Application Properties

This is Spring boot application built-in file created at the time of project creation using STS and initializr named as application.properties file.

Its default location is src/main/resources as mentioned in below screenshot.

This file can contain both system define and custom properties.

Below is an example to define property inside application.properties file.

Here, # denotes for writing a comment.

Create a class UserController.java file having below content in place.

@RestController annotation used to created RESTful web services which can be accessed using http methods like GET, POST, etc. and it is the combination of @Controller and @ResponseBody.

@RequestMapping annotation is used to define header, uri, method type, parameters, path, consume type, etc.

@Value(“${custom.practice.name}”) annotation will help us to access value of a property declared in application.properties file.

If property not declared or found inside application.properites file will throw below exception:

Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder ‘spring.application.name’ in value “${custom.practice.name}”

To Resolve or suppress above exception, we can declare default value while accessing property in Java file like @Value(“${custom.practice.name:javadoubts}”)

Sometime, it doesn’t work with STS, eclipse and show below error.

Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder ‘spring.application.name’ in value “${custom.practice.name}”

Open command prompt and run mvn spring-boot:run command to start the Spring boot application and hit below URL

Hit below URL in browser will give below output: