Spring Data: Bridging Multiple Databases/

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Query Methods

Query Methods

Explore derived and custom query methods of the Spring Data repositories.

We'll cover the following...

Query methods in Spring Data

Every repository method, when invoked, usually runs a query on the underlying database. Let’s look at different ways of running a data access query on the database using Spring Data repositories.

Derived query methods

Spring Data comes with a query builder mechanism that helps us generate derived query methods using keywords, like FirstBy, OrderBy, and Distinct acting as the subject and And, Or, and OrderBy as the predicate, to set conditions on the properties of a POJO.

package com.smartdiscover.repository;
import com.smartdiscover.entity.Customer;
import com.smartdiscover.entity.projection.CustomerFullName;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
@Repository
public interface CustomerRepository extends CrudRepository<Customer, Long> {
    List<Customer> findAllByFirstName(String firstName);
    Optional<Customer> findFirstByLastNameOrderByFirstNameDesc(String lastName);
    Customer findFirstByOrderByFirstNameAsc();
    Stream<Customer> readAllByOrderByIdDesc();
}

Explanation:

  • Line 16: We declare a method to fetch and return a list of customer objects that match the first name passed through an argument.
  • Line 18: We define a query method to return the
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