前言
本文介绍Spring Boot中读取配置属性的几种方式，项目示例中用到的application.yml和application.properties定义如下：
application.yml
application.properties
@Value
@Value是比较常见的注入方式，功能强大但一般可读性较差。
@Value("str")
private String str; // 注入普通字符串
@Value("${hello}")
private String hello; // 注入配置属性
@Value("#{systemProperties['os.name']}")
private String systemPropertiesName; // 注入操作系统属性
@Value("#{ T(java.lang.Math).random() * 100.0 }")
private double randomNumber; //注入表达式结果
@Value("#{userBean.name}")
private String name; // 注入Bean属性
下面通过@Value注解获取定义在配置文件的属性值：
@SpringBootApplication
public class AttributeApplication {
private static final String SPRING_BOOT_HELLO = "spring-boot.hello";
@Value("${" + SPRING_BOOT_HELLO + "}")
private String hello;
/**
* 1. 通过@Value注解获取值
*/
public void getAttrByValueAnnotation() {
System.out.println("1. 通过@Value注解获取值: " + hello);
}
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
AttributeApplication bean = applicationContext.getBean(AttributeApplication.class);
bean.getAttrByValueAnnotation();
}
}
扩展说明：
@SpringBootApplication
public class AttributeApplication {
private static final String SPRING_BOOT_STR_ARRAY = "spring-boot.str-array";
private static final String SPRING_BOOT_INT_ARRAY = "spring-boot.int-array";
/**
* Attention : it is error if use Integer[]
*/
@Value("${" + SPRING_BOOT_INT_ARRAY + "}")
private int[] array;
/**
* 通过@Value注解获取数组
*/
public void getArrayAttr() {
System.out.println("5. 通过@Value注解获取数组: " + Arrays.toString(array));
}
@Value("#{'${" + SPRING_BOOT_STR_ARRAY + "}'.split(',')}")
private List<String> list;
/**
* 通过@Value注解获取List
*/
public void getListAttr() {
System.out.println("6. 通过@Value注解获取List: " + list.toString());
}
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
AttributeApplication bean = applicationContext.getBean(AttributeApplication.class);
bean.getArrayAttr();
bean.getListAttr();
}
}
Environment
通过注入获取Environment对象，然后再获取定义在配置文件的属性值：
@SpringBootApplication
public class AttributeApplication {
private static final String SPRING_BOOT_HELLO = "spring-boot.hello";
@Resource
private Environment environment;
/**
* 2. 通过注入Environment获取值
*/
public void getAttrByEnvironment() {
String property = environment.getProperty(SPRING_BOOT_HELLO);
System.out.println("2-1. 通过注入Environment获取值: " + property);
}
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
AttributeApplication bean = applicationContext.getBean(AttributeApplication.class);
bean.getAttrByEnvironment();
}
}
还可以在启动类中通过ApplicationContext获取Environment对象后再获取值：
@SpringBootApplication
public class AttributeApplication {
private static final String UNDEFINED = "undefined";
private static final String SPRING_BOOT_HELLO = "spring-boot.hello";
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
System.out.println("2-2. 通过ApplicationContext获取Environment后再获取值: " + applicationContext
.getEnvironment().getProperty(SPRING_BOOT_HELLO, UNDEFINED));
}
}
@ConfigurationProperties
@ConfigurationProperties作用在类上，用于注入Bean属性，然后再通过当前Bean获取注入值：
@SpringBootApplication
public class AttributeApplication {
private static final String APPLICATION_YML = "application.yml";
private static final String SPRING_BOOT_PREFIX = "spring-boot";
@Data
@Component
@PropertySource("classpath:" + APPLICATION_YML)
@ConfigurationProperties(prefix = SPRING_BOOT_PREFIX)
class Attribute {
private String hello;
private String world;
}
@Resource
private Attribute attribute;
/**
* 3. 通过@ConfigurationProperties注入对象属性获取
*/
public void getAttrByConfigurationPropertiesAnnotation() {
System.out.println("3. 通过@ConfigurationProperties注入对象属性获取: " + attribute);
}
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
AttributeApplication bean = applicationContext.getBean(AttributeApplication.class);
bean.getAttrByConfigurationPropertiesAnnotation();
}
}
PropertiesLoaderUtils
@SpringBootApplication
public class AttributeApplication {
private static final String UNDEFINED = "undefined";
private static final String APPLICATION_PROPERTIES = "application.properties";
private static final String SPRING_BOOT_HELLO = "spring-boot.hello";
/**
* 4. 通过PropertiesLoaderUtils获取(注意，此工具类仅可处理.properties或.xml配置文件)
*/
public void getAttrByPropertiesLoaderUtils() {
try {
ClassPathResource resource = new ClassPathResource(APPLICATION_PROPERTIES);
Properties properties = PropertiesLoaderUtils.loadProperties(resource);
String property = properties.getProperty(SPRING_BOOT_HELLO, UNDEFINED);
System.out.println("4. 通过PropertiesLoaderUtils获取: " + property);
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(AttributeApplication.class, args);
AttributeApplication bean = applicationContext.getBean(AttributeApplication.class);
bean.getAttrByPropertiesLoaderUtils();
}
}
