org.apache.struts.action
Class ActionServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.apache.struts.action.ActionServlet

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

Direct Known Subclasses:

MockActionServlet, RedeployableActionServlet

public class ActionServlet
extends HttpServlet

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.

Version:

$Rev: 592630 $ $Date: 2005-10-14 19:54:16 -0400 (Fri, 14 Oct 2005) $

See Also:

Serialized Form

Field Summary

protected String	chainConfig Comma-separated list of context or classloader-relative path(s) that contain the configuration for the default commons-chain catalog(s).
protected String	config Comma-separated list of context-relative path(s) to our configuration resource(s) for the default module.
protected org.apache.commons.digester.Digester	configDigester The Digester used to produce ModuleConfig objects from a Struts configuration file.
protected boolean	convertNull The flag to request backwards-compatible conversions for form bean properties of the Java wrapper class types.
protected MessageResources	internal The resources object for our internal resources.
protected String	internalName The Java base name of our internal resources.
protected static Log	log Commons Logging instance.
protected String[]	registrations The set of public identifiers, and corresponding resource names, for the versions of the configuration file DTDs that we know about.
protected String	servletMapping The URL pattern to which we are mapped in our web application deployment descriptor.
protected String	servletName The servlet name under which we are registered in our web application deployment descriptor.

Constructor Summary

ActionServlet()

Method Summary

void	addServletMapping(String servletName, String urlPattern) Remember a servlet mapping from our web application deployment descriptor, if it is for this servlet.
void	destroy() Gracefully shut down this controller servlet, releasing any resources that were allocated at initialization.
protected void	destroyConfigDigester() Gracefully release any configDigester instance that we have created.
protected void	destroyInternal() Gracefully terminate use of the internal MessageResources.
protected void	destroyModules() Gracefully terminate use of any modules associated with this application (if any).
void	doGet(HttpServletRequest request, HttpServletResponse response) Process an HTTP "GET" request.
void	doPost(HttpServletRequest request, HttpServletResponse response) Process an HTTP "POST" request.
MessageResources	getInternal() Return the MessageResources instance containing our internal message strings.
protected ModuleConfig	getModuleConfig(HttpServletRequest request) Return the module configuration object for the currently selected module.
protected RequestProcessor	getRequestProcessor(ModuleConfig config) Look up and return the RequestProcessor responsible for the specified module, creating a new one if necessary.
void	init() Initialize this servlet.
protected void	initChain() Parse the configuration documents specified by the chainConfig init-param to configure the default Catalog that is registered in the CatalogFactory instance for this application.
protected org.apache.commons.digester.Digester	initConfigDigester() 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).
protected void	initInternal() Initialize our internal MessageResources bundle.
protected void	initModuleActions(ModuleConfig config) Initialize the action configs for the specified module.
protected ModuleConfig	initModuleConfig(String prefix, String paths) Initialize the module configuration information for the specified module.
protected void	initModuleConfigFactory() Initialize the factory used to create the module configuration.
protected void	initModuleExceptionConfigs(ModuleConfig config) Initialize the exception handlers for the specified module.
protected void	initModuleFormBeans(ModuleConfig config) Initialize the form beans for the specified module.
protected void	initModuleForwards(ModuleConfig config) Initialize the forwards for the specified module.
protected void	initModuleMessageResources(ModuleConfig config) Initialize the application MessageResources for the specified module.
protected void	initModulePlugIns(ModuleConfig config) Initialize the plug ins for the specified module.
protected void	initModulePrefixes(ServletContext context) Saves a String[] of module prefixes in the ServletContext under Globals.MODULE_PREFIXES_KEY.
protected void	initOther() Initialize other global characteristics of the controller servlet.
protected void	initServlet() Initialize the servlet mapping under which our controller servlet is being accessed.
protected void	parseModuleConfigFile(org.apache.commons.digester.Digester digester, String path) Deprecated. use parseModuleConfigFile(Digester digester, URL url) instead
protected void	parseModuleConfigFile(org.apache.commons.digester.Digester digester, URL url) Parses one module config file.
protected void	process(HttpServletRequest request, HttpServletResponse response) Perform the standard request processing for this request, and create the corresponding response.
protected ActionConfig	processActionConfigClass(ActionConfig actionConfig, ModuleConfig moduleConfig) Checks if the current actionConfig is using the correct class based on the class of its ancestor ActionConfig.
protected void	processActionConfigExtension(ActionConfig actionConfig, ModuleConfig moduleConfig) Extend the action's configuration as necessary.
protected ExceptionConfig	processExceptionConfigClass(ExceptionConfig exceptionConfig, ModuleConfig moduleConfig, ActionConfig actionConfig) Checks if the current exceptionConfig is using the correct class based on the class of its configuration ancestor.
protected void	processExceptionExtension(ExceptionConfig exceptionConfig, ModuleConfig moduleConfig, ActionConfig actionConfig) Extend the exception's configuration as necessary.
protected FormBeanConfig	processFormBeanConfigClass(FormBeanConfig beanConfig, ModuleConfig moduleConfig) Checks if the current beanConfig is using the correct class based on the class of its ancestor form bean config.
protected void	processFormBeanExtension(FormBeanConfig beanConfig, ModuleConfig moduleConfig) Extend the form bean's configuration as necessary.
protected ForwardConfig	processForwardConfigClass(ForwardConfig forwardConfig, ModuleConfig moduleConfig, ActionConfig actionConfig) Checks if the current forwardConfig is using the correct class based on the class of its configuration ancestor.
protected void	processForwardExtension(ForwardConfig forwardConfig, ModuleConfig moduleConfig, ActionConfig actionConfig) Extend the forward's configuration as necessary.
protected List	splitAndResolvePaths(String paths) Takes a comma-delimited string and splits it into paths, then resolves those paths using the ServletContext and appropriate ClassLoader.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

