Struts Configuring Components
web.xml
strutsconfig.xml framework's deployment descriptor. It is used to load and configure various components used by struts framework. application.properties
The web application deployment descriptor required by Java Servlet specification.
Provides message resources to struts based web application
The web application deployment descriptor
Struts framework includes two components that need to be configured through web.xml file: the ActionServlet and optionally, tag libraries.
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd"> <web-app id="WebApp"> <display-name>PRO617Web</display-name> <servlet> <servlet-name>action</servlet-name><!- only one action servlet per application --> <servlet-class>org.apache.struts.action.ActionServlet</servlet-class> <init-param> <param-name>config</param-name><! context relative path to xml resource containing config info --> <param-value>WEB-INF/struts-config.xml</param-value> </init-param> <init-param> <param-name>debug</param-name><!- debug level for this servlet 0 == least serious, 6 = most serious --> <param-value>2</param-value> </init-param> <init-param> <param-name>detail</param-name><!- debug level for Digester to process application config files 0 to 6 -- > <param-value>2</param-value> </init-param> <init-param> <param-name>validate</param-name><!- specifies whether to use validating xml parser to process config file -- > <param-value>true</param-value> </init-param> <load-on-startup>2</load-on-startup><! weighting with the container. 2 allows other resources to load first -- > </servlet> <servlet-mapping> <servlet-name>action</servlet-name> <url-pattern>*.do</url-pattern> </servlet-mapping> <taglib> <taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri> <taglib-location>/WEB-INF/struts-bean.tld</taglib-location> </taglib> </web-app>
strutsconfig.xml file
Struts config file is a living blueprint of application Struts configuration and Action Servlet work together to form a control layer Every component in Struts configuration is a Java object Struts framework use reflection and introspection to automate loading and configuring java objects Struts config file helps your application react to changes quickly with minimal effort. In practice, it is separating things that rarely change the underlying java classes from things that often change the java objects deployed at runtime. Principle of protected variation...Larman Example file <struts-config> <!-- Data Sources --> <data-sources> </data-sources> <!-- Form Beans --> <form-beans> </form-beans> <!-- Global Exceptions --> <global-exceptions> </global-exceptions> <!-- Global Forwards --> <global-forwards> </global-forwards> <!-- Action Mappings --> <action-mappings> </action-mappings> <!-- Message Resources --> <message-resources parameter="pro617web.resources.ApplicationResources"/> </struts-config>
Struts configuration elements
Datasources Element
Datasource Element
Contains zero or more datasource element <!ELEMENT datasources (datasource*)> <!ELEMENT datasource (setproperty*)> Acts as a factory for database connections and provides a single point of control setproperty allows to configure properties that are specific to data source implementation Example:
<data-sources>
<data-source> <set-property <set-property <set-property <set-property </data-source> property="driverClass" value=""/> property="user" value=""/> property="password" value=""/> property="url" value=""/>
</data-sources>
Form-Beans Element
Configures multiple ActionForm classes that are used by views Within form-beans you can configure zero or more form bean child elements Example: <form-beans> <form-bean name="loginForm" type="com.forms.LoginForm"/> </form-beans>
Global Exceptions Element
Configures exception handlers declaratively. Contains zero or more exception elements If no handler is found, a ServletException or IOException will be thrown. <global-exceptions> <exception key="error.login" path="/jsp/login.jsp" scope="request" type="com.exceptions.InvalidLogin" </global-exceptions>
/>
Struts Configuration Elements
Global forwards element
<globalforwards> <forward name="loginForward" path="/jsp/login.jsp" redirect="true"> </globalforwards> Message resources element
Logical name for forwarding or redirecting to a view. The forward element maps a logical name to an application relative URI Hard coding of literal URI is avoided using forward element Example:
Specifies characteristics of the message resource bundles that contain the localized messages for an application. Each strutsconfig file can define one or more message resource bundles E.g. <message-resources parameter="pro617web.resources.ApplicationResources"/> Typically, the bundles are either in a jar file or under WEB-INF/classes folder Specifies a fully qualified class name of a general purpose application plug-in module that receives notification of application startup and shutdown events. Plug-in element may contain zero or more set-property elements, so that extra configuration information may be passed to Plugin class E.g.
<plug-in className="org.apache.struts.tiles.TilesPlugin"> <set-property property="" value=""/> </plug-in>
Plug-in element
Struts Configuration Elements
Actionmappings Element Contains a set of zero or more action elements for Struts application Action element describes a mapping from a specific request path to a corresponding action class Controller selects a particular mapping by matching a URI path in the request with the path attribute in one of the action elements E.g. <action path="/signin" type="com.actions.LoginAction" scope="request" name="loginForm" validate="true" input="/jsp/login.jsp"> <forward name="Success" path="jsp/login.jsp" /> <forward name="Failure" path="jsp/invalidlogin.jsp" /> </action> Path attribute, in other words is the name of the action. It is the application relative path to the submitted request, starting with a "/" character and without filename extension Scope is the scope in which form bean is placed either request or session. Default value is session. It is specified only when name attribute is specified. Name is the name of the form bean element as specified in the form beams element Validate attribute determines if validate method of ActionForm is called before invoking execute method of the action class Type is the type of the action class Unknown attribute determines whether this action should be configured as the default for this application. It is optional and default is false
The application resources file
Capable and flexible messaging system. Text for the messages is stored in this properties ...