Struts2 First Example – Hello World with Maven Setup

Struts2 First Example – Hello World with Maven Setup

Apache Struts2 is an MVC framework for building Java web applications. It uses a front-controller filter, an XML action mapping file (struts.xml), and Action classes instead of plain Servlets. This tutorial builds a complete first Struts2 application from scratch and explains how to display values in JSP using both HTML EL and Struts2 tags.

How Struts2 Works

Browser Request
    ↓
web.xml → StrutsPrepareAndExecuteFilter (intercepts all /*)
    ↓
struts.xml → maps URL to Action class and method
    ↓
Action class (plain POJO with execute() method)
    ↓
Returns result name ("success", "error", etc.)
    ↓
struts.xml → maps result name to JSP file
    ↓
JSP → renders response

Maven Dependencies (pom.xml)

<dependencies>

    <!-- Struts2 core -->
    <dependency>
        <groupId>org.apache.struts</groupId>
        <artifactId>struts2-core</artifactId>
        <version>2.5.33</version>
    </dependency>

    <!-- Servlet API (provided by the container) -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
        <scope>provided</scope>
    </dependency>

    <!-- JSTL -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

</dependencies>

<packaging>war</packaging>

Project Structure

src/
  main/
    java/
      com/java9r/
        HelloAction.java
    resources/
      struts.xml
    webapp/
      WEB-INF/
        web.xml
      index.jsp
      success.jsp

web.xml – Register the Struts2 Filter

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
             http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <display-name>Struts2 First Example</display-name>

    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <!-- Struts2 front-controller filter -->
    <filter>
        <filter-name>struts2</filter-name>
        <filter-class>
            org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter
        </filter-class>
    </filter>

    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

HelloAction.java – The Action Class

An Action class is a plain POJO. Field names become the form parameter names. The execute() method runs when the action is invoked and returns a result name string.

package com.java9r;

public class HelloAction {

    private String name;
    private int    age;
    private String city;

    // execute() is called by default when no method is specified
    public String execute() {
        // Business logic goes here if needed
        return "success";
    }

    // Getters and setters — Struts2 uses these for data binding
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }

    public String getCity() { return city; }
    public void setCity(String city) { this.city = city; }
}

struts.xml – Action Mapping

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
    "http://struts.apache.org/dtds/struts-2.5.dtd">

<struts>

    <constant name="struts.devMode" value="true"/>
    <constant name="struts.enable.DynamicMethodInvocation" value="false"/>

    <package name="default" namespace="/" extends="struts-default">

        <!-- URL /hello → HelloAction.execute() → success.jsp -->
        <action name="hello" class="com.java9r.HelloAction">
            <result name="success">/success.jsp</result>
            <result name="error">/index.jsp</result>
        </action>

    </package>

</struts>

index.jsp – Input Form

Struts2 provides its own tag library (prefix="s"). Struts2 tags integrate automatically with the action's fields and handle OGNL expressions.

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
    <title>Hello Struts2</title>
    <link rel="stylesheet"
          href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css">
</head>
<body>
<div class="container mt-4">
    <h3>Struts2 First Example</h3>
    <hr>

    <!-- action="hello" maps to the <action name="hello"> in struts.xml -->
    <s:form action="hello" method="post" cssClass="col-md-6">

        <div class="mb-3">
            <label>Name:</label>
            <!-- s:textfield name="name" → sets HelloAction.name via setName() -->
            <s:textfield name="name" cssClass="form-control" />
        </div>

        <div class="mb-3">
            <label>Age:</label>
            <s:textfield name="age" cssClass="form-control" />
        </div>

        <div class="mb-3">
            <label>City:</label>
            <s:textfield name="city" cssClass="form-control" />
        </div>

        <s:submit value="Submit" cssClass="btn btn-primary" />

    </s:form>
</div>
</body>
</html>

success.jsp – Displaying Values (Three Ways)

Struts2 exposes action fields to JSP via the Value Stack. There are three ways to read them:

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
    <title>Result</title>
    <link rel="stylesheet"
          href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css">
</head>
<body>
<div class="container mt-4">
    <h3>Three Ways to Display Values in Struts2</h3>
    <hr>

    <h5>1. HTML tag + JSP EL expression: ${name}</h5>
    <!--
        Standard JSP Expression Language.
        Reads from request attributes / value stack.
        CSS class added directly to HTML input.
    -->
    <input type="text" class="form-control mb-2" value="${name}">
    <input type="text" class="form-control mb-2" value="${age}">
    <input type="text" class="form-control mb-2" value="${city}">

    <hr>

    <h5>2. Struts2 tag: value="%{name}"</h5>
    <!--
        OGNL expression inside Struts2 tag.
        %{...} is the OGNL evaluator syntax.
        cssClass= is the Struts2 attribute that renders as class= in HTML.
    -->
    <s:textfield value="%{name}" cssClass="form-control mb-2" />
    <s:textfield value="%{age}"  cssClass="form-control mb-2" />
    <s:textfield value="%{city}" cssClass="form-control mb-2" />

    <hr>

    <h5>3. s:property tag (read-only display)</h5>
    <!--
        s:property renders the value as text (no input box).
        Equivalent to writing ${name} in a span.
    -->
    <p>Name: <s:property value="name" /></p>
    <p>Age:  <s:property value="age"  /></p>
    <p>City: <s:property value="city" /></p>

</div>
</body>
</html>

HTML Tag vs Struts2 Tag – Key Differences

Feature	HTML tag + EL ${name}	Struts2 tag %{name}
Expression language	JSP EL	OGNL (more powerful)
CSS class attribute	class="form-control"	cssClass="form-control"
Automatic validation display	No	Yes (shows field errors)
Theme wrapper HTML	None — pure HTML	Adds extra div/label by default (use theme="simple" to suppress)
Complex object access	${user.address.city}	%{user.address.city}

struts.xml Result Types

<!-- Default: forward to a JSP -->
<result name="success">/success.jsp</result>

<!-- Redirect to another URL -->
<result name="success" type="redirect">/index.jsp</result>

<!-- Redirect to another Struts2 action -->
<result name="success" type="redirectAction">
    <param name="actionName">listUsers</param>
</result>

<!-- Return JSON (requires struts2-json-plugin) -->
<result type="json">
    <param name="root">responseMap</param>
</result>

Summary

A Struts2 application has three main pieces: web.xml registers the StrutsPrepareAndExecuteFilter to intercept all requests, struts.xml maps URLs to Action classes and maps result names to JSP files, and the Action class is a plain POJO whose fields are bound from HTTP parameters via getter/setter pairs. In JSP, use ${name} (JSP EL) or <s:property value="name"/> (Struts2 tag) to display action field values. Struts2 tags add extra features like field-level validation messages, but require cssClass instead of the standard class attribute.