So I have a table of tags. Tag has an id and a name.
As a first step I wanted to sort all the IDs by descending order
List<Tag> findAllByOrderByIdDesc()
Next I wanted just to get first three tags and got it done by doing
List<Tag> findTop3ByOrderByIdDesc()
Now I want to get all tags in descending order from position x until position x+3 but I can't seem to find or figure out what to do here.
You can pass Pageable parameter.
Example:
List<Tag> findTop3ByOrderByIdDesc(Pageable page);
In the Pageable parameter you need to pass page number and offset.
Consider if you want to get values range from id 20 to 30.
PageRequest.of(2,10);
pass this as your Pageable parameter.
Pageable is a good idea but you have to use PagingAndSortingRepository or JpaRepository, not CrudRepository.
Related
in our Spring application we have a table that contains a lot of "Payment" record. Now we need a query that pages the results sorted from the one with the largest total to the smallest, we are facing an error because sometimes the same record is contained in two successive pages.
We are creating a PageRequest passed to the repository. Here our implementation:
Repository:
public interface StagingPaymentEntityRepository extends JpaRepository<StagingPaymentEntity, Long> {
Page<StagingPaymentEntity> findAllByStatusAndCreatedDateLessThanEqualAndOperationTypeOrderByEffectivePaymentDesc(String status, Timestamp batchStartTimestamp, String operationType, Pageable pageable);
}
public class BatchThreadReiteroStorni extends ThreadAbstract<StagingPaymentEntity> {
PageRequest pageRequest = PageRequest.of (index, 170);
Page<StagingPaymentEntity> records = ((StagingPaymentEntityRepository) repository).findAllByStatusAndCreatedDateLessThanEqualAndOperationTypeOrderByEffectivePaymentDesc("REITERO", batchStartTimestamp, "STORNO", pageRequest) ;
}
where index is the index of the page we are requesting.
There is a way to understand why it is happening ? Thank for support
This can have multiple reasons.
Non deterministic ordering: If the ordering you are using isn't deterministic, i.e. there are rows that might com in any order that order might change between selects resulting in items getting skipped or returned multiple times. Fix: add the primary key as a last column to the ordering.
If you change the entities in a way that affects the ordering, or another process does that you might end up with items getting processed multiple times.
In this scenario I see a couple of approaches:
do value based pagination. I.e. don't select pages but select the next N rows after .
Instead of paging use a Stream this allows to use a single select but still processing the results an element at a time. You might have to flush and evict entities and I'm not 100% sure that works, but certainly worth a try.
Finally you can mark all all rows that you want to process in a separate column, then select N marked entities and unmark them once they are processed.
I came to a problem where I need to put ordering by multiplication of two columns of entity, for the sake of imagination entity is:
#Entity
public class Entity {
#Column(name="amount")
private BigDecimal amount;
#Column(name="unitPprice")
private BigDecimal unitPrice;
.
.
.
many more columns
}
My repo interface implements JpaRepository and QuerydslPredicateExecutor,
but I am struggling to find a way to order my data by "amount*unitPrice",
as I can't find a way to put it into
PageRequest (new Sort.Order(ASC, "amount * unitPrice"))
without having PropertyReferenceException: No property amount * unitPrice... thrown.
I can't user named query, as my query takes quite massive filter based on user inputs (can't put where clause into query, because if user hasn't selected any value, where clause can't just be in query).
To make it simple. I need something like findAll(Predicate, Pageable), but I need to force that query to order itself by "amount * unitPrice", but also have my Preditate (filter) and Pageable (offset, limit, other sortings) untouched.
Spring Sort can be used only for sorting by properties, not by expressions.
But you can create a unique sort in a Predicate, so you can add this sort-predicate to your other one before you call the findAll method.
I have an entity as below
Class Person{
String id;
String name;
String numberOfHands;
}
With Spring Data Rest (Gosling Release Train), I'm able to specify
localhost/Person?sort=name,asc
for sorting name name ascending. Now, in a case where I need to sort by numberOfHands descending and name ascending. I'm able to specify
localhost/Person?sort=numberOfHands,name,asc
But, I'm not able to specify
localhost/Person?sort=numberOfHands,desc,name,asc
Is there a way to specify multiple sort order?
Thanks!
Solution (tl;dr)
When wanting to sort on multiple fields you simply put the sort parameter multiple times in the URI. For example your/uri?sort=name,asc&sort=numberOfHands,desc. Spring Data is then capable of constructing a Pageable object with multiple sorts.
