错误：Illegal attempt to associate a collection with two open sessions

错误：Illegal attempt to associate a collection with two open sessions

我的dao层delete方法代码：

/** * 删除用户 *  * @param userIdAry * @return 删除的用户名 */public String deleteUser(String userIdAry) {System.out.println("method is run");String[] userIds = userIdAry.split(",");Long[] ids = new Long[userIds.length - 1];if (userIdAry != null) {for (int i = 0; i < userIds.length; i++) {if (userIds[i] != null && !"".equals(userIds[i])) {ids[i - 1] = Long.valueOf(userIds[i]);}}}String usernameAry = "";for (int i = 0; i < ids.length; i++) {User user = get(ids[i]);if (i == 0) {usernameAry = user.getUsername();} else {usernameAry += "," + user.getUsername();}remove(user);}System.out.println("usernameAry:" + usernameAry);return usernameAry;}

用上面方法删除单个或多个用户会报不能同时连接2个打开的session，而我的web.xml中是要求只能用一个session：

  <init-param>      <param-name>singleSession</param-name>      <param-value>true</param-value>    </init-param>

后来我看了一下GenericDaoHibernate中的公共方法中有2个remove方法：

/**     * {@inheritDoc}     */    public void remove(T object) {        Session sess = getSession();        Transaction tx = sess.beginTransaction();        sess.delete(object);    tx.commit();     //   sess.delete(object);    }    /**     * {@inheritDoc}     */    public void remove(PK id) {        Session sess = getSession();        Transaction tx = sess.beginTransaction();        IdentifierLoadAccess byId = sess.byId(persistentClass);        T entity = (T) byId.load(id);        sess.delete(entity);    tx.commit();    }

我在想，会不会是User user=get(ids[i]);会不会这里打开了另一条session？

最后我将delete方法改成如下就可以了：

/** * 删除用户 *  * @param userIdAry * @return 删除的用户名 */public String deleteUser(String userIdAry) {System.out.println("method is run");String[] userIds = userIdAry.split(",");Long[] ids = new Long[userIds.length - 1];if (userIdAry != null) {for (int i = 0; i < userIds.length; i++) {if (userIds[i] != null && !"".equals(userIds[i])) {ids[i - 1] = Long.valueOf(userIds[i]);}}}String usernameAry = "";for (int i = 0; i < ids.length; i++) {String username = get(ids[i]).getUsername();//这里由User类型换成了String类型if (i == 0) {usernameAry = username;} else {usernameAry += "," + username;}remove(ids[i]);//这里改成根据id来删除用户}System.out.println("usernameAry:" + usernameAry);return usernameAry;}}

究其原因，还不是很清楚。记录下此问题供以后研究，也希望能够为遇到同样问题的朋友们提供一条思路。