why throw an oracle exception "ORA-00972: identifier is too long" in my java web project

The problem is when i call the function "importDBfromAllSheets.insertTables();" in my servlet, it will throw the "ORA-00972: identifier is too long".

But when i call the function in local main() function, it works well.

servlet code:

if (username != null && username.equals(GlobalVariables.defaultUserName)
            && password != null && password.equals(GlobalVariables.defaultPassword)) {
        ImportDBfromAllSheets importDBfromAllSheets = new ImportDBfromAllSheets(
                GlobalVariables.oracleUrl, GlobalVariables.oracleUserName, GlobalVariables.oraclePassword);
        importDBfromAllSheets.insertTables();
        System.out.println("aaaaaaaaaa");
        response.getWriter().print("Updating...");
    } else {
        response.getWriter().print("User/Pwd error");
    }

and main() code:

public static void main(String[] args) {
    ImportDBfromAllSheets importDBfromAllSheets = new ImportDBfromAllSheets(
            GlobalVariables.oracleUrl, GlobalVariables.oracleUserName, GlobalVariables.oraclePassword);
    importDBfromAllSheets.insertTables();
}

and my insertTables() is about:

StringBuilder insert_sql = new StringBuilder();
    StringBuilder subSql1 = new StringBuilder();
    StringBuilder subSql2 = new StringBuilder();
    List<String> columnNames = getColumnNames();
    for (String columnName : columnNames) {
        subSql1.append("\"").append(columnName).append("\",");
        subSql2.append("?,");
    }
    String substring = subSql1.substring(0, subSql1.length() - 1);
    String substring2 = subSql2.substring(0, subSql2.length() - 1);
    insert_sql.append("insert into \"Complaints-All\" (")
            .append(substring).append(") values (").append(substring2).append(")");
    try {
        con.setAutoCommit(false);
        PreparedStatement pst = con.prepareStatement(insert_sql.toString());
        for (List<String> row : rows.subList(1, rows.size())) {
            for (int j = 0; j < columnNames.size(); j++) {
                if (row.get(j).isEmpty())
                    pst.setNull(j + 1, Types.VARCHAR);
                else
                    pst.setString(j + 1, row.get(j));
            }
            pst.addBatch();
        }
        pst.executeBatch();
        con.commit();
        System.out.println("Complaints-All: insert success!");
        fileRename(path);

the exception is "pst.executeBatch();" threw.

It is strange that when i check the table in PL/SQL, it works well after i do main() function.