In this tutorial, you will learn to use @ConfigurationProperties to map properties files to POJO classes in Spring Boot application. Let’s get started to build a simple example with Java and Maven
What you’ll need
Your favorite IDE
JDK 8+ or OpenJDK 8+
Maven 3+
Stack
Java
Spring Boot
Init project structure and dependencies
Project structure
├── src
│ └── main
│ ├── java
│ │ └── com
│ │ └── answerindepth
│ │ └── util
│ │ ├── Application.java
│ │ ├── NestedProperties.java
│ │ └── SimpleProperties.java
│ └── resources
│ └── application.properties
└── pom.xml
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>
<groupId>com.answerindepth.springboot</groupId>
<artifactId>springboot-nested-properties-file</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Define Properties file and handler
Properties file
application.properties
simple.a=Simple property
nested.a.b=Nested property
Mapping Properties file into POJO classes
SimpleProperties.java
package com.answerindepth.util;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties(prefix = "simple")
public class SimpleProperties {
private String a;
public String getA() {
return a;
}
public void setA(String a) {
this.a = a;
}
}
NestedProperties.java
package com.answerindepth.util;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties(prefix = "nested")
public class NestedProperties {
public static class A {
private String b;
public String getB() {
return b;
}
public void setB(String b) {
this.b = b;
}
}
private A a;
public A getA() {
return a;
}
public void setA(A a) {
this.a = a;
}
}
Config and Run
Application Bootstrap
Application.java
package com.answerindepth.util;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
@Slf4j
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Bean
public CommandLineRunner runner(SimpleProperties simpleProperties, NestedProperties nestedProperties) {
return r -> {
log.info(simpleProperties.getA());
log.info(nestedProperties.getA().getB());
};
}
}
Run with Maven
Type the below command at the project root directory
mvn clean spring-boot:run
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