JSF - JSF 实现如何识别动作？答案

【问题标题】：JSF - How does the JSF implementation identify the action?JSF - JSF 实现如何识别动作？
【发布时间】：2013-12-21 17:17:01
【问题描述】：

我试图了解 JSF 实现如何识别用户的各种可能操作。在我整理的简单应用程序中，我在login.xhtml 页面中配置了以下字段。

User name - input field

Password - password field

Login button

Cancel button

login.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core">

<h:head id="head_id" ></h:head>
<h:body id="body_id">
    <h:form id="loginForm_id">
        <h:panelGrid id="loginPanelGrid_id">
            <h:outputText id="nameLabel_id" value="Name"></h:outputText>
            <h:inputText id="nameInput_id" value="#{loginBean.name}"></h:inputText>
            <h:outputText id="passwordLabel_id" value="Password"></h:outputText>
            <h:inputSecret id="passwordInput_id" value="#{loginBean.password}"></h:inputSecret>
        </h:panelGrid>
        <h:commandButton id="loginBtn_id" value="Do Login" action="#{loginBean.login}"></h:commandButton>
        <h:commandButton id="CancelBtn_id" value="Cancel Login" action="#{loginBean.cancel}"></h:commandButton>
    </h:form>
</h:body>
</html>

LoginBean.java

package com.ila;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;

@ManagedBean
@SessionScoped

    public class LoginBean {
        private String name;
        private String password;

        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getPassword() {
            return password;
        }
        public void setPassword(String password) {
            this.password = password;
        }

        public String login() {
            if ("a".equals(name)) return "success";
            else return "failure";
        }

        public String cancel() {
            return "cancel";
        }
    }

从 login.xhtml 生成的 html 代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head></head>
<body>
    <form id="loginForm_id" name="loginForm_id" method="post"
        action="/JSF2TestProject/faces/simple.xhtml"
        enctype="application/x-www-form-urlencoded">

        <input type="hidden" name="loginForm_id" value="loginForm_id" />

        <table id="loginForm_id:loginPanelGrid_id">
            <tbody>
                <tr>
                    <td><span id="loginForm_id:nameLabel_id">Name</span></td>
                </tr>
                <tr>
                    <td><input id="loginForm_id:nameInput_id" type="text"
                        name="loginForm_id:nameInput_id" value="a" /></td>
                </tr>
                <tr>
                    <td><span id="loginForm_id:passwordLabel_id">Password</span></td>
                </tr>
                <tr>
                    <td><input id="loginForm_id:passwordInput_id" type="password"
                        name="loginForm_id:passwordInput_id" value="" /></td>
                </tr>
            </tbody>
        </table>
        <input id="loginForm_id:loginBtn_id" type="submit"
            name="loginForm_id:loginBtn_id" value="Do Login" />

        <input id="loginForm_id:CancelBtn_id" type="submit"
            name="loginForm_id:CancelBtn_id" value="Cancel Login" />

        <input type="hidden" name="javax.faces.ViewState" id="javax.faces.ViewState"
            value="H4sIAAAAAAAAAI1QTUoDMRj9Ou1QW2ztDwouBBduVJgD6MIiWCwqFUQRXWicie2UTBKTzHS6KR7BAwhewEuIawUXbryDHsCVSR2nuij4Qd6XfCHvvbz7d7C5FFDtoQg5ofKJs41kdw9xO//28Dh3/pIFqwlFwpDXRK5iogUF1RVYdhnxYr7RAFPT/SmNFb0sBQuEdXzaZCI48701jqTsM+G1KA+VHoQC6qe7IzmCaMdpX/Swq9Zvno/vKnKZWAAx1zy58AqGkDWM6c7mutJTfihg1fDEziVysXRcFnBGMVXOYasdKi23tC8Yx0INdvBAQlI1rSCgPHawRcPg9yVXYEeIhDgSkIuY78G4Yq5VVyapjv44UdQYL3xz+16a+cjCJmMEI/q0KK5fbz8/LMicJB5inhmah2UFJcJcRI7M9AAraaZV4Nz0Wa5Nz//JnaIAp5n/ZPaPVM2maKBkYMZAzUA90Ula/AXEIFMaOgIAAA=="
            autocomplete="off" />
    </form>
</body>
</html>

faces-config.xml

<?xml version="1.0" encoding="UTF-8"?>

<faces-config
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_1.xsd"
    version="2.1">
    <navigation-rule>
        <display-name>login.xhtml</display-name>
        <from-view-id>/login.xhtml</from-view-id>
        <navigation-case>
            <from-outcome>success</from-outcome>
            <to-view-id>/welcome.xhtml</to-view-id>
        </navigation-case>
    </navigation-rule>
    <navigation-rule>
        <display-name>login.xhtml</display-name>
        <from-view-id>/login.xhtml</from-view-id>
        <navigation-case>
            <from-outcome>failure</from-outcome>
            <to-view-id>/login.xhtml</to-view-id>
        </navigation-case>
    </navigation-rule>
    <navigation-rule>
        <display-name>login.xhtml</display-name>
        <from-view-id>/login.xhtml</from-view-id>
        <navigation-case>
            <from-outcome>cancel</from-outcome>
            <to-view-id>/login.xhtml</to-view-id>
        </navigation-case>
    </navigation-rule>
</faces-config>

UI 渲染（屏幕截图）

问题 1

鉴于生成的 html 没有发送任何参数来标识单击了哪个按钮（至少我看不到），JSF 实现如何确定是单击“登录”按钮还是“取消登录”按钮按钮被点击了？

问题 2

这两个隐藏（由 JSF 实现生成）字段（如下所示）的用途是什么？这些和问题1有关吗？

<input type="hidden" name="loginForm_id" value="loginForm_id" />
<input type="hidden" name="javax.faces.ViewState" id="javax.faces.ViewState"
            value="H4sIAAAAAAAAAI1QTUoDMRj9Ou1QW2ztDwouBBduVJgD6MIiWCwqFUQRXWicie2UTBKTzHS6KR7BAwhewEuIawUXbryDHsCVSR2nuij4Qd6XfCHvvbz7d7C5FFDtoQg5ofKJs41kdw9xO//28Dh3/pIFqwlFwpDXRK5iogUF1RVYdhnxYr7RAFPT/SmNFb0sBQuEdXzaZCI48701jqTsM+G1KA+VHoQC6qe7IzmCaMdpX/Swq9Zvno/vKnKZWAAx1zy58AqGkDWM6c7mutJTfihg1fDEziVysXRcFnBGMVXOYasdKi23tC8Yx0INdvBAQlI1rSCgPHawRcPg9yVXYEeIhDgSkIuY78G4Yq5VVyapjv44UdQYL3xz+16a+cjCJmMEI/q0KK5fbz8/LMicJB5inhmah2UFJcJcRI7M9AAraaZV4Nz0Wa5Nz//JnaIAp5n/ZPaPVM2maKBkYMZAzUA90Ula/AXEIFMaOgIAAA=="
            autocomplete="off" />

【问题讨论】：

标签： jsf-2

【解决方案1】：

动作由控件的名称标识，JSF 在内部将这些映射到 bean 中的实际方法。

ViewState 是表单在渲染之前的状态，这样很容易将之前的表单状态与当前的表单状态进行比较（以便触发更改事件等）。

【讨论】：