java使用multipart/form-data 上传文件和文件存储，pddf，git等的预览（流，stream）

1.文件上传有两种一种是流（instream），另一种是路径（url）的方式

1.1：判断服务器类型window还是linux

	public static boolean isLinux() {
		return System.getProperty("os.name").toLowerCase().indexOf("linux") >= 0;
	}
	
	public static boolean isWindows() {
		return System.getProperty("os.name").toLowerCase().indexOf("windows") >= 0;
	}
	
// 如果是windows的路径是\\，linux的路径是/ ，例子path是文件路径的前缀，filename是文件的名字

		if (isWindows()) {
			fullPathName = path + "\\" + filename;
		} else {
			fullPathName = path + "/" + filename;
		}

1.2：文件存储写入磁盘

//fullPathName是输出的的路径，文件名和类型，例如fullPathName=c:\\file\\testout.pdf
//is是文件流，通过multipartFile.getInputStream()获取
		FileOutputStream fs = new FileOutputStream(fullPathName);
		byte[] buffer = null;
		if (fileSize > (1024 * 1024)) {
			buffer = new byte[1024 * 1024];// 按1M写入
		} else {
			buffer = new byte[fileSize];// 按1M写入
		}
		int byteread = 0;
		while ((byteread = is.read(buffer)) != -1) {
			fs.write(buffer, 0, byteread);
			fs.flush();
		}
		fs.close();
		is.close();

1.3:将文件路径url转为流（instrenm）

//filenurl是输出的的路径，文件名和类型，例如fullPathName=c:\\file\\testin.pdf
 InputStream file = new FileInputStream(filenurl);

1.4:获取文件的类型或者名字方法

//获取文件类型
String suffix = filenurl.substring(filenurl.lastIndexOf("."), filenurl.length());
//获取文件名
String fileName=new File(filenurl).getName();

1.5:如果是多文件上传的需要先获取全部的文件出来MultipartFile

		/* 校验文件是否非空 */
		List<MultipartFile> multipartFiles = request.getMultiFileMap().get("file_data");
		if (null == multipartFiles || multipartFiles.size() == 0) {
			result.put("error", "无法获取需要处理的文件信息");
			return result;
		}
		for (int i = 0; i < multipartFiles.size(); i++) {
			MultipartFile multipartFile = multipartFiles.get(i);
			InputStream is= multipartFile.getInputStream();
		/*补充一下MultipartFile的方法
			String fileType = multipartFile.getContentType();// 文件类型
			long fileSize = multipartFile.getSize();// 文件大小，单位：KB
			String fileOriginalName = multipartFile.getOriginalFilename()//文件的名字	
		*/
		//操作刘读取获取存储********

		}

1.6：文件上传代码

 public static String sendPostUplodFile(String in11) {
        DataOutputStream out = null;
        BufferedReader in = null;
        String result = "";
        try {
//URL realUrl = new URL("http://file.kgfuns.com/fileserver/upload?BusiessId=23");
            URL realUrl = new URL("http://localhost:8102/fileserver/upload?BusiessId=24");
//打开和URL之间的连接
            HttpURLConnection conn = (HttpURLConnection)realUrl.openConnection();

//构建请求头
            String BOUNDARY = "----WebKitFormBoundary07I8UIuBx6LN2KyY";
            conn.setUseCaches(false);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("connection", "Keep-Alive");
//conn.setRequestProperty("user-agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            conn.setRequestProperty("Charsert", "UTF-8");
            conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
//发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.connect();

//设置输出流
            out = new DataOutputStream(conn.getOutputStream());

//添加参数file
//File file = new File(in11);
            File file = new File(String.valueOf(in11));
            StringBuffer sb = new StringBuffer();
            sb.append("--");
            sb.append(BOUNDARY);
            sb.append("\r\n");
            //媒体类型上传的类型
//sb.append("Content-Disposition: form-data; name=\"media\";filename=\"").append(fileName).append(typeName);
//（Instream）流文件上传的时候要指定filename的值
            sb.append("Content-Disposition: form-data;name=\"file_data\";filename=\"" + file.getName() + "\"");
            sb.append("\r\n");
            sb.append("Content-Type: application/octet-stream");
            sb.append("\r\n");
            sb.append("\r\n");
            out.write(sb.toString().getBytes());

//DataInputStream in1 = new DataInputStream(new FileInputStream(file));
            FileInputStream in1 = new FileInputStream(file);
//DataInputStream in1 = new DataInputStream(in11);
            int bytes = 0;
            byte[] bufferOut = new byte[1024];
            while ((bytes = in1.read(bufferOut)) != -1) {
                out.write(bufferOut,0,bytes);
            }
            out.write("\r\n".getBytes());
            in1.close();
            byte[] end_data = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();
            out.write(end_data);
//flush输出流的缓冲
            out.flush();
 //定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
//            HashMap hashMap = JSON.parseObject(result, HashMap.class);
//            JSONObject jsonObject=new JSONObject(JSON.parseObject(result, HashMap.class));
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

