JSF 2.0 命令按钮操作被调用两次

Question

我在使用 JSF 时遇到了问题，希望有人能帮助我。 我有一个 Facelets xhtml 页面，带有 SessionScoped 托管 bean。当在页面上按下命令按钮时，会在 bean 中调用一个方法，该方法会在页面上动态创建另一个带有另一个命令按钮的表单。到目前为止，效果很好，但是当在页面上按下新创建的按钮时，它会以某种方式调用操作方法两次。 以下是我的支持 bean 中的代码示例：

动态创建新表单并且工作正常的方法：（我使用 setActionExpression 将操作绑定到按钮）

public void doCreateScreen() {
    FacesContext context = FacesContext.getCurrentInstance();
    Application application = context.getApplication();

    panelGrid.getChildren().clear();

    HtmlPanelGrid checkBoxGrid = (HtmlPanelGrid) application
            .createComponent(HtmlPanelGrid.COMPONENT_TYPE);
    checkBoxGrid.setColumns(columnNumber + 1);
    checkBoxGrid.getChildren().clear();

    for (int i = 1; i < rowNumber + 1; i++) {
        for (int j = 1; j < columnNumber + 1; j++) {
            HtmlSelectBooleanCheckbox tmpCheckBox = (HtmlSelectBooleanCheckbox) application
                    .createComponent(HtmlSelectBooleanCheckbox.COMPONENT_TYPE);
            String id = String.valueOf(i * columnNumber + j);
            tmpCheckBox.setId("box" + id);
            tmpCheckBox.setValue(true);
            checkBoxGrid.getChildren().add(tmpCheckBox);
        }
    }

    HtmlCommandButton createSeatsButton = (HtmlCommandButton) application
            .createComponent(HtmlCommandButton.COMPONENT_TYPE);
    createSeatsButton.setValue("Create Screen");

    MethodExpression createSeats = application.getExpressionFactory()
            .createMethodExpression(context.getELContext(),
                    "#{screencontroller.doCreateSeats}", null,
                    new Class<?>[0]);
    createSeatsButton.setActionExpression(createSeats);

    panelGrid.getChildren().add(checkBoxGrid);
    panelGrid.getChildren().add(createSeatsButton);

}

这个方法被调用两次：

    public void doCreateSeats() {

        try {
            screen = screenOperator.createScreen(screen);

            for (int i = 1; i < rowNumber + 1; i++) {
                for (int j = 1; j < columnNumber + 1; j++) {
                    Seat seat = new Seat();
                    seat.setRow(i);
                    seat.setSeatNumber(j);
                    seat = screenOperator.createSeat(seat,
                            screen.getIdScreen());
                }
            }

            panelGrid.getChildren().clear();

        } catch (MovieTicketsException e) {
            // TODO
            e.printStackTrace();
        }

}

以及 xhtml 源：

        <div class="addform">
    <h1>Add new screen</h1>

    <h:form prependId="false">
        <h:panelGrid columns="2">
            <h:outputText value="Description:"></h:outputText>
            <h:inputText value="#{screencontroller.screen.description}"
                title="Description" id="Description" required="true"
                class="inputfield">
                <f:validateLength minimum="1" maximum="255"></f:validateLength>
            </h:inputText>


            <h:outputText value="Rows:"></h:outputText>
            <h:selectOneMenu value="#{screencontroller.rowNumber}" title="Rows"
                id="Rows" required="true" class="inputfield">
                <f:selectItems value="#{screencontroller.rowsSelectItems}">
                </f:selectItems>
            </h:selectOneMenu>

            <h:outputText value="Seats in a row:"></h:outputText>
            <h:selectOneMenu value="#{screencontroller.columnNumber}"
                title="Columns" id="Columns" required="true" class="inputfield">
                <f:selectItems value="#{screencontroller.rowsSelectItems}">
                </f:selectItems>
            </h:selectOneMenu>

            <h:outputLabel></h:outputLabel>
            <h:commandButton action="#{screencontroller.doCreateScreen}"
                value="Submit"></h:commandButton>

        </h:panelGrid>
    </h:form> <h:message for="Description" class="errormsg"></h:message> <h:message
        for="Cinema" class="errormsg"></h:message></div>

    <div class="listdiv"><h:form prependId="false">
        <h:panelGrid binding="#{screencontroller.panelGrid}" columns="1">
        </h:panelGrid>
    </h:form></div>

    </div>

I'我刚刚开始学习 jsf，所以也许我做的事情真的错了，但如果有人能解释这一点，我将非常感激。

谢谢