Java

Question

我正在尝试使用 java 将数据写入 csv 文件，但是当我尝试使用 excel 打开生成的文件时，我收到一条错误消息，指出文件已损坏。在记事本中打开文件后，它看起来格式正确，所以我不确定是什么问题。我正在使用 FileWriter class 将数据输出到文件。

FileWriter writer = new FileWriter("test.csv");

writer.append("ID");
writer.append(',');
writer.append("name");
writer.append(',');
...
writer.append('\n');

writer.flush();
writer.close();

我是否需要使用 java 中的某些库才能打印到 csv 文件？我认为只要您使用正确的格式，您就可以在 java 中本地执行此操作。

感谢您的帮助，

肖

Answer 1

基本上是因为 MS Excel 无法决定如何打开包含此类内容的文件。

当您将 ID 作为电子表格类型文件中的第一个字符时，它与 SYLK 文件和 MS Excel（以及可能的其他电子表格应用程序）的规范相匹配尝试将其作为 SYLK 文件打开。但与此同时，它不符合 SYLK 文件的完整规范，因为文件中的其余值是以逗号分隔的。因此，显示错误。

要解决此问题，请将 "ID" 更改为 "id"，它应该会按预期工作。

这很奇怪。但是，是的！

还尝试通过使用 less 文件对象来最小化文件访问。

我测试过，下面的代码工作完美。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class CsvWriter {
  public static void main(String[] args) {

    try (PrintWriter writer = new PrintWriter("test.csv")) {

      StringBuilder sb = new StringBuilder();
      sb.append("id");
      sb.append(',');
      sb.append("Name");
      sb.append('\n');

      sb.append("1");
      sb.append(',');
      sb.append("Prashant Ghimire");
      sb.append('\n');

      writer.write(sb.toString());

      System.out.println("done!");

    } catch (FileNotFoundException e) {
      System.out.println(e.getMessage());
    }

  }
}

Answer 2

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class CsvFile {

    public static void main(String[]args){
        PrintWriter pw = null;
        try {
            pw = new PrintWriter(new File("NewData.csv"));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        StringBuilder builder = new StringBuilder();
        String columnNamesList = "Id,Name";
        // No need give the headers Like: id, Name on builder.append
        builder.append(columnNamesList +"\n");
        builder.append("1"+",");
        builder.append("Chola");
        builder.append('\n');
        pw.write(builder.toString());
        pw.close();
        System.out.println("done!");
    }
}

Answer 3

    String filepath="/tmp/employee.csv";
    FileWriter sw = new FileWriter(new File(filepath));
    CSVWriter writer = new CSVWriter(sw);
    writer.writeAll(allRows);

    String[] header= new String[]{"ErrorMessage"};
    writer.writeNext(header);

    List<String[]> errorData = new ArrayList<String[]>();
    for(int i=0;i<1;i++){
        String[] data = new String[]{"ErrorMessage"+i};
        errorData.add(data);
    }
    writer.writeAll(errorData);

    writer.close();

Answer 4

我认为这是 java 中的一个简单代码，它将在编译此代码后以 CSV 格式显示字符串值：

public class CsvWriter {
    public static void main(String args[]) {
        // File input path
        System.out.println("Starting....");
        File file = new File("/home/Desktop/test/output.csv");
        try {
            FileWriter output = new FileWriter(file);
            CSVWriter write = new CSVWriter(output);
            // Header column value
            String[] header = { "ID", "Name", "Address", "Phone Number" };
            write.writeNext(header);
            // Value
            String[] data1 = { "1", "First Name", "Address1", "12345" };
            write.writeNext(data1);
            String[] data2 = { "2", "Second Name", "Address2", "123456" };
            write.writeNext(data2);
            String[] data3 = { "3", "Third Name", "Address3", "1234567" };
            write.writeNext(data3);
            write.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("End.");
    }
}

Answer 5

 private static final String FILE_HEADER ="meter_Number,latestDate";
    private static final String COMMA_DELIMITER = ",";
    private static final String NEW_LINE_SEPARATOR = "\n";
    static SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:m m:ss");

    private void writeToCsv(Map<String, Date> meterMap) {
        try {
            Iterator<Map.Entry<String, Date>> iter = meterMap.entrySet().iterator();
            FileWriter fw = new FileWriter("smaple.csv");
            fw.append(FILE_HEADER.toString());
            fw.append(NEW_LINE_SEPARATOR);
            while (iter.hasNext()) {
                Map.Entry<String, Date> entry = iter.next();
                try {
                    fw.append(entry.getKey());
                    fw.append(COMMA_DELIMITER);
                    fw.append(formatter.format(entry.getValue()));
                    fw.append(NEW_LINE_SEPARATOR);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    iter.remove();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Answer 6

如果您想在每次重新运行程序时都覆盖您的文件，那么这个问题的答案很好，但是如果您希望在重新运行您的程序时您的记录不丢失，您可能想试试这个

public void writeAudit(String actionName) {
    String whereWrite = "./csvFiles/audit.csv";

    try {
        FileWriter fw = new FileWriter(whereWrite, true);
        BufferedWriter bw = new BufferedWriter(fw);
        PrintWriter pw = new PrintWriter(bw);

        Date date = new Date();

        pw.println(actionName + "," + date.toString());
        pw.flush();
        pw.close();

    } catch (FileNotFoundException e) {
        System.out.println(e.getMessage());
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 7

我看到你已经有了答案，但这是另一个答案，可能更快一个简单的 class 用于传递对象列表并检索 csv 或 excel 或受密码保护的 zip csv 或 excel。 https://github.com/ernst223/spread-sheet-exporter

SpreadSheetExporter spreadSheetExporter = new SpreadSheetExporter(List<Object>, "Filename");
File fileCSV = spreadSheetExporter.getCSV();

Answer 8

Generate CSV file from List of Objects
Finally, following is an example showing how to generate a CSV file from List of objects. The example uses the MyUser class defined in the previous section -

import com.opencsv.CSVWriter;
import com.opencsv.bean.StatefulBeanToCsv;
import com.opencsv.bean.StatefulBeanToCsvBuilder;
import com.opencsv.exceptions.CsvDataTypeMismatchException;
import com.opencsv.exceptions.CsvRequiredFieldEmptyException;

import java.io.IOException;
import java.io.Writer;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class OpenCSVWriter {
    private static final String STRING_ARRAY_SAMPLE = "./example.csv";

    public static void main(String[] args) throws IOException,
            CsvDataTypeMismatchException,
            CsvRequiredFieldEmptyException {

        try ( Writer writer = Files.newBufferedWriter(Paths.get(STRING_ARRAY_SAMPLE));
        ) {
            StatefulBeanToCsv<MyUser> beanToCsv = new StatefulBeanToCsvBuilder(writer)
                    .withQuotechar(CSVWriter.NO_QUOTE_CHARACTER)
                    .build();

            List<MyUser> myUsers = new ArrayList<>();
            myUsers.add(new MyUser("Sundar Pichai ♥", "sundar.pichai@gmail.com", "+1-1111111111", "India"));
            myUsers.add(new MyUser("Satya Nadella", "satya.nadella@outlook.com", "+1-`enter code here`1111111112", "India"));

            beanToCsv.write(myUsers);
        }
    }
}

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