Detailed explanation of http interception in AngularJS_AngularJS

http interception, that is, the $http service allows us to interact with the server. Sometimes we want to do something before making a request and after receiving the response.
$httpProvider contains an array of interceptors.

We create an interceptor like this.

app.factory('myInterceptor', ['$log', function($log){
  $log.debug('');
  
  var myInterceptor = {};
  
  return myInterceptor;
}])

Then register the interceptor.

app.config(['$httpProvider', function($httpProvider){
  $httpProvider.interceptors.push('myInterceptor');
}])
 

The following are some examples of $http interception.

■ Asynchronous operations in interceptors

app.factory('myInterceotpr','someAsyncServcie', function($q, someAsyncServcie){
  var requestInterceptor = {
    request: function(config){
      var deferred = %q.defer();
      someAsyncService.doAsyncOperation().then(function(){
        ...
        deferred.resolve(config);
      }, function(){
        ...
        deferred.resolve(config);
      })
      return deferred.promise;
    }
  };
  
  return requestInterceptor;
})

The above is a request interception, an asynchronous operation is performed, and the config is updated according to the result of the asynchronous operation.

Of course there is also response interception.

app.factory('myInterceptor',['$q', 'someAsyncService', function($q, someAsyncSercice){
  var responseInterceptor = {
    response: function(response){
      var deferred = $q.defer();
      someAsyncService.doAsyncOperation().then(function(response){
        ...
        deferred.resolve(response);
      }, function(response){
        ...
        deferred.resolve(response);
      })
      return deferred.promise;
    }
  };
  return responseInterceptor;
}])

■ Session interception, request interception

The server has two types of verification, one is based on cookies and the other is based on tokens. For token-based authentication, when the user logs in, a token from the server is obtained, and this token is sent to the server with each request.

Create an injector related to the session:

app.factory('sessionInjector',['SessionService', function(SessionService){
  var sessionInjector = {
    request: function(config){
      if(!SessionService.isAnonymous){
        config.headers['x-session-token'] = SessionService.token;
      }
      return config;
    }
  };
  
  return sessionInjector;
}])

It can be seen that the token returned from the server is placed in config.headers.

Register injector:

app.config(['$httpProvider', function($httpProvider){
  $httpProvider.interceptors.push('sessionInjector');
}])

Make a request:

$http.get('');

Before interception it was roughly:

{
  "transformRequest":[null],
  "transformResponse":[null],
  "method":"GET",
  "url":"",
  "headers":{
    "Accept": "application/json, text/plain,*/*"
  }
}

After interception, add two more x-session-token fields in the headers:

{
  "transformRequest":[null],
  "transformResponse":[null],
  "method":"GET",
  "url":"",
  "headers":{
    "Accept": "application/json, text/plain,*/*",
    "x-session-token":......
  }
}

■ Timestamp, request and response interception

app.factory('timestampMarker',[function(){
  var timestampMarker = {
    request:function(config){
      config.requestTimestamp = new Date().getTime();
      return config;
    },
    response: function(response){
      response.config.responseTimestamp = new Date().getTime();
      return config;
    }
  };
  
  return timestampMarker;
}])

Above, intercept during request and response, and assign the current time to config.requestTimestamp and config.responseTimestamp.

Register interceptor:

app.config(['$httpProvider', function($httpProvider){
  $httpProvider.interceptors.push('timestampMarker');
}])
 

Then you can calculate the time it takes for the request to respond when you use it.

$http.get('').then(function(response){
  var time = response.config.responseTime - response.config.requestTimestamp;
  console.log('请求耗去的时间为 ' + time);
})
 

■ Request error recovery, request interception

Simulate an error situation of request interception:

app.factory('requestRejector',['$q', function($q){
  var requestRejector = {
    request: function(config){
      return $q.reject('requestRejector');
    }
  };
  return requestRejector;
}])

Interception request error:

app.factory('requestRecoverer',['$q', function($q){
  var requestRecoverer = {
    requestError: function(rejectReason){
      if(rejectReason === 'requestRejector'){
        //恢复请求
        return {
          transformRequest:[],
          transformResponse:[],
          method:'GET',
          url:'',
          headers:{
            Accept:'application/json, text/plain, */*'
          }
        };
      } else {
        return $q.reject(rejectReason);
      }
    }
  };
  
  return requestRecoverer;
}])

Register interceptor:

app.config(['$httpProvider', function($httpProvider){
  $httpProvider.interceptors.push('requestRejector');
  $httpProvider.interceptors.push('requestRecoverer');
}])
 

■ Session error recovery, response interception

app.factory('sessionRecoverer',['$q','$injector',function($q, $injector){
 var sessionRecoverer = {
  responseError: function(response){
   //如果Session过期
   if(response.status == 419){
    var SessionService = $injector.get('SessionService');
    var $http = $injector.get('$http');
    var deferred = $q.defer();
    
    //创建一个新的session
    SessionService.login().then(deferred.resolve, deferred.reject);
    
    return deferred.promise.then(function(){
     reutrn $http(response.config);
    })
   }
   return $q.reject(response);
  }
 };
 
 return sessionRecoverer;
}])

The above is the entire content of this article, I hope it will be helpful to everyone’s study.