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);
Related
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 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
I wanted to load an object from the database that contains more
attributes, one of which is null (e.g : date), using spring boot JPA
that returns a null object because it found the date is null despite
the object exists in the database. Please who can who can tell me how I solve this problem
#Entity #IdClass(Exemple.class) #Table(name= "table") public class
Exemple implements Serializable{
#Id #Column(columnDefinition = "id_activite") private Integer idActivite;
//the Problem is here
#Column(columnDefinition = "date_debut_prevue") #Nullale private Calendar dateDebutPrevue;
//Other attribute and Id
#Id ...
// Getters && setters
}
//Query Repository
#Query("SELECT ar FROM table ar where ar.idActivity = ?1 ")
List<Activitie> findAllPositionByIdActivitie(Integer idActivitie);
Your query is a native query and not a JPQL query.
The query must use the Entity name in the FROM clause not the table name.
#Query("SELECT ar FROM Exemple ar where ar.idActivity = ?1 ")
List<Activitie> findAllPositionByIdActivitie(Integer idActivitie);
I use Mybatis to access db, and some tables is sharding by id with hash algorithm.
I want to write a Mybatis intecepter to change table name automatic, it need to get the sharding column value.
Table Entity:
#Data
#TableName("m_user")
public class User {
#TableId(type = IdType.AUTO)
private Integer id;
private String name;
private Integer age;
}
UserMapper sql:
#Select("select * from m_user where id = #{id2} and name = #{name2};")
List<User> selectByIdAndName(Integer id2, String name2);
I use boundSql.getParameterObject() and boundSql.getParameterMappings() to check, but I can not make sure whether the sharding column id is in sql and then get the value of the sharding column.
ParameterMappings values and ParameterObject values are here:
parameter mapping:ParameterMapping{property='id2', mode=IN, javaType=class java.lang.Object, jdbcType=null, numericScale=null, resultMapId='null', jdbcTypeName='null', expression='null'}
parameter mapping:ParameterMapping{property='name2', mode=IN, javaType=class java.lang.Object, jdbcType=null, numericScale=null, resultMapId='null', jdbcTypeName='null', expression='null'}
params:{id2=1, param1=1, name2=name1, param2=name1}
The parameters are Mapper function parameters, but I need sharding column id and value, program can only get id2 or param1.
How to get the db column and value from Mybatis?
I want to select Map for each record. Result class looks like
public class Mapping {
private String name;
private Map<Integer, Integer>;
}
SQL table has only three columns namely name, id, partner_id.
How can I create Map of Id to Partner Id for each name using mybatis?
you can use sqlSession.selectForMap, and give mybatis the column which will be processed as the key of map , such as name. then it will return
Map<String,Map<String,Object>>
as a result, but the value is Map, key is the column name, you need to transform it .