helloaction.java

Java Struts的学习经典入门例子

package hello;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionMessage;
import org.apache.struts.action.ActionMessages;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.util.MessageResources;

public final class HelloAction extends Action {

    /**
     * Process the specified HTTP request, and create the corresponding HTTP
     * response (or forward to another web component that will create it).
     * Return an <code>ActionForward</code> instance describing where and how
     * control should be forwarded, or <code>null</code> if the response has
     * already been completed.
     */
    public ActionForward execute(ActionMapping mapping,
                                 ActionForm form,
                                 HttpServletRequest request,
                                 HttpServletResponse response)
    throws Exception {

        // These "messages" come from the ApplicationResources.properties file
        MessageResources messages = getResources(request);

        /*
         * Validate the request parameters specified by the user
         * Note: Basic field validation done in HelloForm.java
         *       Business logic validation done in HelloAction.java
         */
        ActionMessages errors = new ActionMessages();
        String userName = (String)((HelloForm) form).getUserName();

        String badUserName = "Monster";

        if (userName.equalsIgnoreCase(badUserName)) {
           errors.add("username", new ActionMessage("hello.dont.talk.to.monster", badUserName ));
           saveErrors(request, errors);
           return (new ActionForward(mapping.getInput()));
        }

        /*
         * Having received and validated the data submitted
         * from the View, we now update the model
         */
        PersonBean pb = new PersonBean();
        pb.setUserName(userName);
        pb.saveToPersistentStore();

        /*
         * If there was a choice of View components that depended on the model
         * (or some other) status, we'd make the decision here as to which
         * to display. In this case, there is only one View component.
         *
         * We pass data to the View components by setting them as attributes
         * in the page, request, session or servlet context. In this case, the
         * most appropriate scoping is the "request" context since the data
         * will not be neaded after the View is generated.
         *
         * Constants.PERSON_KEY provides a key accessible by both the
         * Controller component (i.e. this class) and the View component
         * (i.e. the jsp file we forward to).
         */

        request.setAttribute( Constants.PERSON_KEY, pb);

        // Remove the Form Bean - don't need to carry values forward
        request.removeAttribute(mapping.getAttribute());

        // Forward control to the specified success URI
        return (mapping.findForward("SayHello"));

    }
}