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Spring Data With JPA and @NamedQueries

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Spring Data With JPA and @NamedQueries

Let's dive into using named queries for JPA entities. The @NamedQuery annotation allows for finer control and enhanced functionality for your databases.

· Java Zone
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If you use Spring Data and @NamedQuery annotations for your JPA entities, you can easily use them in a more convenient way with the Spring Data repository.

In a previous article, we created a Spring Data project using Spring Boot and Docker. We will use pretty much the same project and enhance our repository’s functionality.

We will implement a named query that will fetch employees only if their last names have as many characters as the ones specified.

package com.gkatzioura.springdata.jpa.persistence.entity;
 
import javax.persistence.*;
 
/**
 * Created by gkatzioura on 6/2/16.
 */
@Entity
@Table(name = "employee", schema="spring_data_jpa_example")
@NamedQuery(name = "Employee.fetchByLastNameLength",
        query = "SELECT e FROM Employee e WHERE CHAR_LENGTH(e.lastname) =:length "
)
public class Employee {
 
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Long id;
 
    @Column(name = "firstname")
    private String firstName;
 
    @Column(name = "lastname")
    private String lastname;
 
    @Column(name = "email")
    private String email;
 
    @Column(name = "age")
    private Integer age;
 
    @Column(name = "salary")
    private Integer salary;
 
    public Long getId() {
        return id;
    }
 
    public void setId(Long id) {
        this.id = id;
    }
 
    public String getFirstName() {
        return firstName;
    }
 
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
 
    public String getLastname() {
        return lastname;
    }
 
    public void setLastname(String lastname) {
        this.lastname = lastname;
    }
 
    public String getEmail() {
        return email;
    }
 
    public void setEmail(String email) {
        this.email = email;
    }
 
    public Integer getAge() {
        return age;
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }
 
    public Integer getSalary() {
        return salary;
    }
 
    public void setSalary(Integer salary) {
        this.salary = salary;
    }
}


Pay extra attention to the query name and the convention we follow:

@{EntityName}.{queryName}.

Then, we will add the method to our Spring Data repository.

package com.gkatzioura.springdata.jpa.persistence.repository;
 
import com.gkatzioura.springdata.jpa.persistence.entity.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
 
import java.util.List;
 
/**
 * Created by gkatzioura on 6/2/16.
 */
@Repository
public interface EmployeeRepository extends JpaRepository<Employee,Long>, EmployeeRepositoryCustom {
 
    List<Employee> fetchByLastNameLength(@Param("length") Long length);
}


And last but not least, add some functionality to our controller.

package com.gkatzioura.springdata.jpa.controller;
 
import com.gkatzioura.springdata.jpa.persistence.entity.Employee;
import com.gkatzioura.springdata.jpa.persistence.repository.EmployeeRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
 
import java.util.List;
 
/**
 * Created by gkatzioura on 6/2/16.
 */
@RestController
public class TestController {
 
    @Autowired
    private EmployeeRepository employeeRepository;
 
    @RequestMapping("/employee")
    public List<Employee> getTest() {
 
        return employeeRepository.findAll();
    }
 
    @RequestMapping("/employee/filter")
    public List<Employee> getFiltered(String firstName,@RequestParam(defaultValue = "0") Double bonusAmount) {
 
        return employeeRepository.getFirstNamesLikeAndBonusBigger(firstName,bonusAmount);
    }
 
    @RequestMapping("/employee/lastnameLength")
    public List<Employee> fetchByLength(Long length) {
        return employeeRepository.fetchByLastNameLength(length);
    }
 
}


You can find the source code on GitHub.

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Topics:
java ,spring data ,jpa ,named queries ,tutorial

Published at DZone with permission of Emmanouil Gkatziouras, DZone MVB. See the original article here.

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