Springboot属性加载与覆盖优先级与SpringCloud Config Service配置

参考官方文档：https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html

Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values. Properties are considered in the following order:

1. Devtools global settings properties on your home directory (~/.spring-boot-devtools.properties when devtools is active).
2. @TestPropertySource annotations on your tests.
3. properties attribute on your tests. Available on @SpringBootTest and the test annotations for testing a particular slice of your application.
4. Command line arguments.
5. Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property).
6. ServletConfig init parameters.
7. ServletContext init parameters.
8. JNDI attributes from java:comp/env.
9. Java System properties (System.getProperties()).
10. OS environment variables.
11. A RandomValuePropertySource that has properties only in random.*.
12. Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants).
13. Profile-specific application properties packaged inside your jar (application-{profile}.properties and YAML variants).
14. Application properties outside of your packaged jar (application.properties and YAML variants).
15. Application properties packaged inside your jar (application.properties and YAML variants).
16. @PropertySource annotations on your @Configuration classes.
17. Default properties (specified by setting SpringApplication.setDefaultProperties).

由于SpringCloud config的配置文件属于上面的第14/12，理论上优先级相对java -jar命令行参数来说是要低的，但cloud的配置确默认是：远程覆盖本地(OS/java -jar参数等)overrideSystemProperties = true，需要特别注意。

package org.springframework.cloud.bootstrap.config;

import org.springframework.boot.context.properties.ConfigurationProperties;

/**
 * Properties for Spring Cloud Config bootstrap.
 *
 * @author Dave Syer
 */
@ConfigurationProperties("spring.cloud.config")
public class PropertySourceBootstrapProperties {

    /**
     * Flag to indicate that the external properties should override system properties.
     * Default true.
     */
    private boolean overrideSystemProperties = true;

    /**
     * Flag to indicate that {@link #isOverrideSystemProperties()
     * systemPropertiesOverride} can be used. Set to false to prevent users from changing
     * the default accidentally. Default true.
     */
    private boolean allowOverride = true;

    /**
     * Flag to indicate that when {@link #setAllowOverride(boolean) allowOverride} is
     * true, external properties should take lowest priority and should not override any
     * existing property sources (including local config files). Default false.
     */
    private boolean overrideNone = false;

    public boolean isOverrideNone() {
        return this.overrideNone;
    }

    public void setOverrideNone(boolean overrideNone) {
        this.overrideNone = overrideNone;
    }

    public boolean isOverrideSystemProperties() {
        return this.overrideSystemProperties;
    }

    public void setOverrideSystemProperties(boolean overrideSystemProperties) {
        this.overrideSystemProperties = overrideSystemProperties;
    }

    public boolean isAllowOverride() {
        return this.allowOverride;
    }

    public void setAllowOverride(boolean allowOverride) {
        this.allowOverride = allowOverride;
    }

}