Spring Boot @ConfigurationProperties Example

The Spring Boot @ConfigurationProperties annotation enables us to bind the external property file or YAML file to a Java Bean Object. In this article let’s learn how to use Spring Boot @ConfigurationProperties annotation.

Folder Structure:

Create a Maven project (maven-archetype-quickstart) “SpringBootConfigurationProperties” and create a package for our source files “com.javainterviewpoint” under src/main/java

Now add the following dependency in the POM.xml

<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.javainterviewpoint</groupId>
	<artifactId>SpringBootConfigrationProperties</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>SpringBootConfigrationProperties</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.18.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>
			<version>6.0.5.Final</version>
		</dependency>
		<dependency>
			<groupId>javax.validation</groupId>
			<artifactId>validation-api</artifactId>
			<version>2.0.1.Final</version>
		</dependency>
		<!-- <dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<optional>true</optional>
		</dependency> -->
	</dependencies>

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

Create the Java classes SpringBootApp.java and JdbcProperties.java under com.javainterviewpoint folder.

The spring-boot-starter-parent is a special starter, it provides useful Maven defaults.

Spring Boot @ConfigurationProperties Example

Dependency Tree

[INFO] ------------------------------------------------------------------------
[INFO] Building SpringBootConfigrationProperties 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:3.1.1:tree (default-cli) @ SpringBootConfigrationProperties ---
[INFO] com.javainterviewpoint:SpringBootConfigrationProperties:jar:0.0.1-SNAPSHOT
[INFO] +- org.springframework.boot:spring-boot-starter:jar:2.1.1.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot:jar:2.1.1.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-context:jar:5.1.3.RELEASE:compile
[INFO] |  |     +- org.springframework:spring-aop:jar:5.1.3.RELEASE:compile
[INFO] |  |     +- org.springframework:spring-beans:jar:5.1.3.RELEASE:compile
[INFO] |  |     \- org.springframework:spring-expression:jar:5.1.3.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot-autoconfigure:jar:2.1.1.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-logging:jar:2.1.1.RELEASE:compile
[INFO] |  |  +- ch.qos.logback:logback-classic:jar:1.2.3:compile
[INFO] |  |  |  +- ch.qos.logback:logback-core:jar:1.2.3:compile
[INFO] |  |  |  \- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO] |  |  +- org.apache.logging.log4j:log4j-to-slf4j:jar:2.11.1:compile
[INFO] |  |  |  \- org.apache.logging.log4j:log4j-api:jar:2.11.1:compile
[INFO] |  |  \- org.slf4j:jul-to-slf4j:jar:1.7.25:compile
[INFO] |  +- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO] |  +- org.springframework:spring-core:jar:5.1.3.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-jcl:jar:5.1.3.RELEASE:compile
[INFO] |  \- org.yaml:snakeyaml:jar:1.23:runtime
[INFO] +- org.hibernate.validator:hibernate-validator:jar:6.0.13.Final:compile
[INFO] |  +- org.jboss.logging:jboss-logging:jar:3.3.2.Final:compile
[INFO] |  \- com.fasterxml:classmate:jar:1.4.0:compile
[INFO] \- javax.validation:validation-api:jar:2.0.0.Final:compile
[INFO] ------------------------------------------------------------------------

Defining Properties file [application.properties]

Spring Boot by default loads the application.properties located in the classpath. Place the application.properties file under src/main/resources folder.

# MySQL DB properties
jdbc.driver = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql://localhost:3306/mydb
jdbc.username = root
jdbc.password = admin

equivalent YAML file [application.yaml]

jdbc:
  driver:
    com.mysql.jdbc.Driver
  url:
    jdbc:mysql://localhost:3306/mydb
  username:
    root
  password:
    admin

Binding External Properties using @ConfigurationProperties annotation

The @ConfigurationProperties annotation reads and maps the property file based on the namespace specified through prefix attribute. In our case we have specified the prefix as “jdbc”

We have also added @Configuration annotation to the our JdbcProperties class in order to spring be able find this bean class and make it available for injection.

JdbcProperties class is a simple POJO containing the getters and setters for the properties driver, url, username and password.

package com.javainterviewpoint;

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

@Configuration
@ConfigurationProperties(prefix = "jdbc")
public class JdbcProperties
{
    public String driver;
    public String url;
    public String username;
    public String password;

    public String getDriver()
    {
        return driver;
    }

    public void setDriver(String driver)
    {
        this.driver = driver;
    }

    public String getUrl()
    {
        return url;
    }

    public void setUrl(String url)
    {
        this.url = url;
    }

    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;
    }

    @Override
    public String toString()
    {
        return "JdbcProperties [driver=" + driver + ", url=" + url + ", username=" + username + ", password=" + password
                + "]";
    }
}

SpringBootApp.java

package com.javainterviewpoint;

import javax.annotation.PostConstruct;

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

@SpringBootApplication
public class SpringBootApp
{
    @Autowired
    private JdbcProperties jdbcProperties;

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

    @PostConstruct
    public void display()
    {
        System.out.println("*** Read from Property file ***");
        System.out.println("Url      : "+jdbcProperties.getUrl());
        System.out.println("Driver   : "+jdbcProperties.getDriver());
        System.out.println("Username : "+jdbcProperties.getUsername());
        System.out.println("Password : "+jdbcProperties.getPassword());
    }
}

@SpringBootApplication annotation does the work of @EnableAutoConfiguration, @Configuration and @ComponentScan annotations together
We have injected the JdbcProperties class using the @Autowired annotation
@PostConstruct annotation runs after the service is initialized and prints the property file data.

