Spring运行时手动注入bean的方法实例

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import java.lang.reflect.Field;
import java.util.Map;

@Component
public class SpringUtils implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringUtils.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    public static Object getBean(String name) throws BeansException {
        return applicationContext.getBean(name);
    }

    public static Object getBean(Class name) throws BeansException {
        return applicationContext.getBean(name);
    }

    /**
     * bean注入spring容器
     * map[id,className,...]
     * id 为 bean的标识
     * className 为 类的全限定类名
     * ... 为其他属性
     * @param map
     */
    public static void injectBean(Map<String, String> map) {
        String className = map.get("className");
        Class<?> aClass;
        if (className == null) {
            throw new RuntimeException("map参数缺少className");
        }

        try {
            aClass = Class.forName(className);
            if (aClass == null) {
                throw new RuntimeException("className不存在");
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(aClass);
        Field[] declaredFields = aClass.getDeclaredFields();
        for (int i = 0; i < declaredFields.length; i  ) {
            String fieldName = declaredFields[i].getName();
            if (map.get(fieldName) != null) {
                // 必须设置可访问,否则下面的操作做不了
                // declaredFields[i].setAccessible(true);
                builder.addPropertyValue(fieldName, map.get(fieldName));
            }
        }
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) applicationContext;
        // 注册bean 第一个参数为 name ，第二个为 bean定义类
        String id = map.get("id");
        if (id == null) {
            registry.registerBeanDefinition(className, builder.getBeanDefinition());
            return;
        }
        registry.registerBeanDefinition(id, builder.getBeanDefinition());
    }
}

@Test
   public void test2() {
      HashMap<String, String> map = new HashMap<>();
      map.put("id", "helloTask");
      map.put("className", "com.example.demo.Task.HelloTask4");
      // 注册bean
      SpringUtils.injectBean(map);
//    HelloTask4 helloTask =(HelloTask4) SpringUtils.getBean(HelloTask4.class);
      HelloTask4 helloTask = (HelloTask4) SpringUtils.getBean("helloTask");
      System.out.println(helloTask.getClass());
   }

@Component
//@Controller
//@Service
//@Repository
class Stu{
    
}

@Configuration
class MyConfig{
    @Bean
    public Student getStudent(){
        return new Student();
    }
}