Struts ActionForm working example tutorial

This tutorial explains the Struts form bean ActionForm using a small example application.

Generals

Author:

Sascha Wolski

Sebastian Hennebrueder

http://www.laliluna.de/tutorials.html

Date: February, 8^th 2005

Development Tools

Eclipse 3.x

Dependencies

Struts 1.1

Jboss 3.2.5 or Tomcat

PDF download: http://www.laliluna.de/download/struts-action-form-tutorial-en.pdf

Source download: http://www.laliluna.de/download/struts-action-form-tutorial-source.zip

The ActionForm Klasse

This form type is a normal java class extending the ActionForm class.

Example:

public class ExampleForm extends ActionForm {}

Once it is created, you have to specify a name for the FormBean in the struts configuration file

Example:

<form-beans >
	<form-bean name="exampleForm" type="my.package.ExampleForm" />
</form-beans>

The form bean can be used in an Struts action. Below there is an example of an ActionMapping using our form bean.

Example:

<action attribute="exampleForm"
        name="exampleForm"
        path="/example"
        scope="request"
        type="my.package.ExampleAction" />

Validation of properties

You can implement a �validate� method in the class ActionForm. In this method you can (but you must not) validate the properties. This method is called after a form is submitted, resetted and filled with the new values. You can validate fields, if the content is correct and whatever else. When you return a non empty actionErrors then struts will bring you back to the page you specified with the �input� tag. On this page you can output your error messages.

Example:

public ActionErrors validate(
 		ActionMapping mapping,
 		HttpServletRequest request) {

	//create a new instance of actionErrors
	ActionErrors actionErrors = new ActionErrors();

	//Validate the text property
	 if(text.length() == 0)
 		actionErrors.add("example", new ActionMessage("Field should not be empty!"));

	//Return the errors
	return actionErrors;
}

Initializing the properties of the ActionForm class

Add an reset method to the actionForm class. This method is called by Struts when it initializes an ActionForm. You can define Default values to the form bean attributes in this method.

Example:

public void reset(ActionMapping mapping, 
 			HttpServletRequest request) {

	 //Initialize the property 
	 text = "Hello World";
}

Working example of an ActionForm Bean

Using a simple example we will show you now the usage of an ActionForm.

Create an ActionForm class

Create a new class named ExampleForm in the package .
de.laliluna.tutorials.actionform.form.

The class should extend the class ActionForm.

Add two properties name and age.

Create getter and setter methods for each property.
The class should look like the following.

public class ExampleForm extends ActionForm {

	//properties
	private String name;
	private int age;

	//Getter and Setter methods
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

Create the Action class

Create the class ExampleAction in the package de.laliluna.tutorial.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) {

 //convert the ActionForm 
 ExampleForm exampleForm = (ExampleForm) form;

 //access the properties and output them
 System.out.println(exampleForm.getName());
 System.out.println(exampleForm.getAge());

 return mapping.findForward("success");
 }

}

Create a JSP file

Create a JSP example.jsp in the directory ../WebRoot/form/ .

Below you can see the source code of the JSP file.

<%@ 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="/example">
 <html:errors />
			Name: <html:text property="name" /> <br>
			Age: <html:text property="age" /> <br>			
			<html:submit value="Send"/>
		</html:form>
	</body>
</html>

Configure a FormBean (struts-config.xml)

Open the struts-config.xml and add a form bean declaration, between the <form-beans> tags,
The attribute name defines the name of the FormBean, by which it can be used in action mappings.

type is the name of our class with the complete package name in front of it. In our case is the name ExampleForm.

<form-beans >
	<form-bean name="exampleForm" type="de.laliluna.tutorial.actionform.form.ExampleForm" />
</form-beans>

Configure the Action (struts-config.xml)

Add a action mapping in the struts-config.xml. Add the form bean exampleForm to the action and create a forward to the example.jsp.
name specifies the action of the form bean.
Type is the path to our action class, ExampleAction.
<forward ...> is the forward to our example.jsp.

<action-mappings>
      <action
         attribute="exampleForm"
         input="/form/example.jsp"
         name="exampleForm"
         path="/example"
         scope="request"
         type="de.laliluna.tutorial.actionform.action.ExampleAction">

		<forward name="showExample" path="/form/example.jsp" />

	</action>
</action-mappings>

Initializing the properties of the ActionForm class

Add an reset method to the actionForm class. This method is called by Struts when it initializes an ActionForm. We will initialize our two fields.

public void reset(ActionMapping mapping, 
 		HttpServletRequest request) {

	 //Initializing the properties
	 name = "Adam Weisshaupt";
	 age = 23;
}

Validate the properties in the actionForm class

We will validate if the name is longer than three characters and if the age is greater than 0. As explained before, the validation is only possible in the action class.

The source code below is the validate(..) method of the ExampleForm class.

public ActionErrors validate(
 ActionMapping mapping,
 HttpServletRequest request) {

 //Create a new instance of ActionErrors
 ActionErrors actionErrors = new ActionErrors();

 //validate the properties of the DynaActionForm
 if(exampleForm.get("name").toString().length() < 3){
 actionErrors.add(ActionErrors.GLOBAL_ERROR, new ActionError("error.name"));
 }

 if(Integer.parseInt(exampleForm.get("age").toString()) < 1){
 actionErrors.add(ActionErrors.GLOBAL_ERROR, new ActionError("error.age"));
 }

 //return the actionErrors 
	return actionErrors;
	}

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.dynaactionform.

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>
error.name=Name must have minimum 3 characters
error.age=Age must be greater then 0

Open the struts-config.xml and add the following lines.

<message-resources parameter="de.laliluna.tutorial.dynaactionform.ApplicationResources" />

Test your example

We have finished our example application. Test the example by calling

http://localhost:8080/DynaActionForm/example.do

(We expect a standard installation of JBOSS or Tomcat)