1、开启mybatis驼峰命名规则

mybatis:
  configuration:
    #使用mybatis驼峰功能将达梦返回字段转小写
    map-underscore-to-camel-case: true

2、继承MapWrapper

import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.wrapper.MapWrapper;

import java.util.Map;

public class SqlFieldToLowerCase extends MapWrapper {

    public SqlFieldToLowerCase(MetaObject metaObject, Map<String, Object> map) {
        super(metaObject, map);
    }

    @Override
    public String findProperty(String name, boolean useCamelCaseMapping) {
        if (useCamelCaseMapping) {
            //查询字段转小写
            return name == null ? null : name.toLowerCase();
        }
        return name;
    }


}

3、实现ObjectWrapperFactory

import com.alibaba.fastjson.JSONObject;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.wrapper.ObjectWrapper;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.session.Configuration;
import org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

import java.util.Map;

@Component
public class SqlFieldToLowerCaeFactory implements ObjectWrapperFactory {
    @Override
    public boolean hasWrapperFor(Object o) {
        return o instanceof Map;
    }

    @Override
    public ObjectWrapper getWrapperFor(MetaObject metaObject, Object o) {
        return new SqlFieldToLowerCase(metaObject, (Map) o);
    }

     /**
     *  使用该方式object-wrapper-factory: com.demo.config.SqlFieldToLowerCaeFactory
     *  会报类型转换异常所以使用下面这种方式
     * @return
     */
    @Bean
    public ConfigurationCustomizer mybatisConfigurationCustomizer() {
        return new ConfigurationCustomizer() {
            @Override
            public void customize(Configuration configuration) {

                configuration.setObjectWrapperFactory(new SqlFieldToLowerCaeFactory());
            }
        };
    }

}

注意事项：mybatis返回结果为fastjson:JSONObject类型时，使用该方式将返回字段转小写可能会在遇见达梦数据库字段类型为CLOB、TEXT等类型字段报JSON解析内存溢出

可以尝试在数据库链接上拼接clobAsString=1 或者将字段类型改为varchar

jdbc:dm://127.0.0.1:5236/DEMO?clobAsString=1