Java实现文件图片的预览和下载功能
作者：小徐敲java
这篇文章主要为大家详细介绍了如何使用Java实现文件图片的预览和下载功能,文中的示例代码讲解详细,感兴趣的小伙伴可以跟随小编一起学习一下
Java实现文件（图片）的预览和下载
@ApiOperation("访问文件")
@GetMapping("/download/{name}")
public void getImage(HttpServletResponse response, @PathVariable("name") String name) throws IOException {
//动态获取图片存放位置
// String path = getUploadPath();//获取当前系统路径
String path = upload;
String imagePath = path + File.separator + name;
if (!new File(imagePath).exists()) {
return;
}
if (name.endsWith("jpg") || name.endsWith("png") || name.endsWith("gif") || name.endsWith("jpeg")) {
//预览时不需设置Content-Disposition
response.setContentType("image/jpeg;charset=utf-8");//图片
}else {
//下载
response.setContentType("application/octet-stream");//文件
response.setHeader("Content-Disposition", "inline; filename=" + URLEncoder.encode(name, "UTF-8"));
}
ServletOutputStream outputStream = response.getOutputStream();
outputStream.write(Files.readAllBytes(Paths.get(path).resolve(name)));
outputStream.flush();
outputStream.close();
}
注意：踩过的坑，文件名不可以带*号，带*会报java.io.FileNotFoundException
通过mvc与hutool工具集下载在resources目录下的文件，注意引入的包
package com.example.controller;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.io.IOException;
import java.nio.file.Files;
@RestController
@RequestMapping("/api/files")
public class FileDownloadController {
@GetMapping("/download")
public ResponseEntity<Resource> downloadFile() {
String fileName = "example.txt"; // 要下载的文件名
try {
// 从 resources 目录加载文件
ClassPathResource resource = new ClassPathResource(fileName);
if (!resource.exists()) {
return ResponseEntity.notFound().build();
}
// 设置响应头
HttpHeaders headers = new HttpHeaders();
headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + resource.getFilename());
// 返回文件作为响应
return ResponseEntity.ok()
.headers(headers)
.contentType(org.springframework.http.MediaType.APPLICATION_OCTET_STREAM)
.body(resource);
} catch (IOException e) {
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
}
}
}
方法补充
方法一：
该代码段展示了如何在Spring Boot中实现文件的预览和下载功能。通过HttpServletRequest和HttpServletResponse，根据请求参数判断是预览还是下载，并设置相应的内容类型和Content-Disposition。文件路径为固定目录下，读取文件内容并写入响应流。
具体如下
package com.example.demo.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.OutputStream;
/**
* @author long
* @version 1.0.0
* @ClassName FileController
* @Description TODO
* @createTime 2022.03.18 18:47
*/
@RestController
@RequestMapping("/demo")
public class FileController {
@GetMapping("/file")
public void filePreviewOrDownload(HttpServletRequest request, HttpServletResponse response) throws Exception {
String fileName = request.getParameter("fileName");
//type. p预览，d下载
String type = request.getParameter("type");
response.reset();
response.setCharacterEncoding("UTF-8");
File file = new File("C:\\Users\\long\\Desktop\\" + fileName);
FileInputStream fis = new FileInputStream(file);
if ("d".equalsIgnoreCase(type)) {
//下载
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition", "attachment;filename*=utf-8''" + System.currentTimeMillis() + fileName.substring(fileName.lastIndexOf(".")));
} else {
//预览时不需设置Content-Disposition
// response.setContentType("application/octet-stream");
// response.setContentType("text/html;charset=UTF-8");
// response.setHeader("Content-Disposition","inline;filename=" + System.currentTimeMillis() + fileName.substring(fileName.lastIndexOf(".")));
}
OutputStream os = response.getOutputStream();
byte[] bytes = new byte[1024];
int length = 0;
while ((length = fis.read(bytes)) != -1) {
os.write(bytes, 0, length);
}
os.close();
fis.close();
}
}
方法二：
Java 实现图片或文件在线预览及下载
完整代码
@GetMapping("/downFile")
public void downFile(HttpServletResponse response, HttpServletRequest request) {
try {
// File file = new File("C:\\Users\\hnsh\\Pictures\\铁山靠.png");
File file = new File("F:\\BaiduNetdiskDownload\\activiti教程 (1).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();
}
}
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