为HttpClient添加默认请求报头的四种解决方案

前言

httpclient在web调用中具有广泛的应用，而为它添加默认请求头是我们经常遇到的需求，本文介绍4种为httpclient添加默认请求头的方式。下面话不多说了，来一起看看详细的介绍吧

第一种方式

直接在创建的httpclient对象的defaultrequestheaders集合中添加报头。

class program
{
  static task main()=> sendasync1();

  private static async task sendasync1()
  {
    var httpclient = new httpclient();
    adddefaultheaders(httpclient);
    await httpclient.getstringasync("http://localhost:5000/");
  }

  private static void adddefaultheaders(httpclient httpclient)
  {
    httpclient.defaultrequestheaders.add("x-www-foo", "123");
    httpclient.defaultrequestheaders.add("x-www-bar", "456");
    httpclient.defaultrequestheaders.add("x-www-baz", "789");
  }
}

第二种方式

对于.net core应用来说，我们更推荐的做法是采用依赖注入的方式，利用ihttpclientfactory来创建httpclient对象，那么我们在进行相关服务注册的时候就可以设置默认请求报头。

class program
{
  static task main()=> sendasync2();

  private static async task sendasync2()
  {
    var services = new servicecollection();
    services.addhttpclient("", adddefaultheaders);
    var httpclient = services
      .buildserviceprovider()
      .getrequiredservice<ihttpclientfactory>()
      .createclient();
    await httpclient.getstringasync("http://localhost:5000/");
  }

  private static void adddefaultheaders(httpclient httpclient)
  {
    httpclient.defaultrequestheaders.add("x-www-foo", "123");
    httpclient.defaultrequestheaders.add("x-www-bar", "456");
    httpclient.defaultrequestheaders.add("x-www-baz", "789");
  }
}

第三种方式

由于httpclient在发送请求的时候会利用diagnosticsource对象发送相应的诊断事件，并且将作为请求的httprequestmessage对象作为请求事件内容负载。我们可以订阅该事件，在请求被发送之前将其拦截下来，并添加相应的请求头即可。

class program
{
  static task main()=> sendasync3();

  private static async task sendasync3()
  {
    func<object, httprequestmessage> requestaccessor = null;
    diagnosticlistener.alllisteners.subscribe(listener =>
    {
      if (listener.name == "httphandlerdiagnosticlistener")
      {
        listener.subscribe(kv =>
        {
          if (kv.key == "system.net.http.httprequestout.start")
          {
            requestaccessor ??= buildrequestaccessor(kv.value.gettype());
            var request = requestaccessor(kv.value);
            adddefaultheaders(request);
          }
        });
      }
    });

    var httpclient = new httpclient();
    await httpclient.getstringasync("http://localhost:5000/");
    static func<object, httprequestmessage> buildrequestaccessor(type payloadtype)
    {
      var property = payloadtype.getproperty("request", bindingflags.instance | bindingflags.public);
      var payload = expression.parameter(typeof(object));
      var convertedpayload = expression.convert(payload, payloadtype);
      var getrequest = expression.call(convertedpayload, property.getmethod);
      var convert = expression.convert(getrequest, typeof(httprequestmessage));
      return expression.lambda<func<object, httprequestmessage>>(convert, payload).compile();
    }
  }

  private static void adddefaultheaders(httprequestmessage request)
  {
    request.headers.add("x-www-foo", "123");
    request.headers.add("x-www-bar", "456");
    request.headers.add("x-www-baz", "789");
  }
}

第四种方式

上面这种方式可以采用强类型编程方式，具体的代码如下。

class program
{
  static task main()=> sendasync4();

  private static async task sendasync4()
  {
    diagnosticlistener.alllisteners.subscribe(listener =>
    {
      if (listener.name == "httphandlerdiagnosticlistener")
      {
        listener.subscribewithadapter(new httpclientlistener());
      }
    });
      
    var httpclient = new httpclient();
    await httpclient.getstringasync("http://localhost:5000/");
  }

  private sealed class httpclientlistener
  {
    [diagnosticname("system.net.http.httprequestout.start")]
    public void onsend(httprequestmessage request) => adddefaultheaders(request);

    //must subscribute the system.net.http.httprequestout event.
    [diagnosticname("system.net.http.httprequestout")]
    public void onsend() { }
  }

  private static void adddefaultheaders(httprequestmessage request)
  {
    request.headers.add("x-www-foo", "123");
    request.headers.add("x-www-bar", "456");
    request.headers.add("x-www-baz", "789");
  }
}

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，谢谢大家对的支持。