Spring Bootでセッション属性に保存されたデータを確認する方法【初心者向けに解説】

session.setAttribute("username", "yamada");

import jakarta.servlet.http.HttpSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SessionCheckController {

    private static final Logger logger = LoggerFactory.getLogger(SessionCheckController.class);

    @GetMapping("/check-session")
    public String checkSession(HttpSession session) {
        session.getAttributeNames().asIterator()
            .forEachRemaining(name -> {
                Object value = session.getAttribute(name);
                logger.info("Session Attribute - key: {}, value: {}", name, value);
            });
        return "Session attributes have been logged.";
    }
}

@Controller
@SessionAttributes("user")
public class MyController {

    @ModelAttribute("user")
    public User createUser() {
        return new User();
    }

    @GetMapping("/show-user")
    @ResponseBody
    public String showUser(@ModelAttribute("user") User user) {
        return user.toString();
    }
}

@GetMapping("/session-info")
public String sessionInfo(HttpSession session) {
    StringBuilder sb = new StringBuilder();
    sb.append("セッション属性一覧：\n");
    session.getAttributeNames().asIterator().forEachRemaining(name -> {
        sb.append(String.format("キー：%-15s | 値：%s\n", name, session.getAttribute(name)));
    });
    return sb.toString();
}