org.hibernate.AnnotationException：未知的mappedBy in：error

Question

我正在尝试使用注释的一对一关系 这是代码。

package test.hibernate;

@Entity
@Table(name="EMPLOYEE")

public class Employee {
    @Id
    @GeneratedValue
    @Column(name="EMP_ID")
    private Long empID;

    @Column(name="fName")
    private String fName;

    @Column(name="lName")
    private String lName;

    @OneToOne(mappedBy="employee", cascade=CascadeType.ALL)
    private Address address;


    public Employee(/* Long empID, */String fName, String lName) {
        super();
        // this.empID = empID;
        this.fName = fName;
        this.lName = lName;
    }

    public Employee() {
        super();
    }

    public Long getEmpID() {
        return empID;
    }

    public void setEmpID(Long empID) {
        this.empID = empID;
    }

    public String getfName() {
        return fName;
    }

    public void setfName(String fName) {
        this.fName = fName;
    }

    public String getlName() {
        return lName;
    }

    public void setlName(String lName) {
        this.lName = lName;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
}


package test.hibernate;

@NamedNativeQueries({ @NamedNativeQuery(name = "addressQuery", query = "from Address", resultClass = Address.class) })

public class Address {

    @Column(name = "EMP_ID")
    @GenericGenerator(name = "gen", strategy = "foreign", parameters = @Parameter(name = "property", value = "employee"))
    private Long empID;

    @Column(name = "ADDRESS")
    private String address;

    @Column(name = "CITY")
    private String city;

    @OneToOne
    @PrimaryKeyJoinColumn
    private Employee employee;

    public Address() {
        super();
        // TODO Auto-generated constructor stub
    }

    public Address(/* Long empID, */String address, String city) {
        super();
        // this.empID = empID;
        this.address = address;
        this.city = city;
    }

    public Long getEmpID() {
        return empID;
    }

    public void setEmpID(Long empID) {
        this.empID = empID;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Employee getEmployee() {
        return employee;
    }

    public void setEmployee(Employee employee) {
        this.employee = employee;
    }


}

}

我收到以下异常：

Hibernate one to many (XML Mapping)
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.annotations.Version).
log4j:WARN Please initialize the log4j system properly.
org.hibernate.AnnotationException: Unknown mappedBy in: test.hibernate.Employee.address, referenced property unknown: test.hibernate.Address.employee
    at org.hibernate.cfg.OneToOneSecondPass.doSecondPass(OneToOneSecondPass.java:129)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1127)
    at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:296)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1283)
    at test.hibernate.HibernateUtil.openSession(HibernateUtil.java:14)
    at test.hibernate.Test.main(Test.java:11)
Exception in thread "main" java.lang.NullPointerException
    at test.hibernate.HibernateUtil.openSession(HibernateUtil.java:19)
    at test.hibernate.Test.main(Test.java:11)

我的代码出了什么问题？有人可以帮忙吗？

Answer 1

问题不是mappedBy本身的价值。问题是Address类中没有@Entity注释。添加它将解决问题。在Java SE环境类中也应该添加到persistence.xml。

Answer 2

如果我们没有在hibernate配置文件中指定映射类条目<mapping class="test.hibernate.Address" />，则会发生同样的异常。

Answer 3

地址类中没有@Entity注解

在 Employee 类中，您已经添加了 @Entity 注释，但是在地址类中您没有添加 @Entity 注释，因此您的问题很清楚，只需将 @Entity 添加到你的班级就是这样：

@Entity
public class Address {
  // your code here ....
}

问题在于没有创建 bean，因为 @Entity 注释对此负责，例如 @Service 和/或 @Component 注释。