protected static Log log

Commons Logging instance.

Since:

Struts 1.1

config

protected String config

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

chainConfig

protected String chainConfig

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

configDigester

protected org.apache.commons.digester.Digester configDigester

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

Since:

Struts 1.1

convertNull

protected boolean convertNull

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

Since:

Struts 1.1

internal

protected MessageResources internal

The resources object for our internal resources.

internalName

protected String internalName

The Java base name of our internal resources.

Since:

Struts 1.1

registrations

protected String[] registrations

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!

servletMapping

protected String servletMapping

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

servletName

protected String servletName

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

Constructor Detail

ActionServlet

public ActionServlet()

Method Detail

destroy

public void destroy()

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

Specified by:

destroy in interface Servlet

Overrides:

destroy in class GenericServlet

init

public void init()
          throws ServletException

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.

Overrides:

init in class GenericServlet

Throws:

ServletException - if we cannot configure ourselves correctly

initModulePrefixes

protected void initModulePrefixes(ServletContext context)

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.

Parameters:

context - The servlet context.

Since:

Struts 1.2

doGet

public void doGet(HttpServletRequest request,
                  HttpServletResponse response)
           throws IOException,
                  ServletException

Process an HTTP "GET" request.

Overrides:

doGet in class HttpServlet

Parameters:

request - The servlet request we are processing

response - The servlet response we are creating

Throws:

IOException - if an input/output error occurs

ServletException - if a servlet exception occurs

doPost

public void doPost(HttpServletRequest request,
                   HttpServletResponse response)
            throws IOException,
                   ServletException

Process an HTTP "POST" request.

Overrides:

doPost in class HttpServlet

Parameters:

request - The servlet request we are processing

response - The servlet response we are creating

Throws:

IOException - if an input/output error occurs

ServletException - if a servlet exception occurs

addServletMapping

public void addServletMapping(String servletName,
                              String urlPattern)

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

Parameters:

servletName - The name of the servlet being mapped

urlPattern - The URL pattern to which this servlet is mapped

getInternal

public MessageResources getInternal()

Return the MessageResources instance containing our internal message strings.

Returns:

the MessageResources instance containing our internal message strings.

