Java Doc for ActionServlet.java in  » Web-Framework » struts-1.3.8 » org » apache » struts » action » Java Source Code / Java DocumentationJava Source Code and Java Documentation

ActionServlet provides the "controller" in the Model-View-Controller (MVC) design pattern for web applications that is commonly known as "Model 2". This nomenclature originated with a description in the JavaServerPages Specification, version 0.92, and has persisted ever since (in the absence of a better name).

Generally, a "Model 2" application is architected as follows:

• The user interface will generally be created with server pages, which will not themselves contain any business logic. These pages represent the "view" component of an MVC architecture.
• Forms and hyperlinks in the user interface that require business logic to be executed will be submitted to a request URI that is mapped to this servlet.
• There can be one instance of this servlet class, which receives and processes all requests that change the state of a user's interaction with the application. The servlet delegates the handling of a request to a RequestProcessor object. This component represents the "controller" component of an MVC architecture.
• The RequestProcessor selects and invokes an Action class to perform the requested business logic, or delegates the response to another resource.
• The Action classes can manipulate the state of the application's interaction with the user, typically by creating or modifying JavaBeans that are stored as request or session attributes (depending on how long they need to be available). Such JavaBeans represent the "model" component of an MVC architecture.
• Instead of producing the next page of the user interface directly, Action classes generally return an ActionForward to indicate which resource should handle the response. If the Action does not return null, the RequestProcessor forwards or redirects to the specified resource (by utilizing RequestDispatcher.forward or Response.sendRedirect) so as to produce the next page of the user interface.

The standard version of RequestsProcessor implements the following logic for each incoming HTTP request. You can override some or all of this functionality by subclassing this object and implementing your own version of the processing.

• Identify, from the incoming request URI, the substring that will be used to select an action procedure.
• Use this substring to map to the Java class name of the corresponding action class (an implementation of the Action interface).
• If this is the first request for a particular Action class, instantiate an instance of that class and cache it for future use.
• Optionally populate the properties of an ActionForm bean associated with this mapping.
• Call the execute method of this Action class, passing on a reference to the mapping that was used, the relevant form-bean (if any), and the request and the response that were passed to the controller by the servlet container (thereby providing access to any specialized properties of the mapping itself as well as to the ServletContext).

The standard version of ActionServlet is configured based on the following servlet initialization parameters, which you will specify in the web application deployment descriptor (/WEB-INF/web.xml) for your application. Subclasses that specialize this servlet are free to define additional initialization parameters.

• config - Comma-separated list of context-relative path(s) to the XML resource(s) containing the configuration information for the default module. (Multiple files support since Struts 1.1) [/WEB-INF/struts-config.xml].
• config/${module} - Comma-separated list of Context-relative path(s) to the XML resource(s) containing the configuration information for the module that will use the specified prefix (/${module}). This can be repeated as many times as required for multiple modules. (Since Struts 1.1)
• configFactory - The Java class name of the ModuleConfigFactory used to create the implementation of the ModuleConfig interface.
• convertNull - Force simulation of the Struts 1.0 behavior when populating forms. If set to true, the numeric Java wrapper class types (like java.lang.Integer) will default to null (rather than 0). (Since Struts 1.1) [false]
• rulesets - Comma-delimited list of fully qualified classnames of additional org.apache.commons.digester.RuleSet instances that should be added to the Digester that will be processing struts-config.xml files. By default, only the RuleSet for the standard configuration elements is loaded. (Since Struts 1.1)
• validating - Should we use a validating XML parser to process the configuration file (strongly recommended)? [true]
• chainConfig - Comma-separated list of either context-relative or classloader path(s) to load commons-chain catalog definitions from. If none specified, the default Struts catalog that is provided with Struts will be used.

The set of public identifiers, and corresponding resource names, for the versions of the configuration file DTDs that we know about.

Gracefully release any configDigester instance that we have created.

Look up and return the RequestProcessor responsible for the specified module, creating a new one if necessary.

Initialize this servlet.

Saves a String[] of module prefixes in the ServletContext under Globals.MODULE_PREFIXES_KEY.

Initialize the servlet mapping under which our controller servlet is being accessed.

Checks if the current actionConfig is using the correct class based on the class of its ancestor ActionConfig.

