Page History

In the Hello World Using Tags lesson, we implemented a use case that displayed a message with a dynamic timestamp. In this Logon form. In the Coding Actions lesson, we create a workflow that displays input from a data-entry form.

The form will ask for your name. If you enter "Zaphod" and click the submit button, the page will display "Hello, Zaphod!". If you don't enter a name, the page will display: "Hmmm, you did not enter a name. Please try again!"

HTML Form With Data, Using Getters and Setters

In the Hello World lesson, there were three components: the Action class, the result page, and the action mapping. In this lesson, we will add a fourth component: an input form.

Create a HTML input form

The framework includes a library of special tags that you can use to write dynamic forms, but "plain old HTML" forms work just fine too.

...


<html>
<head>
    <title>A simple HTML form with data</title>
</head>
<body>
    <p>What is your name?</p>

    <form action="HelloName.action" method="post">
        <p><input type="text" name="name"></p>
        <p><input type="submit" value="Submit your name." /></p>
    </form>

</body>
</html>

interpret the Logon form, and return a different result code depending on the circumstances.

If you have coded along, you can open the Logon action

Code Block
http://localhost:8080/tutorial/Logon.action

and enter a likely username and password. Since we haven't given the Action any behavior, the mapping redisplays the default Logon.jsp page.

Let's add an Action class that will make the Logon form more interesting.

The Code

Just as an example, we can examine the username and password values. If either or both properties are empty, return INPUT, so that we can collect a valid Logon. Otherwise, return SUCCESS.

Code Block

format	xml
title	Logon.java
borderStyle	solid


package tutorial;

Create the Action class

The HTML form submits an attribute called "name", and the Action class provides a corresponding JavaBean property.

Code Block

java

title

HelloName.java


package tutorial;

import com.opensymphony.xwork2.ActionSupport;

public class HelloNameLogon extends ActionSupport {

    public String execute() throws Exception {
        if (isInvalid(getNamegetUsername() == null || getName().length() == 0)return INPUT;
        if    (isInvalid(getPassword())) return ERRORINPUT;
        else
            return SUCCESS;
    }

    private String name;

    public String getName(boolean isInvalid(String value) {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Create the action mapping

We can just add a new action mapping to the file we started in the Hello World lesson.

...


<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
  <include file="struts-default.xml" />
    <package name="actions" extends="struts-default">

        <action name="HelloName" class="tutorial.HelloName">
            <result name="success">HelloName-success.jsp</result>
            <result name="error">HelloName-error.html</result>
        </action>

    </package>
</struts>

Create the success and error pages

The Action can select between two outcomes, "success" and "failure".

...


<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
    <title>Success Page</title>
</head>
<body>
    <p>
      Hello, <s:property value="name" />!
    </p>
</body>
</html>

...


<html>
<head>
    <title>Error Page</title>
</head>
<body>
    <p>
        Hmmm, you did not enter a name. Please try again!
    </p>
</body>
</html>

Try it!

If you are coding along, go ahead and try your form now. Open the input page (http://localhost:8080/tutorial/HelloName.html), and click the submit button to see what happens. Try it with and without entering a name.

Warning

title	Don't forget!

Compile your Action to WEB-INF/classes and restart your container if necessary.

How the code works

There are two differences between this example and the previous Hello World lesson.

When the Action is called, setName is passed the contents of the name form field.
When the Action's execute method returns, the framework has two options. If the string "error" returns, the framework will select HelloName-error.html as the result. If the string "success" returns, then HelloName-success.jsp is selected.

Let's try a slightly different approach to solve the same use case.

HTML Form With Data, Without Using Getters and Setters

In our first form, we needed to capture the field name. To do that, we added the getters and setters getName and setName to the Action class, as well as the private variable name. A larger application with dozens of forms and hundreds of form fields could need several hundred getters and setters. Let's try that same use case again, but without the JavaBean methods.

Create the HTML form

Let's use the same HTML form, but change the form Action to HelloName2.action:

...


