###### tags: `SpringBoot` `@Value`

# A Quick Guide to Spring @Value

## 專案結構


## Setting Up the Properties File
src/main/resources/MyConfiguration.properties

config.type.user.name=Robin
config.type.user.id=001
config.type.user.mail=[e-mail]
config.type.user.is.married=true
config.type.demo.default=assign config.type.demo.default value xxx
config.type.string.array=ABC,DEF,GHI
config.type.int.array=7,8,9
#Note that the values in the Map must be in single quotes
config.type.map={key1: '1', key2: '2', key3: '3'}

## Setting Up the Properties Java Class

@Configuration
@PropertySource(
		value = "classpath:MyConfiguration.properties", 
		ignoreResourceNotFound = true, 
		encoding="UTF-8")
public class DemoReadProperties {
	
	@Value("${config.type.user.name}")
    private String configTypeUserName;

	@Value("${config.type.user.id}")
    private String configTypeUserId;
	
	@Value("${config.type.user.mail}")
    private String configTypeUserMail;
	
	@Value("${config.type.user.is.married}")
    private Boolean configTypeUserIsMarried;
	
	@Value("${config.type.demo.default:this is a default value}")
    private String configTypeDemoDefault;
	
	@Value("${config.type.string.array:one,two,three}")
	private String[] configTypeStringArrayWithDefaults;
	
	@Value("${config.type.int.array:1,2,3}")
	private int[] configTypeIntArrayWithDefaults;
	
	@Value("#{systemProperties['os.name'] ?: 'my default system property value'}")
	private String spelWithSystemPropertiesValue;
	
	@Value("#{${config.type.map}}")
	private Map<String, Integer> configTypeMap;
    
    //Getter...Setter
    
    }

## Usage Examples

### 1. Basic and mostly useless example(String, int, double float, boolean)

@Value("${config.type.user.name}")
private String configTypeUserName;

@Value("${config.type.user.is.married}")
private Boolean configTypeUserIsMarried;

### 2. Default values can be provided for properties that might not be defined
> 冒號後面接著default value

@Value("${config.type.demo.default:this is a default value}")
private String configTypeDemoDefault;

### 3. Array properties

config.type.string.array=ABC,DEF,GHI
config.type.int.array=7,8,9

> Array的每個值使用逗號相隔, Spring會自動將值轉成定義的data type

@Value("${config.type.string.array}")
private String[] configTypeStringArrayWithDefaults;

@Value("${config.type.int.array:1,2,3}")
private int[] configTypeIntArrayWithDefaults;

### 4. Using @Value With Maps

#Note that the values in the Map must be in single quotes
config.type.map={key1: '1', key2: '2', key3: '3'}

> Array的每個值使用逗號相隔, Spring會自動將值轉成定義的data type

@Value("#{${config.type.map}}")
private Map<String, Integer> configTypeMap;

## ApplicationRunner (main function)

package person.tsungfuxie.springreadpropertiesexercise;

import java.util.Arrays;
import java.util.Map.Entry;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;

import person.tsungfuxie.springreadpropertiesexercise.properties.DemoReadProperties;

@SpringBootApplication
public class SpringReadPropertiesExerciseApplication implements ApplicationRunner {

	private static Logger logger = LoggerFactory.getLogger(SpringReadPropertiesExerciseApplication.class);
	
	@Autowired
	private DemoReadProperties demoReadProperties;
	
	public static void main(String[] args) {
		SpringApplication.run(SpringReadPropertiesExerciseApplication.class, args);
	}

	@Override
	public void run(ApplicationArguments args) throws Exception {
		// TODO Auto-generated method stub
		logger.info("Hello world!");
		logger.info("====================Read Configuration===================");
		logger.info("user name = {}", demoReadProperties.getConfigTypeUserName());
		logger.info("user id = {}", demoReadProperties.getConfigTypeUserId());
		logger.info("user mail = {}", demoReadProperties.getConfigTypeUserMail());
		logger.info("user is married = {}", demoReadProperties.getConfigTypeUserIsMarried() ? "結婚了" : "單身狗");
		logger.info("ConfigTypeDemoDefault = {}", demoReadProperties.getConfigTypeDemoDefault());
		logger.info("StringArrayWithDefaults(length = {}) = {}", demoReadProperties.getConfigTypeStringArrayWithDefaults().length, demoReadProperties.getConfigTypeStringArrayWithDefaults());
		logger.info("IntArrayWithDefaults(length = {}) = {}", demoReadProperties.getConfigTypeIntArrayWithDefaults().length, demoReadProperties.getConfigTypeIntArrayWithDefaults());
		logger.info("spelWithSystemPropertiesValue = {}", demoReadProperties.getSpelWithSystemPropertiesValue());
		for (Entry<String, Integer> mapEntry : demoReadProperties.getConfigTypeMap().entrySet()) {
			logger.info("Map<{}, {}>", mapEntry.getKey(), mapEntry.getValue());
		}
	}
	
//	@Bean
//	public CommandLineRunner commandLineRunner(ApplicationContext context) {
//		return args -> {
//			logger.info("Let's inspect the beans provided by Spring Boot:");
//			String[] beanNames = context.getBeanDefinitionNames();
//			Arrays.sort(beanNames);
//			for (String beanName : beanNames) {
//				logger.info(beanName);
//			}
//		};
//	}

}

## 測試結果

## 測試專案程式
Git clone: [https://github.com/tsungfuxie/spring-read-properties-exercise.git](https://github.com/tsungfuxie/spring-read-properties-exercise.git)

## 參考資源
[Baeldung Quick Guide to Spring @Value](https://www.baeldung.com/spring-value-annotation)

## mike 的例子

### 思路 20210929 mike add

利用Value註解來讓properties的檔案可以注入Bean裡面，這樣的好處有兩個

1. 如此一來更改預設的Bean attribute時，可以**統一**於properties檔案裡更改
2. 配合application.properties可以去使用切換dev環境或是prod環境

### application.properties

spring.profiles.active=dev

### service-dev.properties

# spread sheet id

SpreadSheet.ID=1sP5BeCtcG4l0MnOfTaKxJKFzUTbkpwLqulxxiYaWrKw

### service properties

package com.example.value.properties;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@PropertySource(value = "classpath:service-${spring.profiles.active}.properties", encoding="UTF-8")
public class ServiceProperties {

	@Value("${SpreadSheet.ID}")
	String MainSpreadSheetID;

	public String getMainSpreadSheetID() {
		return MainSpreadSheetID;
	}

	public void setMainSpreadSheetID(String mainSpreadSheetID) {
		MainSpreadSheetID = mainSpreadSheetID;
	}
	
	
}

> 仔細去觀察spring.profiles.active在這裡起到了微妙的作用

### runner

package com.example.value;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.example.value.properties.ServiceProperties;


@SpringBootApplication
public class GoogleAccountBudgetContractAnnualConsumptionStatisticsApplication implements ApplicationRunner{
	private static Logger logger = LoggerFactory.getLogger(GoogleAccountBudgetContractAnnualConsumptionStatisticsApplication.class);
	
	@Autowired //放在main前面
	ServiceProperties servicePreperties;
	
	public static void main(String[] args) {
		SpringApplication.run(GoogleAccountBudgetContractAnnualConsumptionStatisticsApplication.class, args);
		
	}

	@Override //放在main後面
	public void run(ApplicationArguments args) throws Exception {
		// TODO Auto-generated method stub
		logger.info("Hello world!");	
		String SpreadsheetID=servicePreperties.getMainSpreadSheetID();
		System.out.println(SpreadsheetID);
	}

}