动态代理工厂

public class MapperProxyFactory<T> {
    private final Class<T> mapperInterface;
    public MapperProxyFactory(Class<T> mapperInterface) {
        this.mapperInterface = mapperInterface;
    }
    public T newInstance(Map<String,String>sqlSession){
        final MapperProxy<T> mapperProxy=new MapperProxy<>(sqlSession,mapperInterface);
        return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(),new Class[]{mapperInterface}, mapperProxy);
    }
}

newProxyInstance，方法有三个参数：
loader: 用哪个类加载器去加载代理对象
interfaces:动态代理类需要实现的接口
h:动态代理方法在执行时，会调用h里面的invoke方法去执行

动态代理类

public class MapperProxy<T> implements InvocationHandler, Serializable {
    private Map<String, String> sqlSession;
    private final Class<T> mapperInterface;
    public MapperProxy(Map<String, String> sqlSession, Class<T> mapperInterface) {
        this.sqlSession = sqlSession;
        this.mapperInterface = mapperInterface;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        if (Object.class.equals(method.getDeclaringClass())) {
            return method.invoke(this, args);
        } else {
            return "你的被代理了!" + sqlSession.get(mapperInterface.getName() + "." + method.getName());
        }
    }
}

invoke三个参数：
proxy：就是代理对象，newProxyInstance方法的返回对象
method：调用的方法
args: 方法中的参数

调用案列

创建 接口

public interface IUserDao {
    String queryUser(String uid);
    Integer detailUser(String uid);
}

调用

public class MpTest {
    @Test
    public void test_MapperProxyFactory() {
        //创建代理
        MapperProxyFactory<IUserDao> factory = new MapperProxyFactory<>(IUserDao.class);
        Map<String, String> sqlSession = new HashMap<>();
        sqlSession.put("cn.wh.dao.IUserDao.queryUser", "模拟执行 Mapper.xml 中 SQL 语句的操作：查询用户姓名");
        sqlSession.put("cn.bugstack.mybatis.test.dao.IUserDao.queryUserName", "模拟执行 Mapper.xml 中 SQL 语句的操作：查询用户年龄");
        IUserDao userDao = factory.newInstance(sqlSession);
        //调用方法
        String res = userDao.queryUser("10001");
        System.out.println(res);
    }
}