简单的SpringWebFlow例子及遇到的问题

这段时间在看《Spring 实战》里面有讲Spring Web Flow，觉得里面的例子过于复杂，不适合新手，于是在网上找了个例子，跟着写

以下是项目的目录，我是基于maven搭建项目的

pom.xml文件，插入依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>SpringWebFlow</groupId>
  <artifactId>SpringWebFlow</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SpringWebFlow Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!--SpringMVC所需要的依赖-->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-beans</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-expression</artifactId>
      <version>4.3.7.RELEASE</version>
    </dependency>
    <!--Spring Web Flow所需要的依赖-->
    <dependency>
      <groupId>org.springframework.webflow</groupId>
      <artifactId>spring-binding</artifactId>
      <version>2.4.4.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework.webflow</groupId>
      <artifactId>spring-faces</artifactId>
      <version>2.4.4.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework.webflow</groupId>
      <artifactId>spring-js</artifactId>
      <version>2.4.4.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework.webflow</groupId>
      <artifactId>spring-js-resources</artifactId>
      <version>2.4.4.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework.webflow</groupId>
      <artifactId>spring-webflow</artifactId>
      <version>2.4.4.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.5</version>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>

  </dependencies>

</project>

Spring的配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:webflow="http://www.springframework.org/schema/webflow-config"
       xsi:schemaLocation=" http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://www.springframework.org/schema/webflow-config
    http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.0.xsd">

    <!-- 创建流程执行器，默认表示引用bean id为 'flowRegistry'的流程注册表-->
    <webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry"/>

    <!-- 注册流程注册表 -->
    <webflow:flow-registry id="flowRegistry">
        <webflow:flow-location path="/WEB-INF/flows/hello.xml" id="hello" />
    </webflow:flow-registry>

    <!--作用：帮助DispatcherServlet将流程请求发送给Spring Web Flow-->
    <bean class="org.springframework.webflow.mvc.servlet.FlowHandlerMapping">
        <property name="flowRegistry" ref="flowRegistry"/>
    </bean>

    <!--作用：等同于controller,它会响应发送的流程请求并对其进行处理-->
    <bean id="flowHandlerAdapter" class="org.springframework.webflow.mvc.servlet.FlowHandlerAdapter">
        <property name="flowExecutor" ref="flowExecutor"/>
    </bean>

</beans>

此时流程注册表和jsp文件在同一个文件夹下面，所以不需要配置视图解析器和视图工厂

web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         id="WebApp_ID" version="3.1">
  <servlet>
    <servlet-name>FlowServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>
        classpath:spring-wf.xml
      </param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>FlowServlet</servlet-name>
    <url-pattern>*.flow</url-pattern>
  </servlet-mapping>
</web-app>

流程注册表

<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.springframework.org/schema/webflow
 http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
    <view-state id="cart" >
        <transition on="submit" to="order">
        </transition>
    </view-state>
    <view-state id="order">
        <transition on="confirm" to="finish">
        </transition>
    </view-state>
    <view-state id="finish">
        <transition on="toindex" to="index">
        </transition>
    </view-state>
    <end-state id="index" view="externalRedirect:index.jsp">
    </end-state>
</flow>

<view-state>，如果只有id属性的时候，会在流程文件所在的文件夹寻找id名字的jsp文件作为view。如果明确指定view属性的话，就找这个名字的jsp文件

各种jsp文件

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: I am master
  Date: 2017/5/2
  Time: 14:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
      <h2 align="center">Hello，WebFlow</h2><br/>
      Item1:<a href="hello.flow">加入购物车</a><br/>
      Item2:<a href="hello.flow">加入购物车</a><br/>
      Item2:<a href="hello.flow">加入购物车</a>
</body>
</html>