Since:

Struts 1.1

destroyModules

protected void destroyModules()

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

Since:

Struts 1.1

destroyConfigDigester

protected void destroyConfigDigester()

Gracefully release any configDigester instance that we have created.

Since:

Struts 1.1

destroyInternal

protected void destroyInternal()

Gracefully terminate use of the internal MessageResources.

getModuleConfig

protected ModuleConfig getModuleConfig(HttpServletRequest request)

Return the module configuration object for the currently selected module.

Parameters:

request - The servlet request we are processing

Returns:

The module configuration object for the currently selected module.

Since:

Struts 1.1

getRequestProcessor

protected RequestProcessor getRequestProcessor(ModuleConfig config)
                                        throws ServletException

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

Parameters:

config - The module configuration for which to acquire and return a RequestProcessor.

Returns:

The RequestProcessor responsible for the specified module,

Throws:

ServletException - If we cannot instantiate a RequestProcessor instance a UnavailableException is thrown, meaning your application is not loaded and will not be available.

Since:

Struts 1.1

initModuleConfigFactory

protected void initModuleConfigFactory()

Initialize the factory used to create the module configuration.

Since:

Struts 1.2

initModuleConfig

protected ModuleConfig initModuleConfig(String prefix,
                                        String paths)
                                 throws ServletException

Initialize the module configuration information for the specified module.

Parameters:

prefix - Module prefix for this module

paths - Comma-separated list of context-relative resource path(s) for this modules's configuration resource(s)

Returns:

The new module configuration instance.

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.1

parseModuleConfigFile

protected void parseModuleConfigFile(org.apache.commons.digester.Digester digester,
                                     String path)
                              throws UnavailableException

Deprecated. use parseModuleConfigFile(Digester digester, URL url) instead

Parses one module config file.

Parameters:

digester - Digester instance that does the parsing

path - The path to the config file to parse.

Throws:

UnavailableException - if file cannot be read or parsed

Since:

Struts 1.2

parseModuleConfigFile

protected void parseModuleConfigFile(org.apache.commons.digester.Digester digester,
                                     URL url)
                              throws UnavailableException

Parses one module config file.

Parameters:

digester - Digester instance that does the parsing

url - The url to the config file to parse.

Throws:

UnavailableException - if file cannot be read or parsed

Since:

Struts 1.3

initModulePlugIns

protected void initModulePlugIns(ModuleConfig config)
                          throws ServletException

Initialize the plug ins for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.1

initModuleFormBeans

protected void initModuleFormBeans(ModuleConfig config)
                            throws ServletException

Initialize the form beans for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.3

processFormBeanExtension

protected void processFormBeanExtension(FormBeanConfig beanConfig,
                                        ModuleConfig moduleConfig)
                                 throws ServletException

Extend the form bean's configuration as necessary.

Parameters:

beanConfig - the configuration to process.

moduleConfig - the module configuration for this module.

Throws:

ServletException - if initialization cannot be performed.

processFormBeanConfigClass

protected FormBeanConfig processFormBeanConfigClass(FormBeanConfig beanConfig,
                                                    ModuleConfig moduleConfig)
                                             throws ServletException

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

Parameters:

beanConfig - The form bean to check.

moduleConfig - The config for the current module.

Returns:

The form bean config using the correct class as determined by the config's ancestor and its own overridden value.

Throws:

UnavailableException - if an instance of the form bean config class cannot be created.

ServletException - on class creation error

initModuleForwards

protected void initModuleForwards(ModuleConfig config)
                           throws ServletException

Initialize the forwards for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

processForwardExtension

protected void processForwardExtension(ForwardConfig forwardConfig,
                                       ModuleConfig moduleConfig,
                                       ActionConfig actionConfig)
                                throws ServletException

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.

Parameters:

forwardConfig - the configuration to process.

moduleConfig - the module configuration for this module.

actionConfig - If applicable, the config for the current action.

Throws:

ServletException - if initialization cannot be performed.

processForwardConfigClass

protected ForwardConfig processForwardConfigClass(ForwardConfig forwardConfig,
                                                  ModuleConfig moduleConfig,
                                                  ActionConfig actionConfig)
                                           throws ServletException

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.

