如何从 Spring Boot 项目中的子子表中检索数据？

Posted 2023-04-14

【中文标题】如何从 Spring Boot 项目中的子子表中检索数据？

【英文标题】：How do I retrive data from sub chield table in my Spring Boot Project?

【发布时间】：2021-08-31 17:00:15

【问题描述】：

我有两个实体“User”和“UserOtp”，它们具有一对多的关系。我想在一张表中显示它们，我的用户将显示所有字段，并且只有一个字段来自“UserOtp”。以下是详细代码。

“用户”

import java.util.Date;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Table;

import com.fasterxml.jackson.annotation.JsonIgnore;

@Entity
@Table(name = "users")
public class Users 
    
    @Id
    @Column(name = "userid")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @JsonIgnore
    private int userid;
    private String msisdn;
    private String userPin;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "iduser_role")
    private UserRole roleId;
    
    @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "ud_id")
    private DeviceProfile deviceProfile;
    
    @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "pp_id")
    private PersonalProfile personalProfile;
    
    @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "pa_id")
    private PersonalAccount personalAccount;
    
    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "userid")
    List<UserOtp> userOtp;
    
    @JsonIgnore
    private int status;
    @JsonIgnore
    private Date createDate;
    @JsonIgnore
    private Date updateDate;
    
    public Users() 
    

    public Users(String msisdn, String userPin, UserRole roleId, DeviceProfile deviceProfile,
            PersonalProfile personalProfile, PersonalAccount personalAccount, List<UserOtp> userOtp, int status,
            Date createDate, Date updateDate) 
        super();
        this.msisdn = msisdn;
        this.userPin = userPin;
        this.roleId = roleId;
        this.deviceProfile = deviceProfile;
        this.personalProfile = personalProfile;
        this.personalAccount = personalAccount;
        this.userOtp = userOtp;
        this.status = status;
        this.createDate = createDate;
        this.updateDate = updateDate;
    

--- Getter and Setter --- 

“用户OTP”

import java.util.Date;

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_otp")
public class UserOtp 

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "iduser_otp")
    private int iduserOtp;
    private String otp;
    private Date createDate;
    private Date updateDate;
    private int status;
    
    public UserOtp() 
    

    public UserOtp(String otp, Date createDate, Date updateDate, int status) 
        super();
        this.otp = otp;
        this.createDate = createDate;
        this.updateDate = updateDate;
        this.status = status;
    

------ Getter and Setter -----

“控制器”

@RequestMapping("/admin/index")
    public String Login(Model model) 
        
        long countUsers = userRepositoryService.countUsers();
        
        Users user = userRepositoryService.getUsers(1);
        
        List<Users> users = userRepositoryService.getUsers();
        
        model.addAttribute("usersCount", countUsers);
        model.addAttribute("users", users);
        
        System.out.println(user.getUserOtp().toString());
        
        return "/admin/index";
    

百里香页面

<table class="table table-bordered table-striped">
                        <thead>
                          <tr>
                            <th>#</th>
                            <th>Username</th>
                            <th>OTP</th>
                            <th>Gen. Time</th>
                            <th>Update Time</th>
                            <th>Status</th>
                          </tr>
                        </thead>
                        <tbody>
                          <tr class="odd gradeX" th:each="user : $users">
                            <td th:text="$user.userid">01</td>
                            <td th:text="$user.msisdn">01791631664</td>
                            <td th:text="$user.userOtp">6566</td>
                            <td th:text="$user.CreateDate">July 12, 2012 12:13:00 PM</td>
                            <td th:text="$user.UpdateDate">July 12, 2012 12:13:00 PM</td>
                            <th th:text="$user.status">Active</th>
                          </tr>
                        </tbody>
                      </table>

我得到的输出如下：

我只想显示“otp”字段的最后一个数据。

【问题讨论】：

缺少实际输出。

【参考方案1】：

您可以使用句点（“.”）字符在 Spring EL 中导航对象。

因此，在您的情况下，如果您只想显示状态字段，您可以使用：

    <td th:text="$user.userOtp.status">6566</td>

有关更多信息，您可以查看Spring MVC & Thymeleaf 文档的第 1 部分以了解 Spring EL。

此外，Spring documentation 的第 4.3.2 章也很有用，其中描述了如何访问嵌套属性以及如何使用安全导航。