Springboot自动装配实现过程代码实例

创建一个简单的项目：

<?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <parent> <artifactId>spring-boot-starter-parent</artifactId> <groupId>org.springframework.boot</groupId> <version>2.1.12.RELEASE</version> </parent> <groupId>com.xiazhi</groupId> <artifactId>demo</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> </dependency> </dependencies></project>

首先创建自定义注解：

package com.xiazhi.demo.annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * MyComponent 作用于类上，表示这是一个组件，于component，service注解作用相同 * @author zhaoshuai */@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface MyComponent {}

package com.xiazhi.demo.annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * 作用于字段上，自动装配的注解，与autowired注解作用相同 * @author zhaoshuai */@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface Reference {}

然后写配置类：

package com.xiazhi.demo.config;import com.xiazhi.demo.annotation.MyComponent;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.context.ResourceLoaderAware;import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;import org.springframework.core.io.ResourceLoader;import org.springframework.core.type.AnnotationMetadata;import org.springframework.core.type.filter.AnnotationTypeFilter;/** * @author ZhaoShuai * @company lihfinance.com * @date Create in 2020/3/21 **/public class ComponentAutoConfiguration implements ImportBeanDefinitionRegistrar, ResourceLoaderAware { private ResourceLoader resourceLoader; @Override public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) { String className = annotationMetadata.getClassName(); String basePackages = className.substring(0, className.lastIndexOf('.')); ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(beanDefinitionRegistry, false); scanner.addIncludeFilter(new AnnotationTypeFilter(MyComponent.class)); scanner.scan(basePackages); scanner.setResourceLoader(resourceLoader); } @Override public void setResourceLoader(ResourceLoader resourceLoader) { this.resourceLoader = resourceLoader; }}

上面是配置扫描指定包下被MyComponent注解标注的类并注册为spring的bean，bean注册成功后，下面就是属性的注入了

package com.xiazhi.demo.config;import com.xiazhi.demo.annotation.MyComponent;import com.xiazhi.demo.annotation.Reference;import org.springframework.beans.BeansException;import org.springframework.beans.factory.config.BeanPostProcessor;import org.springframework.boot.SpringBootConfiguration;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import org.springframework.context.annotation.Bean;import org.springframework.util.ReflectionUtils;import java.lang.reflect.Field;/** * @author ZhaoShuai * @company lihfinance.com * @date Create in 2020/3/21 **/@SpringBootConfigurationpublic class Configuration implements ApplicationContextAware { private ApplicationContext applicationContext; @Bean public BeanPostProcessor beanPostProcessor() { return new BeanPostProcessor() { /** * @company lihfinance.com * @author create by ZhaoShuai in 2020/3/21 * 在bean注册前会被调用 * @param [bean, beanName] * @return java.lang.Object **/ @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {return bean; } /** * @company lihfinance.com * @author create by ZhaoShuai in 2020/3/21 * 在bean注册后会被加载，本次在bean注册成功后注入属性值 * @param [bean, beanName] * @return java.lang.Object **/ @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {Class<?> clazz = bean.getClass();if (!clazz.isAnnotationPresent(MyComponent.class)) { return bean;}Field[] fields = clazz.getDeclaredFields();for (Field field : fields) { if (!field.isAnnotationPresent(Reference.class)) { continue; } Class<?> type = field.getType(); Object obj = applicationContext.getBean(type); ReflectionUtils.makeAccessible(field); ReflectionUtils.setField(field, bean, obj);}return bean; } }; } @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; }}

下面开始使用注解来看看效果：

package com.xiazhi.demo.service;import com.xiazhi.demo.annotation.MyComponent;import javax.annotation.PostConstruct;/** * @author ZhaoShuai * @company lihfinance.com * @date Create in 2020/3/21 **/@MyComponentpublic class MyService { @PostConstruct public void init() { System.out.println('hello world'); } public void test() { System.out.println('测试案例'); }}

package com.xiazhi.demo.service;import com.xiazhi.demo.annotation.MyComponent;import com.xiazhi.demo.annotation.Reference;/** * @author ZhaoShuai * @company lihfinance.com * @date Create in 2020/3/21 **/@MyComponentpublic class MyConsumer { @Reference private MyService myService; public void aaa() { myService.test(); }}

启动类要引入配置文件：

import注解引入配置文件。

编写测试类测试：

@SpringBootTest(classes = ApplicationRun.class)@RunWith(SpringRunner.class)public class TestDemo { @Autowired public MyConsumer myConsumer; @Test public void fun1() { myConsumer.aaa(); }}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持好吧啦网。