Map Spring Boot properties to a POJO using ConfigurationProperties

Properties files are useful to externalize Spring Boot configuration. This post will discuss how to map all properties defined in the application.properties file to a POJO using @ConfigurationProperties.

In the previous post, we have seen how to use the @Value("${property}") annotation to inject configuration properties. If we’re working with multiple properties, this can be cumbersome. Spring Boot provides a method of working with properties that lets strongly typed beans govern and validate your application’s configuration. This post will discuss how to map all properties defined in the application.properties file to a POJO.

Consider the following application.properties file that contains few properties.

techiedelight.environment=prod

techiedelight.hosts=https://www.techiedelight.com,https://techiedelight.com

techiedelight.security.username=user1

techiedelight.security.password=pass1

techiedelight.security.roles=admin,editor,moderator

Config.java

The following configuration class uses @ConfigurationProperties annotation to bind and validate the class’s external configuration. Note that the annotation processor will automatically consider inner classes as nested properties.

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

import org.springframework.boot.context.properties.EnableConfigurationProperties;

import org.springframework.context.annotation.Configuration;

import java.util.ArrayList;

import java.util.List;

@Configuration

@EnableConfigurationProperties

@ConfigurationProperties("techiedelight")

public class Config {

private String environment;

private List<String> hosts = new ArrayList<>();

private final Security security = new Security();

public String getEnvironment() {

return environment;

}

public void setEnvironment(String environment) {

this.environment = environment;

}

public List<String> getHosts() {

return hosts;

}

public void setHosts(List<String> hosts) {

this.hosts = hosts;

}

public Security getSecurity() {

return security;

}

public static class Security {

private String username;

private String password;

private List<String> roles = new ArrayList<>();

public String getUsername() {

return username;

}

public void setUsername(String username) {

this.username = username;

}

public String getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

public List<String> getRoles() {

return roles;

}

public void setRoles(List<String> roles) {

this.roles = roles;

}

@Override

public String toString()

{

return "{" + this.getUsername() + ", " + this.getPassword()

+ ", " + this.getRoles() + "}";

}

@Override

public String toString()

{

return "{" + this.getEnvironment() + ", " + this.getHosts()

+ ", " + this.getSecurity() + "}";

}

Inject @ConfigurationProperties beans

Now that all properties are loaded from an application.properties file, we can create an object of the Config class and display the properties using the CommandLineRunner.

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.CommandLineRunner;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

public class Main implements CommandLineRunner {

@Autowired

private Config config;

public static void main(String[] args) {

SpringApplication.run(Main.class, args);

}

@Override

public void run(String... strings) throws Exception {

System.out.println(config);

}

We can also inject @ConfigurationProperties beans in the same way as any other bean, as shown in the following example:

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;

@Service

public class MyService {

private final Config properties;

@Autowired

public MyService(Config properties) {

this.properties = properties;

}

@PostConstruct

public void openConnection() {

System.out.println(properties);

}

Output:

{prod, [https://www.techiedelight.com, https://techiedelight.com],
{user1, pass1, [admin, editor, moderator]}}

That’s all about mapping Spring Boot properties to a POJO using @ConfigurationProperties.

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Read values from the YAML file in Spring Boot