Fork me on GitHub
Edit on GitHub

Migration Guide

Getting here from there.

Version Notes

All Version Notes are available on our Wiki

Struts 2.3 to Struts 2.5

Struts 1 to Struts 2

Tutorials

Comparing Struts 1 and 2

Feature Struts 1 Struts 2
Action classes Struts 1 requires Action classes to extend an abstract base class. A common problem in Struts 1 is programming to abstract classes instead of interfaces. An Struts 2 Action may implement an Action interface, along with other interfaces to enable optional and custom services. Struts 2 provides a base ActionSupport class to implement commonly used interfaces. Albeit, the Action interface is not required. Any POJO object with a execute signature can be used as an Struts 2 Action object.
Threading Model Struts 1 Actions are singletons and must be thread-safe since there will only be one instance of a class to handle all requests for that Action. The singleton strategy places restrictions on what can be done with Struts 1 Actions and requires extra care to develop. Action resources must be thread-safe or synchronized. Struts 2 Action objects are instantiated for each request, so there are no thread-safety issues. (In practice, servlet containers generate many throw-away objects per request, and one more object does not impose a performance penalty or impact garbage collection.)
Servlet Dependency Struts 1 Actions have dependencies on the servlet API since the HttpServletRequest and HttpServletResponse is passed to the execute method when an Action is invoked. Struts 2 Actions are not coupled to a container. Most often the servlet contexts are represented as simple Maps, allowing Actions to be tested in isolation. Struts 2 Actions can still access the original request and response, if required. However, other architectural elements reduce or eliminate the need to access the HttpServetRequest or HttpServletResponse directly.
Testability A major hurdle to testing Struts 1 Actions is that the execute method exposes the Servlet API. A third-party extension, Struts TestCase, offers a set of mock object for Struts 1. Struts 2 Actions can be tested by instantiating the Action, setting properties, and invoking methods. Dependency Injection support also makes testing simpler.
Harvesting Input Struts 1 uses an ActionForm object to capture input. Like Actions, all ActionForms must extend a base class. Since  other JavaBeans cannot be used as ActionForms, developers often create redundant classes to capture input. DynaBeans can used as an alternative to creating conventional ActionForm classes, but, here too, developers may be redescribing existing JavaBeans. \  
Struts 2 uses Action properties as input properties, eliminating the need for a second input object. Input properties may be rich object types which may have their own properties. The Action properties can be accessed from the web page via the taglibs. Struts 2 also supports the ActionForm pattern, as well as POJO form objects and POJO Actions. Rich object types, including business or domain objects, can be used as input/output objects. The ModelDriven feature simplifies taglb references to POJO input objects. \    
     
Expression Language Struts 1 integrates with JSTL, so it uses the JSTL EL. The EL has basic object graph traversal, but relatively weak collection and indexed property support. Struts 2 can use JSTL, but the framework also supports a more powerful and flexible expression language called “Object Graph Notation Language” (OGNL).
Binding values into views Struts 1 uses the standard JSP mechanism for binding objects into the page context for access. Struts 2 uses a “ValueStack” technology so that the taglibs can access values without coupling your view to the object type it is rendering. The ValueStack strategy allows reuse of views across a range of types which may have the same property name but different property types. \
     
Type Conversion Struts 1 ActionForm properties are usually all Strings. Struts 1 uses Commons-Beanutils for type conversion. Converters are per-class, and not configurable per instance. Struts 2 uses OGNL for type conversion. The framework includes converters for basic and common object types and primitives.
Validation Struts 1 supports manual validation via a validate method on the ActionForm, or through an extension to the Commons Validator. Classes can have different validation contexts for the same class, but cannot chain to validations on sub-objects. Struts 2 supports manual validation via the validate method and the XWork Validation framework. The Xwork Validation Framework supports chaining validation into sub-properties using the validations defined for the properties class type and the validation context.
Control Of Action Execution Struts 1 supports separate Request Processors (lifecycles) for each module, but all the Actions in the module must share the same lifecycle. Struts 2 supports creating different lifecycles on a per Action basis via Interceptor Stacks. Custom stacks can be created and used with different Actions, as needed.

(i) See Also

Matt Raible wrote (mid 2005) an interesting whitepaper where he compared various web frameworks. You can view the PDF here: - https://equinox.dev.java.net/framework-comparison/WebFrameworks.pdf - http://www.virtuas.com/files/osl-jwf-01.pdf

##Key Changes From WebWork 2## {#PAGE_26950}

The upgrade path from WebWork 2 to Struts 2 is smooth glide. Here’s the roadmap.

#####System Platform#####

For other changes from WebWork 2, see the “Members to rename”, “New property settings”, “New features or feature changes”, and “Removed or deprecated” sections.

