Springboot自动装配实现过程代码实例

创建一个简单的项目：

  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;


@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;


@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;



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;


@SpringBootConfiguration
public class Configuration implements ApplicationContextAware {
  private ApplicationContext applicationContext;

  @Bean
  public BeanPostProcessor beanPostProcessor() {
    return new BeanPostProcessor() {

      
      @Override
      public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
 return bean;
      }

      
      @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;


@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;


@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();
  }
}

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考高分网。