[Java知识库]SpringCloud自定义配置-PropertySourceLocator

背景

项目上需要在SpringCloud的基础上，拓展SpringCloud的配置文件，所以使用了PropertySourceLocator来拓展SpringCloud的配置文件。

一、PropertySourceLocator

PropertySourceLocator接口主要是需要实现PropertySource<?> locate(Environment environment)接口即可，具体源码如下：

public interface PropertySourceLocator {
    PropertySource<?> locate(Environment environment);

    default Collection<PropertySource<?>> locateCollection(Environment environment) {
        return locateCollection(this, environment);
    }

    static Collection<PropertySource<?>> locateCollection(PropertySourceLocator locator, Environment environment) {
        PropertySource<?> propertySource = locator.locate(environment);
        if (propertySource == null) {
            return Collections.emptyList();
        } else if (CompositePropertySource.class.isInstance(propertySource)) {
            Collection<PropertySource<?>> sources = ((CompositePropertySource)propertySource).getPropertySources();
            List<PropertySource<?>> filteredSources = new ArrayList();
            Iterator var5 = sources.iterator();

            while(var5.hasNext()) {
                PropertySource<?> p = (PropertySource)var5.next();
                if (p != null) {
                    filteredSources.add(p);
                }
            }

            return filteredSources;
        } else {
            return Arrays.asList(propertySource);
        }
    }
}

二、原理

1、源码

SpringCloud类引导类PropertySourceBootstrapConfiguration里面加载所有的PropertySourceLocator Bean实例，然后调用locate接口，获取自定义配置文件的配置信息，引导到上下文中。

@Configuration
@EnableConfigurationProperties(PropertySourceBootstrapProperties.class)
public class PropertySourceBootstrapConfiguration implements
        ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {

      @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        CompositePropertySource composite = new CompositePropertySource(
                BOOTSTRAP_PROPERTY_SOURCE_NAME);
        AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
        boolean empty = true;
        ConfigurableEnvironment environment = applicationContext.getEnvironment();
        for (PropertySourceLocator locator : this.propertySourceLocators) {
            PropertySource<?> source = null;
            source = locator.locate(environment);
            if (source == null) {
                continue;
            }
            logger.info("Located property source: " + source);
            composite.addPropertySource(source);
            empty = false;
        }
        if (!empty) {
            MutablePropertySources propertySources = environment.getPropertySources();
            String logConfig = environment.resolvePlaceholders("${logging.config:}");
            LogFile logFile = LogFile.get(environment);
            if (propertySources.contains(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
                propertySources.remove(BOOTSTRAP_PROPERTY_SOURCE_NAME);
            }
            insertPropertySources(propertySources, composite);
            reinitializeLoggingSystem(environment, logConfig, logFile);
            setLogLevels(applicationContext, environment);
            handleIncludedProfiles(environment);
        }
    }

  private void insertPropertySources(MutablePropertySources propertySources,
            CompositePropertySource composite) {
        MutablePropertySources incoming = new MutablePropertySources();
        incoming.addFirst(composite);
        PropertySourceBootstrapProperties remoteProperties = new PropertySourceBootstrapProperties();
        new RelaxedDataBinder(remoteProperties, "spring.cloud.config")
                .bind(new PropertySourcesPropertyValues(incoming));
        if (!remoteProperties.isAllowOverride() || (!remoteProperties.isOverrideNone()
                && remoteProperties.isOverrideSystemProperties())) {
            propertySources.addFirst(composite);
            return;
        }
        if (remoteProperties.isOverrideNone()) {
            propertySources.addLast(composite);
            return;
        }
        if (propertySources
                .contains(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME)) {
            if (!remoteProperties.isOverrideSystemProperties()) {
                propertySources.addAfter(
                        StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
                        composite);
            }
            else {
                propertySources.addBefore(
                        StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
                        composite);
            }
        }
        else {
            propertySources.addLast(composite);
        }
    }
    
    

}

2.使用

继承PropertySourceLocator，实现自定义的配置文件解析，然后再在Configuration类中创建其Bean实例，并在该项目的spring.factories添加org.springframework.cloud.bootstrap.BootstrapConfiguration对应的Configuration类的全路径名。