outputstream转multipartfile 多个方法

1. 使用Commons IO库

可以使用Commons IO库中的方法将OutputStream转换为MultipartFile。下面是一个示例代码：

import org.apache.commons.io.IOUtils;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.OutputStream;

public MultipartFile convertToMultipartFile(OutputStream outputStream, String fileName) throws IOException {
    byte[] bytes = ((ByteArrayOutputStream) outputStream).toByteArray();
    ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes);
    MultipartFile multipartFile = new CommonsMultipartFile(inputStream, fileName, "application/octet-stream", bytes.length);
    return multipartFile;
}

2. 通过临时文件

此方法需要将OutputStream写入临时文件，然后将文件转换为MultipartFile。下面是一个示例代码：

import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import java.io.*;

public MultipartFile convertToMultipartFile(OutputStream outputStream, String fileName) throws IOException {
    File tempFile = File.createTempFile("temp", ".tmp");
    tempFile.deleteOnExit();
    FileOutputStream fos = new FileOutputStream(tempFile);
    outputStream.writeTo(fos);
    fos.close();
    FileInputStream fis = new FileInputStream(tempFile);
    MultipartFile multipartFile = new CommonsMultipartFile(fileName, fis);
    return multipartFile;
}

3. 自定义类

也可以自定义类实现MultipartFile接口，将OutputStream转换为MultipartFile。下面是一个示例代码：

import org.springframework.web.multipart.MultipartFile;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class OutputStreamMultipartFile implements MultipartFile {

    private final byte[] content;
    private final String name;
    private final String originalFilename;
    private final String contentType;

    public OutputStreamMultipartFile(byte[] content, String name, String originalFilename, String contentType) {
        this.content = content;
        this.name = name;
        this.originalFilename = originalFilename;
        this.contentType = contentType;
    }

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

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

    @Override
    public String getContentType() {
        return 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 {
        throw new UnsupportedOperationException();
    }
}

使用这个类可以将OutputStream转换为MultipartFile：

import org.springframework.web.multipart.MultipartFile;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public MultipartFile convertToMultipartFile(OutputStream outputStream, String fileName) throws IOException {
    byte[] bytes = ((ByteArrayOutputStream) outputStream).toByteArray();
    MultipartFile multipartFile = new OutputStreamMultipartFile(bytes, "file", fileName, "application/octet-stream");
    return multipartFile;
}