您可以通过使用$http
的timeout属性来做到这一点,并使用request
和responseError
回调$http
分别保存和执行每个请求。
脚步:
延迟地$http
在request
回调过程中注入服务,这将是获得$http
服务的唯一方法,因为在工厂函数中注入服务会导致循环依赖。
确定在request
回调中传递的配置是否已处理。如果尚未处理,则将配置添加到请求堆栈中,并按优先级对其进行排序。在配置对象的timeout属性中添加一个已解决的Promise,以取消当前$http
请求。最后返回配置对象。
一旦$http
请求已经被取消了,抓住它的responseError
回调。如果请求堆栈中有项目,请弹出第一个项目(配置),然后使用延迟加载的$http
服务调用它。最后,使用回调提供的拒绝参数返回拒绝的承诺。
angular.module('demo', [])
.config(function($httpProvider) {
$httpProvider.interceptors.push('httpPriorityInterceptor');
})
.factory('httpPriorityInterceptor', function($q, $injector) {
var requestStack = [], // request stack
$http = null; // http service to be lazy loaded
return {
request: request, // request callback
responseError: responseError // responseError callback
};
// comparison function to sort request stack priority
function sort(config1, config2) {
return config1.priority < config2.priority;
}
function request(config) {
// Lazy load $http service
if(!$http) {
$http = $injector.get('$http');
}
// check if configuration has not been requested
if(!config.hasBeenRequested) {
// set indicator that configuration has been requested
config.hasBeenRequested = true;
// set default priority if not present
config.priority = config.priority || 3;
// add a copy of the configuration
// to prevent it from copying the timeout property
requestStack.push(angular.copy(config));
// sort each configuration by priority
requestStack = requestStack.sort(sort);
// cancel request by adding a resolved promise
config.timeout = $q.when();
}
// return config
return config;
}
function responseError(rejection) {
// check if there are requests to be processed
if(requestStack.length > 0) {
// pop the top most priority
var config = requestStack.pop();
console.log(config);
// process the configuration
$http(config);
}
// return rejected request
return $q.reject(rejection);
}
})
.run(function($http) {
// create http request
var createRequest = function(priority) {
$http.get('/priority/' + priority, {priority: priority});
};
createRequest(3);
createRequest(1);
createRequest(4);
createRequest(2);
});
要确保已按正确的顺序调用每个请求,可以检查“控制台”选项卡中的日志或“网络”选项卡中的请求。
如果要按顺序调用请求(第一个请求必须在下一个请求调用之前完成),则可以将responseError
回调中的解决方案调整为以下内容:
function responseError(rejection) {
// check if there are requests to be processed
if(requestStack.length > 0) {
requestStack.reduceRight(function(promise, config) {
return promise.finally(function() {
return $http(config);
});
}, $q.when());
requestStack.length = 0;
}
// return rejected request
return $q.reject(rejection);
}
如评论中所述,优先请求返回的承诺不会返回预期的承诺解决方案或拒绝。我已经通过以下方式更新了拦截器以适应这种情况:
angular.module('demo', [])
.config(function($httpProvider) {
$httpProvider.interceptors.push('httpPriorityInterceptor');
})
.factory('httpPriorityInterceptor', function($q, $injector) {
var requestStack = [], // request stack
$http = null; // http service to be lazy loaded
return {
request: request, // request callback
responseError: responseError // responseError callback
};
// comparison function to sort request stack priority
function sort(config1, config2) {
return config1.priority < config2.priority;
}
function request(config) {
// Lazy load $http service
if(!$http) {
$http = $injector.get('$http');
}
// check if configuration has not been requested
if(!config.hasBeenRequested) {
// set indicator that configuration has been requested
config.hasBeenRequested = true;
// set default priority if not present
config.priority = config.priority || 3;
// add a defered promise relative to the config requested
config.$$defer = $q.defer();
// add a copy of the configuration
// to prevent it from copying the timeout property
requestStack.push(angular.copy(config));
// sort each configuration by priority
requestStack = requestStack.sort(sort);
// cancel request by adding a resolved promise
config.timeout = $q.when();
}
// return config
return config;
}
function responseError(rejection) {
// check if there are requests to be processed
if(requestStack.length > 0) {
requestStack.reduceRight(function(promise, config) {
var defer = config.$$defer;
delete config.$$defer;
return promise.finally(function() {
return $http(config)
.then(function(response) {
defer.resolve(response);
})
.catch(function(error) {
defer.reject(error);
});
});
}, $q.when());
requestStack.length = 0;
}
return rejection.config.$$defer.promise;
}
})
.run(function($http) {
// create http request
var createRequest = function(priority) {
return $http.get(priority + '.json', {priority: priority});
};
createRequest(3);
createRequest(1).then(function(data) { console.log(data); })
createRequest(4);
createRequest(2);
});