java接口下载zip，不生成中间文件，返回前端文件流

程序设计：

前端向后端请求zip文件，zip文件中有多个文件压缩而成，后端操作文件流，而不生成中间文件。最后把zip返回给前端。

代码实现：

    @ApiOperation(value = "下载Zip", notes = "")
    @PostMapping("/getDownLoadZip")
    public void getDownLoadZip(@RequestBody GClientManagementVo vo, HttpServletRequest request,HttpServletResponse response) throws Exception {
        SysUserEntityVo uc = (SysUserEntityVo) request.getAttribute("UC");
        GClientManagementService.getDownLoadZip(vo, uc,response);
    }

中间有业务代码，可酌情删减。代码中注意关闭流，避免影响内存。

 @Override
    public void getDownLoadZip(GClientManagementVo vo, SysUserEntityVo uc, HttpServletResponse response) throws Exception {
        String filename = vo.getProjectName();
        String encodeFileName = URLEncoder.encode(filename);
        ServletOutputStream out = response.getOutputStream();
        // 创建一个ByteArrayOutputStream来存放最终的ZIP流
        ByteArrayOutputStream zipOutputStream = new ByteArrayOutputStream();
        ZipOutputStream zipOut = new ZipOutputStream(zipOutputStream);
        try {
            //写入文件
            createFilePs(vo, zipOut);
            //结束写入
            zipOut.finish();
            // 最终ZIP流的内容
            byte[] zipBytes = zipOutputStream.toByteArray();

            //设置允许跨域的key
            response.setHeader("Access-Control-Expose-Headers", "Content-Disposition");
            //文件名有“，”等特殊字符发送到前端会报错，用""括起来解决
            response.addHeader("Content-Disposition", "attachment;filename=\"" + encodeFileName + "\"");
            //设置文件大小
            response.addHeader("Content-Length", "" + zipBytes.length);
            //设置文件名，避免问题，这个也用""括起来
            response.setHeader("filename,", "filename=\"" + encodeFileName + "\"");
            //设置文件类型
            response.setContentType("application/octet-stream");
            out.write(zipBytes);
            out.flush();

        } catch (Exception e) {
            throw e;
        } finally {
            try {
                out.close();
            } catch (Exception e) {
                throw e;
            }
            try {
                zipOutputStream.close();
            } catch (Exception e) {
                throw e;
            }

            try {
                zipOut.close();
            } catch (Exception e) {
                throw e;
            }

            try {
                out.close();
            } catch (Exception e) {
                throw e;
            }
        }
    }


    private void createFilePs(GClientManagementVo vo, ZipOutputStream zipOut) throws Exception {
        // 创建第一个文件install 或者uninstall
        ByteArrayOutputStream file1 = new ByteArrayOutputStream();
        //install  or uninstall
        String str1 = "";
        String fileName1 = "";
        QueryWrapper<GClientAdmin> queryWrapper = new QueryWrapper();
        if (vo.getFunction().equalsIgnoreCase(ParamsEnum.Install.getValue())) {
            queryWrapper.eq("sign", ParamsEnum.Install.getValue());
        } else {
            queryWrapper.eq("sign", ParamsEnum.Uninstall.getValue());
        }
        queryWrapper.last("limit 1");
        GClientAdmin gClientAdmin = gClientAdminDao.selectOne(queryWrapper);
        fileName1 = gClientAdmin.getScriptName();
        str1 = replaceScriptcode(gClientAdmin.getScriptCode(), vo);
        try {
            // 创建ByteArrayOutputStream来模拟文件流
            writeToFile(file1, str1);
            // 将每个文件流添加到ZIP流中
            addToZipFile(fileName1, file1.toByteArray(), zipOut);
        } catch (IOException ex) {
            ex.printStackTrace();
            throw ex;
        }

        //多个已经上传文件
        List<GClientManagementScriptVo> scriptList = vo.getScriptList();
        if (CollectionUtils.isNotEmpty(scriptList)) {
            scriptList.forEach(e -> {
                List<ParamsObject> paramslist = e.getParamslist();
                if (CollectionUtils.isNotEmpty(paramslist)) {
                    paramslist.forEach(m -> {
                        if (ParamsEnum.File.getValue().equalsIgnoreCase(m.getDataType())) {
                            String str = m.getFileContent();
                            String fileName = m.getFileName();
                            //创建ByteArrayOutputStream来模拟文件流
                            ByteArrayOutputStream file = new ByteArrayOutputStream();
                            try {
                                // 创建ByteArrayOutputStream来模拟文件流
                                writeToFile(file, str);
                                // 将每个文件流添加到ZIP流中
                                addToZipFile(fileName, file.toByteArray(), zipOut);
                            } catch (IOException ex) {
                                ex.printStackTrace();
                            }
                        }
                    });
                }
            });
        }
    }

    private String replaceScriptcode(String scriptcode, GClientManagementVo vo) throws Exception {
        //查找主参数的字符串
        String startParams = ParamsEnum.Params_Replace_Start.getValue();
        String endParams = ParamsEnum.Params_Replace_End.getValue();
        String resultParams = findSubstringBetween(scriptcode, startParams, endParams);
        if (resultParams != null) {
            //开始替换主参数

