Igor Gorbunov's questions

本质：

package com.igorgorbunov3333.core.entities.domain;

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

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

@Entity
@Table(name = "cases")
@NamedQueries({
    @NamedQuery(name = "findAllCases", query = "SELECT c FROM Case c JOIN c.client JOIN c.firstInstance " +
            "JOIN c.secondInstance JOIN c.thirdInstance JOIN c.category"),
})
public class Case {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

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

    @ManyToOne
    @JoinColumn(name = "client_id")
    private Client client;

    @OneToOne
    @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;

    @Temporal(TemporalType.DATE)
    @Column(name = "closing_date")
    private Date closingDate;

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

    private float price;
    .....

如您所见，有一个命名查询findAllCases。我得到所有实体 ( Case) 是这样的：

public List<Case> findAll() {
    Query query = entityManager.createNamedQuery("findAllCases");
    return query.getResultList();
}

但是该方法返回字段secondInstance不为thirdInstance null的所有实体。如何使具有空字段的实体secondInstance被返回thirdInstance？

如果我删除这样的实体：

public void remove(Case lawsuit) {
    Case c = entityManager.find(Case.class, lawsuit.getId());
    entityManager.remove(c);
}

那么它不会被删除，但如果是这样的话：

public void remove(Case lawsuit) {
    Case c = entityManager.find(Case.class, lawsuit.getId());

    entityManager.getTransaction().begin();
    entityManager.remove(c);
    entityManager.getTransaction().commit();
}

它通常被删除。为什么这是我可以删除的唯一方法？这是实体本身：

@Entity
@Table(name = "cases")
public class Case {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String caseNumber;

    private String dataI;

    private String dataII;

    private String dataIII;

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

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

    @ManyToOne
    @JoinColumn(name = "clientID")
    private Client client;

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

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

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

    private String document;

    //геттеры, сеттеры
}

有一个实体：

package com.igorgorbunov3333.core.entities.domain;

import javax.persistence.*;


@Entity
@Table(name = "cases")

public class Case {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String caseNumber;

    private String dataI;

    private String dataII;

    private String dataIII;

    @OneToOne
    @JoinColumn(name = "id")
    private Judge judge;

    @OneToOne
    @JoinColumn(name = "id")
    private Lawyer lawyer;

    @OneToOne
    @JoinColumn(name = "id")
    private Client client;

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

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

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

    private String document;

    // геттеры и сеттеры
}

如您所见，有法官、律师、客户（关联）等字段。我在服务中收到：

public List<Case> findAll() {
    Query query = entityManager.createNamedQuery("getAllCases");
    return query.getResultList();
}

我在一个 servlet 中进行测试，我得到一个 NullPointerException。现在的问题是：如何正确组织协会？. findAll() 方法返回所有对象，但并非实体的所有字段都具有“完整”律师、案件、客户字段。也就是说，我在表中有 20 个案例，10 个律师。1 个律师可以处理多个案例，据我所知，findAll() 返回与 10 个律师相关的第一个 10 个案例，其余案例与无效律师。@ManyToOne 和@OneToMany 都试过了，不知道该用什么。