工作中遇到了将所有数据整合成CSV文件并下载、上传CSV文件并解析，这两个需求。现在把处理方法记录下来，作为总结。
jar包引入
CSV的解析和写入使用到的是commons-csv的包，pom中的定义如下
org.apache.commons commons-csv 1.7
工具类
我把CSV的上传、下载、解析、写入的通用方法，都整合在了CSVUtils类中。
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVPrinter;
import org.apache.commons.csv.CSVRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
/**
* @Description: CSV工具类
**/
public class CSVUtils {
private static Logger logger = LoggerFactory.getLogger(CSVUtils.class);
//行尾分隔符定义
private final static String NEW_LINE_SEPARATOR = "\n";
//上传文件的存储位置
private final static URL PATH = Thread.currentThread().getContextClassLoader().getResource("");
/**
* @return File
* @Description 创建CSV文件
* @Param fileName 文件名，head 表头，values 表体
**/
public static File makeTempCSV(String fileName, String[] head, List values) throws IOException {
// 创建文件
File file = File.createTempFile(fileName, ".csv", new File(PATH.getPath()));
CSVFormat formator = CSVFormat.DEFAULT.withRecordSeparator(NEW_LINE_SEPARATOR);
BufferedWriter bufferedWriter =
new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF-8"));
CSVPrinter printer = new CSVPrinter(bufferedWriter, formator);
// 写入表头
printer.printRecord(head);
// 写入内容
for (String[] value : values) {
printer.printRecord(value);
}
printer.close();
bufferedWriter.close();
return file;
}
/**
* @return boolean
* @Description 下载文件
* @Param response，file
**/
public static boolean downloadFile(HttpServletResponse response, File file) {
FileInputStream fileInputStream = null;
BufferedInputStream bufferedInputStream = null;
OutputStream os = null;
try {
fileInputStream = new FileInputStream(file);
bufferedInputStream = new BufferedInputStream(fileInputStream);
os = response.getOutputStream();
//MS产本头部需要插入BOM
//如果不写入这几个字节，会导致用Excel打开时，中文显示乱码
os.write(new byte[]{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF});
byte[] buffer = new byte[1024];
int i = bufferedInputStream.read(buffer);
while (i != -1) {
os.write(buffer, 0, i);
i = bufferedInputStream.read(buffer);
}
return true;
} catch (IOException e) {
e.printStackTrace();
} finally {
//关闭流
if (os != null) {
try {
os.flush();
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (bufferedInputStream != null) {
try {
bufferedInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (fileInputStream != null) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
file.delete();
}
return false;
}
/**
* @return File
* @Description 上传文件
* @Param multipartFile
**/
public static File uploadFile(MultipartFile multipartFile) {
String path = PATH.getPath() + multipartFile.getOriginalFilename();
try {
File file = new File(path);
if (!file.getParentFile().exists()) {
file.getParentFile().mkdirs();
}
multipartFile.transferTo(file);
logger.info("上传文件成功，文件名===>" + multipartFile.getOriginalFilename() + ", 路径===>" + file.getPath());
return file;
} catch (IOException e) {
logger.error("上传文件失败" + e.getMessage(), e);
return null;
}
}
/**
* @return List>
* @Description 读取CSV文件的内容（不含表头）
* @Param filePath 文件存储路径，colNum 列数
**/
public static List> readCSV(String filePath, int colNum) {
BufferedReader bufferedReader = null;
InputStreamReader inputStreamReader = null;
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(filePath);
inputStreamReader = new InputStreamReader(fileInputStream);
bufferedReader = new BufferedReader(inputStreamReader);
CSVParser parser = CSVFormat.DEFAULT.parse(bufferedReader);
// 表内容集合，外层List为行的集合，内层List为字段集合
List> values = new ArrayList<>();
int rowIndex = 0;
for (CSVRecord record : parser.getRecords()) {
// 跳过表头
if (rowIndex == 0) {
rowIndex++;
continue;
}
// 每行的内容
List value = new ArrayList<>(colNum + 1);
for (int i = 0; i < colNum; i++) {
value.add(record.get(i));
}
values.add(value);
rowIndex++;
}
return values;
} catch (IOException e) {
logger.error("解析CSV内容失败" + e.getMessage(), e);
}finally {
//关闭流
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (inputStreamReader != null) {
try {
inputStreamReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (fileInputStream != null) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
} 控制器
Controller.java
import com.denebola.learnspringboot.CSVUtils;
import lombok.extern.slf4j.Slf4j;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.util.List;
@Slf4j
@RestController
public class Controller {
private static Logger logger = LoggerFactory.getLogger(Controller.class);
//定义自己的服务类接口
@Autowired
private Service service;
/**
* @param response
* @return
* @Description 下载CSV
**/
@GetMapping("/downloadAll")
public String downloadAllUserRoleCSV(HttpServletResponse response) {
String[] head = service.getHead();
List values = service.getValues();
String fileName = service.getName();
File file = CSVUtils.makeTempCSV(fileName, head, values);
response.setCharacterEncoding("utf-8");
response.setContentType("multipart/form-data");
response.setHeader("Content-Disposition", "attachment;fileName=" + fileName +".csv");
CSVUtils.downloadFile(response, file);
return null;
}
/**
* @return
* @Description 上传CSV
* @Param file
**/
@PostMapping(value = "/upload")
public String upload(@RequestParam("file") MultipartFile multipartFile) {
try {
//上传内容不能为空
if (multipartFile.isEmpty()) {
return "500";
}
File file = CSVUtils.uploadFile(multipartFile);
List> userRoleLists = CSVUtils.readCSV(file.getPath(), 2);
service.doSth(userRoleLists);
file.delete();
return "200";
} catch (Exception e) {
e.printStackTrace();
}
return "500";
}
} Tips
需要值得注意的是，在使用Java生成CSV文件时，可能出现中文乱码的问题，这是由于微软的产品为了检测一个字节流是否是UTF-8编码，而添加了BOM标记。而有的文本编辑软件，比如Notepad、VScode、记事本等，不会做这种检测，会当作正常字符处理。所以产生的现象就是，Excel打开是乱码时，记事本打开不是乱码。
为了解决这种问题，我们可以手动的加入BOM。上述代码中添加的方式是os.write(new byte[]{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF});，如果不使用Response的out进行输出的话，可以改用以下代码：
OutputStreamWriter osw = new OutputStreamWriter(resp.getOutputStream(), "UTF-8");
osw.write(new String(new byte[] { (byte) 0xEF, (byte) 0xBB,(byte) 0xBF }));