凡是被Spring管理的类，实现接口 EnvironmentAware 重写方法 setEnvironment 可以在工程启动时，
获取到系 统环境变量和application配置文件中的变量。
@Configuration
public class MyEnvironmentAware implements EnvironmentAware {
//注入application.properties的属性到指定变量中.
@Value("${spring.datasource.url}")
private String myUrl;
@Override
public void setEnvironment(Environment environment) {
//打印注入的属性信息.
System.out.println("myUrl=" + myUrl);
//通过 environment 获取到系统属性.
System.out.println(environment.getProperty("JAVA_HOME"));
//通过 environment 同样能获取到application.properties配置的属性.
System.out.println(environment.getProperty("spring.datasource.url"));
//获取到前缀是"spring.datasource." 的属性列表值.
RelaxedPropertyResolver relaxedPropertyResolver = new RelaxedPropertyResolver(environment, "spring.datasource.");
System.out.println("spring.datasource.url=" + relaxedPropertyResolver.getProperty("url"));
System.out.println("spring.datasource.driverClassName=" + relaxedPropertyResolver.getProperty("driverClassName"));
}
}
@Controller @Service 等被Spring管理的类都支持，注意重写的方法 setEnvironment 是在系统启动的时候被执行。 或者如下Controller:
@Controller
public class PageController implements EnvironmentAware {
@Override
public void setEnvironment(Environment environment) {
String s = environment.getProperty("JAVA_HOME");
System.out.println(s);
}
}