关于File与MultipartFile的用法概述

public String fileSave(HttpServletRequest request, HttpServletResponse response){
	MultipartHttpServletRequest msr = (MultipartHttpServletRequest) request;
    MultipartFile targetFile = msr.getFile("file");
}

// MultipartFile targetFile
// 文件写入路径 每次写文件的时候要保证 路径唯一 不会发生写入文件覆盖的问题
String fileName = targetFile.getOriginalFilename();
LOGGER.info("fileOnlineShowServiceImpl  ==> fileSave() fileName : {}", fileName);
// 临时将文件存放本地存储位置
String tempFilePath = downloadPath + File.separator + ToolsUtil.createUUID() + "_" + fileName;
// 将文件写入到本地 localPath
targetFile.transferTo(new File(tempFilePath));
LOGGER.info("fileOnlineShowServiceImpl ==> fileSave() tempFilePath : {}", tempFilePath);
// 将内存的文件上传阿里云OSS，并转换成图片，返回对应的信息
Map<String, String> fileInfoMaps = fileDealWithService.dealWithFileService(ComonConstant.DIGIT_LONG_ONE, tempFilePath, Boolean.TRUE);
// 将写入后的数据新增到数据记录表中
addNewRecorde(fileSaveReqDTO, fileInfoMaps , yhSystemUsers);

package org.springframework.web.multipart;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import org.springframework.core.io.InputStreamSource;
import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;
public interface MultipartFile extends InputStreamSource {
	//返回参数的名称
    String getName();
	// 获取源文件的名称
    @Nullable
    String getOriginalFilename();
	// 返回文件的内容类型
    @Nullable
    String getContentType();
	// 判断文件内容是否为空
    boolean isEmpty();
	// 返回文件大小 以字节为单位
    long getSize();
	// 将文件内容转化成一个byte[] 返回
    byte[] getBytes() throws IOException;
	// 返回输入的文件流
    InputStream getInputStream() throws IOException;
    default Resource getResource() {
        return new MultipartFileResource(this);
    }
    void transferTo(File var1) throws IOException, IllegalStateException;
	// 将MultipartFile 转换换成 File 写入到指定路径
    default void transferTo(Path dest) throws IOException, IllegalStateException {
        FileCopyUtils.copy(this.getInputStream(), Files.newOutputStream(dest));
    }
}

// 临时将文件存放本地存储位置
String tempFilePath = downloadPath + File.separator + ToolsUtil.createUUID() + "_" + fileName;
// 将文件写入到本地 downloadPath
targetFile.transferTo(new File(tempFilePath));

public void writeFileToLocal(MultipartFile targetFile) {
        //开始时间
        LocalDateTime startTime = LocalDateTime.now();
        BufferedInputStream bufferedReader = null;
        BufferedOutputStream bufferedWriter = null;
        try {
            bufferedReader = new BufferedInputStream(targetFile.getInputStream());
            bufferedWriter = new BufferedOutputStream(new FileOutputStream(downloadPath + File.separator +targetFile.getOriginalFilename()));
            int len=0;
            //字节缓冲区
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            while ((len = bufferedReader.read(buffer.array())) != -1) {
                bufferedWriter.write(buffer.array(),0,len);
                bufferedWriter.flush();
            }
            LOGGER.info("writeFileToLocal ==> 耗时:" + Duration.between(startTime, LocalDateTime.now()).toMillis());
        } catch (Exception e) {
            LOGGER.info("writeFileToLocal 文件写入失败");
        }finally {
            if (null != bufferedReader) {
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                    LOGGER.info("writeFileToLocal 文件写入失败");
                }
            }
            if (null != bufferedWriter) {
                try {
                    bufferedWriter.close();
                } catch (IOException e) {
                    LOGGER.info("writeFileToLocal 文件写入失败");
                }
            }
        }
    }

File file = new File(filePath);  // 文件路径
FileInputStream input = new FileInputStream(file);
// File 转 MultipartFile
MultipartFile targetFiles = new MockMultipartFile("targetFiles",file.getName(),null,IOUtils.toByteArray(input));
String fileName = targetFiles.getOriginalFilename(); // 源文件名

// 切割文件路径 获取"_"后的文件名
String textType = "Af_yta_sder.pdf";
String subRet = StringUtils.substringAfter(textType, "_");
System.out.println("subRet  = " + subRet );

// 获取最后一个"."切割符后的字符串 往往用作获取文件类型
String textType = "Af_yta_sder.pdf";
String subRet = StringUtils.substringAfterLast(textType, ".");
System.out.println("subRet  = " + subRet );

// 获取"."切割符前的字符串 往往用作获取文件名
String textType = "Af_yta_sder.pdf";
String subRet = StringUtils.substringBefore(textType, ".");
System.out.println("subRet  = " + subRet );

// 获取最后一个切割符"_"前的字符串
String textType = "Af_yta_sder.pdf";
String subRet = StringUtils.substringBeforeLast(textType, "_");
System.out.println("subRet  = " + subRet );