JPA 一对多非类型化映射示例

JPA教程 - JPA一对多非类型化映射示例

以下代码表示非类型的java.util.Map的目标实体类。

@OneToMany(targetEntity=Employee.class, mappedBy="department")
@MapKey
private Map employees;

例子

下面的代码来自PersonDaoImpl.java。

package cn.w3cschool.common;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.transaction.annotation.Transactional;

@Transactional
public class PersonDaoImpl {
  public void test() {
    Employee e = new Employee();
    e.setName("Tom");
    Department d = new Department();
  
    d.setName("test");
    d.getEmployees().put(e, e.getId());
    
    
    em.persist(e);    
    em.persist(d);
   

  }

  @PersistenceContext
  private EntityManager em;
}

下面的代码来自Department.java。

package cn.w3cschool.common;

import java.util.HashMap;
import java.util.Map;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MapKey;
import javax.persistence.OneToMany;

@Entity
public class Department {
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int id;
    private String name;
    
    @OneToMany(targetEntity=Employee.class, mappedBy="department")
    @MapKey
    private Map employees;
    
    public Department() {
        employees = new HashMap();
    }
    
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String deptName) {
        this.name = deptName;
    }
    
    public void addEmployee(Employee employee) {
        employees.put(employee.getId(), employee);
        if (employee.getDepartment() != null) {
            employee.getDepartment().getEmployees().remove(employee.getId());
        }
        employee.setDepartment(this);
    }
    
    public Map getEmployees() {
        return employees;
    }

    public String toString() {
        StringBuffer aBuffer = new StringBuffer("Department ");
        aBuffer.append(" id: ");
        aBuffer.append(id);
        aBuffer.append(" name: ");
        aBuffer.append(name);
        aBuffer.append(" employeeCount: ");
        if(null != employees) {           
            aBuffer.append(employees.size());
        }
        return aBuffer.toString();
    }
}

以下代码来自Employee.java。

package cn.w3cschool.common;

import java.util.Map;
import java.util.Set;

import javax.persistence.CollectionTable;
import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.MapKeyClass;
import javax.persistence.MapKeyColumn;

@Entity
public class Employee {
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int id;
    private String name;
    private long salary;

    @ElementCollection(targetClass=String.class)
    @CollectionTable(name="EMP_PHONE")
    @MapKeyColumn(name="PHONE_TYPE")
    @MapKeyClass(String.class)
    @Column(name="PHONE_NUM")
    private Map phoneNumbers;
            
    @ManyToOne
    private Department department;

    
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }

    public long getSalary() {
        return salary;
    }

    public void setSalary(long salary) {
        this.salary = salary;
    }
    
    public Department getDepartment() {
        return department;
    }
    
    public void setDepartment(Department department) {
        this.department = department;
    }

    public Map getPhoneNumbers() {
        return phoneNumbers;
    }

    public void setPhoneNumbers(Map phoneNumbers) {
        this.phoneNumbers = phoneNumbers;
    }

    public String toString() {
        StringBuffer aBuffer = new StringBuffer("Employee ");
        aBuffer.append(" id: ");
        aBuffer.append(id);
        aBuffer.append(" with dept: ");
        if(null != department) {
            aBuffer.append(department.getName());
        }
        aBuffer.append(" phoneNumbers: ");
        for (Map.Entry e : (Set<Map.Entry>)phoneNumbers.entrySet()) {
            aBuffer.append(e.getKey() + "[" + e.getValue() + "] ");
        }        
        return aBuffer.toString();
    }
}

以下是数据库转储。

Table Name: DEPARTMENT
 Row:
    Column Name: ID,
    Column Type: INTEGER:
    Column Value: 1

    Column Name: NAME,
    Column Type: VARCHAR:
    Column Value: test





Table Name: EMPLOYEE
 Row:
    Column Name: ID,
    Column Type: INTEGER:
    Column Value: 1

    Column Name: NAME,
    Column Type: VARCHAR:
    Column Value: Tom

    Column Name: SALARY,
    Column Type: BIGINT:
    Column Value: 0

    Column Name: DEPARTMENT_ID,
    Column Type: INTEGER:
    Column Value: null





Table Name: EMP_PHONE