Utilizing a LoopBack4 Interceptor to access repositories within the application

Question

Utilizing a LoopBack4 Interceptor to access repositories within the application

I am looking to improve the functionality of an Interceptor within my LoopBack4 application. Currently, the Interceptor simply displays the start and end of a controller method call on the command line, as outlined in this documentation.

Here is how my Log-Interceptor currently looks:

export const Log: Interceptor = async (invocationCtx, next) => {
    // Wait until the interceptor/method chain returns
    const req = await invocationCtx.get(RestBindings.Http.REQUEST);

    try
    {
        const stackinfo = 'Class: ' + invocationCtx.targetClass.name + ' | Method: ' + invocationCtx.methodName + " | Request IPs: " + req.ips.concat(', ');

        logger.trace('Starting - ' + stackinfo);

        const result = await next();
        const res = await invocationCtx.get(RestBindings.Http.RESPONSE);

        logger.trace('Ending - ' + stackinfo + ' | Response Status Code: ' + res.statusCode);

        return result;
    }
    catch (e)
    {
        logger.error(e);
        throw e;
    }
};

Now I would like to enhance this Interceptor to also log additional statistics data into my MySQL-Datasource. My challenge lies in figuring out how to access the repository within the interceptor. Should I inject the Repository, and if so, what is the correct way to do that? Alternatively, are there better methods to achieve this goal?

typescript express loopbackjs loopback4

Answer 1

Answer №1

If you want to access repositories within your interceptors, you can do so by using `invocationCtx.target` as shown below:

const exampleInterceptor: Interceptor = async (invocationCtx, next) => {
  const exampleRepo = invocationCtx.target.exampleRepository;
  const anotherExampleRepo = invocationCtx.target.anotherExampleRepository;
};

This method assumes that you have added corresponding @repository decorators in the controller where the interceptor is being used. This approach works for both class-level and method-level interceptors.

@intercept(exampleInterceptor)
export class ExampleController {
  constructor(
    @repository(ExampleRepository)
    public exampleRepository: ExampleRepository,
    @repository(AnotherExampleRepository)
    public anotherExampleRepository: AnotherExampleRepository
  ) {}
}

If you have any other suggestions or recommendations on how to achieve this, please feel free to share them!

Answer 2

If you want to access repositories within your interceptors, you can do so by using `invocationCtx.target` as shown below:

const exampleInterceptor: Interceptor = async (invocationCtx, next) => {
  const exampleRepo = invocationCtx.target.exampleRepository;
  const anotherExampleRepo = invocationCtx.target.anotherExampleRepository;
};

This method assumes that you have added corresponding @repository decorators in the controller where the interceptor is being used. This approach works for both class-level and method-level interceptors.

@intercept(exampleInterceptor)
export class ExampleController {
  constructor(
    @repository(ExampleRepository)
    public exampleRepository: ExampleRepository,
    @repository(AnotherExampleRepository)
    public anotherExampleRepository: AnotherExampleRepository
  ) {}
}

If you have any other suggestions or recommendations on how to achieve this, please feel free to share them!

Answer 3

Answer №2

After some exploration, I managed to come up with a workaround:

Establish a new service:

export class StatisticService
{
    constructor(
        @repository(StatisticRecordRepository) public statisticsRepository: StatisticRecordRepository
    ) {}


    async increment(key: string, addend = 1): Promise<void>
    {
        const existing = await this.statisticsRepository.findOne({where: {StatsKey: key}});
        if(existing !== null)
        {
            // @ts-ignore
            existing.Counter = existing.Counter + addend;
            existing.UpdateTs = (new Date()).toISOString();
            await this.statisticsRepository.update(existing);
        }
        else
        {
            await this.statisticsRepository.create(new StatisticRecord({
                                                                           StatsKey: key,
                                                                           Counter:  addend
                                                                       }));
        }
    }
}


export const StatisticsServiceBindings = {
    VALUE: BindingKey.create<StatisticService>("services.StatisticsService")
};

Register the service in the Application constructor:

this.bind(StatisticsServiceBindings.VALUE).toClass(StatisticService);

Retrieve and implement the Service in the Log-Interceptor:

const stats = await invocationCtx.get(StatisticsServiceBindings.VALUE);
stats.increment(invocationCtx.targetClass.name + '::' + invocationCtx.methodName + ' [' + res.statusCode + ']');

Answer 4

After some exploration, I managed to come up with a workaround:

Establish a new service:

export class StatisticService
{
    constructor(
        @repository(StatisticRecordRepository) public statisticsRepository: StatisticRecordRepository
    ) {}


    async increment(key: string, addend = 1): Promise<void>
    {
        const existing = await this.statisticsRepository.findOne({where: {StatsKey: key}});
        if(existing !== null)
        {
            // @ts-ignore
            existing.Counter = existing.Counter + addend;
            existing.UpdateTs = (new Date()).toISOString();
            await this.statisticsRepository.update(existing);
        }
        else
        {
            await this.statisticsRepository.create(new StatisticRecord({
                                                                           StatsKey: key,
                                                                           Counter:  addend
                                                                       }));
        }
    }
}


export const StatisticsServiceBindings = {
    VALUE: BindingKey.create<StatisticService>("services.StatisticsService")
};

Register the service in the Application constructor:

this.bind(StatisticsServiceBindings.VALUE).toClass(StatisticService);

Retrieve and implement the Service in the Log-Interceptor:

const stats = await invocationCtx.get(StatisticsServiceBindings.VALUE);
stats.increment(invocationCtx.targetClass.name + '::' + invocationCtx.methodName + ' [' + res.statusCode + ']');

Utilizing a LoopBack4 Interceptor to access repositories within the application

Answer №1

Answer №2

Similar questions

Error occurs when attempting to write to a Node stream after it has already

Is it possible to retrieve a union type property as an array of values in order to conduct a flexible type validation process?

Retrieve properly formatted text from the editor.document using the VSCode API

The speed of the OpenLayers web application is significantly hindered when accessed from a mobile device using Android

Determine the size of the resulting zip file with NodeJs

Explain the object type that is returned when a function accepts either an array of object keys or an object filled with string values

Executing several asynchronous functions in Angular 2

"Can you explain the functioning of this Node.js middleware when it doesn't require any

The use of `super` in Typescript is not returning the expected value

You cannot add properties to an object within an async function

Executing a node.js script with a click of a button

Error in Node.js: the function "myFunction" is not defined

Guide to effectively running unit tests on an Express 4 server using Jest

Unable to modify the value of an object variable generated from a query in JavaScript, ExpressJS, and MongoDB

What is the process for changing the name of an element in Angular 2?

Encountering issues with SSL websocket connection after updating node to version 20.10 (previously on 14.7) and socket.io to version 4.7.2 (previously on 1.4.36)

AngularYelp: Node Integration for Enhanced Functionality

Encountering error when using require() with Firebase in Express

Signature in TypeScript for a function that augments the number of elements in a tuple

Creating and sharing a project in Typescript