如何将值更新到appsetting.json？
我正在使用官方文档中IOptions描述的模式.
当我从中读取值时appsetting.json,这可以正常工作,但是如何更新值并将更改保存回来appsetting.json？
在我的例子中,我有几个字段可以从用户界面编辑(由管理员用户在应用程序中).因此,我正在寻找通过选项访问器更新这些值的理想方法.
Matze.. 32
在编写此答案时,似乎没有Microsoft.Extensions.Options包提供的组件具有将配置值写回的功能appsettings.json.
在我的一个ASP.NET Core项目中,我想让用户更改一些应用程序设置 - 这些设置值应该appsettings.json更准确地存储在可选appsettings.custom.json文件中,如果存在,则会添加到配置中.
像这样...
public Startup(IHostingEnvironment env)
{
IConfigurationBuilder builder = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile("appsettings.custom.json", optional: true, reloadOnChange: true)
.AddEnvironmentVariables();
this.Configuration = builder.Build();
}
我宣布IWritableOptions<T>扩展的接口IOptions<T>; 这样我就可以替代IOptions<T>由IWritableOptions<T>每当我想读写设置.
public interface IWritableOptions<out T> : IOptions<T> where T : class, new()
{
void Update(Action<T> applyChanges);
}
此外,我想出了IOptionsWriter一个组件,旨在用于IWritableOptions<T>更新配置部分.这是我对前面提到的接口的实现......
class OptionsWriter : IOptionsWriter
{
private readonly IHostingEnvironment environment;
private readonly IConfigurationRoot configuration;
private readonly string file;
public OptionsWriter(
IHostingEnvironment environment,
IConfigurationRoot configuration,
string file)
{
this.environment = environment;
this.configuration = configuration;
this.file = file;
}
public void UpdateOptions(Action<JObject> callback, bool reload = true)
{
IFileProvider fileProvider = this.environment.ContentRootFileProvider;
IFileInfo fi = fileProvider.GetFileInfo(this.file);
JObject config = fileProvider.ReadJsonFileAsObject(fi);
callback(config);
using (var stream = File.OpenWrite(fi.PhysicalPath))
{
stream.SetLength(0);
config.WriteTo(stream);
}
this.configuration.Reload();
}
}
由于编写器不知道文件结构,我决定将段处理为JObject对象.访问者尝试查找请求的部分并将其反序列化为实例T,使用当前值(如果未找到),或者仅创建新实例(T如果当前值为)null.然后将此持有者对象传递给调用者,调用者将对其应用更改.比更改的对象转换回JToken将要替换该部分的实例...
class WritableOptions<T> : IWritableOptions<T> where T : class, new()
{
private readonly string sectionName;
private readonly IOptionsWriter writer;
private readonly IOptionsMonitor<T> options;
public WritableOptions(
string sectionName,
IOptionsWriter writer,
IOptionsMonitor<T> options)
{
this.sectionName = sectionName;
this.writer = writer;
this.options = options;
}
public T Value => this.options.CurrentValue;
public void Update(Action<T> applyChanges)
{
this.writer.UpdateOptions(opt =>
{
JToken section;
T sectionObject = opt.TryGetValue(this.sectionName, out section) ?
JsonConvert.DeserializeObject<T>(section.ToString()) :
this.options.CurrentValue ?? new T();
applyChanges(sectionObject);
string json = JsonConvert.SerializeObject(sectionObject);
opt[this.sectionName] = JObject.Parse(json);
});
}
}
最后,我实现了一个扩展方法,IServicesCollection允许我轻松配置可写选项访问器...
static class ServicesCollectionExtensions
{
public static void ConfigureWritable<T>(
this IServiceCollection services,
IConfigurationRoot configuration,
string sectionName,
string file) where T : class, new()
{
services.Configure<T>(configuration.GetSection(sectionName));
services.AddTransient<IWritableOptions<T>>(provider =>
{
var environment = provider.GetService<IHostingEnvironment>();
var options = provider.GetService<IOptionsMonitor<T>>();
IOptionsWriter writer = new OptionsWriter(environment, configuration, file);
return new WritableOptions<T>(sectionName, writer, options);
});
}
}
哪个可以用在ConfigureServices......
services.ConfigureWritable<CustomizableOptions>(this.Configuration,
"MySection", "appsettings.custom.json");
在我的Controller课程中,我可以要求一个IWritableOptions<CustomizableOptions>具有相同特征的实例IOptions<T>,但也允许更改和存储配置值.
private IWritableOptions<CustomizableOptions> options;
...
this.options.Update((opt) => {
opt.SampleOption = "...";
});
ceferrari.. 30
简化版Matze的答案:
public interface IWritableOptions<out T> : IOptionsSnapshot<T> where T : class, new()
{
void Update(Action<T> applyChanges);
}
public class WritableOptions<T> : IWritableOptions<T> where T : class, new()
{
private readonly IHostingEnvironment _environment;
private readonly IOptionsMonitor<T> _options;
private readonly string _section;
private readonly string _file;
public WritableOptions(
IHostingEnvironment environment,
IOptionsMonitor<T> options,
string section,
string file)
{
_environment = environment;
_options = options;
_section = section;
_file = file;
}
public T Value => _options.CurrentValue;
public T Get(string name) => _options.Get(name);
public void Update(Action<T> applyChanges)
{
var fileProvider = _environment.ContentRootFileProvider;
var fileInfo = fileProvider.GetFileInfo(_file);
var physicalPath = fileInfo.PhysicalPath;
var jObject = JsonConvert.DeserializeObject<JObject>(File.ReadAllText(physicalPath));
var sectionObject = jObject.TryGetValue(_section, out JToken section) ?
JsonConvert.DeserializeObject<T>(section.ToString()) : (Value ?? new T());
applyChanges(sectionObject);
jObject[_section] = JObject.Parse(JsonConvert.SerializeObject(sectionObject));
File.WriteAllText(physicalPath, JsonConvert.SerializeObject(jObject, Formatting.Indented));
}
}
public static class ServiceCollectionExtensions
{
public static void ConfigureWritable<T>(
this IServiceCollection services,
IConfigurationSection section,
string file = "appsettings.json") where T : class, new()
{
services.Configure<T>(section);
services.AddTransient<IWritableOptions<T>>(provider =>
{
var environment = provider.GetService<IHostingEnvironment>();
var options = provider.GetService<IOptionsMonitor<T>>();
return new WritableOptions<T>(environment, options, section.Key, file);
});
}
}
用法:
services.ConfigureWritable<MyOptions>(Configuration.GetSection("MySection"));
然后:
private readonly IWritableOptions<MyOptions> _options;
public MyClass(IWritableOptions<MyOptions> options)
{
_options = options;
}
要将更改保存到文件:
_options.Update(opt => {
opt.Field1 = "value1";
opt.Field2 = "value2";
});
并且您可以将自定义json文件作为可选参数传递(默认情况下它将使用appsettings.json):
services.ConfigureWritable<MyOptions>(Configuration.GetSection("MySection"), "appsettings.custom.json");
- 我不太确定“ MyOptions”，但是阅读此内容有助于我弄清楚。https://codingblast.com/asp-net-core-configuration-reloading-binding-injecting/ (2认同)