java中InputStream轉(zhuǎn)為MultipartFile的解決方案

更新時間：2025年03月20日 09:07:49 作者：不想CRUD的小凱

這篇文章主要介紹了java中InputStream轉(zhuǎn)為MultipartFile的解決方案,具有很好的參考價值,希望對大家有所幫助,如有錯誤或未考慮完全的地方,望不吝賜教

java中InputStream轉(zhuǎn)為MultipartFile

問題出現(xiàn)原因

我所處理的服務(wù)端需要進行Feign調(diào)用，其中出現(xiàn)了需要文件傳輸?shù)牟襟E。
由于服務(wù)端的文件存于OSS中，我能拿到的只有文件所在url
被調(diào)用方的Client采用MultipartFile接收
因此需要從中進行處理，返回MultipartFile給到對方
但其實，已經(jīng)有其他的實現(xiàn)類，只需要引Maven包即可，而我為了避免引包才編寫如下代碼。

解決方式

自己實現(xiàn)一個MulitpartFile接口

static class DefaultMultiPartFile implements MultipartFile {
    private final String name;
    private String originalFilename;
    @Nullable
    private String contentType;
    private final byte[] content;

    DefaultMultiPartFile(String name, @Nullable byte[] content) {
      this(name, "", (String)null, content);
    }

    DefaultMultiPartFile(String name, String originalFilename, @Nullable String contentType, byte[] content) {
      this.name = name;
      this.originalFilename = originalFilename;
      this.contentType = contentType;
      this.content = content;
    }

    @Override
    public String getName() {
      return this.name;
    }

    @Override
    public String getOriginalFilename() {
      return this.originalFilename;
    }

    @Override
    public String getContentType() {
      return this.contentType;
    }

    @Override
    public boolean isEmpty() {
      return content.length==0;
    }

    @Override
    public long getSize() {
      return content.length;
    }

    @Override
    public byte[] getBytes() throws IOException {
      return content;
    }

    @Override
    public InputStream getInputStream() throws IOException {
      return new ByteArrayInputStream(content);
    }

    @Override
    public void transferTo(File file) throws IOException, IllegalStateException {
      FileCopyUtils.copy(this.content, file);
    }
  }

整合功能之后，最終編寫的Util類：

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.multipart.MultipartFile;

public class MultipartFileUtil {
  
  public static MultipartFile inputStreamToMultipartFile(InputStream inputStream,String name) throws IOException {
    byte[] bytes = readInputStream(inputStream);
    DefaultMultiPartFile defaultMultiPartFile = new DefaultMultiPartFile(name, bytes);
    return defaultMultiPartFile;
  }

  public static MultipartFile multipartFileByUrl(String url,String name) throws IOException{
    URL downloadUrl = new URL(url);
    URLConnection urlConnection = downloadUrl.openConnection();
    // 超時時間20s
    urlConnection.setConnectTimeout(20*1000);
    urlConnection.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
    InputStream inputStream = urlConnection.getInputStream();
    return inputStreamToMultipartFile(inputStream,name);
  }

  private static byte[] readInputStream(InputStream inputStream) throws IOException {
    byte[] buffer = new byte[1024];
    int len = 0;
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    while ((len = inputStream.read(buffer)) != -1) {
      bos.write(buffer, 0, len);
    }
    bos.close();
    return bos.toByteArray();
  }


  static class DefaultMultiPartFile implements MultipartFile {
    private final String name;
    private String originalFilename;
    @Nullable
    private String contentType;
    private final byte[] content;

    DefaultMultiPartFile(String name, @Nullable byte[] content) {
      this(name, "", (String)null, content);
    }

    DefaultMultiPartFile(String name, String originalFilename, @Nullable String contentType, byte[] content) {
      this.name = name;
      this.originalFilename = originalFilename;
      this.contentType = contentType;
      this.content = content;
    }

    @Override
    public String getName() {
      return this.name;
    }

    @Override
    public String getOriginalFilename() {
      return this.originalFilename;
    }

    @Override
    public String getContentType() {
      return this.contentType;
    }

    @Override
    public boolean isEmpty() {
      return content.length==0;
    }

    @Override
    public long getSize() {
      return content.length;
    }

    @Override
    public byte[] getBytes() throws IOException {
      return content;
    }

    @Override
    public InputStream getInputStream() throws IOException {
      return new ByteArrayInputStream(content);
    }

    @Override
    public void transferTo(File file) throws IOException, IllegalStateException {
      FileCopyUtils.copy(this.content, file);
    }
  }

}