java实现从url路径中下载pdf文档到本地

package com.cellstrain.icell.util;


import java.io.*;
import java.net.*;

public class DownloadPdf {

    /**
     * 从网络Url中下载文件
     * @param urlStr
     * @param fileName
     * @param savePath
     * @throws IOException
     */
    public static void  downLoadByUrl(String urlStr,String fileName,String savePath) throws IOException{
        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();
        //设置超时间为3秒
        conn.setConnectTimeout(5*1000);
        //防止屏蔽程序抓取而返回403错误
        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
        //得到输入流
        InputStream inputStream = conn.getInputStream();
        //获取自己数组
        byte[] getData = readInputStream(inputStream);
        //文件保存位置
        File saveDir = new File(savePath);
        if(!saveDir.exists()){
            saveDir.mkdir();
        }
        File file = new File(saveDir+File.separator+fileName);
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(getData);
        if(fos!=null){
            fos.close();
        }
        if(inputStream!=null){
            inputStream.close();
        }
        System.out.println("info:"+url+" download success");

    }


    /**
     * 从输入流中获取字节数组
     * @param inputStream
     * @return
     * @throws IOException
     */
    public 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();
    }

    public static void main(String[] args) {
        try{
            downLoadByUrl("https://www.mybiosource.com/images/tds/protocol_samples/MBS700_Antibody_Set_Sandwich_ELISA_Protocol.pdf",
                    "ELISA.pdf","E:/upload/protocol");
        }catch (Exception e) {
            // TODO: handle exception
        }
    }
}

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class PdfDownloader {
    
    public static void downloadPdf(String pdfUrl, String destinationFile) {
        try {
            URL url = new URL(pdfUrl);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("GET");
            httpURLConnection.setDoOutput(true);
            
            int responseCode = httpURLConnection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) { // 200 status code
                InputStream inputStream = new BufferedInputStream(httpURLConnection.getInputStream());
                FileOutputStream fileOutputStream = new FileOutputStream(destinationFile);
                
                byte[] buffer = new byte[1024];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    fileOutputStream.write(buffer, 0, bytesRead);
                }
                
                fileOutputStream.close();
                inputStream.close();
                System.out.println("PDF downloaded successfully: " + destinationFile);
            } else {
                System.out.println("Failed to download PDF, response code: " + responseCode);
            }
            httpURLConnection.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        String pdfUrl = " // 替换为实际PDF链接
        String destinationFile = "downloaded.pdf"; // 目标文件名
        downloadPdf(pdfUrl, destinationFile);
    }
}

public static void downloadFile(String remoteFilePath, String localFilePath) {
        URL website = null;
        ReadableByteChannel rbc = null;
        FileOutputStream fos = null;
        try {
            website = new URL(remoteFilePath);
            rbc = Channels.newChannel(website.openStream());
            fos = new FileOutputStream(localFilePath);//本地要存储的文件地址 例如：test.txt
            fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(rbc!=null){
                try {
                    rbc.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
 
            }
        }
    }

public static void downloadFile1(String downloadUrl, String path){
        InputStream inputStream = null;
        OutputStream outputStream = null;
        try {
            URL url = new URL(downloadUrl);
            //这里没有使用 封装后的ResponseEntity 就是也是因为这里不适合一次性的拿到结果，放不下content,会造成内存溢出
            HttpURLConnection connection =(HttpURLConnection) url.openConnection();
 
            //使用bufferedInputStream 缓存流的方式来获取下载文件，不然大文件会出现内存溢出的情况
            inputStream = new BufferedInputStream(connection.getInputStream());
            File file = new File(path);
            if (file.exists()) {
                file.delete();
            }
            outputStream = new FileOutputStream(file);
            //这里也很关键每次读取的大小为5M 不一次性读取完
            byte[] buffer = new byte[1024 * 1024 * 5];// 5MB
            int len = 0;
            while ((len = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }
            connection.disconnect();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            IOUtils.closeQuietly(outputStream);
            IOUtils.closeQuietly(inputStream);
        }
    }