In this session, let us learn how to assign values to the instance variable using a properties file. For this, you need to create a properties file inside SRC main resources. And same values using name and value. Basically, a properties file is a key value pair. So here I have assigned values using key and the corresponding value depending upon the data type, then how to invoke it in the Java class, you need to add one other annotation at the rate property source. To invest the values from the properties file, you need to specify the name of the properties file.

That's what I have given at the rate property so classpath colon application dot properties. And the setter method she will be using at the rate value annotation within which using expression language and trying to retrieve the values Courts claim code that rice and coaster duration. Now let us try this out. Let me go back a clip I'm going to work on the same application only that the sanitation demo here I have created a new package comm.or no dot prop Barrett. Here I'm having the class. This is my class and I have annotated the classes at the rate component and the setter method I have added at the rate value annotation.

To start with, I have given hard coded values and I'm having a main class with public static void Main here I am trying to instantiate the container and retrieve the beam causes. Now, let me run this application. I have not started the application that properties it is a simple class which is annotated with a direct component. And I have you set the rate value with the hard coded values. If we run this No, I'm getting the proper output now Let us try with a properties file. So, you need to create a properties file inside SRC main resources, I have already created a properties file, the name of the file is application dot properties, you can just give any name if it is database later you can just give it a database properties, if it is service related you can just give it a service dot properties.

In this case, I have given it as application that properties now I have to give a key value pair either you can do it from properties or you can do it from source which is there on the bottom I have selected source. Now, let me do the name and value course dot name equal to Java course dot, these are just dummy names duration equal to 10 course dot price equal to 5000. Now, I have done this, let me save it I will come to this course is that Java here in the value instead of giving the hard coded values, I have to use expression language to retrieve it from the properties file it is dollar curly brace course dot name and duration, dollar curly brace course the duration and it is dollar curly brace course dot price. Now, I have added this as of now, this will be considered as a hard coded value only why because I need to use one more annotation at the rate property shows from which properties file you need to invoke the case or you need to invoke the values.

So, here I will just go and add it above the class at the rate property source. There are two things property forces and property so, you need to select property source within which you need to specify where exactly this properties file is available. It is available in the classpath. So I'm just giving it a class pop cola application dot properties. This is done. So, what we have done till now is we have created a properties file file and we have given the values using key and value next to retrieve the values from the properties file via use expression language over here dollar curly brace and the key course that encodes the duration and course that tries to ensure that this application that properties file is available for the IOC container we are using at the rate properties source.

So as IOC container will go to this particular application that properties file and retrieve the values based on the key that you have given there is no change in the main class. So let me run this average. Now I have got the output. These values are actually retrieved from the properties file. They are retrieved and assigned to the instance variables. What if I'm having a list?

Let me see Also I'm going to discourses that Java let me add and the stuff since the name is topic, let me add getter and setter methods go to source generate getter and setter method. I need to import list also that is, let me add the annotation at the rate value within which I need to use expression language. When I am using expression language in case of lists, what it will do is it will consider that as a single string only, I want to assign three different values. Let me show you the scenario. First I will explain expression language dollar curly brace course dot what is that list dot topic topics. Now the same name that we just give it over there the application dot properties file equal to so I want to I think three properties I will see sorry three values.

I will see MVC comma three topics I have a thing this is that now in courses fine also. Okay, this is done I'm not going to change this to string. Let me come to this main class here I'll try to retrieve course dot get topics which is empty setlist. Let me save this, let me run it you can see the output what actually it is it is only one value. Basically there's only two that accepting this as only one value even more to make it clear. Let me just show you using a for loop for each string.

Topic. Course dot get topics is a list. So I'm just assigning it directly. to So topic. Let me save this now and I will run it again. You can see the output is there.

Actually only one value I have given printed and if if if these are three different values that have come in one by one line right three different lines basically, now it is coming in a single line it means the array is having ArrayList is having only one value, because it is taken as a single string, how to tell to the IOC container that these are three different values go to this course is that Java here, I'm going to use spring expression language. So, I have to start with hash curly brace, ending here with a curly brace. Now, this is a single string, which is having a list of values splitted using what comma i hope you can understand, cause that list of topics is a single string, it's a string unit, you are taking that string and you are splitting it so that they are three, three different values.

Now, I'm saving this, let me run the application Now you can see the output. Now, there are three different values. I hope you can understand if you are having a list in that scenario, you can do the values directly in application dot properties, no issue at all, but in the Java class you have to split it for splitting what we are doing we are again going in for hat this is nothing but spring expression language it is which is taking a string and you are splitting it using comma. So, this is why you are paying values to the properties of a string using an external properties file. Till now what we are doing is either assigning the values using at the rate value annotation, we are giving hard coded values. Now, we are retrieving the values from a properties file thanks