OpenCSV：实现CSV文件动态分隔符解析

import com.opencsv.bean.ColumnPositionMappingStrategy;
import com.opencsv.bean.CsvToBean;
import com.opencsv.bean.CsvToBeanBuilder;
import com.opencsv.exceptions.CsvException;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.List;

public class CsvUtils {

    /**
     * 解析CSV输入流，自动检测分隔符（支持逗号和分号）。
     *
     * @param inputStream CSV文件的输入流
     * @param type 目标Java对象的Class类型
     * @param columns CSV文件中列的顺序（对应Java对象的属性）
     * @param <T> 目标Java对象的泛型类型
     * @return 转换后的Java对象列表
     * @throws IOException 读取输入流时可能发生的异常
     * @throws CsvException CSV解析时可能发生的异常
     */
    public static <T> List<T> parseFromCsvWithSeparatorDetection(
            InputStream inputStream, Class<T> type, String[] columns)
            throws IOException, CsvException {

        // 1. 读取整个输入流内容到内存字符串
        final StringBuilder textBuilder = new StringBuilder();
        try (Reader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {
            int c;
            while ((c = reader.read()) != -1) {
                textBuilder.append((char) c);
            }
        }
        final String csvContent = textBuilder.toString();

        // 2. 检测分隔符
        final char detectedSeparator;
        if (csvContent.contains(";")) {
            detectedSeparator = ';'; // 如果包含分号，则认为是分号分隔
        } else {
            detectedSeparator = ','; // 否则，默认认为是逗号分隔
        }

        // 3. 使用检测到的分隔符进行CSV解析
        try (Reader reader = new StringReader(csvContent)) {
            // 配置列映射策略
            ColumnPositionMappingStrategy<T> strategy = new ColumnPositionMappingStrategy<>();
            strategy.setColumnMapping(columns);
            strategy.setType(type);

            // 构建 CsvToBean 并进行解析
            CsvToBean<T> csvToBean = new CsvToBeanBuilder<T>(reader)
                    .withMappingStrategy(strategy)
                    .withSeparator(detectedSeparator) // 动态设置分隔符
                    .withIgnoreLeadingWhiteSpace(true) // 忽略前导空格
                    .build();
            return csvToBean.parse();
        }
    }
}

public class Bean {
    private String a;
    private String b;

    public Bean() {
    }

    public String getA() {
        return a;
    }

    public void setA(String a) {
        this.a = a;
    }

    public String getB() {
        return b;
    }

    public void setB(String b) {
        this.b = b;
    }

    @Override
    public String toString() {
        return "Bean{" +
               "a='" + a + '\'' +
               ", b='" + b + '\'' +
               '}';
    }
}

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import com.opencsv.exceptions.CsvException;

public class Demo {
    public static void main(String[] args) {
        // 示例1：使用分号分隔的CSV数据
        String csvDataSemicolon = "A1;B1\nA2;B2";
        InputStream inSemicolon = new ByteArrayInputStream(csvDataSemicolon.getBytes(StandardCharsets.UTF_8));

        // 示例2：使用逗号分隔的CSV数据
        String csvDataComma = "X1,Y1\nX2,Y2";
        InputStream inComma = new ByteArrayInputStream(csvDataComma.getBytes(StandardCharsets.UTF_8));

        String[] columns = new String[]{"a", "b"}; // 对应Bean类的属性名

        try {
            System.out.println("--- 解析分号分隔的CSV ---");
            List<Bean> objectsSemicolon = CsvUtils.parseFromCsvWithSeparatorDetection(inSemicolon, Bean.class, columns);
            objectsSemicolon.forEach(System.out::println);

            System.out.println("\n--- 解析逗号分隔的CSV ---");
            List<Bean> objectsComma = CsvUtils.parseFromCsvWithSeparatorDetection(inComma, Bean.class, columns);
            objectsComma.forEach(System.out::println);

        } catch (IOException | CsvException e) {
            e.printStackTrace();
        }
    }
}

A1;B1
A2;B2

X1,Y1
X2,Y2