知识零食是一类关于零碎知识的笔记，大部分来自于对AI回答和网络搜索的整理，仅供参考
Spring项目如何通过使用配置文件中的占位符（如 ${url}）来动态读取外部配置
pom文件配置，仅导入了spring-context和lombok依赖
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.3.23</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
</dependencies>
1. 配置文件中定义键值对
在 Spring 项目的application.properties或application.yml文件中定义配置信息，例如：
使用application.properties文件：
database.url=localhost:8888 database.username=root database.password=root database.driverName=Driver
使用application.yml文件：
database: url: localhost:8888 username: root password: root driverName: Driver
2. 配置PropertySourcesPlaceholderConfigurer
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
@Configuration
@PropertySource("classpath:application.properties")
public class AppConfig {
@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
return new PropertySourcesPlaceholderConfigurer();
}
}
@PropertySource注解不支持yml文件，由于纯sping项目使用yml文件过程更复杂就不介绍了
3. 使用@Value注解读取配置
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Component
@AllArgsConstructor
@NoArgsConstructor
@Data
public class DataConfig {
@Value("${database.url}") // 读取配置文件中的 database.url
private String url;
@Value("${database.username}") // 读取配置文件中的 database.username
private String username;
@Value("${database.password}") // 读取配置文件中的 database.password
private String password;
@Value("${database.driverName}") // 读取配置文件中的 database.driverName
private String driverName;
}
${}是占位符语法，用于引用配置文件中的键值。- Spring 会自动将配置文件中的值注入到对应的字段中。
4. 测试配置是否生效
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
DataConfig dataConfig = context.getBean(DataConfig.class);
System.out.println("URL: " + dataConfig.getUrl());
System.out.println("Username: " + dataConfig.getUsername());
System.out.println("Password: " + dataConfig.getPassword());
System.out.println("Driver Name: " + dataConfig.getDriverName());
}
}
运行结果：
URL: localhost:8888 Username: root Password: root Driver Name: Driver