DynaValidatorActionForm with example application
This tutorial explains the DynaValidatorActionForm using a working example.
Generals
Autor:
Sascha Wolski
Sebastian Hennebrüder
http://www.laliluna.de/tutorials.htmlDate: February, 16th 2005
Development Tools
Eclipse 3.x
Dependencies
Struts 1.1
Jboss oder Tomcat
PDF download: http://www.laliluna.de/download/struts-dynavalidatoraction-form-en.pdf
Source download: http://www.laliluna.de/download/struts-dynavalidatoraction-form-source.zip
The DynaValidatorActionForm class
The DynaValidatorActionForm class is the dynamic variant of ValidatorActionForm. The developer does not write a Java class but defines the form bean and its properties in the Struts configuration file.
It has the capacity to validate fields of a form using validation rules which are defined in an XML file.
There is one difference between these classes. The validation rules of a ValidatorActionForm are not assigned to the action form but to the action. (/path-to-action/action.do).
So it is possible to reuse a bean in multiple actions but to define different validations for each action.
For the FormBean class a name is defined in the Struts Config.
Example:
<form-beans >
<form-bean name="exampleForm" type="org.apache.struts.validator.DynaValidatorActionForm">
<form-property name="name" type="java.lang.String" initial="Adam"/>
<form-property name="age" type="java.lang.Integer" initial="23"/>
</form-bean>
</form-beans>
The form bean can than be reused in an action definition. Below you see an example for an ActionMapping in the Struts Config.
Example:
<action attribute="exampleForm"
input="/form/example.jsp"
name="exampleForm"
path="/example"
scope="request"
type="my.package.ExampleAction" />
Validation of properties
The form bean DynaValidatorActionForm uses the Struts validation capabilities using validation rules defined in XML files. Struts offers a wide choice of rules, you can all find in the file validator-rules.xml.
You configure the rules for each property of a FormBean. These validations have to be written in the XML file (validation.xml)
Example validation file validation.xml:
<form-validation>
<formset>
<!-- validation mapping f�r example action -->
<form name="/example">
<field
property="name"
depends="required, minlength">
<arg0 key="exampleForm.name" />
<arg1 key="${var:minlength}" resource="false" />
<var>
<var-name>minlength</var-name>
<var-value>3</var-value>
</var>
</field>
</form>
</formset>
</form-validation>
Initializing the properties
The DynaValidatorActionForm class offers a reset method which is called automatically by Struts. In this method you can initialize properties.
Example:
public void reset(ActionMapping mapping,
HttpServletRequest request) {
//Initialisieren der Eigenschaft text
text = "Hello World";
}
Working example using the DynaValidatorActionForm Beans
Using a small working example we will show you the use of the DynaValidatorForm Bean.
Create the form bean (struts-config.xml)
Open the struts-config.xml and add a new form bean tag to the form beans area. Add two properties, name of type String and age of type Integer. Use the initial-tag to define a default setting for your fields.
Below you can see the example code.
<form-beans >
<form-bean name="exampleForm" type="org.apache.struts.validator.DynaValidatorActionForm">
<form-property name="name" type="java.lang.String" initial="Adam Weisshaupt"/>
<form-property name="age" type="java.lang.Integer" initial="23"/>
</form-bean>
</form-beans>
Create the Action class
Create the class ExampleAction in the package de.laliluna.tutorial.dynavalidatoractionform.action.
The class extends the class Action.
Implement the method execute(..).
Output the name and the age to the log.
The complete source code is shown below.
public class ExampleAction extends Action {
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
//ActionForm zuweisen
DynaValidatorActionForm exampleForm = (DynaValidatorActionForm) form;
//Zugriff auf Eigenschaften der BeanValidatorForm
//Klasse innerhalb der Action Klasse
System.out.println(exampleForm.get("name"));
System.out.println(exampleForm.get("age"));
return mapping.findForward("showExample");
}
}
Create the JSP files
Create two JSP named example1.jsp and example2.jsp in the directory ../WebRoot/form/
Copy the source code shown below to your JSP files.
In the JSP example1 change the value of <html:form action=�..�> to /example1
In the JSP example2 change the value to /example2.
<%@ page language="java"%> <%@ taglib uri="http://jakarta.apache.org/struts/tags-bean" prefix="bean"%> <%@ taglib uri="http://jakarta.apache.org/struts/tags-html" prefix="html"%> <html> <head> <title>JSP for exampleForm</title> </head> <body> <html:form action="/example1"> <html:errors /> Name: <html:text property="name" /> <br> Age: <html:text property="age" /> <br> <html:submit value="Send"/> </html:form> </body> </html>
Create two action mappings (struts-config.xml)
We will create two action mappings to show the usage of the DynaValidatorActionForm class. Both actions will use the same form bean.
