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Struts 2 to Spring Boot 3.x Migration Guideline

Metadata

• Source Technology: Apache Struts 2 (struts2-core)
• Target Technology: Spring Boot 3.x with Spring MVC
• Trigger Keywords: struts, struts2, ActionSupport, struts.xml, xwork2, opensymphony, struts-tags
• Version: 1.0.0
• Last Updated: 2025-01-22

Overview

This guideline provides comprehensive skills for migrating Apache Struts 2 applications to Spring Boot 3.x. Each skill addresses a specific migration concern with concrete transformation rules, examples, and validation criteria.

Skill Files

File	Skills	Description
SKILL-config.md	migrate-maven-dependencies, create-spring-boot-application, create-application-properties	Project setup and configuration
SKILL-action.md	convert-action-to-controller, convert-action-properties	Action to Controller conversion
SKILL-view.md	convert-jsp-tags, convert-ognl-to-el, convert-result-types	View layer migration
SKILL-interceptor.md	convert-interceptor, convert-validation	Interceptors and validation
SKILL-xml.md	migrate-struts-xml, migrate-web-xml	XML configuration migration
SKILL-test.md	convert-test-classes, create-exception-handler	Testing and exception handling

---

Migration Checklist

Execute skills in this order:

Phase 1: Project Setup

1. [ ] migrate-maven-dependencies - Update pom.xml (SKILL-config.md)
2. [ ] create-spring-boot-application - Create main class (SKILL-config.md)
3. [ ] create-application-properties - Create configuration (SKILL-config.md)

Phase 2: Configuration Migration

4. [ ] migrate-struts-xml - Plan controller structure (SKILL-xml.md)
5. [ ] migrate-web-xml - Remove Struts filter (SKILL-xml.md)

Phase 3: Action Conversion

6. [ ] convert-action-to-controller - Convert each Action class (SKILL-action.md)
7. [ ] convert-action-properties - Handle Action properties (SKILL-action.md)

Phase 4: Cross-cutting Concerns

8. [ ] convert-validation - Migrate validation logic (SKILL-interceptor.md)
9. [ ] convert-interceptor - Convert interceptors (SKILL-interceptor.md)

Phase 5: View Layer

10. [ ] convert-result-types - Handle result mappings (SKILL-view.md)
11. [ ] convert-jsp-tags - Update JSP files (SKILL-view.md)
12. [ ] convert-ognl-to-el - Fix expressions (SKILL-view.md)

Phase 6: Testing & Polish

13. [ ] convert-test-classes - Update tests (SKILL-test.md)
14. [ ] create-exception-handler - Global exception handling (SKILL-test.md)

---

Complete Transformation Example

Before (Struts)

HelloAction.java:

package com.example.action;

import com.opensymphony.xwork2.ActionSupport;

public class HelloAction extends ActionSupport {
    private String name;
    private String message;
    
    public String execute() {
        if (name == null || name.isEmpty()) {
            return INPUT;
        }
        message = "Hello, " + name + "!";
        return SUCCESS;
    }
    
    public void validate() {
        if (name != null && name.length() > 50) {
            addFieldError("name", "Name too long");
        }
    }
    
    // getters and setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getMessage() { return message; }
}

struts.xml:

<action name="hello" class="com.example.action.HelloAction">
    <result name="success">/WEB-INF/jsp/hello.jsp</result>
    <result name="input">/WEB-INF/jsp/hello-form.jsp</result>
</action>

hello.jsp:

<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<body>
    <s:property value="message"/>
</body>
</html>

After (Spring Boot)

HelloForm.java:

package com.example.form;

import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Size;

public class HelloForm {
    @NotBlank(message = "Name is required")
    @Size(max = 50, message = "Name too long")
    private String name;
    
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

HelloController.java:

package com.example.controller;

import com.example.form.HelloForm;
import jakarta.validation.Valid;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;

@Controller
public class HelloController {
    
    @GetMapping("/hello")
    public String showForm(Model model) {
        model.addAttribute("helloForm", new HelloForm());
        return "hello-form";
    }
    
    @PostMapping("/hello")
    public String execute(@Valid @ModelAttribute HelloForm form,
                         BindingResult result,
                         Model model) {
        if (result.hasErrors()) {
            return "hello-form";
        }
        String message = "Hello, " + form.getName() + "!";
        model.addAttribute("message", message);
        return "hello";
    }
}

hello.jsp:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<body>
    ${message}
</body>
</html>

Application.java:

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

application.properties:

server.port=8080
spring.mvc.view.prefix=/WEB-INF/jsp/
spring.mvc.view.suffix=.jsp