nested exception

nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.sswh.entity.vo.KnowledgeVo and no properties discovered to create BeanSerializer

KnowledgeVo类没有实现序列化，实现序列化方式如下：

1. 实现Serializable接口；
2. 生成serialVersionUID。

举例如下：

public class KnowledgeVo implements Serializable{
    private static final long serialVersionUID = 4326239813592209753L;
    // 其它属性
}

没有序列化类
No serializer found for class com.sswh.entity.vo.KnowledgeVo