标签：文件 data fileLoad 导出 fileName write new CSV csvWriter
大文件的导出 csv
- jar包的导入
<!--csv文件下载-->
<dependency>
<groupId>net.sourceforge.javacsv</groupId>
<artifactId>javacsv</artifactId>
<version>2.0</version>
</dependency>
2.csv工具
import com.csvreader.CsvWriter;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.nio.charset.Charset;
/**
* @author
* @date 2021/3/31 0031 18:33
*/
public class CsvUtil {
public interface WriteCsv {
void write(CsvWriter csvWriter) throws Exception;
}
public static void writeCsv(String fileName,HttpServletResponse response, CsvUtil.WriteCsv writeCsv){
try {
// 创建临时文件
File tempfile = File.createTempFile(fileName, ".csv");
// 创建 CsvWriter 对象
CsvWriter csvWriter = new CsvWriter(tempfile.getCanonicalPath(),',', Charset.forName("GBK"));
// 接口需要实现的方法
writeCsv.write(csvWriter);
// 关闭 CsvWriter 对象
csvWriter.close();
// 获取写入数据的临时文件
File fileLoad=new File(tempfile.getCanonicalPath());
// 返回给前端
CsvUtil.downLoadCsv(fileName+".csv", fileLoad,response);
// 在项目中生成文件
// CsvUtil.downLoadCsvHere(fileName+".csv", fileLoad);
}catch (Exception e){
e.printStackTrace();
}
}
/**
* 在项目中生成文件
* @param fileName
* @param fileLoad
*/
public static void downLoadCsvHere(String fileName, File fileLoad){
try {
byte[] b=new byte[1024];
FileOutputStream out = new FileOutputStream(fileName);
FileInputStream fileInputStream=new FileInputStream(fileLoad);
int n;
while ((n = fileInputStream.read(b)) != -1) {
out.write(b, 0, n); //每次写入out1024字节
}
fileInputStream.close();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 返回给前端
* @param fileName
* @param fileLoad
* @param response
*/
public static void downLoadCsv(String fileName, File fileLoad, HttpServletResponse response) {
try {
byte[] b = new byte[1024];
OutputStream out = response.getOutputStream();
response.reset();
response.setContentType("application/csv");
response.setHeader("content-disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));
Long filelength = fileLoad.length();
response.setHeader("Content_Length", String.valueOf(filelength));
FileInputStream fileInputStream = new FileInputStream(fileLoad);
int n;
while ((n = fileInputStream.read(b)) != -1) {
out.write(b, 0, n); //每次写入out1024字节
}
fileInputStream.close();
out.close();
} catch (IOException e) {
try {
throw new Exception(e.getMessage());
} catch (Exception e1) {
e1.printStackTrace();
}
}
}
}
3.调用示例
public String downUrl(String examId, String type) throws IOException {
List<BksTemVO> listExam;
if ("1".equals(type)) {
//查询分数列表
List<BksScoresTemporary> listOld = bksScoresTemporaryService.lambdaQuery().eq(BksScoresTemporary::getExamId, examId).list();
listExam = JSON.parseArray(JSON.toJSONString(listOld), BksTemVO.class);
} else {
List<BksScoresTemporaryNew> listNew = bksScoresTemporaryNewService.lambdaQuery().eq(BksScoresTemporaryNew::getExamId, examId).list();
listExam = JSON.parseArray(JSON.toJSONString(listNew), BksTemVO.class);
}
String[] titles = new String[]{"考试代码","学籍号","姓名","区县名称","区县原始名称","区县代码","学校名称",
"学校原始名称","学校代码","班级","语文","数学","英语","物理","历史","化学","生物","政治","地理",
"学科组合代码","学科组合名称","学科组合原始名称"}; // 导出列标题
// 调用service层获取list集合;
CsvUtil.writeCsv(examId+"分数"+type, response, new CsvUtil.WriteCsv() {
@Override
public void write(CsvWriter csvWriter) throws Exception {
csvWriter.writeRecord(titles);
if (listExam!=null && !listExam.isEmpty()){
// 遍历List集合，将每条数据对应写入
for (BksTemVO data:listExam) {
csvWriter.write(data.getExamId());
csvWriter.write(data.getStudentCode());
csvWriter.write(data.getStudentName());
csvWriter.write(data.getDistrictName());
csvWriter.write(data.getDistrictNameTemp());
csvWriter.write(data.getDistrictId());
csvWriter.write(data.getUnitName());
csvWriter.write(data.getUnitNameTemp());
csvWriter.write(data.getUnitId());
csvWriter.write(data.getClassName());
csvWriter.write(data.getChinese());
csvWriter.write(data.getMathematics());
csvWriter.write(data.getEnglish());
csvWriter.write(data.getPhysical());
csvWriter.write(data.getHistory());
csvWriter.write(data.getChemical());
csvWriter.write(data.getBiological());
csvWriter.write(data.getPolitical());
csvWriter.write(data.getGeographic());
csvWriter.write(data.getSubjectCombId());
csvWriter.write(data.getSubjectCombName());
csvWriter.write(data.getSubjectCombNameTemp());
csvWriter.endRecord();
}
}
}
});
return null;
}
备注：之前使用easyExcel、POI导出到时数据量较大时会出现不确定问题（自己没能解决），后换成csv
标签：文件,data,fileLoad,导出,fileName,write,new,CSV,csvWriter 来源： https://blog.csdn.net/L1569850979/article/details/115372234
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