I want to select columns based on my input (List < String >)
#Entity
#Table
public class Product {
#Id
private Long id;
private String name;
private String price;
}
I understand that to select distinct specific columns, I can use #Query("SELECT DISTINCT name FROM TABLE")
However, I want to give users the flexibility to select the columns they want. e.g. List < String > columns = Arrays.asList(["name", "price"]). This will then select distinct from both name and price columns.
For this create a custom method implementation and use one of the following (or of the many variants thereof)
construct a SQL or JPQL query using String concatenation (be careful not to introduce SQL injection vulnerabilities).
use some kind of criteria API like
JPA Criteria API
Querydsl
JOOQ
Related
I'm trying to get the list of distinct items by a specific field (userId). Currently I'm using this kind of approach to get records from MongoDB using ReactiveCrudRepository. Additionally, I want this result to be further filtered and get only the distinct items.
How to do this?
#Query(value = "{$and :[{'submitTime':{$ne:null}}, {'gameId': :#{#gameId}} ]}", sort = "{'score': -1, 'timeTaken': 1, 'submitTime': 1}")
Flux<Play> getWinners(#Param("gameId") String gameId, Pageable pageable);
My Play object is like this:
#Document(value = "play")
#Builder
public class Play {
#Id
private String id;
private String gameId;
private int score;
private String userId;
private LocalDateTime submitTime;
private long timeTaken;
}
At the moment #Query annotation doesn't provide a possibility to execute the distinct command.
As a workaround you can
implement a custom method with find, sort and distinct actions
use .distinct() operator after calling your repo method getWinners() to distinct items by key selector, but in this case this operation will not be performed in MongoDB
I have multiple aggregate classes, such as Request, Scribe, Candidate, and Exam.
Sample schema:
Request (id, scribe_id, candidate_id, exam_id, status)
Scribe (id, name)
Candidate (id, name)
Exam (id, name, schedule)
As you can see, Request table has references to Scribe, Candidate, and Exam tables.
For one of the requirements, I need to return all requests based on a condition by including all the corresponding details of scribe, candidate, and exam.
For this, the query in my repository class will be similar to the following:
SELECT r.id, r.status, c.name, s.name,
e.schedule, e.name
FROM request r
JOIN candidate c ON r.candidate=c.id
JOIN scribe s ON r.scribe=s.id
JOIN exam e ON r.exam=e.id
WHERE <some-condition>
Now, is there a way to map the result of this query directly to a custom Java object and return the same in Spring Data JDBC?
I believe another alternative is to use the Spring JDBC template.
Curious, any out-of-the-box support from Spring Data JDBC?
Thanks.
I am able to return custom Java object by setting rowMapperClass value of org.springframework.data.jdbc.repository.query.Query annotation. For this need to define RowMapper for custom Java object.
Changes look similar to the following:
public class RequestResourceRowMapper implements RowMapper<RequestResource> {
#Override
public RequestResource mapRow(ResultSet resultSet, int rowNumber) throws SQLException { ... }
}
In repository class, need to set rowMapper value.
#Query(value = """
SELECT r.id, r.status, c.name, s.name,
e.schedule, e.name
FROM request r
JOIN candidate c ON r.candidate=c.id
JOIN scribe s ON r.scribe=s.id
JOIN exam e ON r.exam=e.id
WHERE <some-condition>
""",
rowMapperClass = RequestResourceRowMapper.class)
List<RequestResource> searchRequestResources(...);
This could have even been possible without using a custom row mapper as well, but in that case, you will have to assign different names to the columns across the tables. You could have defined a simple class and defined all the fields in there and for mapping the java fields with the corresponding columns in the table, you could have used the #Column attributes example:
public class RequestData {
#Column("id")
private Integer requestId;
#Column("scribe_id")
private String scribeId;
#Column("candidate_id")
private Integer candidateId;
#Column("scribe_name")
private String scribeName;
#Column("candidate_name")
private String candidateName;
#Column("exam_name")
private String examName;
#Column("exam_schedule")
private String examSchedule;
}
However, for such case, you need to have different column names across the schema's which might not be possible in your case as you have same column names in multiple schemas.
