Introduction

Author: Kasper Graversen, 12/12/07 Keywords: Struts, Actions, Forwards Abstract: on struts

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Introduction

Model

ActionForm

DynaActionForm

Form state conversion

• Never have your business logic use the ActionForm entities! This will inevitably tie the application to the fact that one of its front-ends are webdriven!
• Have in each ActionForm a convert() method which is able to transform the actionform instance into a databean needed in the other layers of the application
• Explicitly create a converter class that has several overloaded converter methods public Bean convert(SomeActionForm)

Controller/Action

Action Mapping

<form-bean name="formExample" type="com.yourcompany.struts.ExampleActionForm"/>
...
<action path="/urlExampleForm"                        <!-- url in the browser + ".do"
        name="formExample"                            <!-- name of registered form -->
        type="com.yourcompany.actions.ExampleAction"  <!-- the action dealing with valid forms -->
        input="/index.jsp"                            <!-- page/action to visit upon failure of invalid form validation -->
        validate="true"                               <!-- validate the form automatically before invoking the action -->
        scope="request">
</action>

Forward action

• Add a general forward rule <forward name="home" path="/home.do"/>
• Add the action <action path="/home" forward="/index.jsp" />
• Create links to that page using <html:link forward=”home”>Goto home</html:link>

• Add the action <action path="/home" parameter="/index.jsp" type="org.apache.struts.actions.ForwardAction" />
• Create links to that page using <html:link page=”/home.do”>Goto home</html:link>

Include action

• Incorporate the ressource on your page by <jsp:include page="/App/legacy.do" />
• Setup the action in struts-configuration.xml

  <action path="/legacy"
          parameter="/foo/LegacyServlet"
          type="org.apache.struts.actions.IncludeAction" />

DispatchAction

• Create a form action implementing a method for each kind of action possible in the form. Be careful as not to override the execute() method. The execute method will be invoked by the struts framework and using reflection will determine on the basis of a request parameter which method to invoke. This explains the 4 arguments each of the action methods must take.

  class MemberAction extends DispatchAction {
  
      public ActionForward edit(ActionMapping mapping,
                                ActionForm form,
                                HttpServletRequest request,
                                HttpServletResponse response) throws Exception {
          ...
          mapping.findForward("edit-success");
      }
  
      public ActionForward delete...
  ...
  }
  

• Setup the action in the struct-configuration.xml and remember the magic takes place in the parameter attribute below

  <action path="/member-screen-app"
          input="/ListMembers.jsp"
          type="foo.MemberAction"
          parameter="theAction"
          scope="request">
         <forward name="edit-success" path="RejectAppSuccess.jsp" redirect="true"/>
         ...
  </action>
  

• In your view setup submit buttons so the name of the button matches the name of the methods in your action

  <html:submit property="theAction">Delete</html:submit>
  <html:submit property="theAction">Edit</html:submit>
  

  In turn these will be translated into the url's such as ..foo.do?theAction=edit&id=1

View

Tiles

Installing

• Ensure that a struts-tiles.jar is available in the WEB-INF/lib directory of your web application.
• Add this init-param to the Action Servlet definition in web.xml:

   <init-param>
       <param-name>chainConfig</param-name>
       <param-value>org/apache/struts/tiles/chain-config.xml</param-value>
   </init-param>
  

• Configure the Tiles Plugin to load your definitions in the bottom of your struts-config.xml (just after message-ressources)

  <plug-in className="org.apache.struts.tiles.TilesPlugin">
      <set-property property="definitions-config" value="/WEB-INF/tiles-defs.xml"/>
  </plug-in>
  

• At the top of each JSP page that will use the Tiles custom tags, add a line that declares the Tiles custom tag library.

