Java实现从本地读取CSV文件数据

一、前言
最近项目中需要实现这样一个功能，就是从本地读取CSV文件，并以指定行作为标题行，指定行开始作为数据读取行，读取数据并返回给前端，下面具体说下是如何通过java实现。

二、如何实现？
1.引入相关maven依赖

<dependency>
       <groupId>cn.hutool</groupId>
       <artifactId>hutool-all</artifactId>
</dependency>

2.定义一个工具类CsvUtils。

import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.collection.CollectionUtil;
import cn.hutool.core.collection.IterUtil;
import cn.hutool.core.text.csv.CsvData;
import cn.hutool.core.text.csv.CsvReader;
import cn.hutool.core.text.csv.CsvRow;
import cn.hutool.core.text.csv.CsvUtil;

import cn.hutool.core.util.ReUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import java.io.*;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class CsvUtils {
	public static final String FIELD_NAME="column";
    public static List<Map<String, Object>> getCsvFileContent(InputStream in, Long readLine, int headerRowIndex, int readCount,String splitChar) throws IOException {
        InputStreamReader is = null;
        CsvReader reader =null;
        InputStream bufferedInputStreamOne =null;
        InputStream bufferedInputStreamTwo =null;
        ByteArrayOutputStream baos =null;
        try {
            if (in == null) {
                throw new FileStorageRuntimeException("文件读取失败，文件不存在！");
            }
            if (readLine ==null){
                readLine =2l;
            }
            List<Map<String, Object>> resList = new ArrayList<>();
            reader = CsvUtil.getReader();
            baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024*10];
            int len;
            while ((len = in.read(buffer)) > -1 ) {
                baos.write(buffer, 0, len);
            }
            baos.flush();

            bufferedInputStreamOne=new ByteArrayInputStream(baos.toByteArray());
            bufferedInputStreamTwo=new ByteArrayInputStream(baos.toByteArray());
            boolean isUtf8=checkUTF8(bufferedInputStreamOne);
            //从文件中读取CSV数据
            is = new InputStreamReader(bufferedInputStreamTwo,Charset.forName(isUtf8 ? "UTF-8":"GBK"));
            reader.setFieldSeparator(splitChar.charAt(0));
            reader.setSkipEmptyRows(false);
            CsvData data = reader.read(is);
            List<CsvRow> rows = data.getRows();
            //空表格；
            if (rows.isEmpty()) {
                return null;
            }
            List<String> headRowList =new ArrayList<>();
            if (headerRowIndex > 0 && rows.size()>headerRowIndex - 1){
                //获取表头；
                headRowList = rows.get(headerRowIndex - 1).getRawList();
            }else {
                if (CollectionUtil.isNotEmpty(rows)){
                    List<String> rowList=rows.get(0).getRawList();
                    for(int i=1;i<=rowList.size();i++) {
                        headRowList.add(FIELD_NAME+i);
                    }
                }
            }
            List<String> headList=new ArrayList<>();

            for (int i=0;i<headRowList.size();i++) {
                String fieldName = headRowList.get(i);
                if (StrUtil.isBlank(fieldName )) {
                	headList.add(FIELD_NAME+(i+1));
                }else {
                	headList.add(fieldName);
                }
            }
            if (CollUtil.isNotEmpty(rows)){
                CsvRow currCsvRow = rows.get(0);
                if (headList.size() != currCsvRow.getRawList().size()) {
                    throw new FileStorageRuntimeException("列数量与数据数量不一致");
                }
            }
            if (readLine>1) {
                //加上一行
                List<String> addRawListNew = headRowList.stream().map(s -> StrUtil.trim(s)).collect(Collectors.toList());
                Map map = IterUtil.toMap(headList, (Iterable) addRawListNew,true);
                resList.add(map);
            }
            //遍历行
            for (int i = (int)((long)readLine)-1; i < rows.size(); i++) {
                CsvRow csvRow = rows.get(i);
                //getRawList返回一个List列表，列表的每一项为CSV中的一个单元格（既逗号分隔部分）
                List<String> rawList = csvRow.getRawList();
                List<String> rawListNew = rawList.stream().map(s -> StrUtil.trim(s)).collect(Collectors.toList());

                Map map = IterUtil.toMap(headList, (Iterable) rawListNew,true);
                resList.add(map);
                if(readCount>=0 && i>=readCount){
                    break;
                }
            }
            return resList;
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException("get inputStreamReader failed");
       } finally {
            if (in!=null){
                in.close();
            }
            if (is!=null){
                is.close();
            }
            if (reader!=null){
                reader.close();
            }
            if(bufferedInputStreamTwo !=null){
                bufferedInputStreamTwo.close();
            }
            if(bufferedInputStreamOne !=null){
                bufferedInputStreamOne.close();
            }
            if (baos!=null){
                baos.close();
            }
        }

    }
     /**
     * 判断文件内容是否为 UTF-8 编码
     * @author
     */
    public static boolean checkUTF8(InputStream fis) {
        //请注意fis是流，是不能复用的！
        try {
            while (true) {
                int curr = fis.read();
                if (curr == -1) {
                    return true;
                }
                if (curr < 0x80) {// (10000000): 值小于0x80的为ASCII字符
                } else if (curr < (0xC0)) { // (11000000): 值介于0x80与0xC0之间的为无效UTF-8字符
                    return false;
                } else if (curr < (0xE0)) { // (11100000): 此范围内为2字节UTF-8字符
                    if ((fis.read() & (0xC0)) != 0x80) {
                        return false;
                    }
                    return true;
                } else if (curr < (0xF0)) { // (11110000): 此范围内为3字节UTF-8字符
                    if ((fis.read() & (0xC0)) != 0x80 || (fis.read() & (0xC0)) != 0x80) {
                        return false;
                    }
                    return true;
                } else {
                    return false;
                }
            }
        } catch (IOException e) {
            return true;
        }
    }
    
}

接着通过main方法调用下。

   public static void main(String[] args) throws IOException {
        FileInputStream inputStream = new FileInputStream(new File("D:\\111.csv"));

        List<Map<String, Object>> list=getCsvFileContent(inputStream,2l,1,50,",");
        System.err.println(list);
  }