Can I add condition to provided interface method like "findAll" of spring data? For example, if the table has columns "name" and "deleted" - I can create a query asfindByNameAndDeletedIsNull which will give all names which have not been deleted. I tried "findAllAndDeletedIsNull" but this does not work - is this possible?
I know it can be achieved with #query, but was curios as how can we augment the standard methods with conditions.
You can do "findByDeletedIsNull"
See here for more info on what key words can be used in a method name.
According to the documentation, there's a specific way to name the method to have it parsed into the correct SQL. Look at this section: Spring Data JPA reference - query.
If you have the query ready, you can easily reverse-engineer which method name may help you get the same result. You can compose quite complex queries by building up from those foundation bricks. However, you cannot just create a string representation of the "where" clause as a named method.
From the document, if you want to get all records where a field is null:
IsNull | findByAgeIsNull | … where x.age is null
will mean a method name such as findByDeletedIsNull.
Related
I am wondering how does Spring JPA derive queries from methods. As an example, if I was to type
interface CarRepo extends CrudRepository<Car, Long>{ findByCarMake(Make make) }
my query would be automatically derived from the method and would be something as "SELECT * from Car WHERE carMake = xxxxx"
I do understand this concepts but I would like to understand how it works behind the scenes. So, how does it actually derive a query from the method name?
I am aiming at creating a similar thing to suit our needs for a NestJs project so in Typescript not Java and also for an..."unorthodox" database which does not have such support out of the box( Neo4J).
I ll be very grateful to whom can and will help me.
Spring Data JPA derives the queries from the method names in your repository.
There are certain keywords that are reserved by Spring. One the one hand, there are query subject keywords like findBy, existsBy, countBy, etc. which influence the return type of the method. On the other hand, there are operators like and, or, isIn, between, etc. that are applied to the actual query logic.
You start your query with a query subject keyword like findBy and then the fields of your entity (and optionally operators and more fields). You can even have nested fields like findByProviderName where your entity has a field provider which has a field name. If you define an invalid property or property path (e.g. findByProviderNamw), your Spring Boot application would fail on startup. You can find more about defining query methods in the official spring reference.
Spring Data using part tree JPA queries, than map them into SQL query by pre-defined parts.
I created a method which through spring data automatically create the query. The problem is about the return param, because dismatch from the name definition.
In fact by specifying only one parameter, it return 4 parameters.
The springData method is that:
Optional<Comunicazioni> getCommIDByExtIDAndCommSAndCommT(
BigDecimal extID, String commS, String commT);
and I access to the type like so:
getCommIDByExtIDAndCommSAndCommT(extId, commS, commT).get().getCommID()
how can I retrieve only the column I need?
Thank you
Unfortunately, this is not possible with the current implementation of Spring Data JPA (i.e. Using method name only).
Instead, the current solution is to use #Query to define the return values. You can find an example of that here.
However, if your Entity object is not too large, you would be able to achieve the result in the example you posted by simply retrieving the entire entity:
Optional<Comunicazioni> findByExtIDAndCommSAndCommT(BigDecimal extID, String commS, String commT);
and then calling it as
repo.findByExtIDAndCommSAndCommT(extId, commS, commT).get().getCommID();
It would be nice to see this functionality in the future, but for now, it is not so difficult to work around.
I'm getting the "No data type for node" error when I run this query:
session.createQuery("select nextval( 'next_num_seq' )")
which I know means that I need to make it a property of a class, but I haven't been able to find a way to add a sequence to a class, only how to make a sequence generate IDs for a class.
Is there a way to include a sequence in a Hibernate mapping that isn't an ID generator?
As such, this question is valid, yet the path to the solution is headed in the wrong direction. Mapping a Sequence into a managed domain entity is not a "good" idea, as these are two separate concepts.
Sequences, such as the one you are trying to query from a PostgreSQL backend, are a central concept for the generation of unique IDs for primary key values of tuples or - from an ORM application perspective - Java objects. Thus, it is not clever to map their current state to a domain entity. Instead, one sets a single, particular value drawn from such a sequence - e.g. next_num_seq - into one particular object to be persisted in a relational database. Therefore, the related class of such an domain object is linked to this sequence by, for instance, dedicated ORM annotations (or via similar approaches).
In the JavaDoc of the Session interface we find the method createNativeQuery(String sql) which is inherited from the EntityManager interface, see also here.
It is described as follows:
Query createNativeQuery(java.lang.String sqlString)
Create an instance of Query for executing a native SQL statement, e.g., for update or delete.
Parameters:
sqlString - a native SQL query string
Returns:
the new query instance
Thus, you could modify your code to execute the native query against your PostgreSQL database as follows:
Query q = session.createNativeQuery("select nextval( 'next_num_seq' )");
This gives you the option to read the next valid sequence value as a long or Number instance for your programming purposes.
Note well: Be careful not to reuse this value multiple times (for several objects), as this might cause consistency trouble in your backend when used, for instance, in the context of separate threads.
Hope this helps.
I have a Java, GraphQL, Hibernate, PostgreSQL, QueryDSL application that queries a very large PostgreSQL table with over 275 columns.
I've created a GraphQL schema with the 25 most popular columns as query-able fields. I'd like to add a generic "field" input type that consists of a name (the db column name + "_" + operation (like gte, gt, contains, etc.) and a value (the value the user is searching for).
So when the user (in GraphiQL) enters something like (field:{name:"age_gt", value:"50"}) as a search input to the GraphQL query, I can come up with: "age > 50".
All that works fine, but when it's time to create the Predicate and add it to the whole query ( booleanBuilder.and(new Predicate) ), I cannot figure out how to create a Predicate that just contains a raw String of SQL ("age > 50").
I've created several Predicates the "right" way using my entity POJO tied to Hibernate and the jpa generated "Q" object. But I need the ability to add one or more Predicates that are just a String of SQL. I'm not even sure if the ability exists, the documentation for QueryDSL Predicates is non-existent.
I'm thinking PredicateOperation() might be the answer, but again, no documentation and I cannot find any examples online.
My apologies for not posting code, all my stuff is behind a firewall on a different network so there's no cut and paste to my internet machine.
In Hibernate its possible to inject arbitrary SQL using custom functions or the FUNCTION-function (introduced in JPA 2.1). In QueryDSL its possible to inject arbitrary JPQL/HQL through TemplateExpressions. Combined you get:
Expressions.numberTemplate("FUNCTION('SUM', {0}), x)
However, age > 50 as expression is probably valid JPQL as well, so one can just write:
Expressions.numberTemplate("SUM(age)")
Either way, its probably best to create a visitor that traverses the GraphQL query and creates the proper expression in QueryDSL, as TemplateExpressions are prone to SQL injection.
I'm using Spring PagingAndSortingRepository and I have a very easy findAll query:
inventoryDao.findAll(new Sort(Sort.Direction.DESC,"startTime"))
It's working fine, I just was wondering: is it possible to replace the query above using Method Name generation instead? (Somethnig like: inventoryDao.findAllOrderByStartTime() )
You have to use findAllByOrderBy...
As the Spring Data documentation says, the first by in the method name acts as delimiter to indicate the start of the actual criteria, in your case the sorting so it's necessary to add this in the method name before Order word.