How to Properly Inject JwtService into a Controller in NestJS

Описание: Learn how to resolve dependency issues in NestJS when injecting `JwtService` in your controller and how to successfully decode JWT tokens.
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This video is based on the question https://stackoverflow.com/q/63889773/ asked by the user 'Maturano' ( https://stackoverflow.com/u/1304447/ ) and on the answer https://stackoverflow.com/a/63889876/ provided by the user 'Jay McDoniel' ( https://stackoverflow.com/u/9576186/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Properly Inject JwtService into a Controller in NestJS

When developing applications with NestJS, you may encounter challenges with dependency injection. A common issue arises when trying to use the JwtService to decode access tokens in a controller. In this guide, we'll walk you through the problem and provide a clear, step-by-step solution.

Understanding the Problem

You're likely trying to inject the JwtService service into your controller but facing an error message similar to this:

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This error indicates that NestJS can't find the JwtService that you intend to use in your controller. Let's dive into the solution.

The Solution

Step 1: Import the JwtModule

To properly use the JwtService, you need to ensure that the JwtModule is imported into your module. Here’s how to do it:

Locate your Event Module: This would be the module where your EventController is declared.

Import the JwtModule: Modify your module file to add the JwtModule to the imports array.

Here's what your EventModule might look like:

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Step 2: Register and Inject the JwtService

After you have imported the JwtModule, the next step involves the JwtService injection. In your EventController, you have already done the initial setup correctly in the constructor:

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Step 3: Ensure Correct Arguments in the Controller

Make sure that when you call the JwtService, you're passing the access token correctly. It's good practice to validate the token before processing it.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the steps above, you should be able to resolve the dependency injection issue with JwtService in your NestJS application. Remember to always check that the necessary module imports and exports are correctly configured in your application.

If you encounter other dependency injection issues, always check the corresponding module file to ensure required services are properly provided.

With a clear understanding of how to inject services in NestJS, you're now better equipped to manage JWTs effectively in your applications!