J F W

HOW TO : CORE

action and data validation (struts 2)

In the other section we have learned how to use a simple action, now it is time to learn how to use an action in combination with a form that returns data that must be validated. For this purpose we will create a simple application that checks the number of digits in a number. For this we need an action:

<action name="home_submit" class="com.jfw.example.struts2.action.HomeSubmitAction"> <result name="input" type="tiles">home</result> <result name="success" type="tiles">home_submit</result> <result name="success2">/index.html</result> </action>

As we can see in the text area above, the declaration of the action is a little different, more precisely there are more attributes in the action element.
What is missing is a decalration of bean-class to use for saving the request parameters. In Struts 2, this kind of declaration is done inside the action class. We have to implement the method getModel as you can see in this example:

private HomeActionForm homeActionForm; public Object getModel() { if(homeActionForm == null) homeActionForm = new HomeActionForm(); return homeActionForm; }

In this way, the framework will take the instance of the class returned by method getModel, in this example an instance of class HomeActionForm and load the data from the form into the bean. Here follows the HomeActionForm class:

public final class HomeActionForm { private int test; public HomeActionForm() { super(); } public int getTest() { return test; } public void setTest(int test) { this.test = test; } }

The bean has a member String named test. The action class will retrieve the string from the bean and based on its content, will choose one of the two forwarding results previously declared in the jfwexamples.xml file.

public final class HomeSubmitAction extends ProjectAction { private HomeActionForm homeActionForm; public String myExecute(HttpServletRequest request, HttpServletResponse response, HashMap outputData) throws Exception { int test = homeActionForm.getTest(); JFWLogger.debug(className, "myExecute", "", "", "test field value=" + test); String exitPage = null; if(test == 1) exitPage = "success2"; else exitPage = "success"; return exitPage; } public Object getModel() { if(homeActionForm == null) homeActionForm = new HomeActionForm(); return homeActionForm; } }

The code above shows us how to retrieve the bean containing the data of the form.

But how and when does the validation occur? All we have to do is create a file with the name of the action and suffix -validation.xml. This file must be saved in the same package of the action class. Here is an example:

<validators> <field name="test"> <field-validator type="requiredstring"> <message> ${getText("errors.required.1")} ${getText("test_input")} ${getText("errors.required.2")} </message> </field-validator> </field> </validators>

In the previous code we have defined the validation of field test. The validation type is declared in the attribute type of the tag field-validator. If the validation fails, then the message declared in tag message will be shown. You can find more information on validation here.

The input value declared inside the tag action is the resource (can be a jsp page, an html page, a tile definition or another action) will be returned to the user. For printing the validation error message, the jsp page must contain this tag:

<struts2:fielderror/>