Migrating Beer Expert Struts 1 application

(from the Head First Servlets and JSP Book)

used resources:

• Migrating Struts Apps to Struts 2
• Migrating to Struts 2 - Part II
• Struts 2 Simple Login Example

1. Edit web.xml. Front Controller is not a servlet anymore. Now it is a filter. Delete the servlet definition and add following lines:
   <filter> <filter-name>webwork</filter-name> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> </filter> <filter-mapping> <filter-name>webwork</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
2. Move the file struts.xml to the folder resources. Delete form-beans and action-mappings definitions and define interceptors:
   <interceptors> <interceptor name="myconfig" class="com.example.web.MyConfigInterceptor"> </interceptor> <interceptor name="mylogging" class="com.example.web.MyLoggingInterceptor"> </interceptor> <interceptor-stack name="myinterceptorStack"> <interceptor-ref name="myconfig" /> <interceptor-ref name="mylogging" /> <interceptor-ref name="defaultStack" /> </interceptor-stack> </interceptors>
   and actions:
   <action name="BeerSelect" class="com.example.web.BeerSelectAction"> <!-- method="execute"> --> <interceptor-ref name="myinterceptorStack" /> <result name="success">/result.jsp</result> </action>
3. implement the interceptors. MyConfigInterceptor makes the action request aware:
   package com.example.web; import javax.servlet.http.HttpServletRequest; import org.apache.struts2.interceptor.ServletConfigInterceptor; import com.opensymphony.xwork2.ActionContext; import com.opensymphony.xwork2.ActionInvocation; public class MyConfigInterceptor extends ServletConfigInterceptor { /** * gets the <code>HttpServletRequest</code> from <code>context</code> and * makes <code>Action</code> aware of the intercepted request */ private static final long serialVersionUID = 1L; @Override public String intercept(ActionInvocation invocation) throws Exception { BeerSelectAction action = (BeerSelectAction) invocation.getAction(); ActionContext context = ActionContext.getContext(); HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST); action.setServletRequest(request); return super.intercept(invocation); } }
4. Then delete the Form bean, since the Action class will take the bean function and refactor the action class. In Struts 2 method execute has no arguments and the action interceptor MyConfigInterceptor makes the action aware of the ServletRequest.
   package com.example.web; import java.util.List; import javax.servlet.http.HttpServletRequest; import com.example.model.BeerExpert; import com.opensymphony.xwork2.ActionSupport; public class BeerSelectAction extends ActionSupport implements ServletRequestAware // extends Action { private static final long serialVersionUID = 8450666311336329411L; private HttpServletRequest request; private String color; private static final String VALID_COLORS = "amber,dark,light,brown"; /** * * @return the result of the method execution */ public String execute() { // Process the business logic // checks if the color is set and if it has valid value // if not reports an error if (color != null && VALID_COLORS.indexOf(color) == -1) { addActionError("error"); return "error"; } else { // for chosen color gets the advice from the <code>BeerExpert</code> BeerExpert be = new BeerExpert(); List<String> result = be.getBrands((getColor() != null) ? getColor() : "light"); // stores the result in the request-scope request.setAttribute("styles", result); // reports that action was executed successfully return "success"; } } @Override public void setServletRequest(HttpServletRequest request) { this.request = request; } /** * setter for the form parameter <code>color</code> * * @param color */ public void setColor(String color) { this.color = color; } /** * getter for the form parameter <code>color</code> * * @return the color chosen in the form */ public String getColor() { return color; } }