如何使用findBy ..（）方法为一条记录编写查询

Question

我有一个实体类User_Details

package vl.cybersecurityapplication.model;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "User_Details")
public class User_Details implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "UserId")
    private int userId;
    @Column(name = "FirstName")
    private String firstName;
    @Column(name = "LastName")
    private String lastName;
    @Column(name = "Password")
    private String password;
    @Column(name = "E_Mail")
    private String eMail;
    @Column(name = "Mobile_Num")
    private int mobileNumber;

    //getters and setters
}

这是我的repo界面

package vl.cybersecurityapplication.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;

import vl.cybersecurityapplication.model.User_Details;

public interface IUserRepository extends JpaRepository<User_Details, Long> {

    public Integer findMobileNumberByName(String userName);


}

这是我的回购课程

package vl.cybersecurityapplication.repository;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.transaction.Transactional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

import vl.cybersecurityapplication.model.User_Roles;

@Transactional
@Repository
public class UserRepository{

    @Autowired
    IUserRepository userRepository;

    public Integer findMobileNumberByName(@PathVariable String lastName) {
        int mobileNumber = userRepository.findMobileNumberByName("shaik");
        System.out.println("Mobile Number : "+mobileNumber);
        return mobileNumber;
    }
}

我是Spring Boot和JPA的新手。在这里，我需要使用lastname在User_Details表中查询手机号码。即，从User_Details中选择Mobile_Num，其中LastName =“xyz”;有人能帮助我如何在我的repo类中编写这个查询。

Answer 1

你可以写这样的。但你不能只获取MobileNumber。你会得到一个完整的对象。

 List<User> findByLastName(String lastname).  

如果你想只获得一些领域，那么你应该看看Projections

Answer 2

无需使用本机查询。 JPA支持基于对象的查询。您可以使用List findByLastName（String lastname），它将在后端生成该查询并返回结果。