Members to rename

WebWork 2 Struts 2
com.opensymphony.xwork.* com.opensymphony.xwork2.*
com.opensymphony.webwork.* org.apache.struts2.*
xwork.xml struts.xml
webwork.properties struts.properties
DispatcherUtil Dispatcher
com.opensymphony.webwork.config.Configuration org.apache.struts2.config.Settings

The tag prefix conventions in the example applications have changed.

JSP s: <s:form …>
Freemarker s. <@s.form …>
Velocity s #sform ( … )

New property settings

|struts.enable.DynamicMethodInvocation | Enable support for the hardwired action!alias syntax (Default is TRUE)| |—————————————-|————————————————————————|

It is recommended that all applications specify the DynamicMethodInvocation setting for now, since the default may change. The recommended approach to action aliasing is to use wildcard aliases instead of the hardwired bang.

New features and feature changes

prepare

interceptor now uses reflection to call prepare_Method_ where method is the action method configured for the particular action in

struts.xml

.


   <action name="myAction" method="insert" ....>
     .....
   </action>

   // with the above configuration, and PrepareInterceptor in play, 
   // callsequence will be 
   1] prepareInsert() (If it exists)
   2] prepare() (Unless Interceptor's alwaysInvokePrepare parameter is set to false)
   3] insert()


workflow

in

struts-default.xml

) now uses reflection to call

validateMethod

on the action class that implements Validateable interface where

method

is the action method configured for the particular action in

struts.xml

.


<action name="myAction" method="insert" ...>
       ...
    </action>

    // with the above configuration, and DefaultWorkflowInterceptor in play, 
    // call sequence for action that implements Validateable interface will be 
    1] validateInsert()
    2] validate() (unless Interceptor's alwaysInvokeValidate parameter is set to false)
    3] insert()

Removed or deprecated

|AroundInterceptor| The AroundInterceptor has been removed. If your application extends the AroundInterceptor, either import the class into your source code form WebWork 2 (pursuant to the Open Symphony License) and modify it to server as your own base class, or rewrite your interceptor. | |—————–|——————————————————————————————————————————————————————————————————————————————————————————–| |oldSyntax| Support for the “oldSyntax” is removed. | | Rich text editor tag | Rich text editor tag is removed and replaced by Dojo’s rich text editor^[http://dojotoolkit.org/docs/rich_text.html]| |doActionMethod| The convention of trying a “do” form of an action method is not supported. \ \ <action name=”…” method=”submit”>\ …\ </action>\ In WebWork,\ \ + try to execute submit method in the action, fail \ \ + try to execute doSubmit method in the action if Step 1, fail \ \ + fail \ \ In Struts,\ \ + try to execute submit method in the action, fail \ \ + fail \ | | |default method| Calling the “default” method via “doDefault” is not supported. | | IOC framework | Deprecated in WebWork 2.2, the internal IOC framework is removed in Struts 2. Spring is the ObjectFactory default. |

##Migration Strategies## {#PAGE_14221}

The migration strategy of Struts 1 developers moving to Struts 2 involves four non-exclusive paths:

  1. Dual processor, shared resources - Add the Struts 2.0 JARs to your exisitng Struts 1.3 application. Configure S2 to handle
*.action

requests s and let S1 handle

*.do

requests. S1 and S2 can run side by side, within the same web application. Teams can implement new features in the latest version, and migrate older pieces as needed. Optionally, some common resources may be shared between S1 and S2, like messages, validation rules, and Tiles configurations, making for an even smoother migration.

  1. Study known Struts 1 applications, rewritten for Struts 2 - Familiar applications such as the Struts Mailreader are being rewritten to demonstrate best practices for Struts 2.

  2. Use a conversion wizard - It may be possible to create a tool that reads the

web.xml

and S1 configuration files, and generates the corresponding S2 classes, pages, and configuration files. While 100% compatibility is unlikely, we could make a strong effort to convert the application, marking areas that need attention. Comparing the converted files with the originals could also serve as a training tool.

####Next:####

This page originally adopted from http://wiki.apache.org/struts/MigrationStrategy.

##Migration Tools## {#PAGE_13954}

Struts 2 migration tools include the notions of

| (!) | This is a whiteboard describing tools that volunteers might write, given sufficient interest. | |——|—————————————————————————————————|

####Dual Processor, Shared Resources####

#####Struts 1 Emulation#####

execute()

invokes

execute(...)

using properties; return ActionForward name.

####Conversion Wizards####

struts-config.xml

to

struts.xml

,

validations.xml

to a global s2

validations.xml

, and Struts message resources to global s2

resource.properties

.

####Next:####

This page adopted from http://wiki.apache.org/struts/MigrationTools.