报错：Java ClassCastException: xxx cannot be cast to xxx are in unnamed module of loader ‘app‘

这就是典型的类型转换问题，出现这个错误就说明类型转换有误，大概是出现在domain层，vo层和bo层之间的混乱

1：首先在mapper层也就是dao层，我们记住我们一定是用domain实体类去接收查询出来的参数

2：然后我们在serviceImpl层接收到后，我们要将查询出来的数据赋值给vo层返回给前端，这里使用BeanCopyUtils将mapper层查询出来的数据赋给vo层

3：BeanCopyUtils

package com.zhi.common.utils;import cn.hutool.core.collection.CollUtil;import cn.hutool.core.lang.SimpleCache;import cn.hutool.core.map.MapUtil;import cn.hutool.core.util.ObjectUtil;import cn.hutool.core.util.ReflectUtil;import cn.hutool.core.util.StrUtil;import lombok.AccessLevel;import lombok.NoArgsConstructor;import org.springframework.cglib.beans.BeanCopier;import org.springframework.cglib.beans.BeanMap;import org.springframework.cglib.core.Converter;import java.util.List;import java.util.Map;@NoArgsConstructor(access = AccessLevel.PRIVATE)public class BeanCopyUtils {        public static <T, V> V copy(T source, Class<V> desc) {        if (ObjectUtil.isNull(source)) {            return null;        }        if (ObjectUtil.isNull(desc)) {            return null;        }        final V target = ReflectUtil.newInstanceIfPossible(desc);        return copy(source, target);    }        public static <T, V> V copy(T source, V desc) {        if (ObjectUtil.isNull(source)) {            return null;        }        if (ObjectUtil.isNull(desc)) {            return null;        }        BeanCopier beanCopier = BeanCopierCache.INSTANCE.get(source.getClass(), desc.getClass(), null);        beanCopier.copy(source, desc, null);        return desc;    }        public static <T, V> List<V> copyList(List<T> sourceList, Class<V> desc) {        if (ObjectUtil.isNull(sourceList)) {            return null;        }        if (CollUtil.isEmpty(sourceList)) {            return CollUtil.newArrayList();        }        return StreamUtils.toList(sourceList, source -> {            V target = ReflectUtil.newInstanceIfPossible(desc);            copy(source, target);            return target;        });    }        @SuppressWarnings("unchecked")    public static <T> Map<String, Object> copyToMap(T bean) {        if (ObjectUtil.isNull(bean)) {            return null;        }        return BeanMap.create(bean);    }        public static <T> T mapToBean(Map<String, Object> map, Class<T> beanClass) {        if (MapUtil.isEmpty(map)) {            return null;        }        if (ObjectUtil.isNull(beanClass)) {            return null;        }        T bean = ReflectUtil.newInstanceIfPossible(beanClass);        return mapToBean(map, bean);    }        public static <T> T mapToBean(Map<String, Object> map, T bean) {        if (MapUtil.isEmpty(map)) {            return null;        }        if (ObjectUtil.isNull(bean)) {            return null;        }        BeanMap.create(bean).putAll(map);        return bean;    }        public enum BeanCopierCache {                INSTANCE;        private final SimpleCache<String, BeanCopier> cache = new SimpleCache<>();                public BeanCopier get(Class<?> srcClass, Class<?> targetClass, Converter converter) {            final String key = genKey(srcClass, targetClass, converter);            return cache.get(key, () -> BeanCopier.create(srcClass, targetClass, converter != null));        }                private String genKey(Class<?> srcClass, Class<?> targetClass, Converter converter) {            final StringBuilder key = StrUtil.builder()                .append(srcClass.getName()).append('#').append(targetClass.getName());            if(null != converter){                key.append('#').append(converter.getClass().getName());            }            return key.toString();        }    }}

出现上述错误大概是在想要get到mapper层查询数据的List<实体类>时候出现了错误，一定要记住mapper层查询出来的是对应实体层的，而不是vo层

来源地址：https://blog.csdn.net/justleavel/article/details/128613595