mybatis查询text类型字段时返回Nclob,导致json格式化时报错

package cn.yuanqiao.archive.common.typeHandler;

import com.alibaba.druid.proxy.jdbc.NClobProxyImpl;
import org.apache.ibatis.type.*;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.sql.*;

/**
 *
 *@AUTHOR:赵常飞
 *@date 2023/10/10 16:50
 */
@MappedTypes(Clob.class)
@MappedJdbcTypes(JdbcType.CLOB)
@Component
public class NClobTypeHandler extends BaseTypeHandler<String> {
    @Value("${YQ_DATABASE}")
    private Integer databaseId;
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException {
        StringReader reader=new StringReader(parameter);
        ps.setCharacterStream(i,reader,parameter.length());
    }

    @Override
    public String getNullableResult(ResultSet rs, String columnName) throws SQLException {
        String clobToString="";
        try {
            switch (databaseId) {
                case 4://达梦数据库
                    NClobProxyImpl aa=(NClobProxyImpl) rs.getObject(columnName);
                    Clob rawClob = aa.getRawClob();
                    clobToString = ClobToString(rawClob);
                    break;
                default:
                    clobToString="长文本类型,无法显示";
                    break;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return clobToString;
    }

    @Override
    public String getNullableResult(ResultSet rs, int i) throws SQLException {
        String clobToString="";
        try {
            switch (databaseId) {
                case 4:
                    NClobProxyImpl aa=(NClobProxyImpl) rs.getObject(i);
                    Clob rawClob = aa.getRawClob();
                    clobToString = ClobToString(rawClob);
                    break;
                default:
                    clobToString="长文本类型,无法显示";
                    break;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return clobToString;
    }

    @Override
    public String getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        String clobToString="";
        try {
            switch (databaseId) {
                case 4:
                    NClobProxyImpl aa=(NClobProxyImpl) callableStatement.getObject(i);
                    Clob rawClob = aa.getRawClob();
                    clobToString = ClobToString(rawClob);
                    break;
                default:
                    clobToString="长文本类型,无法显示";
                    break;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return clobToString;
    }


    private String ClobToString(Clob clob) throws SQLException, IOException {
        String reString = "";
        Reader is = clob.getCharacterStream();// 得到流
        BufferedReader br = new BufferedReader(is);
        String s = br.readLine();
        StringBuffer sb = new StringBuffer();
        while (s != null) {// 执行循环将字符串全部取出付值给StringBuffer由StringBuffer转成STRING
            sb.append(s);
            s = br.readLine();
        }
        reString = sb.toString();
        return reString;
    }
}