<html>
<head>
  <title>A simple form with data</title>
</head>
<body>
    <p>What is your name?</p>

    <form action="HelloName2.action" method="post">
        <p><input type="text" name="name"></p>
        <p><input type="submit" value="Submit your name." /></p>
    </form>
</body>
</html>

Create the Action class

Code Block

java

title

HelloName2.java


package tutorial;

import com.opensymphony.xwork2.ActionSupport;
import org.apache.struts2.interceptor.ParameterAware;
import java.util.Map;

public class HelloName2 extends ActionSupport implements ParameterAware {

    public static String NAME = "name";

(value == null || value.length() == 0);
    }

    private String username;
    public String executegetUsername() {
        String[] name = (String[]) parameters.get(NAME)return username;
    }
    ifpublic (name == null || name[0] == null || name[0].length() == 0)
            return ERROR;void setUsername(String username) {
        else
this.username            return SUCCESS= username;
    }

    Mapprivate String parameterspassword;

    public MapString getParametersgetPassword() {
        return parameterspassword;
    }

    public void setParameterssetPassword(MapString parameterspassword) {
        this.parameterspassword = parameterspassword;
    }

}

Create the action mapping

...


<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
        "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <include file="struts-default.xml"/>
    <package name="actions" extends="struts-default">

        <action name="HelloName" class="tutorial.HelloName">
            <result name="success">/HelloName-success.jsp</result>
            <result name="error">HelloName-error.html</result>
        </action>

        <action name="HelloName2" class="tutorial.HelloName2">
            <result name="success">HelloName2-success.jsp</result>
            <result name="error">HelloName-error.html</result>
        </action>

    </package>
</struts>

Create the success and error pages

We can use the same error page, but we'll need a slightly different success page HelloName2-success.jsp. The only difference is the <s:property> tag.

...


<%@ taglib prefix="s" uri="/tags" %>
<html>
<head>
    <title>Success Page - Without Using Getters and Setters</title>
</head>

<body>
<p>
    Hello, <s:property value="parameters.name"/>!
</p>
</body>
</html>

How The Code Works

The framework automatically populates the username and password properties for us. All that's left to do is checking to see if either property is empty.

What to Remember

The Actions do the "heavy lifting" in a web application. Actions interact with data base systems and business rule engines, so that we can turn "billboard" HTML into a rich, dynamic web experience.

After doing its work, an Action returns a result code to indicate what the framework should do next. Often, the next step is to go onto the "success" result. Other times, we might need to go to an "error" result instead. In either case, the Action does not worry about generating the response, only deciding which logical result to present next.

For more about Actions, see Big Picture in the Core Developers Guide.

Next	Onward to Selecting Results
Prev	Return to Using Tags

Try it!

Go ahead and try it now. Load (http://localhost:8080/tutorial/HelloName2.html), enter "Zaphod" in the text field, and click the form submit button. You should see HelloName2-success.jsp saying "Hello, Zaphod!"

Warning

title	Don't forget!

Compile your Action to WEB-INF/classes and restart your container if necessary.

How the code works

Instead of a setter setName accessing a private variable name in the Action class, setParameters magically extracts everything from the request object and puts the attributes into a private local Map, parameters. In the execute method, we can get the value from the parameters Map instead of looking for a name property. So far so good.

Back on the HelloName2-success.jsp page, <s:property value="name" /> isn't going to work any more, because there is no getName() method in the Action. Instead, <s:property value="parameters.name" /> calls the getParameters method, and is able to get the value of the "name" field. Pretty neat!

Summary

Before processing an Action, the framework matches any Action properties with request attributes. If a match is found, the attribute value is set to the Action property. The Action can process the value, and the Struts tags can present the value too. Rather than define a separate property for each attribute, you can define a single Map property instead. In that case, all the request attributes will be set to the Map automatically.

Next	Onward to Understanding Results
Prev	Return to Hello World

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Versions Compared

Old Version 22

New Version Current

Key

HTML Form With Data, Using Getters and Setters

Create a HTML input form

The Code

Create the Action class

Create the action mapping

Create the success and error pages

Try it!

How the code works

HTML Form With Data, Without Using Getters and Setters

Create the HTML form

Create the Action class

Create the action mapping

Create the success and error pages

How The Code Works

What to Remember

Try it!

How the code works

Summary