Postman 401 Unauthorized Error with Spring Backend

I’m developing a backend application using Spring. The user registration API is functioning correctly, and it creates entries in the database. However, attempting to execute a GET request results in a 401 Unauthorized error.

I’ve activated basic authentication in Postman and entered the credentials of an existing user, yet I still encounter the same 401 error. Can anyone help me identify what might be causing this issue?

Here’s the relevant code snippets for your reference:

Security Configuration

package com.example.app.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.web.SecurityFilterChain;

@Configuration
public class SecurityConfiguration {
    @Bean
    public BCryptPasswordEncoder getPasswordEncoder() {
        return new BCryptPasswordEncoder();
    }
    @Bean
    public SecurityFilterChain configureSecurity(HttpSecurity http) throws Exception {
        http
            .csrf().disable() // CSRF is disabled for testing purposes;
            .authorizeHttpRequests(req -> req
                .requestMatchers("/api/users/signup").permitAll() // Allow signup without auth
                .anyRequest().authenticated() // Requires authentication for other requests
            )
            .httpBasic(); // Enables basic auth
        return http.build();
    }
}

User Controller

package com.example.app.controller;

import com.example.app.model.User;
import com.example.app.service.UserManagementService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/users")
public class UserController {
    private final UserManagementService userManagementService;

    @Autowired
    public UserController(UserManagementService userManagementService) {
        this.userManagementService = userManagementService;
    }

    @PostMapping("/signup")
    public void createUser(@RequestBody User user) {
        userManagementService.createUser(user);
    }

    @GetMapping("/{userId}")
    public User getUser(@PathVariable String userId) {
        return userManagementService.getUserById(userId);
    }
}

User Class

package com.example.app.model;

import jakarta.persistence.*;

@Entity
@Table(name = "application_user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(unique = true, nullable = false)
    private String username;

    @Column(nullable = false)
    private String password;

    public void setPassword(String encoded) {
        this.password = encoded;
    }

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }
}

User Management Service

package com.example.app.service;

import com.example.app.model.User;
import com.example.app.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.stereotype.Service;

@Service
public class UserManagementService {

    private final UserRepository userRepository;
    private final BCryptPasswordEncoder passwordEncoder;

    @Autowired
    public UserManagementService(UserRepository userRepository, BCryptPasswordEncoder passwordEncoder) {
        this.userRepository = userRepository;
        this.passwordEncoder = passwordEncoder;
    }

    public void createUser(User user) {
        if (user.getPassword() == null || user.getPassword().isEmpty()) {
            throw new IllegalArgumentException("Password cannot be null or empty");
        }

        if (user.getUsername() == null) {
            throw new IllegalArgumentException("Username cannot be null");
        }

        String encryptedPassword = passwordEncoder.encode(user.getPassword());
        user.setPassword(encryptedPassword);
        userRepository.save(user);
    }

    public User getUserById(String userId) {
        return userRepository.findByUsername(userId)
                .orElseThrow(() -> new RuntimeException("User not found"));
    }
}

User Repository

package com.example.app.repository;

import com.example.app.model.User;
import org.springframework.data.jpa.repository.JpaRepository;
import java.util.Optional;

public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByUsername(String username);
}

I also attempted to send the request without encoding the password, but the issue remains. If I allow unauthenticated users to access the endpoint, the request goes through successfully.

Hey there! Could it be something related to how Postman sends the username and password? Are you sure that the credentials are correctly entered and match what’s in your db? Sometimes even a small typo can trip things up! Also, curious how your user repository set up is. Any insights there?

If your credentials in Postman are correct and match those stored in your database, another thing you should verify is if the password is being correctly encoded in your application. Ensure that the password saved in the database is not only being stored but also retrieved in its encrypted form. It might be that during authentication, the plain text password entered in Postman is not being correctly encrypted, leading to a mismatch with the stored encrypted password. Additionally, double-check your authentication sequence to ensure that Spring Security correctly retrieves and matches the user details.