cart.jsp

<%--
  Created by IntelliJ IDEA.
  User: I am master
  Date: 2017/5/2
  Time: 14:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
       <h2 align="center">购物车</h2><br/>
       衣服:<a href="${flowExecutionUrl}&_eventId=submit">买买买!!!</a><br/>
       裤子:<a href="${flowExecutionUrl}&_eventId=submit">买买买!!!</a><br/>
       鞋子:<a href="${flowExecutionUrl}&_eventId=submit">买买买!!!</a>
</body>
</html>

order.jsp

<%--
  Created by IntelliJ IDEA.
  User: I am master
  Date: 2017/5/2
  Time: 14:45
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
      <h2 align="center">订单</h2><br/>
      <a href="${flowExecutionUrl}&_eventId=confirm">确认支付</a>
</body>
</html>

finish.jsp

<%--
  Created by IntelliJ IDEA.
  User: I am master
  Date: 2017/5/2
  Time: 14:45
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
      <h2 align="center">确认支付</h2><br/>
      <a href="${flowExecutionUrl}&_eventId=toindex">恭喜你，支付成功..</a>
</body>
</html>

运行结果

遇到的问题：

自己写完以后，运行不起来，报404

表达式没有解析，一开始以为是缺少jar包，胡乱加了很多不必要的jar包，但是还是没有解决

错误原因:maven搭建项目web.xml文件默认的版本是2.3，但是我们需要的是3.1,因此将web.xml改为3.1的版本就可以了

很多情况下，我们会将流程注册表和jsp放在不同的文件夹下，这就需要视图解析器和视图工厂

则Spring的配置文件应该为如下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:webflow="http://www.springframework.org/schema/webflow-config"
    xsi:schemaLocation=" http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://www.springframework.org/schema/webflow-config
    http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.0.xsd">  

    <!-- 流程注册器 隐含一句 flow-registry="flowRegistry"
        默认表示引用bean id为 'flowRegistry'的流程注册表-->
    <webflow:flow-executor id="flowExecutor" />  

    <!-- 流程注册表 -->
    <webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices">
        <webflow:flow-location path="/WEB-INF/flows/hello.xml" id="hello" />
    </webflow:flow-registry>  

    <!-- WebFlow 视图解析器 -->
    <bean id="flowViewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
         <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView">
        </property>
        <property name="prefix" value="/WEB-INF/flowView/">
        </property>
        <property name="suffix" value=".jsp">
        </property>
    </bean>  

    <!-- WebFlow 视图工厂构建服务 -->
    <webflow:flow-builder-services id="flowBuilderServices" view-factory-creator="mvcViewFactoryCreator" />  

    <!-- WebFlow 视图工厂创建器，表示使用视图解析器将流程配置(xml)中的逻辑视图交给视图解析器解析 → jsp -->
    <bean id="mvcViewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator">
        <property name="viewResolvers" ref="flowViewResolver" />
    </bean>  

    <!-- 配置WebFlow 处理器映射器-->
    <bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <!-- 这个逻辑视图名的 前缀 必须与流程注册表中的
                    webflow:flow-location 的 id一致，
                    而 后缀 必须是当前DispatcherServlet匹配的地址,也就是
                    必须以.flow结束,否则不被前端控制器处理(视图名必须匹配*.flow)
                 -->
                <!-- 这里代表将请求路径为hello.flow的url交给flowController处理 -->
                <prop key="hello.flow">flowController</prop>
            </props>
        </property>
    </bean>  

    <!--WebFlow 处理器，根据逻辑视图名到流程执行器中找到对应的注册表，进而找到流程配置文件，转到不同的物理视图-->
    <!--主要工作就是负责将url转化成逻辑视图交给视图解析器解析 → jsp-->
    <bean id="flowController" class="org.springframework.webflow.mvc.servlet.FlowController">
        <property name="flowExecutor" ref="flowExecutor" />
    </bean>
</beans>  

小结：

相同点：SpringMVC和流程都实现了mvc设计模式

不同点：在mvc设计模式的实现方面不同

SpringMVC通过编写controller,service类来实现

而流程则通过bean来实现，底层已经帮你实现了，帮你来处理请求跳转到对应的视图界面