java多个pdf合并为一个pdf，并通过feign下载

1.首先pom文件添加依赖，操作pdf文件工具类

<dependency><groupId>org.apache.pdfbox</groupId><artifactId>pdfbox</artifactId><version>2.0.21</version></dependency>

2.pdf合并操作

public ResponseEntity<byte[]> mergePdf(MultipartFile[] files) {//pdf合并工具类PDFMergerUtility mergePdf = new PDFMergerUtility();//合并pdf生成的文件名String filename = "d:/"+new Date().getTime()+".pdf";for (MultipartFile multipartFile : files) {try {byte[] bytes = multipartFile.getBytes();InputStream in = new ByteArrayInputStream(bytes);mergePdf.addSource(in); // 合并pdf} catch (IOException e) {throw new BaseException("Error merging pdf files- " + filename, e);}}try {// 设置合并生成pdf文件名称及路径mergePdf.setDestinationFileName(filename);mergePdf.mergeDocuments(MemoryUsageSetting.setupMainMemoryOnly());} catch (IOException e) {e.printStackTrace();}return exportFile(new File(filename), filename);}

注意：在feign之间传输二进制流时，返回值必须为 ResponseEntity 类型，所以封装了个私有方法，如下：

private ResponseEntity<byte[]> exportFile(File file, String filename) {HttpHeaders headers = new HttpHeaders();ResponseEntity<byte[]> entity = null;InputStream in=null;try {in=new FileInputStream(file);byte[] bytes = new byte[in.available()];filename = URLEncoder.encode(filename, "utf-8");in.read(bytes);headers.add("Content-Disposition", "attachment;filename="+filename);entity = new ResponseEntity<>(bytes, headers, HttpStatus.OK);} catch (Exception e) {e.printStackTrace();}finally {if(in!=null) {try {in.close();} catch (IOException e) {e.printStackTrace();}}}return entity;}

注意：feign层代码接收类型 必须为 feign.Response

Response mergePdf(@RequestPart("file") MultipartFile[] file);

3.消费层 controller代码：

public void mergePdf(@RequestPart("file") MultipartFile[] file, HttpServletResponse response){InputStream inputStream = null;OutputStream outputStream = null;try {// 调用feign层代码获取Response Response responseEntity = orderService.mergePdf(file);// Response 获取响应体Response.Body body = responseEntity.body();// 通过响应体来获取 一个输入流inputStream = body.asInputStream();BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);// 设置http 响应头信息等response.setContentType("multipart.form-data");response.setHeader("Content-Disposition", responseEntity.headers().get("Content-Disposition").toString().replace("[","").replace("]",""));outputStream = new BufferedOutputStream(response.getOutputStream());int length = 0;byte[] temp = new byte[1024 * 10];while ((length = bufferedInputStream.read(temp)) != -1) {// 输出二进制流outputStream.write(temp, 0, length);}outputStream.flush();} catch (IOException e) {e.printStackTrace();} finally {if (inputStream != null) {try {inputStream.close();} catch (IOException e) {e.printStackTrace();}}if (outputStream != null) {try {outputStream.close();} catch (IOException e) {e.printStackTrace();}}}}

最后调用接口，可以发现浏览器响应一个 blob 协议地址，最终由前端处理为二进制文件

总结

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