@Import导入ImportSelector实现类demo

1、测试类接口

package com.fh.imports.dao;

public interface TestDao {

    void test();
}

测试类实现

package com.fh.imports.dao;

import org.springframework.stereotype.Component;

@Component(value = "testDao")
public class TestDaoImpl implements TestDao {
    @Override
    public void test() {
        System.out.println("TestDaoImpl");
    }
}

2、添加一个ImportSelector的实现类

package com.fh.imports;

import com.fh.imports.dao.TestDaoImpl3;
import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

/**
 * 可以做开关
 */
public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        //返回需要实例化的对象的名称
        return new String[]{TestDaoImpl3.class.getName()};
    }
}

3、添加上面的TestDaoImpl3这个类

package com.fh.imports.dao;

import com.fh.imports.ProxyInvocationHandler;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

import java.lang.reflect.Proxy;

public class TestDaoImpl3 implements  BeanPostProcessor {


    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if("testDao".equals(beanName)){
            bean =  Proxy.newProxyInstance(this.getClass().getClassLoader(),new Class[]{TestDao.class},new ProxyInvocationHandler(bean));
        }
        return bean;
    }

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

4、添加对应的InvocationHandler类

package com.fh.imports;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class ProxyInvocationHandler implements InvocationHandler {

    Object target;

    public ProxyInvocationHandler(Object object){
        this.target = object;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("代理类执行!!!");
        return method.invoke(target,args);
    }
}

5、添加注解类导入

package com.fh.imports;

import org.springframework.context.annotation.Import;

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)
@Import(MyImportSelector.class)
public @interface EnableProxy {
}

6、添加一个配置类，进行注解配置即可

package com.fh.imports;

import org.springframework.context.annotation.Configuration;


@Configuration
@EnableProxy
public class ImportConfig {

//    @Bean
//    public TestDao getTest(){
//        return new TestDaoImpl();
//    }
}

7、最后添加测试类，从容器中获取相关的实例，查看是否被代理

TestDao testDao = (TestDao) context.getBean("testDao");
testDao.test();

最后，项目的目录结构：

完

来源：https://www.cnblogs.com/nihaofenghao/p/12652270.html

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