更新/删除查询中的 javax.persistence.TransactionRequiredException

Question

我正在开发一个简单的应用程序，其中数据库中的用户记录显示在 primefaces 数据表中，用户可以编辑或删除这些记录。这是 jsf 文件

<h:form>
            <p:dataTable var="user" value="#{userBean.users}" >
                <p:column headerText="username">
                    <h:inputText value="#{user.username}" rendered="#{userBean.editable}" />
                    <h:outputText value="#{user.username}" rendered="#{not userBean.editable}" />
                    <!--<h:outputText value="#{user.username}" />-->
                </p:column>

                <p:column headerText="edit">
                    <h:commandLink value="Edit" action="#{userBean.editAction(index)}" rendered="#{not userBean.editable}" />
                </p:column>

                <p:column headerText="save">
                    <p:commandButton value="Save" id="save" disabled="false" action="#{userBean.saveAction(user)}"/>
                </p:column>

                <p:column headerText="delete">
                    <p:commandButton value="Delete" id="delete" disabled="false" action="#{userBean.deleteAction(user)}"/>
                </p:column>

            </p:dataTable>

        </h:form>

这是我在 bean 中调用的保存和更新操作方法

public String saveAction(User user) {

    this.setEditable(false);
    DB db = new DB();
    db.updateUser(user);
    return "editSuccess";
}

public String deleteAction(User user) {

    DB db = new DB();
    db.deleteUser(user);
    return "editSuccess";
}

这里是dao层的方法

EntityManagerFactory emf = javax.persistence.Persistence.createEntityManagerFactory("RegisterationFormJPAPU");
EntityManager em = emf.createEntityManager();
public void updateUser(User user) {
    Query query = em.createQuery("update User set username = :uname where username = :uname");
    query.setParameter("uname", user.getUsername());
    query.executeUpdate();
}

public void deleteUser(User user) {
    Query query = em.createQuery("delete from User where username = :uname");
    query.setParameter("uname", user.getUsername());
    query.executeUpdate();
}

但是当我按下编辑链接或删除按钮时，会出现此错误

    Severe:   javax.faces.el.EvaluationException: javax.persistence.TransactionRequiredException: 
Exception Description: No transaction is currently active

谁能告诉我问题出在哪里。

Answer 1

很高兴尝试这个:

em.getTransaction().begin();
   Query query = em.createQuery("update User set username = :uname where username = :uname");
    query.setParameter("uname", user.getUsername());
    query.executeUpdate();
    em.getTransaction().commit();

如果这可以解决您的问题，请告诉我。