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Java报错：Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.

发布时间 2023-04-25 10:01:40作者: 徐滨

报错内容

 Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class oracle.jdbc.OracleConnection]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Direct self-reference leading to cycle (through reference chain: cn.newangels.common.MarsResult["data"]->java.util.HashMap["list"]->java.util.ArrayList[0]->java.util.HashMap["I_RE_MSG"]->oracle.sql.CLOB["physicalConnection"]->oracle.jdbc.driver.T4CConnection["wrapper"])] with root cause

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Direct self-reference leading to cycle (through reference chain: cn.newangels.common.MarsResult["data"]->java.util.HashMap["list"]->java.util.ArrayList[0]->java.util.HashMap["I_RE_MSG"]->oracle.sql.CLOB["physicalConnection"]->oracle.jdbc.driver.T4CConnection["wrapper"])

截图

错误原因
从oracle获取的数据类型为CLOB类型导致输出异常

解决方式（两种方法）

  1. 在配置文件application.xml中添加代码：
    spring: jackson: serialization:

    注意：这样可以解决报错问题但输出异常，不建议使用
  2. 添加方法
    /**
     * @param clob
     * @return String
     * @ clobl类型的数据转换为字符串输出
     * @throws SQLException
     * @throws IOException
     */
    public String ClobToString (Clob clob) throws SQLException, IOException{
        String reString = "";
        java.io.Reader is = clob.getCharacterStream();//得到流
        BufferedReader br = new BufferedReader(is);
        String s = br.readLine();
        StringBuffer sb = new StringBuffer();
        while (s != null) {
            sb.append(s);
            s = br.readLine();
        }
        reString = sb.toString();
        return reString;
    }

使用方法

        try {
            for (Map m : list) {
                for (Map col : columns) {
                    String colName = String.valueOf(col.get("COLUMN_NAME"));    //列名
                    String colType = String.valueOf(col.get("DATA_TYPE"));      //列的类型
                    Object objItem = m.get(colName);                            //数据内容
                    if (colType.equals("CLOB")) {
                        try {
                            if(objItem != null) {
                                String str = ClobToString((Clob) objItem);
                                m.put(colName,str);
                            }
                        } catch (SQLException e) {
                            throw new RuntimeException(e);
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    }
                }
            }
        } catch (Exception e) {
            throw new Exception(e);
        }