  <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
  

Defining tiles and extending existing tiles

Best usage tiles

• To set up a number of page definitions
• Make them accessible using forwarding in an action <forward name="success" path=".simple.admin.main" /> i.e. in case of success or failures.
• Make them accessible using them as inputs for actions <action path="/MyFormHandler" input=".simple.admin.main"..., i.e. when simple validation (within the actionformbean) fails and the form needs be redisplayed.
• Notice you cannot set them up as global forwarders

Simple usage tiles

• // somepage.jsp
  <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
  <tiles:insert definition="templateDefinition" />
  

• // tiles-defs.xml
  <?xml version="1.0" encoding="ISO-8859-1" ?>
  <!DOCTYPE tiles-definitions PUBLIC "-//Apache Software Foundation//DTD Tiles Configuration 1.1//EN" "http://struts.apache.org/dtds/tiles-config_1_1.dtd">
  <tiles-definitions>
      <definition name="templateDefinition" path="/layouts/layout.jsp">
         <put name="title"  value="This is the title." type="string"/>
         <put name="header" value="/layouts/header.jsp" type="page"/>
         <put name="body"   value="/layouts/body.jsp" type="page"/>
      </definition>
  </tiles-definitions>
  

• view page /somepage.jsp

Using CSS

<%@ taglib uri="/tags/struts-tiles" prefix="tiles" %>
<html>
<head>
<style type="text/css" media="screen">
@import "<%= request.getContextPath() %>/styles/styles.css";
</style>
<title> <tiles:getAsString name="title"/> </title>
</head>

Error Handling

1. The ressoure property file can include the l8n string for the errror message.
2. The action must be configured in struts-configuration.xml to validate by setting the validation="true" attribute.
3. The action class must implement validate()

   @Override
   public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {
       ActionErrors errors = super.validate(mapping, request);
   
       if(...) {
           errors.add("warehouseName", new ActionMessage("foo.bar.passwordtooshort")); // using a key from the ressource file
   	}
       return errors;
   }
   

4. In the view, the error will be displayed in the view using the tag <html:errors property="password"/>

Configuration file magic and Modularization

Splitting struts-configuration.xml

<servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>
        <param-name>config</param-name>
        <param-value>
            /WEB-INF/struts-config.xml,
            /WEB-INF/struts-config-global.xml,
            /WEB-INF/struts-config-admin.xml
            /WEB-INF/struts-config-reports.xml
            /WEB-INF/struts-config-user.xml
        </param-value>
    </init-param>
</servlet>

Struts modules

Configuration file wildcards

<action path="/ContractFormHandler_full"
    type="foo.action.ContractAction"
    name="ContractFormBean"
    scope="request"
    validate="true"
    input="/full.jsp">
    <forward name="success" path="/full.jsp"/>
</action>
<action path="/ContractFormHandler_mini"
    type="foo.action.ContractAction"
    name="ContractFormBean"
    scope="request"
    validate="true"
    input="/mini.jsp">
    <forward name="success" path="/mini.jsp"/>
</action>

<action path="/ContractFormHandler_*"
    type="foo.action.ContractAction"
    name="ContractFormBean"
    scope="request"
    validate="true"
    input="/{1}.jsp">
    <forward name="success" path="/{1}.jsp"/>
</action>

Struts best practices

Disallow direct access to *.jsp files

<security-constraint>
	<web-resource-collection>
		<web-resource-name>Deny Direct Access</web-resource-name>
		<description>Deny access to JSP's by associating them with denied role</description>
		<url-pattern>*.jsp</url-pattern>
	</web-resource-collection>
	<auth-constraint><role-name>Denied</role-name></auth-constraint>
</security-constraint>

<security-role>
	<role-name>Denied</role-name>
</security-role>

Date in actionform

public DateForm extends ActionForm {
	Date start;

    public void setStart(String startDate) {
        start = DateFormat.getDateInstance().parse(startDate);
	}

	public String getStart() {
		return DateFormat.getDateInstance().format(start);
	}
}

Error messages

avax.servlet.jsp.JspException: No getter method for property
distributorAccount of bean org.apache.struts.taglib.html.BEAN

       at org.apache.struts.util.RequestUtils.lookup(RequestUtils.java:968)

       at org.apache.struts.taglib.html.BaseFieldTag.doStartTag(BaseFieldTag.java:176)

       at org.apache.struts.taglib.html.HiddenTag.doStartTag(HiddenTag.java:123)

       at _newreturns._searchPopup1._jspService(_searchPopup1.java:111)

       [SRC:/newreturns/searchPopup1.jsp:19]

How to have 2 submit buttons in a form

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