[JAVA] Procedure to make the value of the property file visible in Spring Boot

Introduction

This page is mainly for your own memory.

procedure

If you write it very roughly, it will be in the following order.

1. Write the value you want to set in the property file
Create a settings read class
1. Use with Autowired

Property file (application.yml)

For example, if you have the following application.yml

ymlSetting:
  stringKey: "Some kind of string"
  mapA:
    key1: "value1"
    key2: "value2"

Class to read property file

Create a class to read and store values from application.yml. Set the application.yml key to the prefix of the "@ConfigurationProperties" annotation. Then, you can define that this class will read this definition. (In the example, the Setting class defines that the setting value under ymlSetting is read.)

Each defined item is stored as a member variable. The non-nested item (stringKey) is of type String Items with child elements (mapA) can be declared as Maps.

When referencing the value in the property file, the value will be referenced using the Getter of the declared member variable.

Settings.java

package jp.co.sample;
 
import java.util.Map;
 
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
 
@Component
@ConfigurationProperties(prefix = "ymlSetting")
public class Settings {
    private String stringKey;
    private Map<String, String> mapA;
     
    public void setStringKey(String stringKey){
        this.stringKey = stringKey;
    }
     
    public String getStringKey(){
        return stringKey;
    }
     
    public void setMapA(Map<String, String> mapA){
        this.mapA = mapA;
    }
     
    public Map<String, String> getMapA(){
        return mapA;
    }
}

Usage example

For example, when the property value is output as standard, it looks like this.

SpringBootConfigApplication.java

package jp.co.sample;
 
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 SpringBootConfigApplication implements CommandLineRunner{
    @Autowired
    private Setting setting; //Property file reading class
     
  public static void main(String[] args) {
    SpringApplication.run(SpringBootConfigApplication.class, args);
  }
   
  @Override
    public void run(String... args) {
        System.out.println("string = " + Settings.getStringKey());
        System.out.println("key1 = " + Settings.getMapA().get("key1"));
        System.out.println("key2 = " + Settings.getMapA().get("key2"));
    }
}