Checks if the current exceptionConfig is using the correct class based on the class of its configuration ancestor.

Extend the exception's configuration as necessary.

Checks if the current beanConfig is using the correct class based on the class of its ancestor form bean config.

Checks if the current forwardConfig is using the correct class based on the class of its configuration ancestor.

Extend the forward's configuration as necessary.

Takes a comma-delimited string and splits it into paths, then resolves those paths using the ServletContext and appropriate ClassLoader.

Comma-separated list of context or classloader-relative path(s) that contain the configuration for the default commons-chain catalog(s).

Comma-separated list of context-relative path(s) to our configuration resource(s) for the default module.

The Digester used to produce ModuleConfig objects from a Struts configuration file.

The flag to request backwards-compatible conversions for form bean properties of the Java wrapper class types.

The resources object for our internal resources.

The Java base name of our internal resources.

Commons Logging instance.

The set of public identifiers, and corresponding resource names, for the versions of the configuration file DTDs that we know about. There MUST be an even number of Strings in this list!

The URL pattern to which we are mapped in our web application deployment descriptor.

The servlet name under which we are registered in our web application deployment descriptor.

Remember a servlet mapping from our web application deployment descriptor, if it is for this servlet.

Gracefully shut down this controller servlet, releasing any resources that were allocated at initialization.

Gracefully release any configDigester instance that we have created.

Gracefully terminate use of the internal MessageResources.

Gracefully terminate use of any modules associated with this application (if any).

Process an HTTP "GET" request.

Process an HTTP "POST" request.

Return the MessageResources instance containing our internal message strings.

Return the module configuration object for the currently selected module.

Look up and return the RequestProcessor responsible for the specified module, creating a new one if necessary.

Initialize this servlet. Most of the processing has been factored into support methods so that you can override particular functionality at a fairly granular level.

Parse the configuration documents specified by the chainConfig init-param to configure the default org.apache.commons.chain.Catalog that is registered in the CatalogFactory instance for this application.

Create (if needed) and return a new Digester instance that has been initialized to process Struts module configuration files and configure a corresponding ModuleConfig object (which must be pushed on to the evaluation stack before parsing begins).

Initialize our internal MessageResources bundle.

Initialize the action configs for the specified module.

Initialize the module configuration information for the specified module.

Initialize the factory used to create the module configuration.

Initialize the exception handlers for the specified module.

Initialize the form beans for the specified module.

Initialize the forwards for the specified module.

Initialize the application MessageResources for the specified module.

Initialize the plug ins for the specified module.

Saves a String[] of module prefixes in the ServletContext under Globals.MODULE_PREFIXES_KEY. NOTE - the "" prefix for the default module is not included in this list.

Initialize other global characteristics of the controller servlet.

Initialize the servlet mapping under which our controller servlet is being accessed. This will be used in the &html:form> tag to generate correct destination URLs for form submissions.

Parses one module config file.

Parses one module config file.

Perform the standard request processing for this request, and create the corresponding response.

Checks if the current actionConfig is using the correct class based on the class of its ancestor ActionConfig.

Extend the action's configuration as necessary.

Checks if the current exceptionConfig is using the correct class based on the class of its configuration ancestor. If actionConfig is provided, then this method will process the exceptionConfig as part of that actionConfig. If actionConfig is null, the exceptionConfig will be processed as a global forward.

Extend the exception's configuration as necessary. If actionConfig is provided, then this method will process the exceptionConfig as part of that actionConfig. If actionConfig is null, the exceptionConfig will be processed as a global forward.

Checks if the current beanConfig is using the correct class based on the class of its ancestor form bean config.

Extend the form bean's configuration as necessary.

Checks if the current forwardConfig is using the correct class based on the class of its configuration ancestor. If actionConfig is provided, then this method will process the forwardConfig as part of that actionConfig. If actionConfig is null, the forwardConfig will be processed as a global forward.

Extend the forward's configuration as necessary. If actionConfig is provided, then this method will process the forwardConfig as part of that actionConfig. If actionConfig is null, the forwardConfig will be processed as a global forward.

Takes a comma-delimited string and splits it into paths, then resolves those paths using the ServletContext and appropriate ClassLoader. When loading from the classloader, multiple resources per path are supported to support, for example, multiple jars containing the same named config file.