Question

有两个实体：

案例

package com.igorgorbunov3333.core.entities.domain;

import javax.persistence.*;

/**
 * Created by Игорь on 03.04.2016.
 */

@Entity
@Table(name = "cases")
@NamedQueries({
    @NamedQuery(name = "findAllCases", query = "SELECT c FROM Case c"),

    @NamedQuery(name = "findCasesWithJudge", query = "SELECT c FROM Case c " +
            "WHERE c.firstInstance.judge.id = :id OR c.secondInstance.judge.id = :id OR c.thirdInstance.judge.id = :id")
})
public class Case {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column(name = "case_number")
    private String caseNumber;

    @Column(name = "client")
    private String clientName;

    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "first_instance_id")
    private FirstInstance firstInstance;

    @OneToOne
    @JoinColumn(name = "second_instance_id")
    private SecondInstance secondInstance;

    @OneToOne
    @JoinColumn(name = "third_instance_id")
    private ThirdInstance thirdInstance;

    @ManyToOne
    @JoinColumn(name = "category_id")
    private Category category;

    private float price;
}

第二个实体 FirstInstance：

package com.igorgorbunov3333.core.entities.domain;

import com.igorgorbunov3333.core.entities.enums.CaseStatus;

import javax.persistence.*;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

/**
 * Created by Игорь on 19.09.2016.
 */
@Entity
@Table(name = "first_instance")
public class FirstInstance {

    @Id
    private long id;

    @Temporal(TemporalType.DATE)
    private Date date;

    @ManyToOne
    @JoinColumn(name = "judge_id")
    private Judge judge;

    @ManyToOne
    @JoinColumn(name = "lawyer_id")
    private Lawyer lawyer;

    @Enumerated(value = EnumType.ORDINAL)
    private CaseStatus status;

    @OneToMany(mappedBy = "firstInstance")
    private List<CourtHearingFirst> hearings = new ArrayList<>();
}

如您所见，字段FirstInstance具有引用类型，但与我的数据库中的数字列相关，它等于FirstInstances id。
我坚持Case实体和FirstInstance，同时坚持FirstInstance它的id字段等于，例如35，但字段实体FirstInstance的{{1}}总是等于0，为什么？它也可能等于35 ...... 这是我的Servlet代码：

Case

这是代码，它向您展示我如何持久化实体：

@WebServlet(name = "DoCreateCase", urlPatterns = "/doCreateCase")
public class DoCreateCase extends HttpServlet {
private final CategoryService categoryService = SpringAppContextManager.getAppContext()
        .getBean("CategoryService", CategoryService.class);

private final JudgeService judgeService = SpringAppContextManager.getAppContext()
        .getBean("JudgeService", JudgeService.class);

private final LawyerService lawyerService = SpringAppContextManager.getAppContext()
        .getBean("LawyerService", LawyerService.class);

private final FirstInstanceService firstInstanceService = SpringAppContextManager.getAppContext()
        .getBean("FirstInstanceService", FirstInstanceService.class);

private final CaseService caseService = SpringAppContextManager.getAppContext()
        .getBean("CaseService", CaseService.class);

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doGet(request, response);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    Case lawsuit = new Case();
    FirstInstance firstInstance = new FirstInstance();

    String caseNumber = request.getParameter("case-number");
    lawsuit.setCaseNumber(caseNumber);

    String clientName = request.getParameter("client-name");
    lawsuit.setClientName(clientName);

    String dayOpen = request.getParameter("day-open"),
           monthOpen = request.getParameter("month-open"),
           yearOpen = request.getParameter("year-open");
    Date date = DateUtil.toDate(yearOpen, monthOpen, dayOpen);
    firstInstance.setDate(date);

    long categoryId = Long.valueOf(request.getParameter("category"));

    Category category = categoryService.findById(categoryId);
    lawsuit.setCategory(category);

    float price = Float.valueOf(request.getParameter("price"));
    lawsuit.setPrice(price);

    long judgeId = Long.valueOf(request.getParameter("judge"));
    Judge judge = judgeService.findById(judgeId);
    firstInstance.setJudge(judge);

    long lawyerId = Long.valueOf(request.getParameter("lawyer"));
    Lawyer lawyer = lawyerService.findById(lawyerId);
    firstInstance.setLawyer(lawyer);

    lawsuit.setFirstInstance(firstInstance);

    caseService.create(lawsuit);


 }
}

有什么问题？

Answer 1

我同时坚持Case实体和firstInstance ......

您的代码中没有任何地方{}持续存在firstInstance。无论是否存在，您都不会将firstInstance与lawsuit相关联。

所以你需要打电话：

lawsuit.setFirstInstance(firstInstance);

然后调用entityManager.persist(lawsuit);将：

（a）由于在关联上指定的Cascade选项，插入新的FirstInstance记录。

（b）插入Case实例，将FK设置为新持久化的FIrstInstance记录的ID。

Answer 2

我认为你的实体类应该实现Serializable，并且应该具有如下的serialversionUID：

public class FirstInstance implements Serializable{
    private static final long serialVersionUID = 1L;
    .....
}

public class Case implements Serializable{
    private static final long serialVersionUID = 1L;
    .....
}

JPA坚持相关实体

2 个答案: