java如何将一个图片的url转换成File,然后将File对象转换成二进制流byte呢?

实现思路:
    使用 HttpURLConnection对象，然后下载文件
    使用fileInputStream的构造函数即可将file对象转换为byte对象

package com.java265;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
//java将图片的url转换成File，File转换成二进制流byte
public class PictureUtils {
	//将Url转换为File
    public static File UrltoFile(String url) throws Exception {
        HttpURLConnection httpUrl = (HttpURLConnection) new URL(url).openConnection();
        httpUrl.connect();
        InputStream ins=httpUrl.getInputStream();
        File file = new File(System.getProperty("java.io.tmpdir") + File.separator + "xia");//System.getProperty("java.io.tmpdir")缓存
        if (file.exists()) {
            file.delete();//如果缓存中存在该文件就删除
        }
        OutputStream os = new FileOutputStream(file);
        int bytesRead;
        int len = 8192;
        byte[] buffer = new byte[len];
        while ((bytesRead = ins.read(buffer, 0, len)) != -1) {
            os.write(buffer, 0, bytesRead);
        }
        os.close();
        ins.close();
        return file;

    }
    //将File对象转换为byte[]的形式
    public static byte[] FileTobyte(File file){
        FileInputStream fileInputStream = null;
        byte[] imgData = null;

        try {

            imgData = new byte[(int) file.length()];

            //read file into bytes[]
            fileInputStream = new FileInputStream(file);
            fileInputStream.read(imgData);

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fileInputStream != null) {
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }
        return imgData;
    }
}