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Spring Boot @ConfigurationProperties tutorial

Spring Boot @ConfigurationProperties tutorial shows how to bind properties to an object with @ConfigurationProperties in a Spring Boot application.

Spring is a popular Java application framework and Spring Boot is an evolution of Spring that helps create stand-alone, production-grade Spring based applications easily.

@ConfigurationProperties

@ConfigurationProperties allows to map the entire Properties and Yaml files into an object easily. It also allows to validate properties with JSR-303 bean validation. By default, the annotation reads from the application.properties file. The source file can be changed with @PropertySource annotation.

Spring Boot @ConfigurationProperties example

The following application reads configuration data from the application.properties file, which is the default Spring Boot configuration file.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           │   Application.java
│   │           │   MyRunner.java
│   │           └───conf
│   │                   AppProperties.java
│   └───resources
│           application.properties
└───test
    └───java

This is the project structure.

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.zetcode</groupId>
    <artifactId>springbootconfigurationproperties</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
    </parent>

    <dependencies>

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

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

This is the Maven pom.xml file.

resources/application.properties
spring.main.banner-mode=off

app.colour=steelblue
app.lang=en
app.theme=dark

In the application.properties file we have three custom properties. They have the app prefix.

com/zetcode/conf/AppProperties.java
package com.zetcode.conf;

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

@Configuration
@ConfigurationProperties(prefix = "app")
public class AppProperties {

    private String colour;
    private String lang;
    private String theme;

    public String getColour() {
        return colour;
    }

    public void setColour(String colour) {
        this.colour = colour;
    }

    public String getLang() {
        return lang;
    }

    public void setLang(String lang) {
        this.lang = lang;
    }

    public String getTheme() {
        return theme;
    }

    public void setTheme(String theme) {
        this.theme = theme;
    }
}

The properties are going to be bind to this configuration object.

@Configuration
@ConfigurationProperties(prefix = "app")
public class AppProperties {

The @Configuration annotation makes it a Spring-managed bean. In the @ConfigurationProperties, we set the prefix for our properties.

com/zetcode/MyRunner.java
package com.zetcode;

import com.zetcode.conf.AppProperties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class MyRunner implements CommandLineRunner {

    private static final Logger logger = LoggerFactory.getLogger(Application.class);

    @Autowired
    private AppProperties appProperties;

    @Override
    public void run(String... args) throws Exception {

        logger.info("Colour: {}", appProperties.getColour());
        logger.info("Language: {}", appProperties.getLang());
        logger.info("Theme: {}", appProperties.getTheme());
    }
}

In the MyRunner, we inject the AppProperties into a field and read its values.

com/zetcode/Application.java
package com.zetcode;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

Application is the entry point which sets up Spring Boot application.

Spring Boot @ConfigurationProperties example II

In the second application, we will also validate the properties.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           │   Application.java
│   │           │   MyRunner.java
│   │           └───config
│   │                   MailProperties.java
│   └───resources
│           application.properties
│           mail.properties
└───test
    └───java

This is the project structure.

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.zetcode</groupId>
    <artifactId>springbootconfigurationpropertiesvalidation</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
    </parent>

    <dependencies>

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

        <dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

This is the pom.xml file. We have an additional hibernate-validator dependency.

resources/application.properties
spring.main.banner-mode=off

This is the application.properties file.

resources/mail.properties
hostname=info@example.com
port=9000
from=admin@example.com

recipients[0]=user1@example.com
recipients[1]=user2@example.com
recipients[2]=user3@example.com
recipients[3]=user4@example.com

We have a custom mail.properties file.

com/zetcode/config/MailProperties.java
package com.zetcode.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.validation.annotation.Validated;

import javax.validation.constraints.Max;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import java.util.List;

@Configuration
@PropertySource("classpath:mail.properties")
@ConfigurationProperties
@Validated
public class MailProperties {

    @NotNull
    private String hostname;

    @Min(1000)
    @Max(10000)
    private int port;

    @NotNull
    private String from;

    @NotNull
    private List<String> recipients;

    public String getHostname() {
        return hostname;
    }

    public void setHostname(String hostname) {
        this.hostname = hostname;
    }

    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }

    public String getFrom() {
        return from;
    }

    public void setFrom(String from) {
        this.from = from;
    }

    public List<String> getRecipients() {
        return recipients;
    }

    public void setRecipients(List<String> recipients) {
        this.recipients = recipients;
    }
}

We use the @PropertySource annotation set the path to the custom properties file. The @Validated annotation validates the properties.

com/zetcode/MyRunner.java
package com.zetcode;

import com.zetcode.config.MailProperties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class MyRunner implements CommandLineRunner {

    private static final Logger logger = LoggerFactory.getLogger(Application.class);

    @Autowired
    private MailProperties mailProperties;

    @Override
    public void run(String... args) throws Exception {

        logger.info("Hostname: {}", mailProperties.getHostname());
        logger.info("Port: {}", mailProperties.getPort());
        logger.info("From: {}", mailProperties.getFrom());
        logger.info("Recipients: {}", mailProperties.getRecipients());
    }
}

We inject the MailProperties and read them in the run() method.

com/zetcode/Application.java
package com.zetcode;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

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

This is the Application class.

We run the application with mvn -q spring-boot:run.

In this tutorial, we have shown how to use @ConfigurationProperties to read configuration properties from an external file. You might also be interested in the related tutorials: Spring PropertySource tutorial, Spring Boot CommandLineRunner tutorial, Java tutorial, or list all Spring Boot tutorials.