SpringBoot源码解析之ConfigurationProperties原理
ConfigurationProperties的作用
配置文件的信息，读取并自动封装成实体类。
public class Bean {
private String name;
private String user;
private int age;
//省略get set 方法
}
student:
name: 1111
user: bbbb
age: 11
对于这样的数据封装为Bean就需要用到@ConfigurationProperties注解。
ConfigurationProperties注解源码解析
ConfigurationProperties源码
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ConfigurationProperties {
//前缀,多个用逗号隔开
@AliasFor("prefix")
String value() default "";
//前缀,多个用逗号隔开
@AliasFor("value")
String prefix() default "";
//是否忽略不可用的字段
boolean ignoreInvalidFields() default false;
//是否忽略Java类不存在的字段
boolean ignoreUnknownFields() default true;
}
ConfigurationProperties注解激活
通过 EnableConfigurationProperties 来处理激活 ConfigurationProperties 注解配置的类。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({ ConfigurationPropertiesBeanRegistrar.class, ConfigurationPropertiesBindingPostProcessorRegistrar.class })
public @interface EnableConfigurationProperties {
//配置用ConfigurationProperties注解的类
Class<?>[] value() default {};
}
EnableConfigurationProperties 注解被 @Import 导入两个类。下面来看一下这两个类源码分析：
- ConfigurationPropertiesBeanRegistrar
- ConfigurationPropertiesBindingPostProcessorRegistrar
那么解析来一一分析这两个类。
ConfigurationPropertiesBeanRegistrar源码分析
class ConfigurationPropertiesBeanRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
ConfigurableListableBeanFactory beanFactory = (ConfigurableListableBeanFactory) registry;
getTypes(metadata).forEach(
(type) -> ConfigurationPropertiesBeanDefinitionRegistrar.register(registry, beanFactory, type));
}
private List<Class<?>> getTypes(AnnotationMetadata metadata) {
MultiValueMap<String, Object> attributes = metadata
.getAllAnnotationAttributes(EnableConfigurationProperties.class.getName(), false);
return collectClasses((attributes != null) ? attributes.get("value") : Collections.emptyList());
}
private List<Class<?>> collectClasses(List<?> values) {
return values.stream().flatMap((value) -> Arrays.stream((Class<?>[]) value))
.filter((type) -> void.class != type).collect(Collectors.toList());
}
}
通过分析源码发现 ConfigurationPropertiesBeanRegistrar 主要的作用是把注解 EnableConfigurationProperties 中的 value 中配置的 Class 的 BeanDefinition 注入到Spring中。这个就是这样的简单。那么解析来分析 ConfigurationPropertiesBindingPostProcessorRegistrar。
ConfigurationPropertiesBindingPostProcessorRegistrar源码分析
public class ConfigurationPropertiesBindingPostProcessorRegistrar implements ImportBeanDefinitionRegistrar {
/**
* 验证器 bean的名称
*/
public static final String VALIDATOR_BEAN_NAME = "configurationPropertiesValidator";
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
if (!registry.containsBeanDefinition(ConfigurationPropertiesBinder.BEAN_NAME)) {
registerConfigurationPropertiesBinder(registry);
}
if (!registry.containsBeanDefinition(ConfigurationPropertiesBindingPostProcessor.BEAN_NAME)) {
registerConfigurationPropertiesBindingPostProcessor(registry);
registerConfigurationBeanFactoryMetadata(registry);
}
}
//注入ConfigurationPropertiesBinder
private void registerConfigurationPropertiesBinder(BeanDefinitionRegistry registry) {
GenericBeanDefinition definition = new GenericBeanDefinition();
definition.setBeanClass(ConfigurationPropertiesBinder.class);
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
definition.getConstructorArgumentValues().addIndexedArgumentValue(0, VALIDATOR_BEAN_NAME);
registry.registerBeanDefinition(ConfigurationPropertiesBinder.BEAN_NAME, definition);
}
//注入ConfigurationPropertiesBindingPostProcessor
private void registerConfigurationPropertiesBindingPostProcessor(BeanDefinitionRegistry registry) {
GenericBeanDefinition definition = new GenericBeanDefinition();
definition.setBeanClass(ConfigurationPropertiesBindingPostProcessor.class);
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registry.registerBeanDefinition(ConfigurationPropertiesBindingPostProcessor.BEAN_NAME, definition);
}
//注入ConfigurationBeanFactoryMetadata
private void registerConfigurationBeanFactoryMetadata(BeanDefinitionRegistry registry) {
GenericBeanDefinition definition = new GenericBeanDefinition();
definition.setBeanClass(ConfigurationBeanFactoryMetadata.class);
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registry.registerBeanDefinition(ConfigurationBeanFactoryMetadata.BEAN_NAME, definition);
}
}
上面的代码注入了两个关键的类：
- ConfigurationPropertiesBinder
由配置文件中的属性转换成对应类 - ConfigurationPropertiesBindingPostProcessor
bean初始化的处理
通过两个的配合来实现的。
ConfigurationPropertiesBindingPostProcessor源码分析
ConfigurationPropertiesBindingPostProcessor 这个主要是处理Bean。
public class ConfigurationPropertiesBindingPostProcessor
implements BeanPostProcessor, PriorityOrdered, ApplicationContextAware, InitializingBean {
private ConfigurationBeanFactoryMetadata beanFactoryMetadata;
private ApplicationContext applicationContext;
private ConfigurationPropertiesBinder configurationPropertiesBinder;
//省略代码
}
实现了 BeanPostProcessor 这个接口，主要是处理bean。下面看一下这个接口的主要方法：
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
//bean的处理--获取bean是否有ConfigurationProperties配置
ConfigurationProperties annotation = getAnnotation(bean, beanName, ConfigurationProperties.class);
if (annotation != null && !hasBeenBound(beanName)) {
bind(bean, beanName, annotation);
}
return bean;
}
通过判断bean是否配置了ConfigurationProperties注解，如果配置了就调用 bind 方法。下面来看一下bind方法源码：
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 {
this.configurationPropertiesBinder.bind(target);
}
catch (Exception ex) {
throw new ConfigurationPropertiesBindException(beanName, bean.getClass(), annotation, ex);
}
}
上面的代码主要就实现了配置。
总结
总结一下如何使用：
- 给bean配置ConfigurationProperties
- 用EnableConfigurationProperties注解配置配置ConfigurationProperties了bean的class