Question

我有一个Hibernate Entity＆＃34; Intranet＆＃34;它有这段代码：

// Imports removed

@Entity
@Table(name = "intranets", uniqueConstraints = @UniqueConstraint(columnNames = "company_name"))
@Cacheable
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Intranet {

    @Id
    @Column(name = "INTRANET_ID")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int intranetId;

    @Column(name = "owner_id")
    private int ownerId;

    @Column(name = "setup_done")
    private boolean isSetUp = false;

    @Column(name = "company_name")
    private String companyName;

    @ElementCollection
    @CollectionTable(name = "employees")
    @Column(name = "employee")
    private List<Integer> employeeIds;


    public int getIntranetId() {

        return intranetId;
    }

    public void setIntranetId(int intranetId) {

        this.intranetId = intranetId;
    }

    public boolean isSetUp() {

        return isSetUp;
    }

    public void setSetUp(boolean isSetUp) {

        this.isSetUp = isSetUp;
    }

    public String getCompanyName() {

        return companyName;
    }

    public void setCompanyName(String companyName) {

        this.companyName = companyName;
    }

    public int getOwnerId() {

        return ownerId;
    }

    public void setOwnerId(int ownerId) {

        this.ownerId = ownerId;
    }

    public List<Integer> getEmployeeIds() {

        return employeeIds;
    }

    public void setEmployeeIds(List<Integer> employeeIds) {

        this.employeeIds = employeeIds;
    }

    public void addEmployee(int id) {
        this.employeeIds.add(id);
    }

    public void removeEmployee(int id) {
        this.employeeIds.remove(new Integer(id));
    }
}

正如您所看到的，我添加了两种不直接是getter和setter的方法，但他们喜欢方便的方法来轻松访问该集合并添加/删除员工。

当我打电话给＆＃34; addEmployee（）＆＃34;在我的程序中，我得到一个简单的NullPointerException。问题基本上是我如何初始化集合而没有null ，因为我读到Hibernate使用集合的内部实现而不仅仅是ArrayList。

提前感谢您的帮助。

Answer 1

您有一个NullPointerException，因为您必须自己初始化列表。使用哪种实现并不重要。这将解决您的问题：

@ElementCollection
@Column(name = "employee")
private List<Integer> employeeIds = new ArrayList<>();

在Hibernate中添加Employee时出现NullPointerException

1 个答案: