15.4. New Web Flow Concepts
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## 15.4. 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.

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15.3. Web Flow Configuration | Home | Appendix A. Flow Definition Language 1.0 to 2.0 Mappings