Parameters:

forwardConfig - The forward to check.

moduleConfig - The config for the current module.

actionConfig - If applicable, the config for the current action.

Returns:

The forward config using the correct class as determined by the config's ancestor and its own overridden value.

Throws:

UnavailableException - if an instance of the forward config class cannot be created.

ServletException - on class creation error

initModuleExceptionConfigs

protected void initModuleExceptionConfigs(ModuleConfig config)
                                   throws ServletException

Initialize the exception handlers for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.3

processExceptionExtension

protected void processExceptionExtension(ExceptionConfig exceptionConfig,
                                         ModuleConfig moduleConfig,
                                         ActionConfig actionConfig)
                                  throws ServletException

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.

Parameters:

exceptionConfig - the configuration to process.

moduleConfig - the module configuration for this module.

actionConfig - If applicable, the config for the current action.

Throws:

ServletException - if initialization cannot be performed.

processExceptionConfigClass

protected ExceptionConfig processExceptionConfigClass(ExceptionConfig exceptionConfig,
                                                      ModuleConfig moduleConfig,
                                                      ActionConfig actionConfig)
                                               throws ServletException

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.

Parameters:

exceptionConfig - The config to check.

moduleConfig - The config for the current module.

actionConfig - If applicable, the config for the current action.

Returns:

The exception config using the correct class as determined by the config's ancestor and its own overridden value.

Throws:

ServletException - if an instance of the exception config class cannot be created.

initModuleActions

protected void initModuleActions(ModuleConfig config)
                          throws ServletException

Initialize the action configs for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.3

processActionConfigExtension

protected void processActionConfigExtension(ActionConfig actionConfig,
                                            ModuleConfig moduleConfig)
                                     throws ServletException

Extend the action's configuration as necessary.

Parameters:

actionConfig - the configuration to process.

moduleConfig - the module configuration for this module.

Throws:

ServletException - if initialization cannot be performed.

processActionConfigClass

protected ActionConfig processActionConfigClass(ActionConfig actionConfig,
                                                ModuleConfig moduleConfig)
                                         throws ServletException

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

Parameters:

actionConfig - The action config to check.

moduleConfig - The config for the current module.

Returns:

The config object using the correct class as determined by the config's ancestor and its own overridden value.

Throws:

ServletException - if an instance of the action config class cannot be created.

initModuleMessageResources

protected void initModuleMessageResources(ModuleConfig config)
                                   throws ServletException

Initialize the application MessageResources for the specified module.

Parameters:

config - ModuleConfig information for this module

Throws:

ServletException - if initialization cannot be performed

Since:

Struts 1.1

initConfigDigester

protected org.apache.commons.digester.Digester initConfigDigester()
                                                           throws ServletException

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).

Returns:

A new configured Digester instance.

Throws:

ServletException - if a Digester cannot be configured

Since:

Struts 1.1

initInternal

protected void initInternal()
                     throws ServletException

Initialize our internal MessageResources bundle.

Throws:

ServletException - if we cannot initialize these resources

UnavailableException - if we cannot load resources

initChain

protected void initChain()
                  throws ServletException

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

Throws:

ServletException - if an error occurs.

initOther

protected void initOther()
                  throws ServletException

Initialize other global characteristics of the controller servlet.

Throws:

ServletException - if we cannot initialize these resources

initServlet

protected void initServlet()
                    throws ServletException

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.

Throws:

ServletException - if error happens while scanning web.xml

splitAndResolvePaths

protected List splitAndResolvePaths(String paths)
                             throws ServletException

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.

Parameters:

paths - A comma-delimited string of paths

Returns:

A list of resolved URL's for all found resources

Throws:

ServletException - if a servlet exception is thrown

process

protected void process(HttpServletRequest request,
                       HttpServletResponse response)
                throws IOException,
                       ServletException

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

Parameters:

request - The servlet request we are processing

response - The servlet response we are creating

Throws:

IOException - if an input/output error occurs

ServletException - if a servlet exception is thrown