# 應(yīng)用信息
app.name=My Awesome App
app.version=1.2

# 作者信息
author.name=Alice
author.email=alice@example.com

# 功能開(kāi)關(guān)和配置
feature.email.enabled=true
max.pool.size=100

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

@Service
public class AppInfoService {

    // 1. 注入字符串
    @Value("${app.name}")
    private String appName;

    // 2. 注入數(shù)字（Spring會(huì)自動(dòng)進(jìn)行類(lèi)型轉(zhuǎn)換）
    @Value("${app.version}")
    private double appVersion;

    @Value("${max.pool.size}")
    private int maxPoolSize;

    // 3. 注入布爾值
    @Value("${feature.email.enabled}")
    private boolean isEmailEnabled;

    // 4. 提供默認(rèn)值
    // 如果配置文件中沒(méi)有 `app.description`，則使用默認(rèn)值 "A great application"
    @Value("${app.description:A great application}")
    private String appDescription;

    public void displayAppInfo() {
        System.out.println("Application Name: " + appName);
        System.out.println("Application Version: " + appVersion);
        System.out.println("Max Pool Size: " + maxPoolSize);
        System.out.println("Is Email Feature Enabled: " + isEmailEnabled);
        System.out.println("Description: " + appDescription);
    }
}

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

@Component
public class SpelExamples {

    // 1. 執(zhí)行簡(jiǎn)單的數(shù)學(xué)運(yùn)算
    @Value("#{10 * 60}") // 注入 600
    private int secondsInTenMinutes;

    // 2. 引用另一個(gè)Bean的屬性
    // 假設(shè)容器中有一個(gè)名為 appInfoService 的Bean
    @Value("#{appInfoService.appName}") 
    private String anotherAppName;

    // 3. 調(diào)用靜態(tài)方法
    @Value("#{T(java.lang.Math).random() * 100.0}")
    private double randomNumber;

    // 4. 引用系統(tǒng)屬性
    @Value("#{systemProperties['user.home']}")
    private String userHomeDirectory;

    // 5. 結(jié)合屬性占位符使用
    // 先從配置文件找到 `some.value`，如果不存在則使用 `default`，然后轉(zhuǎn)為大寫(xiě)
    @Value("#{'${some.value:default}'.toUpperCase()}")
    private String uppercaseValue;

    public void display() {
        System.out.println("Seconds in 10 minutes: " + secondsInTenMinutes);
        System.out.println("Copied App Name: " + anotherAppName);
        System.out.println("Random Number: " + randomNumber);
        System.out.println("User Home: " + userHomeDirectory);
        System.out.println("Uppercase Value: " + uppercaseValue);
    }
}

@Value("This is a hardcoded message")
private String message;