企业网站网站建设电话,云服务器费用,展示型网站的特点,贵州省建设银行网站前言 我们在项目开发中都用到Spring#xff0c;知道对象是交由Spring去管理。那么将一个对象加入到Spring容器中#xff0c;有几种方法呢#xff0c;我们来总结一下。
ComponentScan Component ComponentScan可以放在启动类上#xff0c;指定要扫描的包路径#xff1b;…前言 我们在项目开发中都用到Spring知道对象是交由Spring去管理。那么将一个对象加入到Spring容器中有几种方法呢我们来总结一下。
ComponentScan Component ComponentScan可以放在启动类上指定要扫描的包路径该包路径下被Component修饰的类都会被注入到Spring容器中。
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;ComponentScan(basePackages com.gs.beanRegister)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);bean.say();}}com.gs.beanRegister包下
import org.springframework.stereotype.Component;Component
public class A {public void say() {System.out.println(这是a);}}注在SpringBoot中由于其自动装配的特性所以ComponentScan可以不加只要Component修饰的类和启动类在同一包下或者在启动类所在包的子包下。 Configuration Bean Configuration用来声明一个配置类如果它的方法被Bean修饰那么该方法返回的对象也会被注入到Spring容器中。 代码方面BootStrap 类不动A类的Component去掉com.gs.beanRegister包下建个配置类
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;Configuration
public class MyConfiguration {Beanpublic A a() {return new A();}}通过Import注解 这个注解可能平时大家接触得不多它有好几种使用方式。 1.直接导入类的class
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;Import(A.class)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);//B bean context.getBean(B.class);bean.say();}}A类不用添加任何注解
public class A {public void say() {System.out.println(这是a);}}2.导入配置类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Import;Import(MyConfiguration.class)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);bean.say();}}import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;// 使用Import导入配置类时Configuration可以不加
//Configuration
public class MyConfiguration {Beanpublic A a() {return new A();}}3.导入ImportSelector的实现类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Import;Import(MyImportSelector.class)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);bean.say();}}import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;public class MyImportSelector implements ImportSelector {Overridepublic String[] selectImports(AnnotationMetadata metadata) {// 返回要注入的bean的全路径A类不用任何注解修饰// SpringBoot的自动装配就用到了这种方式return new String[] { A.class.getName() };}}4.导入ImportBeanDefinitionRegistrar的实现类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Import;Import(MyImportBeanDefinitionRegistrar.class)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);bean.say();}}import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {Overridepublic void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {// 构建bean的元数据A类不用任何注解修饰// spring-mybatis扫描mapper接口生成代理类就是用的这种方式BeanDefinition definition new RootBeanDefinition(A.class);registry.registerBeanDefinition(a, definition);}}借助FactoryBean接口 实现FactoryBean接口的类除了本身会被注入外getObject方法返回的对象也会被注入到Spring容器中。
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Import;Import(MyFactoryBean.class)
public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext(BootStrap.class);A bean context.getBean(A.class);bean.say();}}import org.springframework.beans.factory.FactoryBean;public class MyFactoryBean implements FactoryBean {Overridepublic Object getObject() throws Exception {return new A();}Overridepublic Class? getObjectType() {return A.class;}}借助BeanDefinitionRegistryPostProcessor接口 在Spring容器启动时会调用该接口的postProcessBeanDefinitionRegistry方法大概意思是等BeanDefinition(上面提到的bean的元数据)加载完成后再对它进行后置处理。所以可以在此调整BeanDefinition从而把对应的bean注入。
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class BootStrap {public static void main(String[] args) {AnnotationConfigApplicationContext context new AnnotationConfigApplicationContext();BeanDefinitionRegistryPostProcessor postProcessor new MyBeanDefinitionRegistryPostProcessor();context.addBeanFactoryPostProcessor(postProcessor);context.refresh();A a context.getBean(A.class);a.say();}}import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.RootBeanDefinition;public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {Overridepublic void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {BeanDefinition definition new RootBeanDefinition(A.class);registry.registerBeanDefinition(a, definition);}Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {}
}
