I am trying to understand how the Session scoped bean work and have tried the example from here. HelloMessageGenerator.java HelloMessageBean.java HelloMessageController.java When I go to http://localhost:8080/scopes/session I get an error. scopesExample.html The error I am getting is as if the mapping would not exist: Answer I was missing the thymeleaf dependency in the pom. This is why I was getting

Spring Boot session scoped bean

I am trying to understand how the Session scoped bean work and have tried the example from here.

HelloMessageGenerator.java

public class HelloMessageGenerator {
    private String message;

    public HelloMessageGenerator() {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

}

HelloMessageBean.java

@Configuration
public class HelloMessageBean {
    @Bean
    @Scope(value = WebApplicationContext.SCOPE_SESSION, proxyMode = ScopedProxyMode.TARGET_CLASS)
    public HelloMessageGenerator requestScopedBean() {
        System.out.println("bean created");
        return new HelloMessageGenerator();
    }
}

HelloMessageController.java

@Controller
public class HelloMessageController {
    @Resource(name = "sessionScopedBean")
    HelloMessageGenerator sessionScopedBean;

    @RequestMapping("/scopes/session")
    public String getSessionScopeMessage(final Model model) {
        model.addAttribute("previousMessage", sessionScopedBean.getMessage());
        sessionScopedBean.setMessage("Good afternoon!");
        model.addAttribute("currentMessage", sessionScopedBean.getMessage());
        return "scopesExample";
    }

}

When I go to http://localhost:8080/scopes/session I get an error.

scopesExample.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="https://www.thymeleaf.org"
          xmlns:sec="https://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
    <head>
        <title>Hello World!</title>
    </head>
    <body>
    
    <p th:text="${previousMessage}">previous message</p>
    <p th:text="${currentMessage}">current message</p>
    
    </body>
    </html>

The error I am getting is as if the mapping would not exist:

This application has no explicit mapping for /error, so you are seeing this as a fallback. There was an unexpected error (type=Not Found, status=404).

Answer

I was missing the thymeleaf dependency in the pom.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

This is why I was getting a 404 when going to localhost:8080/scopes/request

After adding the thymeleaf dependency the bean scope was working as expected. For a session scope bean the bean is created only once per session or after the configured session timeout. For a request scope bean it is created for every request (ie. each time one hits the endpoint).

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Answer