文件下载，文件转换

import org.apache.commons.io.FileUtils;
import org.springframework.mock.web.MockMultipartFile;
import org.springframework.web.multipart.MultipartFile;

import java.io.*;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Files;

public class UrlToMultipartFileUtil {
    /**
     * description 网络TRL中下载图片
     *
     * @param uri
     * @param folder 存放文件的文件夹
     * @return java.lang.String
     */
    private String downloadByUrl(String uri, String folder) {
        ReadableByteChannel readableByteChannel = null;
        FileChannel fileChannel = null;
        File file;
        URL url;
        FileOutputStream fileOutputStream = null;
        try {
            url = new URL(uri);
            //首先从 URL stream 中创建一个 ReadableByteChannel 来读取网络文件
            readableByteChannel = Channels.newChannel(url.openStream());
            String fileName = System.currentTimeMillis() + url.getPath().substring(url.getPath().lastIndexOf("."));
            String path = folder + "/" + fileName;
            file = new File(path);
            if (!file.getParentFile().exists() && !file.getParentFile().isDirectory()) {
                file.getParentFile().mkdirs();
            }
            //通过 ReadableByteChannel 读取到的字节会流动到一个 FileChannel 中，然后再关联一个本地文件进行下载操作
            fileOutputStream = new FileOutputStream(file);
            fileChannel = fileOutputStream.getChannel();
            //最后用 transferFrom()方法就可以把 ReadableByteChannel 获取到的字节写入本地文件
            fileChannel.transferFrom(readableByteChannel, 0, Long.MAX_VALUE);
            return fileName;
        } catch (Exception e) {
            e.printStackTrace();
            return "";
        } finally {
            try {
                if (null != readableByteChannel) {
                    readableByteChannel.close();
                }
                if (null != fileChannel) {
                    fileChannel.close();
                }
                if (null != fileOutputStream) {
                    fileOutputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     * @param
     * @return
     * @author:liuyu
     * @功能说明：File转MultipartFile
     */
    private static MultipartFile fileToMultipartFile(File file) throws Exception {
        InputStream inputStream = new FileInputStream(file);
        MultipartFile multipartFile = new MockMultipartFile(file.getName(), inputStream);
        return multipartFile;

    }

//通过url将文件下载到本地
    public static int downloadFileFromUrl(String url, String localFilePath) {
        try {
            URL httpUrl = new URL(url);
            File f = new File(localFilePath);
            FileUtils.copyURLToFile(httpUrl, f);
        } catch (Exception e) {
            e.printStackTrace();
            return 0;
        }
        return 1;
    }

}

 

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-mock</artifactId>
    <version>2.0.8</version>
</dependency>