Using Angular HTTP interceptor is an excellent way to handle HTTP requests in your application. HTTP requests come in a variety of formats, so this pattern allows you to handle each in a unique way. This feature is especially useful when implementing deferred/promise APIs, since all cached responses are in a single location. Adding HTTP interceptors to your app is a powerful way to ensure that your application loads quickly and reliably.
Angular Interceptors to Manage HTTP Requests
An Angular app can use HTTP interceptors to provide error handling, retry logic, and time delay for requests. You can also use Angular HTTP interceptors to provide a custom middleware chain. An example scenario uses Angular HTTP interceptors for authentication and error handling. In addition, you can customize the interceptors by providing an optional attribute named multi to tell Angular that it is a multi-provider.
To create an interceptor, you first need to implement the HttpInterceptor interface. The intercept method identifies the HTTP request and returns an Observable. This Observable can be used by future functionality. To understand how this works, you can see a fully working example of this code here. After implementing an interceptor, you need to define the methods that it calls.
The Interceptor interface provides an elegant way to handle HTTP requests. You can use interceptors to handle authentication, error handling, and more. They also help you log incoming responses. The HttpClientModule calls the first interceptor, and each one thereafter. This way, you can control which HTTP requests are handled by which interceptor. By defining a simple interface, interceptors make it easy to manage your HTTP requests with Angular.
Angular Architecture Patterns
Angular HTTP modules define interceptors, which are services injected into the HttpClientModule to process HTTP requests. Interceptors modify the contents of a request as it passes through a chain of handlers. A chain of handlers may be composed of many services, but they all share a common interface. To create a chain, you must wrap each interceptor in a HttpHandler, one for each HTTP request.
Using a promise-based interceptor architecture pattern lets you easily chain together multiple interceptors with minimal code. Promises orchestrate complex preprocess and postprocess transformations, and rejection handlers fall back to cached values if the request fails. The source code for a request interceptor is shown below. To chain multiple interceptors together, use then(onFulfilled, onRejected) to chain them together.
HTTP Interceptors can handle both outgoing requests and incoming responses. The interceptor’s default class will always be the last one on the execution chain. You cannot alter this order or remove it later. This means you’ll have to build a dynamic interceptor if you need to modify the way HTTP requests are handled. If you need dynamic interceptors, you’ll need to implement a custom pattern to achieve that.
Software architecture
The Software architecture for Angular HTTP interceptor is simple and concise. It uses Promises to orchestrate pre and postprocess transformations. Its rejection handler handles errors and falls back to cached values if a request fails. Using Promises to chain request interceptors has several interesting implications. For example, each interceptor can handle multiple incoming and outgoing requests. It can also transform incoming requests and return without passing them on to the next interceptor.
The default Angular HTTP interceptor is used for backend server calls. It is applied last on the execution chain. Users cannot change the order of interceptors. If a user wants to use a dynamic interceptor, they will have to build this capability into the interceptor. Luckily, there are many Angular HTTP interceptor examples available online. Here is an overview of the architecture for each.
Service definitions are important to understand the architecture of a web application. A service is anything that does a specific task. In Angular, this service is known as an injector. An injector needs to register a service provider (a service class)