Comparing Struts 1 and 2

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Feature Struts 1 Struts 2 Action classes Threading Model Servlet Dependency Testability Harvesting Input Expression Language Binding values into views Type Conversion Validation Control Of Action Execution

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 Actionmayimplement 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即使, the Action interface isnotrequired. Any POJO object with a`execute`signature can be used as an Struts 2 Action object.
Struts 1 Actions are singletons单例 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限制 on what can be done with Struts 1 Actions and requires extra额外的 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问题. (In practice, servlet containers容器 generate many throw-away objects per request, and one more object does not impose强制 a performance penalty or impact影响 garbage collection.)
Struts 1 Actions have dependencies依赖 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耦合to a container. Most often the servlet contexts are represented as simple Maps, allowing Actions to be tested in isolation隔离. Struts 2 Actions can still access进入 the original最初的 request and response, if required. However, other architectural构架 elements reduce减少 or eliminate消除the need to access the HttpServetRequest or HttpServletResponse directly.
A major主要 hurdle障碍 to testing Struts 1 Actions is that the`execute`method exposes直接暴露 the Servlet API. A third-party extension扩展, Struts TestCase, offers a set组of mock object for Struts 1.	Struts 2 Actions can be tested by instantiating the Action, setting properties, and invoking methods. Dependency依赖 Injection注入 support also makes testing simpler.
Struts 1 uses an ActionForm object to capture捕获 input. Like Actions, all ActionForms must extend a base class. Since other JavaBeans cannot be used as ActionForms, developers often create redundant多余 classes to capture input. DynaBeans can used as an alternative选择 to creating conventional传统 ActionForm classes, but, here too, developers may be redescribing重新描述existing JavaBeans.	Struts 2 uses Action properties as input properties, eliminating消除 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模式, 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.
Struts 1 integrates with JSTL, so it uses the JSTL EL. The EL has basic object graph traversal, but relatively相对 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).
Struts 1 uses the standard标准 JSP mechanism机制 for binding绑定 objects into the page context for access.	Struts 2 uses a "ValueStack" technology技术so that the taglibs标签库 can access values without coupling耦合 your view to the object type it is rendering. The ValueStack strategy策略 allows reuse重用 of views across a range of types which may have the same property name but different property types.
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框架 includes converters for basic and common object types and primitives.
Struts 1 supports manual手动 validation验证 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.
Struts 1 supports separate单独 Request Processors处理器(lifecycles) for each module, but all the Actions in the module模块 must share the same lifecycle.	Struts 2 supports creating different lifecycles on a per Action basis via Interceptor Stacks. Custom定制stacks can be created and used with different Actions, as needed.