Java 如何在循环JPA中持久化实体？

我试图在for循环中保存实体。但它只保存数据库中的最后一个实体。我的实体如下所示

@Entity
@Table(name = "users_departments")
public class Users_Departments extends AbstractBaseEntity {
......
}

@Override
@Transactional
public T create(T entity) {
    entityManager.persist(entity);
    entityManager.flush();
    entityManager.refresh(entity);
    return entity;
}

 @Transactional
    public List<Users_Departments> addUserstoDepartments(Long deptId,List<Long> useridList){
       Users_Departments object = new Users_Departments() ;
       List <Users_Departments> userDeptList = new ArrayList<>();
            for(int a=0 ; a < useridList.size();a++){                   
            object.setDepartment(departmentDao.find(deptId));
            object.setStation(userDao.find(useridList.get(a)));
            object.setCreatedDate(new Date());
            object.setUpdatedDate(new Date());

            Users_Departments newlyCreated = users_departmentsDao.create(object);
            userDeptList.add(newlyCreated);
        }
        return  userDeptList;
    }

我编写了一个通用crud方法，将实体保存在数据库中，如下所示

@Entity
@Table(name = "users_departments")
public class Users_Departments extends AbstractBaseEntity {
......
}

@Override
@Transactional
public T create(T entity) {
    entityManager.persist(entity);
    entityManager.flush();
    entityManager.refresh(entity);
    return entity;
}

 @Transactional
    public List<Users_Departments> addUserstoDepartments(Long deptId,List<Long> useridList){
       Users_Departments object = new Users_Departments() ;
       List <Users_Departments> userDeptList = new ArrayList<>();
            for(int a=0 ; a < useridList.size();a++){                   
            object.setDepartment(departmentDao.find(deptId));
            object.setStation(userDao.find(useridList.get(a)));
            object.setCreatedDate(new Date());
            object.setUpdatedDate(new Date());

            Users_Departments newlyCreated = users_departmentsDao.create(object);
            userDeptList.add(newlyCreated);
        }
        return  userDeptList;
    }

在服务方法中，我将用户列表和部门以及其他详细信息保存在数据库中，如下所示

@Entity
@Table(name = "users_departments")
public class Users_Departments extends AbstractBaseEntity {
......
}

@Override
@Transactional
public T create(T entity) {
    entityManager.persist(entity);
    entityManager.flush();
    entityManager.refresh(entity);
    return entity;
}

 @Transactional
    public List<Users_Departments> addUserstoDepartments(Long deptId,List<Long> useridList){
       Users_Departments object = new Users_Departments() ;
       List <Users_Departments> userDeptList = new ArrayList<>();
            for(int a=0 ; a < useridList.size();a++){                   
            object.setDepartment(departmentDao.find(deptId));
            object.setStation(userDao.find(useridList.get(a)));
            object.setCreatedDate(new Date());
            object.setUpdatedDate(new Date());

            Users_Departments newlyCreated = users_departmentsDao.create(object);
            userDeptList.add(newlyCreated);
        }
        return  userDeptList;
    }

@Transactional
公共列表addUserstoDepartments（长deptId，列表useridList）{
用户\部门对象=新用户\部门（）；
List userDeptList=new ArrayList（）；
对于（inta=0；a

调试时，此方法返回具有更新值的列表，但每个项都具有与“id”相同的值。因此，数据库中只有最后一条记录可用。我想所有其他记录都被替换了。有什么原因吗？

---

我不能在for循环中创建实体吗？怎么可能呢

每次在循环中都应该实例化

Users\u Departments对象

，如下所示：

List <Users_Departments> userDeptList = new ArrayList<>();
for(int a=0 ; a < useridList.size();a++){   
    Users_Departments object = new Users_Departments();             
    object.setDepartment(departmentDao.find(deptId));
    object.setStation(userDao.find(useridList.get(a)));
    object.setCreatedDate(new Date());
    object.setUpdatedDate(new Date());

    Users_Departments newlyCreated = users_departmentsDao.create(object);
    userDeptList.add(newlyCreated);
}

List userDeptList=new ArrayList（）；
对于（inta=0；a

您总是保存同一个对象（因此会对其进行更新），请移动

Users_Departments object = new Users_Departments() ;

---

在循环中创建一个新对象，每次它仍然是同一个对象。移动

用户\部门对象=新用户\部门（）在loop@XtremeBaumer非常感谢：）作为旁注，没有必要在
create
内部调用
refresh
（并且
flush
手动更改可能也是多余的，除非您需要自动生成的id）