springboot 获取enviroment.Properties的几种方式 - ppjj - 博客园

PropertySourcesPlaceholderConfigurer:(通过配置资源替换表达式)
PropertySourcesPropertyResolver：（根据key获取value。）

Enviroment 对象源码解析。

同上第三步，直接通过PropertySourcesPropertyResolver获取值。

2.4也能发现Enviroment new的PropertyResolver是PropertySourcesPropertyResolver

@ConfigurationProperties实现原理

核心类：
ConfigurationPropertiesBindingPostProcessor

//通过自动配置，@EnableConfigurationProperties注入
//ConfigurationPropertiesBindingPostProcessor
@Configuration
@EnableConfigurationProperties
public class ConfigurationPropertiesAutoConfiguration {

}

//绑定数据
private void bind(Object bean, String beanName, ConfigurationProperties annotation) {
        ResolvableType type = getBeanType(bean, beanName);
        Validated validated = getAnnotation(bean, beanName, Validated.class);
        Annotation[] annotations = (validated != null)
                ? new Annotation[] { annotation, validated }
                : new Annotation[] { annotation };
        Bindable<?> target = Bindable.of(type).withExistingValue(bean)
                .withAnnotations(annotations);
        try {
            //绑定方法
            this.configurationPropertiesBinder.bind(target);
        }
        catch (Exception ex) {
            throw new ConfigurationPropertiesBindException(beanName, bean, annotation,
                    ex);
        }
}

//调用ConfigurationPropertiesBinder .bind方法。
class ConfigurationPropertiesBinder {
  public void bind(Bindable<?> target) {
        ConfigurationProperties annotation = target
                .getAnnotation(ConfigurationProperties.class);
        Assert.state(annotation != null,
                () -> "Missing @ConfigurationProperties on " + target);
        List<Validator> validators = getValidators(target);
        BindHandler bindHandler = getBindHandler(annotation, validators);
        //调用getBinder方法
        getBinder().bind(annotation.prefix(), target, bindHandler);
    }

   //getBinder方法初始化Binder对象
   // 传入熟悉的PropertySources：也来自PropertySourcesPlaceholderConfigurer对象同@Value
   //PropertySourcesPlaceholdersResolver
   private Binder getBinder() {
        if (this.binder == null) {
            this.binder = new Binder(getConfigurationPropertySources(),
                    getPropertySourcesPlaceholdersResolver(), getConversionService(),
                    getPropertyEditorInitializer());
        }
        return this.binder;
    }
}

//很深，最后通过JavaBeanBinder 来绑定数据
//为何ConfigurationProperties无法绑定静态对象：
//JavaBeanBinder会过滤掉静态方法
private boolean isCandidate(Method method) {
            int modifiers = method.getModifiers();
            return Modifier.isPublic(modifiers) && !Modifier.isAbstract(modifiers)
                    && !Modifier.isStatic(modifiers)//非静态方法
                    && !Object.class.equals(method.getDeclaringClass())
                    && !Class.class.equals(method.getDeclaringClass());
}