASP.NET MVC project) and in the view I want to have strongly typed model (with intellisense) object. Is this possible? if not, I may have to reconsider using EF for my project due to this limitation. I am using EF 4.1 version.
Yes the option in this case is special object for each subset of properties you want to select. You can call the object DTO because it is just a result of the projection. This is the correct approach because if your UI doesn't need other properties of entity type it is correct to pass it only specialized ViewModel.
Another more complex (and worse) option is selecting anonymous type inside your Linq-to-entities query, calling ToList and after that construction the real entity type. Partial entity selection is not allowed and projecting to mapped entity types is not allowed as well. That is the reason why you have to use such a cumbersome approach. Example:
// Select anonymous projection
var query = from x in context.Entities
where ...
select new { ... };
// Repopulate entity type
var reultSet = query.ToList().Select(x => new Entity { ... });
Yes, what you want is totally possible using viewmodels instead of entities. Here is example controller code:
var productEntities = productRepos.GetProducts(6);
var productViewModels = Automapper.Mapper
.Map<IEnumerable<ProductViewModel>>(productEntities);
return View(productViewModels);
Your view model will have only the properties it needs for the view. Check out automapper.