Springboot如何实现自动装配
这篇文章主要为大家展示了Springboot如何实现自动装配，内容简而易懂，希望大家可以学习一下，学习完之后肯定会有收获的，下面让小编带大家一起来看看吧。
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创建一个简单的项目：
<?xml version="1.0" encoding="UTF-8"?>4.0.0 spring-boot-starter-parent org.springframework.boot 2.1.12.RELEASE com.xiazhi demo 1.0-SNAPSHOT org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-test
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
**/
@SpringBootConfiguration
public 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
**/
@MyComponent
public 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
**/
@MyComponent
public 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();
}
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