Introduction to the usage of $http service in AngularJS_AngularJS

We can use the built-in $http service to communicate directly with the outside world. The $http service simply encapsulates the browser's native XMLHttpRequest object.

1. Chain call

$http service is a function that can only accept one parameter. This parameter is an object that contains the configuration content used to generate HTTP requests. This function returns a promise object with two methods: success and error.

$http({
url:'data.json',
method:'GET'
}).success(function(data,header,config,status){
//响应成功
}).error(function(data,header,config,status){
//处理响应失败
});

2. Return a promise object

var promise=$http({
method:'GET',
url:"data.json"
});

Since the $http method returns a promise object, we can use the then method to handle the callback when the response returns. If you use the then method, you will get a special parameter, which represents the success or failure information of the corresponding object, and can also accept two optional functions as parameters. Or you can use success and error callbacks instead.

promise.then(function(resp){
//resp是一个响应对象
},function(resp){
//带有错误信息的resp
});

Or this:

promise.success(function(data,status,config,headers){
//处理成功的响应
});
promise.error(function(data,status,hedaers,config){
//处理失败后的响应
});

then() method and the other two methods is that it will receive a complete response object, while success() and error() will destruct the response object.

3. Quick get request

①$http.get('/api/users.json');

The get() method returns the HttpPromise object.

You can also send, for example: delete/head/jsonp/post/put. Please refer to page 148 for specific parameters acceptable in the function

② Take the example of sending a jsonp request again: In order to send a JSONP request, the url must contain the word JSON_CALLBACK.

jsonp(url,config) where config is optional

var promise=$http.jsonp("/api/users.json?callback=JSON_CALLBACK");

4. You can also use $http as a function. In this case, you need to pass in a settings object to explain how to construct the XHR object.

$http({
method:'GET',
url:'/api/users.json',
params:{
'username':'tan'
});

The settings object can contain the following main keys:

①method

Can be: GET/DELETE/HEAD/JSONP/POST/PUT

②url: absolute or relative request target
③params (string map or object)
The value of this key is a string map or object, which will be converted into a query string and appended to the URL. If the value is not a string, it will be JSON serialized.
For example:

//参数会转为？name=ari的形式
$http({
params:{'name':'ari'}
});

④data (string or object)

This object contains the data that will be sent to the server as the message body. Typically used when sending POST requests.

Starting from AngularJS 1.3, it can also send binary data in POST requests. To send a blob object, you can simply pass it by using the data parameter.
For example:

var blob=new Blob(['Hello world'],{type:'text/plain'});
$http({
method:'POST',
url:'/',
data:blob
});

4. Response object

The response object passed by AngularJS to the then() method contains four properties.

data

This data represents the converted response body (if conversion is defined)

status

Response HTTP status code

headers

This function is the getter function of header information, which can accept a parameter to obtain the corresponding name value

For example, use the following code to get the value of X-Auth-ID:

$http({
method: 'GET',
url: '/api/users.json'
}).then (resp) {
// 读取X-Auth-ID
resp.headers('X-Auth-ID');
});

config

This object is the complete settings object used to generate the original request.

statusText(String)

This string is the HTTP status text of the response.

5. Caching HTTP requests

By default, the $http service does not cache requests locally. When making individual requests, we can enable caching by passing a boolean value or a cache instance to the $http request.

$http.get('/api/users.json',{ cache: true })
.success(function(data) {})
.error(function(data) {});

The first time a request is sent, the $http service will send a GET request to /api/users.json. When the same GET request is sent for the second time, the $http service will retrieve the request result from the cache without actually sending an HTTP GET request.

In this example, because caching is enabled, AngularJS will use $cacheFactory by default. This service is automatically created by AngularJS when it starts.

If you want more custom control over the cache used by AngularJS, you can pass a custom cache instance to the request instead of true.

Let me tell you about AngularJS $http knowledge.

AngularJS $http is a service for reading data on the web server.

$http.get(url) is a function used to read server data.

AngularJS Example

<div ng-app="myApp" ng-controller="customersCtrl"> 
<ul>
<li ng-repeat="x in names">
{{ x.Name + ', ' + x.Country }}
</li>
</ul>
</div>
<script>
var app = angular.module('myApp', []);
app.controller('customersCtrl', function($scope, $http) {
$http.get("http://www.runoob.com/try/angularjs/data/Customers_JSON.php")
.success(function(response) {$scope.names = response.records;});
});
</script>