            String result = resultParams
                    //projectName
                    .replace(ParamsEnum.ProjectName.getValue(), "\"" + vo.getProjectName() + "\"")
                    //applicationName
                    .replace(ParamsEnum.MSIApplicationName.getValue(), "\"" + vo.getApplicationName() + "\"")
                    //cmdRcopt
                    .replace(ParamsEnum.CmdRCOpt.getValue(), vo.getCmdRcopt())
                    //maxRunTime
                    .replace(ParamsEnum.MaxRunTime.getValue(), vo.getMaxRunTime().toString())
                    //startStopService
                    .replace(ParamsEnum.StartStopService.getValue(), "\"" + vo.getStartStopService() + "\"")
                    //debugEnable
                    .replace(ParamsEnum.DebuggingEnabled.getValue(), "$" + vo.getDebugEnable())
                    //defaultMsicLine
                    .replace(ParamsEnum.DefaultMSICmdLine.getValue(), "\"" + vo.getDefaultMsicLine() + "\"")
                    //uDriveMap
                    .replace(ParamsEnum.UDriveMap.getValue(), "$" + vo.getuDriveMap())
                    //function
                    .replace(ParamsEnum.sFunction.getValue(), "\"" + vo.getFunction().toUpperCase(Locale.ROOT) + "\"")
                    //ifsScript
                    .replace(ParamsEnum.bIsIFSScript.getValue(), "$" + vo.getIfsScript());

            //替换主脚本字符串
            // 使用 replaceAll 方法和正则表达式来替换所有匹配的子字符串
            // 注意：这里使用了正则表达式，所以需要对特殊字符进行转义
            int startIndex = scriptcode.indexOf(startParams);
            if (startIndex != -1) {
                int endIndex = scriptcode.indexOf(endParams, startIndex);
                if (endIndex != -1) {
                    scriptcode = scriptcode.substring(0, startIndex) + result + scriptcode.substring(endIndex + endParams.length());
                } else {
                    throw new Exception("End tag not found.");
                }
            } else {
                throw new Exception("Start tag not found.");
            }

            //查找子参数的字符串
            String startCommand = ParamsEnum.Command_Replace_Start.getValue();
            String endCommand = ParamsEnum.Command_Replace_End.getValue();
            AtomicReference<String> codeStr = new AtomicReference<>("");
            if (CollectionUtils.isNotEmpty(vo.getScriptList())) {
                vo.getScriptList().forEach(e -> {

                    AtomicReference<String> finalCode = new AtomicReference<>(e.getScriptCode());
                    if (CollectionUtils.isNotEmpty(e.getParamslist())) {
                        e.getParamslist().forEach(m -> {
                            String value = "";
                            String name = "";
                            if (m.getDataType().equalsIgnoreCase(ParamsEnum.Boolean.getValue())) {
                                value = "$" + m.getValue();
                                name = "${" + m.getName() + "}";
                            } else if (m.getDataType().equalsIgnoreCase(ParamsEnum.String.getValue())) {
                                //CustomParameters特殊情况，全string参数
                                if(m.getName().equalsIgnoreCase(ParamsEnum.CustomParameters.getValue())){
                                    if(StringUtils.startsWith(m.getValue().toString(),"\"")&&StringUtils.endsWith(m.getValue().toString(),"\"")){
                                        value = m.getValue().toString();
                                    }else {
                                        value = "\"" + m.getValue() + "\"";
                                    }

                                }else {
                                    value = "\"" + m.getValue() + "\"";
                                }

                                name = "${" + m.getName() + "}";
                            } else if (m.getDataType().equalsIgnoreCase(ParamsEnum.Int.getValue())) {
                                value = m.getValue().toString();
                                name = "${" + m.getName() + "}";
                            } else if (m.getDataType().equalsIgnoreCase(ParamsEnum.File.getValue())) {
                                value = "\"\\" + m.getFileName() + "\"";
                                name = "${" + m.getName() + "}";
                            }
                            finalCode.set(finalCode.get().replace(name, value));
                        });
                    }
                    codeStr.set(codeStr.get() + "\n" + finalCode.get());
                });
            }
            //子参数替换
            int startIndex2 = scriptcode.indexOf(startCommand);
            if (startIndex2 != -1) {
                int endIndex2 = scriptcode.indexOf(endCommand, startIndex2);
                if (endIndex2 != -1) {
                    scriptcode = scriptcode.substring(0, startIndex2) + codeStr.get() + scriptcode.substring(endIndex2 + endCommand.length());
                } else {
                    throw new Exception("End tag not found.");
                }
            } else {
                throw new Exception("Start tag not found.");
            }

        } else {
            throw new Exception("error");
        }
        return scriptcode;

    }

    public static String findSubstringBetween(String source, String start, String end) {
        // 找到开始字符串的位置
        int startIndex = source.indexOf(start);
        // 开始字符串不存在
        if (startIndex == -1) {
            return null;
        }
        // 在开始字符串之后找到结束字符串的位置
        int endIndex = source.indexOf(end, startIndex + start.length());
        // 结束字符串不存在
        if (endIndex == -1) {
            return null;
        }
        // 提取并返回子字符串
        return source.substring(startIndex + start.length(), endIndex);
    }


    private void writeToFile(ByteArrayOutputStream out, String content) throws IOException {
        try (OutputStreamWriter writer = new OutputStreamWriter(out, "UTF-8")) {
            writer.write(content);
            writer.flush();
        } finally {
            try {
                out.close();
            } catch (Exception e) {
                throw e;
            }
        }
    }

    private void addToZipFile(String fileName, byte[] fileContent, ZipOutputStream zipOut) throws IOException {
        ZipEntry zipEntry = new ZipEntry(fileName);
        zipOut.putNextEntry(zipEntry);
        zipOut.write(fileContent);
        zipOut.closeEntry();
    }