How to read a file in AWS Lambda Function written in Java ?

Question

I have written an AWS Lambda Handler as below :

package com.lambda;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.r         


        

Answer 1

This is how I did it, let's say this is how your project structure looks like -

And you want to read the file config.properties which is inside the project-dir/resources directory.

The code for reading the content of the file would be -

InputStream input = null;
try {
    Path path = Paths.get(PropertyUtility.class.getResource("/").toURI());

    // The path for config file in Lambda Instance -
    String resourceLoc = path + "/resources/config.properties";

    input = new FileInputStream(resourceLoc);
} catch(Exception e) {
    // Do whatever
}

If you are following this project structure and using this code, then it will work in AWS Lambda.

PropertyUtility is just a utility class that I have created to read the contents of the config file. The PropertyUtility class looks like this -

As you can see in the above code, the path of the config file is different in the local system and in Lambda Instance.

In your local machine, PropertyUtility.class.getResource("/") points to bin, that is why you have to do path.getParent(), to point it to the project-directory which is HelloLambda in this example.

For the Lambda Instance, PropertyUtility.class.getResource("/") points directly to the project-directory.