I have a Customer entity from which I only want to select a few fields and their associated CustomerAddresses. I've defined a Spring Data JPA projection interface as follows:
public interface CustomerWithAddresses {
Integer getId();
String getFirstName();
String getLastName();
String getBrandCode();
String getCustomerNumber();
Set<CustomerAddress> getCustomerAddresses();
}
But from my Repository method:
CustomerWithAddresses findCustomerWithAddressesById(#Param("id") Integer id);
I keep getting NonUniqueResultException for Customers with multiple CustomerAddresses. Do projections have to have a flat structure, i.e. they don't support Collections the same way true Entities do?
you have Set<CustomerAddress> getCustomerAddresses(); it's X-to-Many relation. When spring data do select for CustomerWithAddresses it does join , in result set N-records (N - amount of CustomerAddress for CustomerWithAddresses with id = id). You can check if it you change CustomerWithAddresses to List of CustomerWithAddresses .
List<CustomerWithAddresses> findCustomerWithAddressesById(#Param("id") Integer id);
when you use entity sping data gropu multiply result into one element , gouped it by id as id it's unique identifier.
you can do :
1) add into CustomerWithAddresses interface
#Value("#{target.id}")
Integer getId();
and use your query
2) use #Query
#Query("select adr from CustomerWithAddressesEntity adr where adr.id=:id")
CustomerWithAddresses findCustomerWithAddressesById(#Param("id") Integer id);
I have a category tree structure, using JPA with eclipse link.
Each category in the tree includes items, and I want to select all categories along with their items count.
The code I inherited used to calculate the number of items offline, and update the category, and use the cool JPA trick for selecting the categories like so:
#Entity
#Table(name = "categories")
#NamedNativeQuery(name = "topLevel", query = "SELECT categories.* FROM categories WHERE categories.parent_id IS NULL")
public class Category {
#Id
private Long id;
private String name;
private Integer item_count;
private Long parent_id;
#JoinColumn(name = "parent_id")
private List<Categories> categories;
}
When running the native query - I get all the categories populated in the tree structure.
However, now I have a new filter that doesn't allow the user to see all the items in the category. So I can no longer calculate the items offline.
I tried to use a join so I can calculate it online, like this:
#NamedNativeQuery(name = "topLevel", query = "SELECT categories.*, count(*) as item_count FROM categories, items_to_categories WHERE categories.id = items_to_categories.category_id and some_user_specific_query and categories.parent_id IS NULL GROUP BY categories.id")
but this doesn't populate the lower levels with the right items count.
Since I am using Eclipse Link, I can't use a formula field that is not supported in this JPA implementation.
Any ideas on how to change my model in order to get it to work?
Thanks in advance!
If you want an Item count you can either query for it, such as using JPQL. This will return an Object[] including the Category and its Integer item count. If you want to use a native SQL query, then you will need to use a SqlResultSetMapping.
If you want the item count in Category, then you could define a database VIEW that makes this appear as a column and map to the view.
Another option is to map the items of the Category, then to get the item count, just access the size() of the items in Java (you could use join or batch fetching to load the items efficiently).
I have a named native query and I am trying to map it to the return results of the named native query. There is a field that I want to add to my entity that doesn't exist in the table, but it will exist in the return result of the query. I guess this would be the same with a stored proc...
How do you map the return results of a stored proc in JPA?...
How do you even call a stored proc?
here is an example query of what I would like to do...
select d.list_id as LIST_ID, 0 as Parent_ID, d.description from EPCD13.distribution_list d
The Result will be mapped to this entity...
public class DistributionList implements Serializable {
#Id
#Column(name="LIST_ID")
private long listId;
private String description;
private String owner;
private String flag;
#Column(name="PARENT_ID", nullable = true)
private long parentID;
}
parent ID is not in any table in my database. I will also need to use this entity again for other calls, that have nothing to do with this call, and that will not need this parent_id? Is there anything in the JPA standard that will help me out?
If results from database are not required for further manipulation, just for preview, you can consider using database view or result classes constructor expression.
If entities retrieved from database are required for further manipulation, you can make use of multiple select expression and transient fields.
Replace #Column annotation with #Transient annotation over parentID.
After retrieving multiple columns from database, iterate over results and manually set parentID.