SpringBoot如何读取application.properties配置文件

import java.util.Properties;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
 
public static Properties readPropertiesFile(String fileName) {
    try {
        Resource resource = new ClassPathResource(fileName);
        Properties props = PropertiesLoaderUtils.loadProperties(resource);
        return props;
    } catch (Exception e) {
        System.out.println("读取配置文件：" + fileName + "异常，读取失败");
        e.printStackTrace();
    }
    return null;
}

Properties properties = readPropertiesFile("application.properties");
System.out.println(properties.getProperty("spring.rabbitmq.host"));

import org.springframework.core.env.Environment;
 
@Autowired
private Environment environment;
 
System.out.println(environment.getProperty("spring.rabbitmq.host"));

import org.springframework.beans.factory.annotation.Value;
 
@Value("${spring.rabbitmq.host}")
private String rabbitmqHost;
 
System.out.println(rabbitmqHost);

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;
 
@Getter
@Setter
@ConfigurationProperties(prefix = "spring.rabbitmq")
public class TestProperties {
    private String host;
    private String port;
    private String username;
    private String password;
}

import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
 
@EnableConfigurationProperties(TestProperties.class)
@SpringBootConfiguration
public class TestConfiguration {
}

@Autowired
private TestProperties testProperties;
 
System.out.println(testProperties.getHost());

@Component
public class UserUtil {
    // 使用@Value注解读取配置
    @Value("${user.name}")
    private String name;
 
    // 设置静态成员变量用来接收@Value注入的值
    private static String userName;
 
    // 使用@PostConstruct注解用于静态变量赋值
    @PostConstruct
    public void getUserName() {
        userName = this.name;
    }
 
    // 测试方法静态变量是否被赋值
    public static String test() {
        return userName;
    }
}

String name = UserUtil.test();