.NET Core生成JWT遇阻：Post请求在Postman中无法正常生效求助

Hey there! Let's break down the common issues that might be stopping your JWT auth setup in .NET Core from working with Postman. Based on what you've shared, here are the key areas to troubleshoot step by step:

First, make sure your app is properly configured to handle JWT authentication:

• Double-check your appsettings.json for valid JWT parameters. The secret key needs to be at least 16 characters long for HS256 algorithm:

  "Jwt": {
    "Issuer": "YourAppIssuer",
    "Audience": "YourAppAudience",
    "SecretKey": "YourSecureSecretKeyThatIsAtLeast16CharsLong"
  }
  

• Confirm you've registered JWT authentication in your startup code (Program.cs for .NET 6+):

  builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
      .AddJwtBearer(options =>
      {
          options.TokenValidationParameters = new TokenValidationParameters
          {
              ValidateIssuer = true,
              ValidIssuer = builder.Configuration["Jwt:Issuer"],
              ValidateAudience = true,
              ValidAudience = builder.Configuration["Jwt:Audience"],
              ValidateIssuerSigningKey = true,
              IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(builder.Configuration["Jwt:SecretKey"]))
          };
      });
  

• Critical: Ensure the middleware order is correct in your request pipeline. Authentication must come before authorization:

  app.UseAuthentication();
  app.UseAuthorization();
  

Your login method needs to correctly validate users and generate a valid token:

• Always hash passwords (never store plain text!). Use a library like BCrypt to verify hashed passwords:

  [HttpPost("login")]
  public async Task<IActionResult> Login([FromBody] LoginRequest model)
  {
      // Find user by username
      var user = await _context.Users.FirstOrDefaultAsync(u => u.UserName == model.UserName);
      
      // Validate user and password
      if (user == null || !BCrypt.Net.BCrypt.Verify(model.Password, user.Password))
      {
          return Unauthorized("Invalid username or password");
      }
  
      // Build token claims
      var claims = new List<Claim>
      {
          new Claim(ClaimTypes.Name, user.UserName)
      };
  
      // Generate token
      var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_configuration["Jwt:SecretKey"]));
      var signingCreds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);
      
      var token = new JwtSecurityToken(
          issuer: _configuration["Jwt:Issuer"],
          audience: _configuration["Jwt:Audience"],
          claims: claims,
          expires: DateTime.UtcNow.AddMinutes(30),
          signingCredentials: signingCreds);
  
      return Ok(new { AccessToken = new JwtSecurityTokenHandler().WriteToken(token) });
  }
  

• Make sure you're using [FromBody] to bind the login request, and that your LoginRequest model matches the JSON you send in Postman.

Postman misconfiguration is a super common culprit:

• Set the request method to POST and use the correct endpoint URL (e.g., https://localhost:5001/api/auth/login if your controller uses [Route("api/[controller]")]).
• In the Headers tab, add Content-Type: application/json—this is easy to forget and will break JSON request body parsing.
• Send your credentials as raw JSON in the Body tab:

  {
    "userName": "testuser",
    "password": "testpassword"
  }
  

• If you've already received a token, for protected endpoints, go to the Authorization tab, select Bearer Token, and paste the token value.

• Confirm your EF Core migrations were applied successfully and your test user exists in the database.
• If you're using password hashing, make sure the stored password is a valid hash (not plain text). Test the hash verification logic with a breakpoint to ensure it's passing.

Start with checking the middleware order and Postman headers—those are the most frequent fixes. If you're still stuck, add breakpoints in your login endpoint to see where the flow fails (e.g., user not found, password verification failing, token generation error).

内容的提问来源于stack exchange，提问作者Isaías Orozco Toledo