[JAVA] Transition from Struts2 to Spring MVC (Controller)

Prerequisites for migrating from Struts 2 to Spring MVC

The simplest procedure is

• Install Spring-plugin in Struts2
• Write an Action class using the Struts2 Convention plugin
• Since the logic to be executed from the Action class of Struts2 is under the control of Spring framwork
• Replace Strut2 Action with SpringMVC Controller

Other replacements include Validation, View, and Interceptor, but they can be modules that are independent of Struts2, so they can be replaced sequentially. This time is the Controller edition.

Action class assumptions

The Action class of Struts2 is supposed to be described by annotation using ** Convention plug-in **. If you have not installed the Convention plugin, first apply the Convention plugin and add Struts2 annotations to the Action class.

Struts2 Official: Convention Plugin: https://struts.apache.org/docs/convention-plugin.html Qiita: Write Struts2 Action class based on annotation (2016 Spring Ver.) Http://qiita.com/alpha_pz/items/4a97df916102dad2e2bc

Action class after applying the Convention

The implementation of Action class is as follows

• Input / output with Web layer
• Screen transition
• Calling logic

Just keep it.

DisplayListAction.java

// Struts2-Convention
@Namespace("/")        // (1)
@ParentPackage("struts-thymeleaf")
@Results({@Result(name=ActionSupport.SUCCESS,type="thymeleaf-spring",location="list")})        // (3)
// Spring framework
@Controller
@Scope("prototype")
public class DisplayListAction extends ActionSupport {

    @Action("list") // Struts2-Convention        // (2)
    public String execute() throws Exception {
        products = service.search(param);
        return SUCCESS;
    }

    @Autowired // Spring framework
    ProductService service;

    @Setter        // (4)
    private String param;

    @Getter @Setter // Lombok        // (5)
    List<SampleProduct> products;
}

If you narrow down to this point, you can replace it with the Spring MVC Controller.

To Controller of Spring MVC

DisplayListController.java

@Controller
@RequestMapping("/")        // (1)
public class DisplayListController {

    @GetMapping("list")        // (2)
    public ModelAndView index(@RequestParam String param, ModelAndView mnv) {        // (4)
        List<SampleProduct> products = service.search(param);

        mnv.addObject("products", products);        // (5)
        mnv.setViewName("/list");        // (3)

        return mnv;
    }
}

This allows for one-to-one mapping.

• 1: So-called private field and set method
• 2: So-called private field and get method

The important thing to migrate is to bring the Controller-Service relationship to the Action-Service relationship following Spring MVC, and to have the request / response object handled in the Action class field in the Controller method. Is to go.