# Upgrading from 1.0

## Introduction

This chapter shows you how to upgrade existing Web Flow 1 application to Web Flow 2.

## Flow Definition Language

The core concepts behind the flow definition language have not changed between Web Flow 1 and 2. However, some of the element and attribute names have changed. These changes allow for the language to be both more concise and expressive. A complete list of mapping changes is available as an appendix.

### Flow Definition Updater Tool

An automated tool is available to aid in the conversion of existing 1.x flows to the new 2.x style. The tool will convert all the old tag names to their new equivalents, if needed. While the tool will make a best effort attempt at conversion, there is not a one-to-one mapping for all version 1 concepts. If the tool was unable to convert a portion of the flow, it will be marked with a `WARNING` comment in the resulting flow.

The conversion tool requires spring-webflow.jar, spring-core.jar and an XSLT 1.0 engine. Saxon 6.5.5 is recommended.

The tool can be run from the command line with the following command. Required libraries must be available on the classpath. The source must be a single flow to convert. The resulting converted flow will be sent to standard output.

    java org.springframework.webflow.upgrade.WebFlowUpgrader flow-to-upgrade.xml

#### Flow Definition Updater Tool Warnings

##### argument parameter-type no longer supported

Bean actions have been deprecated in favor of EL based evaluate expressions. The EL expression is able to accept method parameters directly, so there is no longer a need for the argument tag. A side effect of this change is that method arguments must be of the correct type before invoking the action.

##### inline-flow is no longer supported

Inline flows are no longer supported. The contents of the inline flow must be moved into a new top-level flow. The inline flow's content has been converted for your convenience.

##### mapping target-collection is no longer supported

Output mappings can no longer add an item to a collection. Only assignment is supported.

##### var bean is no longer supported

The var bean attribute is no longer needed. All spring beans can be resolved via EL.

##### var scope is no longer supported

The var element will place all variable into flow scope. Conversation scope was previously allowed.

### EL Expressions

EL expressions are used heavily throughout the flow definition language. Many of the attributes that appear to be plain text are actually interpreted as EL. The standard EL delimiters (either ${} or #{}) are not necessary and will often cause an exception if they are included.

EL delimiters should be removed where necessary by the updater tool.

## Web Flow Configuration

In Web Flow 1 there were two options available for configuring Web Flow, one using standard spring bean XML and the other using the `webflow-config-1.0` schema. The schema configuration option simplifies the configuration process by keeping long internal class names hidden and enabling contextual auto-complete. The schema configuration option is the only way to configure Web Flow 2.

### Web Flow Bean Configuration

The `FactoryBean` bean XML configuration method used in Web Flow 1 is no longer supported. The schema configuration method should be used instead. In particular beans defining `FlowExecutorFactoryBean` and `XmlFlowRegistryFactoryBean` should be updated. Continue reading Web Flow Schema Configuration for details.

### Web Flow Schema Configuration

The `webflow-config` configuration schema has also changed slightly from version 1 to 2. The simplest way to update your application is modify the version of the schema to 2.0 then fix any errors in a schema aware XML editor. The most common change is add 'flow-' to the beginning of the elements defined by the schema.

    <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">

#### flow-executor

The flow executor is the core Web Flow configuration element. This element replaces previous `FlowExecutorFactoryBean` bean definitions.

    <webflow:flow-executor id="flowExecutor" />

#### flow-execution-listeners

Flow execution listeners are also defined in the flow executor. Listeners are defined using standard bean definitions and added by reference.

    <webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
        <webflow:flow-execution-listeners>
            <webflow:listener ref="securityFlowExecutionListener"/>
        </webflow:flow-execution-listeners>
    </webflow:flow-executor>

    <bean id="securityFlowExecutionListener"
          class="org.springframework.webflow.security.SecurityFlowExecutionListener" />

#### flow-registry

The `flow-registry` contains a set of `flow-location`s. Every flow definition used by Web Flow must be added to the registry. This element replaces previous `XmlFlowRegistryFactoryBean` bean definitions.

    <webflow:flow-registry id="flowRegistry">
        <webflow:flow-location path="/WEB-INF/hotels/booking/booking.xml" />
    </webflow:flow-registry>

### Flow Controller

The package name for flow controllers has changed from `org.springframework.webflow.executor.mvc.FlowController` and is now `org.springframework.webflow.mvc.servlet.FlowController` for Servlet MVC requests. The portlet flow controller `org.springframework.webflow.executor.mvc.PortletFlowController` has been replaced by a flow handler adapter available at `org.springframework.webflow.mvc.portlet.FlowHandlerAdapter`. They will need to be updated in the bean definitions.

### Flow URL Handler

The default URL handler has changed in Web Flow 2. The flow identifier is now derived from the URL rather then passed explicitly. In order to maintain comparability with existing views and URL structures a `WebFlow1FlowUrlHandler` is available.

    <bean name="/pos.htm" class="org.springframework.webflow.mvc.servlet.FlowController">
        <property name="flowExecutor" ref="flowExecutor" />
        <property name="flowUrlHandler">
            <bean class="org.springframework.webflow.context.servlet.WebFlow1FlowUrlHandler" />
        </property>
    </bean>

### View Resolution

Web Flow 2 by default will both select and render views. View were previously selected by Web Flow 1 and then rendered by an external view resolver.

In order for version 1 flows to work in Web Flow 2 the default view resolver must be overridden. A common use case is to use Apache Tiles for view resolution. The following configuration will replace the default view resolver with a Tiles view resolver. The `tilesViewResolver` in this example can be replaced with any other view resolver.

    <webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices">
    	<web:flow-location path="..." />
        ...
    </webflow:flow-registry>

    <webflow:flow-builder-services id="flowBuilderServices"
                                   view-factory-creator="viewFactoryCreator"/>

    <bean id="viewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator">
        <property name="viewResolvers" ref="tilesViewResolver" />
    </bean>

    <bean id="tilesViewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.tiles.TilesJstlView" />
    </bean>

    <bean class="org.springframework.web.servlet.view.tiles.TilesConfigurer">
        <property name="definitions" value="/WEB-INF/tiles-def.xml" />
    </bean>

## New Web Flow Concepts

### Automatic Model Binding

Web Flow 1 required Spring MVC based flows to manually call `FormAction` methods, notably: `setupForm`, `bindAndValidate` to process form views. Web Flow 2 now provides automatic model setup and binding using the `model` attribute for `view-state`s. Please see the Binding to a Model section for details.

### OGNL vs EL

Web Flow 1 used OGNL exclusively for expressions within the flow definitions. Web Flow 2 adds support for Unified EL. United EL is used when it is available, OGNL will continue to be used when a Unified EL implementation is not available. Please see the Expression Language chapter for details.

### Flash Scope

Flash scope in Web Flow 1 lived across the current request and into the next request. This was conceptually similar to Web Flow 2's view scope concept, but the semantics were not as well defined. In Web Flow 2, flash scope is cleared after every view render. This makes flashScope semantics in Web Flow consistent with other web frameworks.

### Spring Faces

Web Flow 2 offers significantly improved integration with JavaServerFaces. Please see the JSF Integration chapter for details.

### External Redirects

External redirects in Web Flow 1 were always considered context relative. In Web Flow 2, if the redirect URL begins with a slash, it is considered servlet-relative instead of context-relative. URLs without a leading slash are still context relative.