Spring @Value Annotation

Spring @Value annotation is used to assign default values to variables and method arguments. We can read spring environment variables as well as system variables using @Value annotation. Spring @Value annotation also supports SpEL. Let’s look at some of the examples of using @Value annotation.

Spring @Value – Default Value

We can assign default value to a class property using @Value annotation.

@Value("Default DBConfiguration")
    private String defaultName;
    @Value annotation argument can be a string only, but spring tries to convert it to the specified type. Below code will work fine and assign the boolean and integer values to the variable.
    @Value("true")
    private boolean defaultBoolean;
    @Value("10")
    private int defaultInt;

Spring @Value – Spring Environment Property

Spring @Value with methods

When the @Value annotation is found on a method, Spring context will invoke it when all the spring configurations and beans are getting loaded. If the method has multiple arguments, then every argument value is mapped from the method annotation. If we want different values for different arguments then we can use @Value annotation directly with the argument.

@Value("Test")
    public void printValues(String s, String v){} //both 's' and 'v' values will be 'Test' 
    @Value("Test")
    public void printValues(String s, @Value("Data") String v){}
    // s=Test, v=Data

Spring @Value Example

Let’s create a simple Spring application where we will use @Value annotation to read properties and assign them to class variables. Create a maven project and add spring core dependencies.

<groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.0.6.RELEASE</version> </dependency>

Our final project structure will look like below image, we will look each of the components one by one.

Create a component class where we will inject variable values through @Value annotation.

public void printDBConfigs() { System.out.println("Driver Class = " + driverClass); System.out.println("DB URL = " + dbURL); System.out.println("User Name = " + userName); // Never do below in production environment :D System.out.println("Password = " + String.valueOf(password));

Now we have to create a Configuration class and provide a @Bean method for DBConnection class.

import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.PropertySource; @Configuration @PropertySource("classpath:db.properties") @PropertySource(value = "classpath:root.properties", ignoreResourceNotFound = true) public class DBConfiguration { @Value("Default DBConfiguration") private String defaultName; @Value("true") private boolean defaultBoolean; @Value("10") private int defaultInt; @Value("${APP_NAME_NOT_FOUND:Default}") private String defaultAppName; @Value("${java.home}") private String javaHome; @Value("${HOME}") private String homeDir; @Bean public DBConnection getDBConnection() { DBConnection dbConnection = new DBConnection(); return dbConnection; @Value("Test") public void printValues(String s, @Value("another variable") String v) { System.out.println("Input Argument 1 =" + s); System.out.println("Input Argument 2 =" + v); System.out.println("Home Directory = " + homeDir); System.out.println("Default Configuration Name = " + defaultName); System.out.println("Default App Name = " + defaultAppName); System.out.println("Java Home = " + javaHome); System.out.println("Boolean = " + defaultBoolean); System.out.println("Int = " + defaultInt);

Here is our main class where we are creating annotation-based spring context.

import java.sql.SQLException; import org.springframework.context.annotation.AnnotationConfigApplicationContext; public class SpringMainClass { public static void main(String[] args) throws SQLException { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(); context.scan("com.journaldev.spring"); context.refresh(); System.out.println("Refreshing the spring context"); DBConnection dbConnection = context.getBean(DBConnection.class); dbConnection.printDBConfigs(); // close the spring context context.close();

When you will run the class, it will produce following output.

Input Argument 2 = another variable Home Directory = /Users/pankaj Default Configuration Name = Default DBConfiguration Default App Name = Default Java Home = /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home Boolean = true Int = 10 Refreshing the spring context Driver Class = com.mysql.jdbc.Driver DB URL = jdbc:mysql://localhost:3306/Test User Name = journaldev Password = journaldev

Notice that Configuration class printValues() is getting called before our context is ready to serve user requests. That’s all for Spring @Value annotation example, you can download the example code from our GitHub Repository – A Comprehensive Guide.