How do I inject a buffered reader into a class with a file reader as its parameter using Spring boot?

Question

I have this spring boot application in which I have the below line inside a method.

BufferedReader reader = new BufferedReader(new FileReader("somePath"));

How can I inject this into my code so I can mock it for my unit tests? Using guice I could use a provider. But how can I achieve this using spring boot? Any help would be much appreciated.

Answer 1

If you want to mock the class which have the below line inside a method.

BufferedReader reader = new BufferedReader(new FileReader("somePath"));

Create a Mock instance of the class and define the mock behaviour like :

@MockBean
private TestClass testClass;

when(testClass.readFile()).thenReturn(content);

where content is the output you want to return.

you can create a bean of buffered reader and inject :

    @Bean
BufferedReader reader(@Value("${filename}") String fileName) throws FileNotFoundException{

    return new BufferedReader(new FileReader(fileName));
}

-Dfilename=SOMEPATH