get value from spring application properties with code examples

When developing an application in Spring, it is essential to control the application's configuration. Spring provides various ways to do this, but one way is through application properties. Application properties can store configuration settings for the application, such as database configuration, logging settings, and more. In this article, we're going to dive deeper into getting value from Spring application properties with code examples.

Accessing Application Properties

Spring application properties are typically stored in a file named application.properties or application.yml. These files are usually located in the src/main/resources folder within your project. Spring boot by default will read the application.properties and application.yml files in the classpath, but you can also specify the location of the file using the –spring.config.name, –spring.config.location, or -Dspring.config.additional-location properties.

To get the value of a property, we can use the @Value annotation or the Environment object in Spring.

@Value Annotation

The @Value annotation is used to inject values from application.properties to fields in beans. The syntax for using @Value is as follows:

@Value("${property.key}")

Here, property.key is the key of the property that we want to get the value of.

For example, consider the following application.properties file:

foo.bar=baz

We can get the value of foo.bar by using the @Value annotation as follows:

@Value("${foo.bar}")
private String foobarValue;

The value of foobarValue will be "baz".

Environment Object

The Environment interface in Spring provides methods to access the application properties. To use the Environment object, we must inject it into our bean using the @Autowired annotation.

For example, consider the following code snippet:

@Autowired
private Environment environment;

public String getProperty(String key) {
    return environment.getProperty(key);
}

Here, the getProperty method accepts a string, which is the key of the property we want to access. The method then returns the value of the property.

Using Default Values

We can also specify default values for properties using the @Value annotation. If the property is not present in the properties file, the default value will be used.

Consider the following code snippet:

@Value("${non.existent.property:default}")
private String defaultValue;

Here, if the non.existent.property is not present in the properties file, defaultValue will be set to "default".

Using Multiple Properties

We can also use multiple properties in a single expression. To do this, we can use the ${property.key} syntax and concatenate the properties using the + operator.

For example, consider the following application.properties file:

foo.bar=baz
foo.baz=qux

We can get the concatenated value of foo.bar and foo.baz as follows:

@Value("${foo.bar}" + "${foo.baz}")
private String concatenatedValue;

The value of concatenatedValue will be "bazqux".

Conclusion

In this article, we have looked at various examples of getting values from Spring application properties. We have seen how to use the @Value annotation and the Environment object to access properties, how to set default values, and how to use multiple properties in a single expression. These techniques are essential for controlling the configuration of your Spring application.

here are some more details about the different topics we covered in the previous article.

@Value Annotation

The @Value annotation is a powerful way to access and inject Spring application properties into your application's beans. This annotation can be used on fields, constructors, and methods. However, the most common use case is to inject a value into a field.

When using the @Value annotation, Spring will search for the specified property key in the application's properties file. If the property is found, its value will be injected into the annotated field. If the property is not found, you can provide a default value as part of the annotation, like we saw in the previous article.

Here's an example of how to use the @Value annotation to inject a property value into a field:

@Component
public class MyComponent {
    
    @Value("${my.property.key}")
    private String myPropertyValue;
    
    // other code...
}

In this example, we have a Spring component called MyComponent. We're using the @Value annotation to inject the value of a property with the key "my.property.key" into the myPropertyValue field.

Environment Object

The Environment object is a Spring utility that provides access to the application's properties and profile information. This object can be injected into Spring components using the @Autowired annotation.

Once you have an instance of the Environment object, you can use its getProperty() method to access a specific property value. You can also use the getProperty() method with a default value, just like we did with the @Value annotation.

Here's an example of how to use the Environment object to access a property value:

@Component
public class MyComponent {
    
    @Autowired
    private Environment environment;
    
    public void doSomething() {
        String myPropertyValue = environment.getProperty("my.property.key");
        // use the property value...
    }
}

In this example, we have a Spring component called MyComponent. We're using the @Autowired annotation to inject an instance of the Environment object into the component. We can then use the object's getProperty() method to get the value of a property with the key "my.property.key".

In conclusion, both the @Value annotation and the Environment object provide convenient ways to access and inject Spring application properties. Which one you choose to use will depend on your specific requirements and preferences.

Popular questions

  1. What are Spring application properties?

Spring application properties are configuration settings for the application, such as database configuration, logging settings, and more. These properties are typically stored in a file named application.properties or application.yml, which are located in the src/main/resources folder within the project.

  1. How can we access application properties in Spring?

Spring provides several ways to access application properties. Two of the most common ways are using the @Value annotation and the Environment object. The @Value annotation can be used to inject values from the properties file to fields in beans. The Environment object provides methods to access properties and profile information.

  1. How can we use the @Value annotation to access a property value with a default value?

We can specify a default value for a property using the ":" operator in the @Value annotation. For example, the following line of code specifies a default value of "default" for the "my.property.key" property.

@Value("${my.property.key:default}")
private String myPropertyValue;
  1. How can we use multiple properties in a single expression in Spring?

We can use multiple properties in a single expression by using the "${property.key}" syntax and concatenating the properties using the "+" operator. For example, the following line of code concatenates the values of the "foo.bar" and "foo.baz" properties.

@Value("${foo.bar}" + "${foo.baz}")
private String concatenatedValue;
  1. What is the Environment object in Spring?

The Environment object is a Spring utility that provides access to the application's properties and profile information. We can inject an instance of the Environment object into Spring components using the @Autowired annotation. Once we have an instance of the Environment object, we can use its getProperty() method to access a specific property value.

Tag

Configuration

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