Spring @PropertySource example

By mkyong | Updated: September 4, 2023

Viewed: 39,645 (+421 pv/w)

Tags: external config properties file spring

Spring default loads application.properties into the application’s environment, and we can use @PropertySource to load custom .properties files.

file.path=/server1/file/path

@Configuration
@PropertySource("classpath:file.properties")
public class Application {

    @Value("${file.path}")
    private String path;

    //...
}

Table of contents:

• 1. Project Structure
• 2. Properties Files
• 3. @PropertySource and @Value
• 4. Loads property files from multiple sources
• 5. Placeholder ${}
  • 5.1 Set system property
  • 5.1 Default value
• 6. Handle missing property file – ignoreResourceNotFound
• 7. Tests the @PropertySource
• 8. Download Source Code
• 9. References

P.S. Tested with Spring Boot 3.1.2

1. Project Structure

This article shows how to use @PropertySource to read a few of the .properties files and inject the property values via @Value.

2. Properties Files

Below are two .properties files for testing.

# Database
db.name=PostgreSQL
db.cluster.ip=127.0.0.1, 127.0.0.2, 127.0.0.3

# File Server
file.path=/server1/file/path

3. @PropertySource and @Value

We can use @PropertySource to load the property values from the properties files and access the property values via @Value.

package com.mkyong.config;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.List;

@Component
@PropertySource("classpath:/server/db.properties")
public class DatabaseProperties {

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

  @Value("${db.cluster.ip}")
  private List<String> clusterIp;

  //getters and setters
}

package com.mkyong.config;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource("classpath:/server/file.properties")
public class FileProperties {

  @Value("${file.path}")
  private String path;

  //
}

Starts the Spring Boot application and displays the property values.

package com.mkyong;

import com.mkyong.config.DatabaseProperties;
import com.mkyong.config.FileProperties;
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 Application implements CommandLineRunner {

  @Autowired
  private DatabaseProperties db;

  @Autowired
  private FileProperties file;

  @Override
  public void run(String... args) {
      System.out.println(db);
      System.out.println(file);
  }

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

}

Output

DatabaseProperties{name='PostgreSQL', clusterIp=[127.0.0.1, 127.0.0.2, 127.0.0.3]}
FileProperties{path='/server1/file/path'}

4. Loads property files from multiple sources

Below examples show how to load properties from multiple files.

4.1 @PropertySource with an argument of arrays of properties file location.

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.PropertySource;

@SpringBootApplication
@PropertySource({"classpath:/server/db.properties", "classpath:/server/file.properties"})
public class Application implements CommandLineRunner {

  @Autowired
  private DatabaseProperties db;

  @Autowired
  private FileProperties file;

  //...
}

4.2 Alternatively, try @PropertySources (extra s).

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.annotation.PropertySources;

@SpringBootApplication
@PropertySources({
      @PropertySource("classpath:/server/db.properties"),
      @PropertySource("classpath:/server/file.properties")
})
public class Application implements CommandLineRunner {

  @Autowired
  private DatabaseProperties db;

  @Autowired
  private FileProperties file;

  //...
}

5. Placeholder ${}

Spring will resolve the ${app.home} by fetching the values from the system property or environment variable app.home.

  file.path=${app.home}/server1/file/path

5.1 Set system property

We can set the app.home via the system property.

  java -Dapp.home=/home/mkyong -jar spring-boot-app.jar

5.1 Default value

In addition, we can provide a default value for the placeholder ${}.

  file.path=${app.home:defaultValue}/server1/file/path

6. Handle missing property file – ignoreResourceNotFound

If Spring can’t find the properties file, it prompts FileNotFoundException and fails to start the application.

@SpringBootApplication
@PropertySource("classpath:missing.properties")
public class Application {
  //...
}

Caused by: java.io.FileNotFoundException:
class path resource [missing.properties] cannot be opened because it does not exist

In @PropertySource, we can set ignoreResourceNotFound = true to ignore the missing properties file and continue to start the application.

  @SpringBootApplication
  @PropertySource(value = "classpath:missing.properties", ignoreResourceNotFound = true)
  public class Application {
    //...
  }

7. Tests the @PropertySource

Read the comments for self-explanatory.

package com.mkyong;

import com.mkyong.config.DatabaseProperties;
import com.mkyong.config.FileProperties;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;

import java.util.List;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

// easy but load entire context, no good.
// @SpringBootTest

// Keep test in minimal configuration
@SpringJUnitConfig
public class ApplicationTest {

    @Autowired
    private DatabaseProperties dbServer;

    @Autowired
    private FileProperties fileServer;

    @BeforeAll
    public static void setUp() {
        System.setProperty("app.home", "/home/other");
    }

    @Test
    public void testFileServer() {
        assertEquals("/home/other/server1/file/path", fileServer.getPath());
    }

    @Test
    public void testDatabaseServer() {

        assertEquals("PostgreSQL", dbServer.getName());
        List<String> clusterIp = dbServer.getClusterIp();
        assertEquals(3, clusterIp.size());
        assertTrue(clusterIp.contains("127.0.0.1"));
        assertTrue(clusterIp.contains("127.0.0.2"));
        assertTrue(clusterIp.contains("127.0.0.3"));

    }

    // Mock Configuration within the test class
    @Configuration
    @PropertySource({"classpath:/server/db.properties",
        "classpath:/server/file.properties"})
    static class TestConfig {
        @Bean
        public DatabaseProperties dbServer() {
            return new DatabaseProperties();
        }

        @Bean
        public FileProperties fileServer() {
            return new FileProperties();
        }

        // supports List from .properties file.
        @Bean
        public ConversionService conversionService() {
            return new DefaultConversionService();
        }
    }

}

8. Download Source Code

9. References

• SpringDoc – PropertySource
• SpringDoc – PropertySources
• SpringDoc – Configuration
• Spring Boot – Externalized Configuration
• Testing JSON in Spring Boot
• Spring Boot @ConfigurationProperties example
• Access values from application.properties in Spring Boot
• Spring @Value default values
• How to load custom properties files in Spring Boot
• Java Properties file examples