Spring Boot Value & ConfigurationProperties Annotation examples

This tutorial shows how to use @Value & @ConfigurationProperties annotations to read configuration from properties file.

@Value vs @ConfigurationProperties Annotation

@Value annotation is provide by Spring Bean factory & is used at the field or method/constructor parameter level that indicates a default value expression for the annotated element. It supports SpEL (Spring Expression Language) expressions for setting the value.

@ConfigurationProperties annotation is provided by SpringBoot & is used for externalized configuration. You can add this to a class definition or a @Bean method in a @Configuration class if you want to bind and validate some external Properties (e.g. from a .properties file or .yml file). Contrary to @Value, SpEL expressions are not evaluated since property values are externalized.

Create pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	
    <modelVersion>4.0.0</modelVersion>
	
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/>
    </parent>
	
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

    </dependencies>
    <!-- To create an executable jar -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>    

db.username=scott
db.password=tiger
listOfTables=Students,Subjects,Teachers
valuesMap={John: '1', Mark: '2', David: '3'}    

Create AppConfig & ConfigurationApplication classes. AppConfig class will read the application.properties with the help of @PropertySource and uses @Value annotation to store the value into attributes. It reads simple key value pair using username, password attributes, reads list of tables into a string array, and map into valuesMap attribute.

package com.example.demo;
    
import java.util.Map;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@PropertySource("classpath:application.properties")
public class AppConfig {

    @Value("${db.username}")
    private String username;

    @Value("${db.password}")
    private String password;
    
    // reads data into a string array
    @Value("${listOfTables}")
    private String[] tableValues;
        
    // reads data into a map    
    @Value("#{${valuesMap}}")
    private Map<String, Integer> valuesMap;
    
    // reads single value from key value pair
    @Value("#{${valuesMap}['John']}")
    private Integer value1;

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }
        
    public String[] getTableValues() {
        return tableValues;
    }

    public Map<String, Integer> getValuesMap() {
        return valuesMap;
    }

    public Integer getValue1() {
        return value1;
    }
	
}	

package com.example.demo;    
import java.util.Arrays;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class ConfigurationApplication {

    @Autowired
    private AppConfig appConfig;

    public static void main(String[] args) {
        SpringApplication.run(ConfigurationApplication.class, args);
    }

    @Bean
    public ApplicationRunner printDataBaseConfig() {
        return args -> {
            System.out.println(appConfig.getUsername());
            System.out.println(appConfig.getPassword());
            System.out.println(Arrays.toString(
                appConfig.getTableValues()));
            System.out.println(appConfig.getValuesMap());
            System.out.println(appConfig.getValue1());            
        };
    }

}	

scott
tiger
[Students, Subjects, Teachers]
{John=1, Mark=2, David=3}
1		

app.username=scott
app.password=tiger
app.tableValues[0]=Students
app.tableValues[1]=Subjects
app.tableValues[2]=Teachers
app.valuesMap.John=1
app.valuesMap.Mark=2
app.valuesMap.David=3
app.value1=1    

Create AppProperties & ConfigurationApplication classes. AppProperties class will read the application.properties with the help of @ConfigurationProperties annotation to store the value into attributes. It reads simple key value pair using username, password attributes, reads list of tables into a string array, and map into valuesMap attribute.

import java.util.Map;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties("app")
public class AppProperties {
	
    private String username;

    private String password;
        
    private String[] tableValues;
        
    private Map<String, Integer> valuesMap;
        
    private Integer value1;

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }
	
    public String[] getTableValues() {
        return tableValues;
    }

    public Map<String, Integer> getValuesMap() {
        return valuesMap;
    }

    public Integer getValue1() {
        return value1;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public void setTableValues(String[] tableValues) {
        this.tableValues = tableValues;
    }

    public void setValuesMap(Map<String, Integer> valuesMap) {
        this.valuesMap = valuesMap;
    }

    public void setValue1(Integer value1) {
        this.value1 = value1;
    }

}
	

import java.util.Arrays;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class ConfigurationApplication {

    @Autowired
    private AppProperties appProperties;

    public static void main(String[] args) {
        SpringApplication.run(ConfigurationApplication.class, args);
    }

    @Bean
    public ApplicationRunner printDataBaseConfig() {
        return args -> {
            System.out.println(appProperties);
            System.out.println(appProperties.getUsername());
            System.out.println(appProperties.getPassword());
            System.out.println(Arrays.toString(
                appProperties.getTableValues()));
            System.out.println(appProperties.getValuesMap());
            System.out.println(appProperties.getValue1());
        };
    }

}	

scott
tiger
[Students, Subjects, Teachers]
{John=1, Mark=2, David=3}
1