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.
|