Explanation
There is not really a defined standard on how to submit multiple values for a parameter in a URI. See Correct way to pass multiple values for same parameter name in GET request.
However there is some information in the Java Servlet Spec which hints on how Java servlet containers parse request parameters.
The getParameterValues method returns an array of String objects containing all the parameter values associated with a parameter name. ... - Java Servlet Spec, section 3.1
The sample further in that section states (although it mixes request and body data)
For example, if a request is made with a query string of a=hello and a post body of a=goodbye&a=world, the resulting parameter set would be ordered a=hello, goodbye, world.
This sample shows that when a parameter (a in the example) is presented multiple times the results will be aggregated into a String[].
Here is how to construct the multi Sort object manually/programatically.
Sort sort = Sort.by(
Sort.Order.asc("name"),
Sort.Order.desc("numberOfHands"));
return personRepository.findAll(sort);
Note: This solution does not directly solve the original question asked, but may help visitors that landed on this question while searching for a solution how to sort on multiple properties from a backend perspective / in a somewhat "hardcoded" way. (this solution does not require/take any URI parameters)
When dynamic fields are there then you simply do match with fields and add in sorting list like.
List<Sort.Order> sorts= new ArrayList<>();
if (sort == "name" && sortingOrder.equalsIgnoreCase("DESC")) {
sorts.add(new Sort.Order(Sort.Direction.DESC,"name"));
} else if (sort == "numberOfHands" && sortingOrder.equalsIgnoreCase("DESC")) {
sorts.add(new Sort.Order(Sort.Direction.DESC,"numberOfHands"));
}
return personRepository.findAll(Sort.by(sorts));
If you are using Pagination then directly add in PageRequest Request.
return personRepository.findPersons(PageRequest.of(pageNo, pageSize, Sort.by(sorts)));
I have in a Spring Repo something like this:
findTop10ItemsByCategIdInOrderByInsertDateDesc(List ids)
I want the first 10 items where category id in list of ids ordered by insert date.
Another similar query:
findTop10ItemsByDomainIdAndCategIdInOrderByInsertDateDesc(List ids, #Param Integer domainId)
Here I want that the domain id is equal to the given param and the categId to be in given list.
I managed to resolve it using #Query but I wonder if there is an one liner for the above queries.
thanks
EDIT
The top works fine. Initially I had findTop10ItemsByDomainIdAndCategIdOrderByInsertDateDesc. Now I want the results from a list of category ids. That's the new requirement.
SECOND EDIT
My query works for find the set o results where domain id is equal to a given param and categ id is contained in a given list. BUT I found out that HQL doesn't support a setMaxResult kind of thing as top or limit.
#Query("select i from Items i where i.domainId = :domainId and i.categId in :categoryIds order by i.insertDate desc")
The params for this method were (#Param("domainid") Integer domainid,List<Integer> categoryIds) but it seams that I'm alowed to use either #Param annotation to each parameter or no #Param at all ( except for Pageable return; not my case )
I still don't know how to achieve this think:
extract top n elements where field a eq to param, field b in set of param, ordered by another field.
ps: sorry for tags but there is no spring-crudrepository :)
The method to resolve your problem is:
List<MyClass> findTop10ByDomainIdAndCategIdInOrderByInsertDateDesc(Long domainId, List<Long> ids);
Top10 limits the results to first 10.
ByDomainId limits results to those that have passed domainId.
And adds another constraint.
CategIdIn limits results to those entries that have categId in the passed List.
OrderByInsertDateDesc orders results descending by insert date before limiting to TOP10.
I have tested this query on the following example:
List<User> findTop10ByEmailAndPropInOrderByIdDesc(String email, List<Long> props);
Where User is:
private Long id;
private String username;
private String password;
private String email;
private Long prop;
Currently I would recommend using LocalDate or LocalDateTime for storing dates using Spring Data JPA.
I am using MongoTemplate for my DB operations. Now i want to fetch the maximum fields values from the selected result. Can someone guide me how i write the query so that when i pass the query to find method it will return me the desired maximum fields of document . Thanks in advance
Regards
You can find "the object with the maximum field value" in spring-data-mongodb. Mongo will optimize sort/limit combinations IF the sort field is indexed (or the #Id field). Otherwise it is still pretty good because it will use a top-k algorithm and avoid the global sort (mongodb sort doc). This is from Mkyong's example but I do the sort first and set the limit to one second.
Query query = new Query();
query.with(new Sort(Sort.Direction.DESC, "idField"));
query.limit(1);
MyObject maxObject = mongoTemplate.findOne(query, MyObject.class);