As we are lazy we will also use the same action class ExampleAction.
Create the action mappings in between the <action-mappings> tags. Use the form bean exampleForm and forward to the JSP files.
The first action mapping has the path /example1, the second one /example2.
name is the name of the form bean
input defines the JSP which is shown when an error occured during the validation. In our case this is the same JSP we used to show the form.
type defines the action class which is called for the action
<forward ...> defines the forwards of the action. Here the JSP file are example1.jsp and example2.jsp.
<action-mappings >
<action
attribute="exampleForm"
input="/form/example1.jsp"
name="exampleForm"
path="/example1"
scope="request"
type="de.laliluna.tutorial.dynavalidatoractionform.action.ExampleAction">
<forward name="showExample" path="/form/example1.jsp" />
</action>
<action
attribute="exampleForm"
input="/form/example2.jsp"
name="exampleForm"
path="/example2"
scope="request"
type="de.laliluna.tutorial.dynavalidatoractionform.action.ExampleAction">
<forward name="showExample" path="/form/example2.jsp" />
</action>
</action-mappings>
Validating properties with XML validation rules
To validate the user input, if a name's length is greater than 3 character or the age is between 0 and 150, you have to configure this validations in an XML file.
Create the XML file validation.xml in the
directory
/WebRoot/WEB-INF/.
<form name=�..�> defines the Form Bean to which the validations are applied.
<field property=�..�> defines a property of a form bean. The attribute depends configures the used rule from the Struts rule set. (All rules are defined in the validator-rules.xml ).
<arg0 key=�..�> defines a parameter which is passed to the error message. In the error message for intRange, there is one parameter expected. (more informations at MessageResouce).
<var-name> sets the name of the variable used in the validation rule and <var-value> the value of the variable.
We will create validation rules for each mapping.
<form-validation>
<formset>
<!-- validation mapping for action /example1 -->
<form name="/example1">
<field
property="name"
depends="required, minlength">
<arg0 key="exampleForm.name" />
<arg1 key="${var:minlength}" resource="false" />
<var>
<var-name>minlength</var-name>
<var-value>3</var-value>
</var>
</field>
<field
property="age"
depends="required, intRange, integer">
<arg0 key="exampleForm.age"/>
<arg1 name="intRange" key="${var:min}" resource="false" />
<arg2 name="intRange" key="${var:max}" resource="false" />
<var>
<var-name>min</var-name>
<var-value>1</var-value>
</var>
<var>
<var-name>max</var-name>
<var-value>150</var-value>
</var>
</field>
</form>
<!-- validation mapping for action /example2 -->
<form name="/example2">
<field
property="name"
depends="required, minlength">
<arg0 key="exampleForm.name" />
<arg1 key="${var:minlength}" resource="false" />
<var>
<var-name>minlength</var-name>
<var-value>6</var-value>
</var>
</field>
</form>
</formset>
</form-validation>
Configure the ValidatorPlugins in the Struts Config file
In order to use the Struts-Validator you must add the ValidatorPlugin in the Struts Config. Otherwise Struts does not know your validation files and will not use them.
Open the struts-config.xml and add the following properties to the end of the struts config file.into the tag <struts-config> .
<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
<set-property
property="pathnames"
value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml"/>
</plug-in>
Create a Message Resource file
The Message Resource file is needed for the output of the error messages, we used in the execute method.
Create a new file named ApplicationResources.properties in the package de.laliluna.tutorial.dynavalidatoractionform.
You can find more information about
message resource files in our Message Resource tutorial.
http://www.laliluna.de/articles/posts/struts-message-resources-tutorial.html
Add the following to the file:
errors.suffix=<br>
# -- default error messages for struts validator
errors.required='{0}' is required.
errors.minlength='{0}' can not be less than {1} characters.
errors.range='{0}' is not in the range {1} through {2}.
# -- field names
exampleForm.name=Name
exampleForm.age=Age
Open the struts-config.xml and add the following lines to configure your resource file.
<message-resources parameter="de.laliluna.tutorial.dynavalidatoractionform.ApplicationResources" />
Test your example
We have finished our example application. Test the example by calling
http://localhost:8080/DynaValidatorActionForm/example1.do
(Validation of name and age)
http://localhost:8080/DynaValidatorActionForm/example2.do
(Validation of name)