将 CSV 转换为 Json 的 java 应用程序

Question

我正在尝试创建一个 Java 应用程序来将 Excel/csv 文件内容转换为 JSON 格式， 因为我所有的输出 json 文件都有相同的标题。我选择使用带有 BufferedReader 和 BufferedWriter 的经典方法来简化。这是我的代码的一部分：

BufferedReader csvFile= new BufferedReader(new FileReader("DataTextCsv.csv"));
BufferedWriter jsonFile=new BufferedWriter(new FileWriter("converted.txt"));

String fileContent = csvFile.readLine();

// set the constant header 
String jsonScript="constant header of json content";

while (fileContent !=null){
    fileContent=csvFile.readLine();
    String[] tab = fileContent.split(",");
    // variable content from csv file
    jsonScript+="\""+tab[0]+"\" :";
    jsonScript+=tab[1]+","+"\n";

    // End of json content construction
    jsonScript=jsonScript.substring(0,jsonScript.length()-2);
    jsonScript+="}";

    String[] tabWrite=jsonScript.split("\n");
    for (String item:tabWrite){
        jsonFile.write(item);
        jsonFile.newLine(); 
    }
    csvFile.close();
    jsonFile.close();
}

应用程序可以正确读取 csv 文件的第一行，但无法继续到最后，并且我不断收到此错误（即使我尝试将所有 csv 数据设置在一行中：

Exception in thread "main" java.io.IOException: Stream closed
    at java.io.BufferedReader.ensureOpen(Unknown Source)
    at java.io.BufferedReader.readLine(Unknown Source)
    at java.io.BufferedReader.readLine(Unknown Source)
    at CSVConverter.main(CSVConverter.java:17)

我意识到使用更具体的库会更简单，但由于我是 Java 新手，我无法找到合适的包来下载和安装

Answer 1

将close 语句移出while 循环（最好移到finally 块中）

csvFile.close();
jsonFile.close();

Answer 2

请参阅以下内容，您的关闭方法位于错误的位置。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class NewClass {

    public static void main(String[] args) {
        BufferedReader csvFile = null;
        BufferedWriter jsonFile = null;
        try {
            csvFile = new BufferedReader(new FileReader("DataTextCsv.csv"));
            jsonFile = new BufferedWriter(new FileWriter("converted.txt"));
            String fileContent = csvFile.readLine();
            // set the constant header
            String jsonScript = "constant header of json content";
            while (fileContent != null) {
                fileContent = csvFile.readLine();
                String[] tab = fileContent.split(",");
                // variable content from csv file
                jsonScript += "\"" + tab[0] + "\" :";
                jsonScript += tab[1] + "," + "\n";
                // End of json content construction
                jsonScript = jsonScript.substring(0, jsonScript.length() - 2);
                jsonScript += "}";
                String[] tabWrite = jsonScript.split("\n");
                for (String item : tabWrite) {
                    jsonFile.write(item);
                    jsonFile.newLine();
                }
            }
        } catch (FileNotFoundException ex) {
            Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            try {
                csvFile.close();
                jsonFile.close();
            } catch (IOException ex) {
                Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }
}

或者选项二使用try-with资源

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

   public class NewClass {
    public static void main(String[] args) {
        try (BufferedReader csvFile = new BufferedReader(new FileReader("DataTextCsv.csv")); BufferedWriter jsonFile = new BufferedWriter(new FileWriter("converted.txt"))) {
            String fileContent = csvFile.readLine();
            // set the constant header
            String jsonScript = "constant header of json content";
            while (fileContent != null) {
                fileContent = csvFile.readLine();
                String[] tab = fileContent.split(",");
                // variable content from csv file
                jsonScript += "\"" + tab[0] + "\" :";
                jsonScript += tab[1] + "," + "\n";
                // End of json content construction
                jsonScript = jsonScript.substring(0, jsonScript.length() - 2);
                jsonScript += "}";
                String[] tabWrite = jsonScript.split("\n");
                for (String item : tabWrite) {
                    jsonFile.write(item);
                    jsonFile.newLine();
                }
            }
            csvFile.close();
            jsonFile.close();
        } catch (FileNotFoundException ex) {
            Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

Answer 3

您需要在 while 循环中为 null 值添加另一个捕获。另外，我不确定您是否打算像现在一样重复所有行。这种方式只返回最后一行/完整的数据集

            while (fileContent !=null){
                  fileContent=csvFile.readLine();
                  if (fileContent != null){
                      String[] tab = fileContent.split(",");
                      // variable content from csv file
                      jsonScript+="\""+tab[0]+"\" :";
                      jsonScript+=tab[1]+","+"\n";

                      // End of json content construction
                      jsonScript=jsonScript.substring(0,jsonScript.length()-2);
                      jsonScript+="}";
                  }else{
                      String[] tabWrite=jsonScript.split("\n");
                      for (String item:tabWrite){
                          result.append(item);
                          jsonFile.write(item);
                          jsonFile.newLine(); 
                      }

                  }
              }
              csvFile.close();
              jsonFile.close();