@loopback/docs

--- lang: en title: 'API docs: rest.middlewaresequence' keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI sidebar: lb4_sidebar editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/rest permalink: /doc/en/lb4/apidocs.rest.middlewaresequence.html ---  [Home](./index.md) > [@loopback/rest](./rest.md) > [MiddlewareSequence](./rest.middlewaresequence.md) ## MiddlewareSequence class A sequence implementation using middleware chains **Signature:** ```typescript export declare class MiddlewareSequence implements SequenceHandler ``` **Implements:** [SequenceHandler](./rest.sequencehandler.md) ## Constructors <table><thead><tr><th> Constructor </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [(constructor)(context, invokeMiddleware, options)](./rest.middlewaresequence._constructor_.md) </td><td markdown="1"> </td><td markdown="1"> Constructor: Injects `InvokeMiddleware` and `InvokeMiddlewareOptions` </td></tr> </tbody></table> ## Properties <table><thead><tr><th> Property </th><th> Modifiers </th><th> Type </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [defaultOptions](./rest.middlewaresequence.defaultoptions.md) </td><td markdown="1"> `static` </td><td markdown="1"> InvokeMiddlewareOptions </td><td markdown="1"> </td></tr> <tr><td markdown="1"> [invokeMiddleware](./rest.middlewaresequence.invokemiddleware.md) </td><td markdown="1"> `readonly` </td><td markdown="1"> InvokeMiddleware </td><td markdown="1"> </td></tr> <tr><td markdown="1"> [options](./rest.middlewaresequence.options.md) </td><td markdown="1"> `readonly` </td><td markdown="1"> InvokeMiddlewareOptions </td><td markdown="1"> </td></tr> </tbody></table> ## Methods <table><thead><tr><th> Method </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [handle(context)](./rest.middlewaresequence.handle.md) </td><td markdown="1"> </td><td markdown="1"> Runs the default sequence. Given a handler context (request and response), running the sequence will produce a response or an error. Default sequence executes these groups of middleware: - `cors`: Enforces `CORS` - `openApiSpec`: Serves OpenAPI specs - `findRoute`: Finds the appropriate controller method, swagger spec and args for invocation - `parseParams`: Parses HTTP request to get API argument list - `invokeMethod`: Invokes the API which is defined in the Application controller method In front of the groups above, we have a special middleware called `sendResponse`, which first invokes downstream middleware to get a result and handles the result or error respectively. - Writes the result from API into the HTTP response (if the HTTP response has not been produced yet by the middleware chain. - Catches error logs it using 'logError' if any of the above steps in the sequence fails with an error. </td></tr> </tbody></table>