How to access a value defined in the application.properties file in Spring Boot

You can use the @Value annotation and access the property in whichever Spring bean you're using

@Value("${userBucket.path}")
private String userBucketPath;

The Externalized Configuration section of the Spring Boot docs, explains all the details that you might need.

Another way is injecting org.springframework.core.env.Environment to your bean.

@Autowired
private Environment env;
....

public void method() {
    .....  
    String path = env.getProperty("userBucket.path");
    .....
}

Currently, I know about the following three ways:

1. The @Value annotation

    @Value("${<property.name>}")
    private static final <datatype> PROPERTY_NAME;

• In my experience there are some situations when you are not able to get the value or it is set to null. For instance, when you try to set it in a preConstruct() method or an init() method. This happens because the value injection happens after the class is fully constructed. This is why it is better to use the 3'rd option.

2. The @PropertySource annotation

@PropertySource("classpath:application.properties")

//env is an Environment variable
env.getProperty(configKey);

• PropertySouce sets values from the property source file in an Environment variable (in your class) when the class is loaded. So you able to fetch easily afterword.
• Accessible through System Environment variable.

3. The @ConfigurationProperties annotation.

• This is mostly used in Spring projects to load configuration properties.

• It initializes an entity based on property data.

• @ConfigurationProperties identifies the property file to load.

• @Configuration creates a bean based on configuration file variables.

  @ConfigurationProperties(prefix = "user")
    @Configuration("UserData")
    class user {
      //Property & their getter / setter
    }
  
    @Autowired
    private UserData userData;
  
    userData.getPropertyName();

@ConfigurationProperties can be used to map values from .properties( .yml also supported) to a POJO.

Consider the following Example file.

.properties

cust.data.employee.name=Sachin
cust.data.employee.dept=Cricket

Employee.java

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;

@ConfigurationProperties(prefix = "cust.data.employee")
@Configuration("employeeProperties")
public class Employee {

    private String name;
    private String dept;

    //Getters and Setters go here
}

Now the properties value can be accessed by autowiring employeeProperties as follows.

@Autowired
private Employee employeeProperties;

public void method() {

   String employeeName = employeeProperties.getName();
   String employeeDept = employeeProperties.getDept();

}