How to find out the currently logged-in user in Spring Boot?

How to find out the currently logged-in user in Spring Boot?

In a Spring Boot application, you can find out the currently logged-in user using Spring Security, which provides authentication and authorization support. To access the currently logged-in user, you can use the SecurityContextHolder class provided by Spring Security. Here are the steps to do it:

  1. Add Spring Security Dependency: First, make sure you have Spring Security added as a dependency in your pom.xml or build.gradle file. Here's an example for a Maven project:

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

  2. Configure Spring Security: You may need to configure Spring Security to specify how users are authenticated and authorized in your application. This typically involves creating a SecurityConfig class that extends SecurityConfigurerAdapter and configuring authentication and authorization rules. Here's a simple example:

    import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder; import org.springframework.security.config.annotation.web.builders.HttpSecurity; import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity; import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter; import org.springframework.security.crypto.password.NoOpPasswordEncoder; import org.springframework.security.crypto.password.PasswordEncoder; @Configuration @EnableWebSecurity public class SecurityConfig extends WebSecurityConfigurerAdapter { @Override protected void configure(AuthenticationManagerBuilder auth) throws Exception { // Configure your authentication method here (e.g., in-memory or database-based authentication) auth .inMemoryAuthentication() .withUser("user") .password("password") .roles("USER"); } @Override protected void configure(HttpSecurity http) throws Exception { http .authorizeRequests() .antMatchers("/public/**").permitAll() .anyRequest().authenticated() .and() .formLogin() .and() .httpBasic(); } @Bean public PasswordEncoder passwordEncoder() { return NoOpPasswordEncoder.getInstance(); } }

    This is a basic configuration where users are authenticated with in-memory credentials.

  3. Access the Currently Logged-In User: To access the currently logged-in user, you can use the SecurityContextHolder class in your Spring components or controllers. Here's an example of how to do it:

    import org.springframework.security.core.Authentication; import org.springframework.security.core.context.SecurityContextHolder; import org.springframework.security.core.userdetails.UserDetails; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.ResponseBody; @Controller public class UserController { @GetMapping("/user") @ResponseBody public String getCurrentUser() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); if (authentication != null && authentication.getPrincipal() instanceof UserDetails) { UserDetails userDetails = (UserDetails) authentication.getPrincipal(); String username = userDetails.getUsername(); return "Current user: " + username; } return "No user logged in."; } }

    In this example, the /user endpoint retrieves the currently logged-in user from the SecurityContextHolder and returns their username. You can customize this logic according to your application's requirements.

With these steps in place, you can find out the currently logged-in user in a Spring Boot application using Spring Security. Remember to adapt the authentication and authorization configuration to your specific needs, such as using a database for user storage or integrating with third-party authentication providers.

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