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servlet多重映射_关于多重映射问题，很奇怪

發布時間：2024/10/12 编程问答 26 豆豆

生活随笔收集整理的這篇文章主要介紹了 servlet多重映射_关于多重映射问题，很奇怪小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

發表時間：2004-03-29

我說說我的情況吧！

我的表是多對多關聯！

schema如下

drop table if exists course_employee_link

drop table if exists employee

drop table if exists course

create table course_employee_link (

employee_id BIGINT not null,

course_id BIGINT not null,

primary key (course_id, employee_id)

)

create table employee (

employee_id BIGINT not null,

email VARCHAR(30),

password VARCHAR(30),

user_name VARCHAR(30),

primary key (employee_id)

)

create table course (

course_id BIGINT not null,

course_description VARCHAR(255),

course_name VARCHAR(30),

quantity INTEGER,

sign_up_quantity INTEGER,

primary key (course_id)

)

alter table course_employee_link add index (course_id), add constraint FKA34265C7575ED7BF foreign key (course_id) references course (course_id)

alter table course_employee_link add index (employee_id), add constraint FKA34265C7367BE44C foreign key (employee_id) references employee (employee_id)

具體的處理函數：

public ActionForward performSignIn(

ActionMapping mapping,

ActionForm form,

HttpServletRequest request,

HttpServletResponse response) {

CourseForm courseForm = (CourseForm) form;

//get session

HttpSession httpSession = request.getSession();

//get employee

Employee employee =

(Employee) httpSession.getAttribute(IntelConstants.EMPLOYEE_KEY);

if (null == employee) {

return mapping.findForward(IntelConstants.GLOBAL_FORWARD_LOGON);

} else {

//get course

Course course =

getControl().findByPrimaryKey(courseForm.getCourseId());//getControl() return a dao object

//get employee set

Set employees = course.getEmployees();

//add employee to set

employees.add(employee);

course.setSignUpQuantity(employees.size());

//update course

if (getControl().updateCourse(course)) {

transferProperties(courseForm, course, true);

return this.performDetail(

mapping,

courseForm,

request,

response);

} else {

return mapping.findForward(IntelConstants.GLOBAL_ERROR);

}

具體的錯誤信息：

net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 2, of class: com.edynasty.intel.employee.jdo.Employee

at net.sf.hibernate.impl.SessionImpl.checkUniqueness(SessionImpl.java:1642)

at net.sf.hibernate.impl.SessionImpl.doUpdateMutable(SessionImpl.java:1414)

at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1440)

at net.sf.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:1364)

at net.sf.hibernate.engine.Cascades$4.cascade(Cascades.java:114)

at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:436)

at net.sf.hibernate.engine.Cascades.cascadeCollection(Cascades.java:526)

at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:452)

at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:503)

at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:482)

at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1445)