方法读取 csv 输入流与 csv 文件不同

Question

我的任务是编写一个方法，该方法将接收一个 csv 文件并将其数据保存到数据库中的适当空间中。当直接输入csv数据时，我编写的函数就成功了。但是，当使用 cURL 并输入整个 csv 文件时，它不会读取换行符。实际上，csv 然后变成一行 x 列数，其中 x 是文件中的单元格数。我尝试更改 csv 格式（例如使用回车与换行），但似乎没有任何效果。附件是通过csv运行的代码，它接受InputStream csvData：

CSVReader reader = new CSVReader(new InputStreamReader(csvData));
String[] line;
int bookNum = 1, lineNum = 2; // skip headers
while ((line = reader.readNext()) != null) {
    // map line
    String productCode = line[0]; 
    String author = line[1];
    String description = line[2];
    Integer edition;
    try {
        edition = Integer.parseInt(line[3].replaceAll("[^\\d.]", ""));
    } catch (NumberFormatException nfe) {
        edition = null;
    }
    String copyright = line[4];
    String publisher = line[5];
    BigDecimal listPrice = !line[6].equals("") ? new BigDecimal(line[6]) : null;

    // do stuff with data...

    if (bookNum == 1) System.out.println("1 book has been processed");
    else System.out.println(bookNum + " books have been processed");
    ++bookNum;
    ++lineNum;
}

Answer 1

这对我有用。我认为问题在于您的输入 csvData 是如何形成的。当您尝试时，这是否有效？

import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import com.opencsv.CSVReader;
import com.opencsv.exceptions.CsvValidationException;

public class TestCsv {

    private static final String TEST_CSV = "ISBN,Author,Title,Edition,Copyright,Publisher,Value,Grade\n"
            + "1781435460553,1ALTEN,1WORKING WITH AUDIO (PB),12,,1CENGAGE L,0.01,1\n"
            + "2781435460553,2ALTEN,1WORKING WITH AUDIO (PB),22,,2CENGAGE L,0.02,2\r\n"
            + "3781435460553,3ALTEN,1WORKING WITH AUDIO (PB),32,,3CENGAGE L,0.03,3\r\n";

    public static void main(String[] args) throws CsvValidationException, UnsupportedEncodingException, IOException {
        System.out.println("String Test");
        parseCsv(new ByteArrayInputStream(TEST_CSV.getBytes("UTF-8"))); // from String
        
        System.out.println("\n\n---------------------\nFrom File Test");
         String fileName = "/tmp/test.csv";

            try (FileInputStream fis = new FileInputStream(fileName)) {
                parseCsv(fis);
            }
        
        
        
    }

    public final static void parseCsv(InputStream csvData) throws CsvValidationException, IOException {
        CSVReader reader = new CSVReader(new InputStreamReader(csvData));
        String[] line;
        int bookNum = 1, lineNum = 2; // skip headers
        while ((line = reader.readNext()) != null) {
            // map line
            String productCode = line[0];
            String author = line[1];
            String description = line[2];
            Integer edition;
            try {
                edition = Integer.parseInt(line[3].replaceAll("[^\\d.]", ""));
            } catch (NumberFormatException nfe) {
                edition = null;
            }
            String copyright = line[4];
            String publisher = line[5];
            String listPrice = line[6];

            // do stuff with data...

            if (bookNum == 1) {
                System.out.println("1 book has been processed");
            } else {
                System.out.println(bookNum + " books have been processed");
            }
            
            ++bookNum;
            ++lineNum;
        }

    }

}

这也适用于我，所以不太确定您遇到了什么问题：

    System.out.println("standard input");
    try {
        parseCsv(System.in);
    } catch (IOException e) {
        // If nothing is passed in
        e.printStackTrace();
    }

Answer 2

我认为没有办法实现你想要的 reader.readNext() 本身返回数组表示 CSV 文件的列，数组中的列按 CSV 文件中列的顺序索引，您可以通过事先知道列标题来操作数组，以便您可以正确获取数据。 基于此：

line[0] 将是您的第一列 / line[1] 将是第二列，依此类推。

更新添加一些代码，请尝试此代码而不是您的代码，并告诉我们结果如何

InputStream inputStream = Files.newInputStream(Paths.get(ClassLoader.getSystemResource("csv/test.csv").toURI()));
    List<String[]> list = new ArrayList<>();
    CSVReader csvReader = new CSVReader(new 
                                     InputStreamReader(inputStream));
    String[] line;
    while ((line = csvReader.readNext()) != null) {
        System.out.println(line[0]+" --- "+line[1]);
        list.add(line);
    }
    inputStream.close();
    csvReader.close();
    return list;

我的文件在同一个项目的类路径中，我假设数据如下：

colA | colB
 A   | B
 C   | D
 D   | E

输出如下：

colA --- colB
 A --- B
 C --- D
 E --- F