java - 错误如下所述

Question

有一个员工类别，其中有一组他知道的语言。

error :Exception in thread "main" org.hibernate.MappingException: Could not determine type for: java.util.Set, at table: Employee_Table, for columns: [org.hibernate.mapping.Column(languages)]

员工.java

    package Mapping.Collection.Set;

    import java.util.*;

    import javax.persistence.*;
    @Entity
    @Table(name="Employee_Table")
    public class Employee {
        @Id
        @GeneratedValue(strategy=GenerationType.AUTO)
        private int empId;
        @Column(name="EMP_NAME",nullable=false)
        private String empName;
        public int getEmpId() {
            return empId;
        }
        public void setEmpId(int empId) {
            this.empId = empId;
        }
        public String getEmpName() {
            return empName;
        }
        public void setEmpName(String empName) {
            this.empName = empName;
        }
        public int getSalary() {
            return salary;
        }
        public void setSalary(int salary) {
            this.salary = salary;
        }
        private int salary;


        @ElementCollection(targetClass=String.class)
        @JoinColumn(name="Languages_Known")
        private Set<String> languages=new HashSet<>();

        public Set<String> getLanguages() {
            return languages;
        }
        public void setLanguages(Set<String> languages) {
            this.languages = languages;
        }




    }


    TestMain.java
    package Mapping.Collection.Set;

    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.Transaction;
    import org.hibernate.cfg.AnnotationConfiguration;

    public class TestMain {

        /**
         * @param args
         */
        public static void main(String[] args) {
            Employee emp=new Employee();
            emp.setEmpId(1);
            emp.setEmpName("Shrini Jaiswal");
            emp.setSalary(10000000);
            emp.getLanguages().add("Hindi");
            emp.getLanguages().add("English");
            SessionFactory factory=new AnnotationConfiguration().configure().buildSessionFactory();
            Session session=factory.openSession();
            Transaction tx=session.beginTransaction();  
            tx.begin();
            session.save(emp);
            tx.commit();
                session.close();
        }

    }

Answer 1

在 Hibernate Annotation 中，@ElementCollection 是从另一个表获取列值的功能，无需映射两个表。

您应该在另一个表中有语言列表，然后只有您像这样使用..

@ElementCollection
@CollectionTable(name="languages", joinColumns=@JoinColumn(name="empId"))
private Set<String> languages;

请read this发帖获取更多信息。