Spring boot外部配置（配置中心化）详解

前言

在项目中为了灵活配置，我们常采用配置文件，常见的配置文件就比如xml和properties，springboot允许使用properties和yaml文件作为外部配置。现在编译器对于yaml语言的支持还不够好，目前还是使用properties文件作为外部配置。

在spring cloud config出来之前, 自己实现了基于zk的配置中心, 杜绝了本地properties配置文件, 原理很简单, 只是重载了propertyplaceholderconfigurer的mergeproperties() :

/**
 * 重载合并属性实现
 * 先加载file properties， 然后并入zk配置中心读取的properties
 *
 * @return 合并后的属性集合
 * @throws ioexception 异常
 */
@override
protected properties mergeproperties() throws ioexception {
 properties result = new properties();
 // 加载父类的配置
 properties mergeproperties = super.mergeproperties();
 result.putall(mergeproperties);
 // 加载从zk中读取到的配置
 map<string, string> configs = loadzkconfigs();
 result.putall(configs);
 return result;
}

这个实现在spring项目里用起来还是挺顺手的, 但是近期部分spring-boot项目里发现这种placeholder的实现跟spring boot的@configurationproperties(prefix = "xxx") 不能很好的配合工作,

也就是属性没有被resolve处理, 用@value的方式确可以读到, 但是@value配置起来如果属性多的话还是挺繁琐的, 还是倾向用@configurationproperties的prefix, 于是看了下spring boot的文档发现 propertysource

order:

* devtools global settings properties on your home directory (~/.spring-boot-devtools.properties when devtools is active).

* @testpropertysource annotations on your tests.

* @springboottest#properties annotation attribute on your tests.

* command line arguments.

* properties from spring_application_json (inline json embedded in an environment variable or system property)

* servletconfig init parameters.

* servletcontext init parameters.

* jndi attributes from java:comp/env.

* java system properties (system.getproperties()).

* os environment variables.

* a randomvaluepropertysource that only has properties in random.*.

* profile-specific application properties outside of your packaged jar (application-{profile}.properties and yaml variants)

* profile-specific application properties packaged inside your jar (application-{profile}.properties and yaml variants)

* application properties outside of your packaged jar (application.properties and yaml variants).

* application properties packaged inside your jar (application.properties and yaml variants).

* @propertysource annotations on your @configuration classes.

* default properties (specified using springapplication.setdefaultproperties).

不难发现其会检查java system propeties里的属性, 也就是说, 只要把mergerproperties读到的属性写入java system props里即可, 看了下源码, 找到个切入点

/**
 * 重载处理属性实现
 * 根据选项, 决定是否将合并后的props写入系统属性, spring boot需要
 *
 * @param beanfactorytoprocess
 * @param props    合并后的属性
 * @throws beansexception
 */
@override
protected void processproperties(configurablelistablebeanfactory beanfactorytoprocess, properties props) throws beansexception {
 // 原有逻辑
  super.processproperties(beanfactorytoprocess, props);
 // 写入到系统属性
 if (writepropstosystem) {
  // write all properties to system for spring boot
  enumeration<?> propertynames = props.propertynames();
  while (propertynames.hasmoreelements()) {
    string propertyname = (string) propertynames.nextelement();
    string propertyvalue = props.getproperty(propertyname);
    system.setproperty(propertyname, propertyvalue);
  }
 }
}

为避免影响过大, 设置了个开关, 是否写入系统属性, 如果是spring boot的项目, 就开启, 这样对线上非spring boot项目做到影响最小, 然后spring boot的@configurationproperties完美读到属性;

具体代码见: org.springframework.boot.context.properties.configurationpropertiesbindingpostprocessor

@override
public object postprocessbeforeinitialization(object bean, string beanname)
  throws beansexception {
 configurationproperties annotation = annotationutils
   .findannotation(bean.getclass(), configurationproperties.class);
 if (annotation != null) {
  postprocessbeforeinitialization(bean, beanname, annotation);
 }
 annotation = this.beans.findfactoryannotation(beanname,
 configurationproperties.class);
 if (annotation != null) {
  postprocessbeforeinitialization(bean, beanname, annotation);
 }
 return bean;
}

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。