.NET MAUI实现RESTful API POST获取access_token的入门疑问

核心问题解答 #

必须创建与Postman请求Body参数对应的实体类，JsonContent.Create<Part>(part)需要通过强类型对象将参数序列化为符合接口要求的JSON格式，确保参数名、类型和必填项完全匹配接口定义。

分步实现教程 #

1. 创建POST请求参数实体类 #

根据Postman里的必填参数定义实体类，比如假设你的POST请求Body包含grant_type、username、password、client_id四个必填项，实体类代码如下：

using System.Text.Json.Serialization;

public class TokenRequestModel
{
    [JsonPropertyName("grant_type")] // 必须和接口字段名完全一致，大小写敏感
    public string GrantType { get; set; } = "password"; // 密码模式通常固定为该值

    [JsonPropertyName("username")]
    public string Username { get; set; } = string.Empty;

    [JsonPropertyName("password")]
    public string Password { get; set; } = string.Empty;

    [JsonPropertyName("client_id")]
    public string ClientId { get; set; } = string.Empty;
}

提示：如果接口有其他参数，直接添加对应属性并标记JsonPropertyName即可。

2. 创建Token响应实体类 #

接口返回的access_token通常包含固定字段，定义实体类方便解析：

public class TokenResponseModel
{
    [JsonPropertyName("access_token")]
    public string AccessToken { get; set; } = string.Empty;

    [JsonPropertyName("token_type")]
    public string TokenType { get; set; } = string.Empty;

    [JsonPropertyName("expires_in")]
    public int ExpiresIn { get; set; }
}

3. 发送POST请求获取Token #

在.NET MAUI中推荐先在MauiProgram.cs注册单例HttpClient：

// MauiProgram.cs
builder.Services.AddHttpClient();

然后在ViewModel或页面后台注入HttpClient实现请求逻辑：

using System.Net.Http.Json;

public class AccountViewModel
{
    private readonly HttpClient _httpClient;

    // 构造函数注入HttpClient
    public AccountViewModel(HttpClient httpClient)
    {
        _httpClient = httpClient;
        _httpClient.BaseAddress = new Uri("https://你的接口域名/"); // 设置接口基础地址
    }

    public async Task<string> GetAccessToken(string username, string password)
    {
        try
        {
            var tokenRequest = new TokenRequestModel
            {
                Username = username,
                Password = password,
                ClientId = "你的客户端ID" // 替换为实际值
            };

            var response = await _httpClient.PostAsJsonAsync("api/auth/token", tokenRequest);
            response.EnsureSuccessStatusCode(); // 确保请求成功

            var tokenResponse = await response.Content.ReadFromJsonAsync<TokenResponseModel>();
            return tokenResponse?.AccessToken ?? string.Empty;
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine($"获取Token失败: {ex.Message}");
            return string.Empty;
        }
    }
}

4. 使用Token调用GET验证接口 #

拿到access_token后，在GET请求Header中添加授权信息：

public async Task<bool> VerifyAccount(string accessToken)
{
    if (string.IsNullOrEmpty(accessToken))
        return false;

    try
    {
        var request = new HttpRequestMessage(HttpMethod.Get, "api/auth/verify");
        request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", accessToken);

        var response = await _httpClient.SendAsync(request);
        return response.IsSuccessStatusCode;
    }
    catch (HttpRequestException ex)
    {
        Console.WriteLine($"验证账号失败: {ex.Message}");
        return false;
    }
}

5. 在页面中调用方法 #

比如在登录按钮点击事件中执行流程：

private async void LoginButton_Clicked(object sender, EventArgs e)
{
    // 若使用依赖注入，直接从容器获取ViewModel即可
    var viewModel = new AccountViewModel(HttpClientFactory.CreateClient());
    var token = await viewModel.GetAccessToken(UsernameEntry.Text, PasswordEntry.Text);
    
    if (!string.IsNullOrEmpty(token))
    {
        bool isVerified = await viewModel.VerifyAccount(token);
        if (isVerified)
        {
            await Navigation.PushAsync(new MainPage());
        }
        else
        {
            await DisplayAlert("错误", "账号验证失败", "确定");
        }
    }
    else
    {
        await DisplayAlert("错误", "获取Token失败", "确定");
    }
}

内容的提问来源于stack exchange，提问作者Bob