SpringBoot中@ConfigurationProperties注解的使用与源码详解

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Indexed
public @interface ConfigurationProperties {
	// 匹配的前缀
    @AliasFor("prefix")
    String value() default "";

	// 同上
    @AliasFor("value")
    String prefix() default "";

	// 忽略属性类型不匹配的字段
    boolean ignoreInvalidFields() default false;

	// 忽略类中未知的属性，ignoreUnknownFields=false后当出现未知字段时会出现异常
    boolean ignoreUnknownFields() default true;
}

package com.morris.spring.boot.config;

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Data
@Component
@ConfigurationProperties(prefix = "database")
public class DatabaseProperties {

	private String username;

	private String password;

	private String driverClass;

	private String connectionUrl;

}

package com.morris.spring.boot.config;

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Map;

@Configuration
public class FlowRuleConfig {

	@Bean
	@ConfigurationProperties("flow.config")
	public RuleProperties ruleProperties() {
		return new RuleProperties();
	}

	@Data
	public static class RuleProperties {
		private Map<String, Integer> rules;
	}
}

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties
public class ConfigurationPropertiesAutoConfiguration {

}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EnableConfigurationPropertiesRegistrar.class)
public @interface EnableConfigurationProperties {

	/**
	 * The bean name of the configuration properties validator.
	 * @since 2.2.0
	 */
	String VALIDATOR_BEAN_NAME = "configurationPropertiesValidator";

	/**
	 * Convenient way to quickly register
	 * {@link ConfigurationProperties @ConfigurationProperties} annotated beans with
	 * Spring. Standard Spring Beans will also be scanned regardless of this value.
	 * @return {@code @ConfigurationProperties} annotated beans to register
	 */
	Class<?>[] value() default {};

}

public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
	// 注入ConfigurationPropertiesBindingPostProcessor
	// 注入BoundConfigurationProperties
	registerInfrastructureBeans(registry);
	// 注入MethodValidationExcludeFilter
	registerMethodValidationExcludeFilter(registry);

	// 注入@EnableConfigurationProperties注解指定的ConfigurationProperties
	// 例如org.springframework.boot.autoconfigure.web.ServerProperties
	ConfigurationPropertiesBeanRegistrar beanRegistrar = new ConfigurationPropertiesBeanRegistrar(registry);
	getTypes(metadata).forEach(beanRegistrar::register);
}

public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
	bind(ConfigurationPropertiesBean.get(this.applicationContext, bean, beanName));
	return bean;
}

private void bind(ConfigurationPropertiesBean bean) {
	if (bean == null || hasBoundValueObject(bean.getName())) {
		return;
	}
	Assert.state(bean.getBindMethod() == BindMethod.JAVA_BEAN, "Cannot bind @ConfigurationProperties for bean '"
				 + bean.getName() + "'. Ensure that @ConstructorBinding has not been applied to regular bean");
	try {
		// 主要是通过ConfigurationPropertiesBinder来完成配置文件的属性与对象的属性的绑定
		// 最终会调用Binder这个类来完成绑定
		this.binder.bind(bean);
	}
	catch (Exception ex) {
		throw new ConfigurationPropertiesBindException(bean, ex);
	}
}

ConfigurationPropertiesBinder(ApplicationContext applicationContext) {
	this.applicationContext = applicationContext;
	this.propertySources = new PropertySourcesDeducer(applicationContext).getPropertySources();
	this.configurationPropertiesValidator = getConfigurationPropertiesValidator(applicationContext);
	this.jsr303Present = ConfigurationPropertiesJsr303Validator.isJsr303Present(applicationContext);
}

BindResult<?> bind(ConfigurationPropertiesBean propertiesBean) {
	Bindable<?> target = propertiesBean.asBindTarget();
	ConfigurationProperties annotation = propertiesBean.getAnnotation();
	BindHandler bindHandler = getBindHandler(target, annotation);
	return getBinder().bind(annotation.prefix(), target, bindHandler);
}

private Binder getBinder() {
	if (this.binder == null) {
		this.binder = new Binder(getConfigurationPropertySources(), getPropertySourcesPlaceholdersResolver(),
								 getConversionServices(), getPropertyEditorInitializer(), null,
								 ConfigurationPropertiesBindConstructorProvider.INSTANCE);
	}
	return this.binder;
}

DatabaseProperties databaseProperties = applicationContext.getBean(DatabaseProperties.class);
System.out.println(databaseProperties);

// test refresh @ConfigurationProperties
// 这里使用app.properties模拟
ClassPathResource classPathResource = new ClassPathResource("app.properties");
ResourcePropertySource resourcePropertySource = new ResourcePropertySource(classPathResource);
ConfigurationPropertySource configurationPropertySource = ConfigurationPropertySource.from(resourcePropertySource);
Binder binder = new Binder(configurationPropertySource);
Bindable<DatabaseProperties> bindable = Bindable.ofInstance(databaseProperties);
binder.bind("database", bindable);
System.out.println(databaseProperties);