如何解决java。lang.NoSuchFieldError：在java中返回_NULL_和_BLANK

Question

public class SpreadsheetGenerator {
void dailyreport( Connection con) throws SQLException, IOException {
    Statement statement = con.createStatement();
    ResultSet resultSet = null;
    try {
        resultSet = statement.executeQuery("select * from ssa_msg_daily");
    } catch (Exception e) {

    } finally {
        ResultSet resultSet = statement.executeQuery("select * from ssa_msg_daily");
        XSSFWorkbook workbook = new XSSFWorkbook();
        XSSFSheet spreadsheet = workbook.createSheet("employe db");

        XSSFRow row = spreadsheet.createRow(1);
        XSSFCell cell;
        cell = row.createCell(1);
        cell.setCellValue("id");
        cell = row.createCell(2);
        cell.setCellValue("Sender");
        cell = row.createCell(3);
        cell.setCellValue("Service");
        cell = row.createCell(4);
        cell.setCellValue("Message_identifier");
        cell = row.createCell(5);
        cell.setCellValue("Date");
        cell = row.createCell(6);
        cell.setCellValue("Incoming");
        cell = row.createCell(7);
        cell.setCellValue("Outgoing");
        int i = 2;

        while (resultSet.next()) {
            row = spreadsheet.createRow(i);
            cell = row.createCell(1);
            cell.setCellValue(resultSet.getInt("id"));
            cell = row.createCell(2);
            cell.setCellValue(resultSet.getString("Sender"));
            cell = row.createCell(3);
            cell.setCellValue(resultSet.getString("Service"));
            cell = row.createCell(4);
            cell.setCellValue(resultSet.getString("Message_identifier"));
            cell = row.createCell(5);
            cell.setCellValue(resultSet.getDate("Date"));
            cell = row.createCell(6);
            cell.setCellValue(resultSet.getString("Incoming"));
            cell = row.createCell(7);
            cell.setCellValue(resultSet.getString("Outgoing"));
            i++;
        }

        FileOutputStream out = new FileOutputStream(new File("exceldatabase.xlsx"));
        workbook.write(out);
        out.close();
        System.out.println("exceldatabase.xlsx written successfully");
    }
    }


}

这里ssa_msg_daily在表中包含空值或空值，因此
在编译时，我得到的错误如下：

线程“main”java中出现异常。lang.NoSuchFieldError:返回_NULL_和_BLANK

在@XSSF工作簿=新建XSSF工作簿（）时发生；我如何处理这种情况？我正在使用resultset使用ApachePOI转换为spreedsheet

Answer 1

也许你会用“try”和“catch”来尝试。

public class SpreadsheetGenerator {
void dailyreport( Connection con) throws SQLException, IOException {
Statement statement = con.createStatement();
ResultSet resultSet = null;
try {
    resultSet = statement.executeQuery("select * from ssa_msg_daily");
} catch (Exception e) {

} 
    //ResultSet resultSet = statement.executeQuery("select * from ssa_msg_daily");
    XSSFWorkbook workbook = new XSSFWorkbook();
    XSSFSheet spreadsheet = workbook.createSheet("employe db");

    XSSFRow row = spreadsheet.createRow(1);
    XSSFCell cell;
    cell = row.createCell(1);
    cell.setCellValue("id");
    cell = row.createCell(2);
    cell.setCellValue("Sender");
    cell = row.createCell(3);
    cell.setCellValue("Service");
    cell = row.createCell(4);
    cell.setCellValue("Message_identifier");
    cell = row.createCell(5);
    cell.setCellValue("Date");
    cell = row.createCell(6);
    cell.setCellValue("Incoming");
    cell = row.createCell(7);
    cell.setCellValue("Outgoing");
    int i = 2;

    if(resultSet!=null){
    while (resultSet.next()) {
        row = spreadsheet.createRow(i);
        cell = row.createCell(1);
        cell.setCellValue(resultSet.getInt("id"));
        cell = row.createCell(2);
        cell.setCellValue(resultSet.getString("Sender"));
        cell = row.createCell(3);
        cell.setCellValue(resultSet.getString("Service"));
        cell = row.createCell(4);
        cell.setCellValue(resultSet.getString("Message_identifier"));
        cell = row.createCell(5);
        cell.setCellValue(resultSet.getDate("Date"));
        cell = row.createCell(6);
        cell.setCellValue(resultSet.getString("Incoming"));
        cell = row.createCell(7);
        cell.setCellValue(resultSet.getString("Outgoing"));
        i++;
    }}

    FileOutputStream out = new FileOutputStream(new File("exceldatabase.xlsx"));
    workbook.write(out);
    out.close();
    System.out.println("exceldatabase.xlsx written successfully");
}
}
 

}

Answer 2

您遇到了类路径问题。您的类路径上有Apache POI项目的混合版本。这种版本组合导致其中一个类的较新版本尝试与较旧版本之一通信，但它们不兼容。

解决方案是检查类路径（因此，如果您使用的是maven、gradle或其他依赖系统，那么就是依赖链），并对其进行修复。这可能很简单，就像在构建系统上运行“clean”命令一样。

NB：您的代码风格非常糟糕——不要在最终块中放置大量代码。此外，您的粘贴中有99.9%是转移注意力的。这一行已经会导致您的问题：

XSSFWorkbook workbook = new XSSFWorkbook();

其余的都无关紧要。