Output:

Select the Project –>Run As –> Run Configuration –>Maven –> New. In the Main tab, key in the Goals as “spring-boot:run” and click on Run.

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.1.RELEASE)

2018-12-21 22:58:46.525  INFO 7468 --- [           main] com.javainterviewpoint.SpringBootApp     : Starting SpringBootApp on Jack-PC with PID 7468 (D:\sts-3.8.3.RELEASE\Workspace\SpringBootConfigurationProperties\target\classes started by Jack in D:\sts-3.8.3.RELEASE\Workspace\SpringBootConfigurationProperties)
2018-12-21 22:58:46.531  INFO 7468 --- [           main] com.javainterviewpoint.SpringBootApp     : No active profile set, falling back to default profiles: default
*** Read from Property file ***
Url      : jdbc:mysql://localhost:3306/mydb
Driver   : com.mysql.jdbc.Driver
Username : root
Password : admin

Validation of properties

Additionally we can validate the properties with validation constraints like @NotNull, @NotEmpty, @Email etc. In order to enable validation we need to add @Validated annotation to the @ConfigurationProperties class.

Lets add the validation constraint annotation and check

package com.javainterviewpoint;

import javax.validation.constraints.NotEmpty;
import javax.validation.constraints.NotNull;

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

@Configuration
@ConfigurationProperties(prefix = "jdbc")
public class JdbcProperties
{
    @NotNull
    public String driver;
    @NotEmpty
    public String url;
    public String username;
    public String password;

    public String getDriver()
    {
        return driver;
    }

    public void setDriver(String driver)
    {
        this.driver = driver;
    }

    public String getUrl()
    {
        return url;
    }

    public void setUrl(String url)
    {
        this.url = url;
    }

    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;
    }

    @Override
    public String toString()
    {
        return "JdbcProperties [driver=" + driver + ", url=" + url + ", username=" + username + ", password=" + password
                + "]";
    }
}

We have missed to provide value to the url property and lets see if spring is throwing a validation error.

# MySQL DB properties
jdbc.driver = com.mysql.jdbc.Driver
jdbc.url
jdbc.username = root
jdbc.password = admin

Output

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.8.RELEASE)

2018-12-21 23:19:53.418  INFO 3228 --- [           main] com.javainterviewpoint.SpringBootApp     : Starting SpringBootApp on Jack-PC with PID 3228 (D:\sts-3.8.3.RELEASE\Workspace\SpringBootConfigurationProperties\target\classes started by Jack in D:\sts-3.8.3.RELEASE\Workspace\SpringBootConfigurationProperties)
2018-12-21 23:19:53.423  INFO 3228 --- [           main] com.javainterviewpoint.SpringBootApp     : No active profile set, falling back to default profiles: default
2018-12-21 23:19:54.684 ERROR 3228 --- [           main] o.s.b.b.PropertiesConfigurationFactory   : Properties configuration failed validation
2018-12-21 23:19:54.684 ERROR 3228 --- [           main] o.s.b.b.PropertiesConfigurationFactory   : Field error in object 'jdbc' on field 'url': rejected value []; codes [NotEmpty.jdbc.url,NotEmpty.url,NotEmpty.java.lang.String,NotEmpty]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [jdbc.url,url]; arguments []; default message [url]]; default message [must not be empty]
2018-12-21 23:19:54.685  WARN 3228 --- [           main] s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'springBootApp': Unsatisfied dependency expressed through field 'jdbcProperties'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jdbcProperties': Could not bind properties to JdbcProperties (prefix=jdbc, ignoreInvalidFields=false, ignoreUnknownFields=true, ignoreNestedProperties=false); nested exception is org.springframework.validation.BindException: org.springframework.boot.bind.RelaxedDataBinder$RelaxedBeanPropertyBindingResult: 1 errors
Field error in object 'jdbc' on field 'url': rejected value []; codes [NotEmpty.jdbc.url,NotEmpty.url,NotEmpty.java.lang.String,NotEmpty]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [jdbc.url,url]; arguments []; default message [url]]; default message [must not be empty]
2018-12-21 23:19:54.698  INFO 3228 --- [           main] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2018-12-21 23:19:54.702 ERROR 3228 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Binding to target JdbcProperties [driver=com.mysql.jdbc.Driver, url=, username=root, password=admin] failed:

    Property: jdbc.url
    Value: 
    Reason: must not be empty


Action:

Update your application's configuration

Spring Boot @ConfigurationProperties Example

Folder Structure:

Spring Boot @ConfigurationProperties Example

Defining Properties file [application.properties]

Binding External Properties using @ConfigurationProperties annotation

SpringBootApp.java

Validation of properties

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Folder Structure:

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Spring Boot @ConfigurationProperties Example

Defining Properties file [application.properties]

Binding External Properties using @ConfigurationProperties annotation

SpringBootApp.java

Validation of properties

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