[Java知识库]mybatis/feign使用JDK动态代理自动装配

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;

/**
 * 类 名: MyAutoConfiguredMyBatisRegistrar
 * 描 述: 测试动态注入Bean到Spring容器中
 */
public class MyAutoConfiguredMyBatisRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, BeanFactoryAware {

    private ResourceLoader resourceLoader;
    /**
     * 动态置顶扫描包路径下特殊的类加载到Bean中
     * @param importingClassMetadata
     * @param registry
     */
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        Class[] classes = {IOrderMapper.class,IVipMapper.class,IProductMapper.class};
        for(Class c : classes){
            BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition();
            AbstractBeanDefinition beanDefinition = beanDefinitionBuilder.getBeanDefinition();
            beanDefinition.getConstructorArgumentValues().addGenericArgumentValue(c);
            beanDefinition.setBeanClass(CustomFactoryBean.class);
            System.out.println("-----------------c.getName()---------------------------"+c.getName());
            registry.registerBeanDefinition(c.getName(), beanDefinition);
        }
    }

    /**
     * 获取Spring中的一些元数据
     * @param resourceLoader
     */
    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
    }
}

import com.fen.dou.factorybeanStu.annotation.TableName;
import com.fen.dou.factorybeanStu.utils.ConnectionUtils;
import com.fen.dou.factorybeanStu.vo.OrderVo;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.FactoryBean;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

/**
 * @author yangcai
 * @version 1.1.6
 * @Description TODO
 * @createTime 2022年03月21日 14:23:00
 */

public class CustomFactoryBean implements FactoryBean , InvocationHandler, BeanNameAware {


    @Override
    public void setBeanName(String name) {
        System.out.println("----------------------------实例化Name----------------------------"+name);
    }

    private Class aClass;

    public CustomFactoryBean(Class c){
        System.out.println("----------------------------实例化----------------------------"+c.getName());
        this.aClass = c;
    }

    @Override
    public Object getObject()  {
        System.out.println("----------------------------getObject----------------------------");
        return Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[] {aClass}, this);
    }

    @Override
    public Class<?> getObjectType() {
        return aClass;
    }

    Connection getConnection()  {
        try {
            String url = "jdbc:mysql://localhost:3306/mycat?useUnicode=true&characterEncoding=utf8&serverTimezone=UTC";
            String mysqlusername ="root";
            String password = "123456";
            return DriverManager.getConnection(url, mysqlusername, password);
        }catch (Exception e){
            System.out.println("============创建连接失败============");
        }
        return null;
    }


    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Connection connection  =  ConnectionUtils.getConnection();
        String tableName = null;
        Annotation[] annotation = aClass.getAnnotations() ;
        for(Annotation anno : annotation){
            if(anno.annotationType().equals(TableName.class)){
                TableName tableNamaAnno = (TableName)anno;
                tableName = tableNamaAnno.value();
            }
        }
        List<OrderVo> list = new ArrayList<>();
        if(method.getName().equals("queryById")){
            System.out.println("---------jdbc查询数据库--------------");
            PreparedStatement preparedStatement = connection.prepareStatement("select  * from "+tableName+" where id = ?");
            preparedStatement.setInt(1,Integer.valueOf(String.valueOf(args[0])));
            ResultSet rs = preparedStatement.executeQuery();
            while (rs.next()) {
                OrderVo orderVo = new OrderVo();
                Integer id =  rs.getInt(1);
                if(id != null){
                    orderVo.setId(id);
                }
                String name =  rs.getString(2);
                if(name != null){
                    orderVo.setName(name);
                }
                list.add(orderVo);
            }
        }
        return list;
    }
}

@TableName("order_info")
public interface IOrderMapper {
    public List<OrderVo> queryById(Integer id);
}

@TableName("product_info")
public interface IProductMapper {
    public void update();
}

@TableName("vip_info")
public interface IVipMapper {
    public void update();
}

其中使用ImportBeanDefinitionRegistrar接口，去创建beanDefinition

beanDefinition.getConstructorArgumentValues().addGenericArgumentValue(c);

是给带参构造器传入参数的，如果添加一个参数则调动一个参数的构造器

    public CustomFactoryBean(Class c){
        System.out.println("----------------------------实例化----------------------------"+c.getName());
        this.aClass = c;
    }

如果添加两个构造器参数：

beanDefinition.getConstructorArgumentValues().addGenericArgumentValue(c);
beanDefinition.getConstructorArgumentValues().addGenericArgumentValue("dsadsadasdasdsadsadsa");

则调用两个参数的构造器

    public CustomFactoryBean(Class c,String name){
        System.out.println("----------------------------实例化----------------------------"+c.getName());
        this.aClass = c;
        System.out.println("----------带参构造器-----------"+name);
    }

则上述代码，创建了三个beanDefinition

?

?

在后续通过反射调用构造器实例化的时候，把beanDefinition变成bean,则singletonObjects单例池中会生成三个bean，并且类型都是CustomFactoryBean.class

com.fen.dou.factorybeanStu.IOrderMapper -->??CustomFactoryBean.class

com.fen.dou.factorybeanStu.IProductMapper-->??CustomFactoryBean.class

com.fen.dou.factorybeanStu.IVipMapper-->??CustomFactoryBean.class

?当我们执行

CustomFactoryBean orderMapper = (CustomFactoryBean)ac.getBean("&com.fen.dou.factorybeanStu.IOrderMapper");

会把&去掉，用com.fen.dou.factorybeanStu.IOrderMapper去获取实例bean

当我们执行：

IOrderMapper or = (IOrderMapper)ac.getBean("com.fen.dou.factorybeanStu.IOrderMapper");

也是用com.fen.dou.factorybeanStu.IOrderMapper去获取实例bean，然后调用bean的 getObject()方法去实例化bean，放入FactoryBean实例池中去

其实这两者的不同点就是通过?& 来判断的，具体可以去看源码