spring的钩子_spring提供的钩子，你知道哪些
俗話說得好“工欲善其事必先利其器”，現如今springboot與springcloud已成為快速構建web應用的利器。作為一個爪洼工程師，知道如下的spring擴展點，可能會讓你編寫出擴展性、維護性更高的代碼。
spring提供的鉤子，你知道哪些
bean的生命周期
BeanFactoryPostProcessor接口
spring源碼中對該類功能描述如下：
/*Factory hook that allows for custom modification of an application context's
bean definitions, adapting the bean property values of the context's underlying
bean factory.*/
翻譯過來的意思大致是：工廠鉤子允許自定義應用上下文中的bean定義，調整上下文bean
工廠中bean的屬性值。直白點的意思就是允許修改bean定義的屬性值。
通過一個簡單的例子，來了解下鉤子的簡單應用：定義一個類GoodEntity和DemoBeanFactoryProcessor。自定義的DemoBeanFactoryProcessor功能很簡單就是從BeanFactory中獲取goodEntity的bean定義，然后設置了goodentity的name屬性值。
@Slf4j
@Component
@Data
public class GoodEntity {
private String name;
}
@Component
public class DemoBeanFactoryProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
BeanDefinition goodEntity = beanFactory.getBeanDefinition("goodEntity");
goodEntity.getPropertyValues().addPropertyValue("name", "測試設置貨品名稱");
}
}
@SpringBootApplication
public class CourseApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(CourseApplication.class, args);
System.err.println(run.getBean(GoodEntity.class).getName());
}
}
輸出結果如下，可以到打印出了我們設置name屬性值。
2021-01-15 15:33:28.818 INFO 7112 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/mall] : Initializing Spring embedded WebApplicationContext
2021-01-15 15:33:28.818 INFO 7112 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 819 ms
2021-01-15 15:33:28.943 INFO 7112 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-01-15 15:33:29.054 INFO 7112 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '/mall'
2021-01-15 15:33:29.062 INFO 7112 --- [ main] c.i.s.s.course.CourseApplication : Started CourseApplication in 1.409 seconds (JVM running for 2.186)
測試設置貨品名稱
PS:通常情況下如果對兩個bean的初始化順序有要求，我們可以通過BeanDefinition的setDependsOn，來保證兩個Bean的初始順序。
BeanDefinitionRegistryPostProcessor接口
該接口是BeanFactoryPostProcessor的擴展接口，允許在普通的BeanFactoryPostProcessor生效前，向beanfactory中注冊BeanDefinition。通過一段代碼我們了解下該接口的作用
@Component
public class DemoBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
String beanClassName = OrderEntity.class.getName();
AbstractBeanDefinition beanDefinition =
BeanDefinitionBuilder.genericBeanDefinition(beanClassName).getBeanDefinition();
beanDefinition.getPropertyValues().addPropertyValue("orderId", "id-0001");
String beanName = AnnotationBeanNameGenerator.INSTANCE.generateBeanName(beanDefinition, registry);
registry.registerBeanDefinition(beanName, beanDefinition);
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
}
}
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class OrderEntity implements Serializable {
private String orderId;
private String address;
private List goods;
private LocalDateTime createTime;
private String userId;
private Integer pay;
private BigDecimal cost;
}
@SpringBootApplication
public class CourseApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(CourseApplication.class, args);
System.err.println(run.getBean(OrderEntity.class).getOrderId());
}
}
大致意思是通過DemoBeanDefinitionRegistryPostProcessor向beanfactory中注冊bean定義，然后從spring容器中獲取該bean，打印屬性。
BeanPostProcessor接口
源碼中對該類的描述
/*Factory hook that allows for custom modification of new bean instances —
for example, checking for marker interfaces or wrapping beans with proxies.*/
翻譯過來的大致意思是：工廠鉤子允許自定義修改新的bean實例，例如檢查標記的接口或者使用代理包裹bean。下面我們通過代碼來看看該鉤子的作用，before修改orderid，after打印。
@Component
public class DemoBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof OrderEntity) {
OrderEntity entity = (OrderEntity)bean;
System.err.println("before");
System.err.println("orderId " + entity.getOrderId());
entity.setOrderId("id-0002");
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof OrderEntity) {
OrderEntity entity = (OrderEntity)bean;
System.err.println("after");
System.err.println("orderId " + entity.getOrderId());
}
return bean;
}
}
輸出結果如下：
2021-01-15 17:41:17.783 INFO 9488 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
before
orderId id-0001
after
orderId id-0002
2021-01-15 17:41:17.904 INFO 9488 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '/mall'
2021-01-15 17:41:17.912 INFO 9488 --- [ main] c.i.s.s.course.CourseApplication : Started
PS:感興趣的朋友可以看看，spring的aop生成代理對象就是依賴該鉤子完成的。
Aware接口
BeanFactoryAware —— 獲取BeanFactory對象
BeanClassLoaderAware —— 獲取加載Bean的ClassLoader
BeanNameAware —— 獲取beanName
ApplicationContextAware —— 獲取ApplicationContext
EnvironmentAware —— 獲取spring的上下文環境Environment
看看具體的示例：
@Slf4j
@Component
@Data
public class DemoAware
implements BeanFactoryAware, BeanClassLoaderAware, BeanNameAware, ApplicationContextAware, EnvironmentAware {
private ClassLoader classLoader;
private BeanFactory beanFactory;
private String name;
private ApplicationContext applicationContext;
private Environment environment;
@Override
public void setBeanClassLoader(ClassLoader classLoader) {
this.classLoader = classLoader;
log.info("classloader {}", classLoader.getClass());
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
this.beanFactory = beanFactory;
log.info("beanFactory {}", beanFactory.getClass());
}
@Override
public void setBeanName(String name) {
this.name = name;
log.info("name {}", name);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
log.info("applicationContext {}", applicationContext.getClass());
}
@Override
public void setEnvironment(Environment environment) {
this.environment = environment;
log.info("environment {}", environment.getClass());
}
}
PS:這些個Aware我個人最喜歡用的是ApplicationContextAware和EnvironmentAware。可以獲取Spring的上下文和Spring運行時的環境配置信息，就可以隨意獲取bean和環境配置信息了。
InitializingBean接口
spring中對該接口功能的描述
/* Interface to be implemented by beans that need to react once all their properties
have been set by a {@link BeanFactory}: e.g. to perform custom initialization,
or merely to check that all mandatory properties have been set*/
翻譯過來的意思大致是：實現該接口的bean，會在所有的屬性都被(BeanFactory)設置完成后執行。例如，實現自定義的初始化，或者檢查必要的屬性是否被設置了。
@Component
public class DemoInitializingBean implements InitializingBean {
@Autowired
private OrderEntity orderEntity;
private String name;
@Override
public void afterPropertiesSet() throws Exception {
if (orderEntity != null) {
System.out.println("setted");
}
name = "already";
}
}
在整個spring啟動的過程中，提供了很多鉤子可以供我們來定制化spring啟動。實現我們自身的業務邏輯。今天只是給大家介紹了一部分的鉤子，還有其他的也請大家留言告訴我：我們共勉。。
總結
以上是生活随笔為你收集整理的spring的钩子_spring提供的钩子，你知道哪些的全部內容，希望文章能夠幫你解決所遇到的問題。
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