1.7：流形式的文件保存,下载代码

    private void savePic(InputStream inputStream, String fileName) {
        OutputStream os = null;
        try {
            String path = "D:\\testFile\\";

            byte[] bs = new byte[1024];
            int len;
            File tempFile = new File(path);
            if (!tempFile.exists()) {
                tempFile.mkdirs();
            }
            os = new FileOutputStream(tempFile.getPath() + File.separator + fileName);
            while ((len = inputStream.read(bs)) != -1) {
                os.write(bs, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                os.close();
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

1.7：URL形式的文件保存,下载代码

    public static File saveUrlAs( String pdfUrl) {
        File file = new File("D:\\testFile");
        if (!file .exists()) {
            file .mkdirs();
           }        
        FileOutputStream fileOut = null;
        HttpURLConnection conn = null;
        InputStream inputStream = null;
        try {
            URL httpUrl = new URL(pdfUrl);
            conn = (HttpURLConnection) httpUrl.openConnection();
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.connect();
            inputStream = conn.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(inputStream);
            fileOut = new FileOutputStream("D:\\testFile\\" + "test.pdf");
            BufferedOutputStream bos = new BufferedOutputStream(fileOut);

            byte[] buf = new byte[4096];
            int length = bis.read(buf);
            while (length != -1) {
                bos.write(buf, 0, length);
                length = bis.read(buf);
            }
            bos.close();
            bis.close();
            conn.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("抛出异常！！");
        }
        return file;

    }

1.8：URL(远程)形式的上传文件

    public static String sendPostUplodFile2(String in11) throws IOException {
        DataOutputStream out = null;
        BufferedReader in = null;
        String result = "";
        HttpURLConnection conn1 = null;
        InputStream inputStream = null;
        BufferedInputStream bis=null;
        try {
            URL httpUrl = new URL(in11);
            conn1 = (HttpURLConnection) httpUrl.openConnection();
            conn1.setRequestMethod("GET");
            conn1.setDoInput(true);
            conn1.setDoOutput(true);
            conn1.setUseCaches(false);
            conn1.connect();
            inputStream = conn1.getInputStream();
            URL realUrl = new URL("上传文件服务器的URL");
            //打开和URL之间的连接
            HttpURLConnection conn = (HttpURLConnection)realUrl.openConnection();
            //发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);

            String BOUNDARY = "----WebKitFormBoundary07I8UIuBx6LN2KyY";
            conn.setUseCaches(false);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36");
            conn.setRequestProperty("Charsert", "UTF-8");
            conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
            conn.connect();

            out = new DataOutputStream(conn.getOutputStream());
            byte[] end_data = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();
            //添加参数file
            StringBuffer sb = new StringBuffer();
            sb.append("--");
            sb.append(BOUNDARY);
            sb.append("\r\n");
            //pdf的名字可以通过 new File(url).getName() 的方式获取
            sb.append("Content-Disposition: form-data;name=\"file_data\";filename=\"" + "pdf.pdf" + "\"");
            sb.append("\r\n");
            sb.append("Content-Type: application/octet-stream");
            sb.append("\r\n");
            sb.append("\r\n");
            out.write(sb.toString().getBytes());
            DataInputStream in1 = new DataInputStream(inputStream);
            int bytes = 0;
            byte[] bufferOut = new byte[1024];
            while ((bytes = in1.read(bufferOut)) != -1) {
                out.write(bufferOut,0,bytes);
            }
            out.write("\r\n".getBytes());
            in1.close();
            out.write(end_data);

            //flush输出流的缓冲
            out.flush();
            //定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
                if (conn1!=null) {
                    conn1.disconnect();
                }
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
        }
//        JSONObject jsonStr = JSONObject.parseObject(result);
//        JSONArray jsonArray=jsonStr.getJSONArray("BusinessFileResults");
//        JSONObject jsonObject1 = (JSONObject) jsonArray.get(0);
//        String url= (String) jsonObject1.get("url");
//        result=url;
        return result;
    }

1.9：pdf预览图片预览或者下载

@GetMapping("/viewFile")
    public void downFile(HttpServletResponse response, HttpServletRequest request) {
        try {
            //File file = new File("C:\\xx.png");
            File file = new File("C:\\xx.pdf");
            String filename = file.getName();
            String fileType = filename.substring(filename.indexOf(".") + 1);

            // 以流的形式下载文件。
            FileInputStream fileInputStream = new FileInputStream(file);
            InputStream fis = new BufferedInputStream(fileInputStream);
            byte[] buffer = new byte[1024];
            int len = 0;
            // 清空response
            response.reset();
            // 设置response的Header
            // 解决跨域
            response.addHeader("Access-Control-Allow-Origin", "*");
            boolean b = "jpg".equalsIgnoreCase(fileType) || "png".equalsIgnoreCase(fileType) || "gif".equalsIgnoreCase(fileType);
            // 图片预览
            if (b) {
                response.setContentType("image/" + fileType);
            } else if ("pdf".equalsIgnoreCase(fileType)) {
                // pdf 预览
                response.setContentType("application/pdf");
            } else {
                // 直接下载
                response.setContentType("application/text;chartset=utf-8");
                response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));
                response.addHeader("Content-Length", "" + file.length());
            }
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            int a = 0;
            while ((len = fis.read(buffer)) != -1) {
                a = len + a;
                toClient.write(buffer, 0, len);
            }
            toClient.flush();
            toClient.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }