让我详细为您介绍一下“基于html5+java实现大文件上传实例代码”的完整攻略和代码实现。
简介
为了解决传统文件上传方式在处理大文件上传时所面临的性能瓶颈和功能缺失，我们需要使用一些新的技术手段。html5提供了File API来处理客户端文件读取，而java的高性能能力则可以处理并发上传和分片上传等复杂操作，两者结合起来，就能够实现一套优秀的大文件上传解决方案。
实现过程
下面，我们将以实际代码为例，一步一步地介绍如何基于html5+java实现大文件上传。
- 使用html5的File API读取客户端上传文件，并将文件进行分片处理：
<input id="fileupload" type="file" name="uploadFile" multiple accept="" />
<script>
var file = document.getElementById("fileupload").files[0];
var fileSize = file.size;
var chunkSize = 1024 * 1024; // 每个文件块的大小为1MB
var chunks = Math.ceil(fileSize / chunkSize);
for (var i = 0; i < chunks; i++) {
var start = i * chunkSize;
var end = start + chunkSize;
if (end > fileSize) end = fileSize;
var chunk = file.slice(start, end);
var formData = new FormData();
formData.append('file', chunk);
formData.append('filename', file.name);
formData.append('total_chunks', chunks);
formData.append('chunk_index', i);
//通过ajax上传到后端
}
</script>
- 在java后端接收上传文件的每一个分片，并存储在服务器上。
@RequestMapping(value = "/uploadChunk", method = RequestMethod.POST)
public ResponseEntity uploadChunk(@RequestParam("chunk") MultipartFile file, HttpServletRequest request) {
String realPath = request.getSession().getServletContext().getRealPath("/");
String fileName = request.getParameter("filename");
int totalChunks = Integer.parseInt(request.getParameter("total_chunks"));
int chunkIndex = Integer.parseInt(request.getParameter("chunk_index"));
String chunkName = fileName + "_part_" + chunkIndex;
try {
File tempFile = new File(realPath, chunkName);
file.transferTo(tempFile);
} catch (Exception e) {
e.printStackTrace();
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("upload failed!");
}
return ResponseEntity.ok("upload success!");
}
- 当文件的所有分片都上传完毕后，由java后端将它们合并。
@RequestMapping(value = "/mergeChunks", method = RequestMethod.POST)
public ResponseEntity mergeChunks(HttpServletRequest request) {
String realPath = request.getSession().getServletContext().getRealPath("/");
String fileName = request.getParameter("filename");
int totalChunks = Integer.parseInt(request.getParameter("total_chunks"));
try {
File targetFile = new File(realPath, fileName);
FileOutputStream outputStream = new FileOutputStream(targetFile);
for (int i = 0; i < totalChunks; i++) {
String chunkName = fileName + "_part_" + i;
File chunkFile = new File(realPath, chunkName);
FileInputStream inputStream = new FileInputStream(chunkFile);
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, len);
}
inputStream.close();
chunkFile.delete();
}
outputStream.close();
} catch (Exception e) {
e.printStackTrace();
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("merge failed!");
}
return ResponseEntity.ok("merge success!");
}
通过以上3步骤就可以实现大文件的分片上传和合并，同时也避免了浏览器crash的问题。
示例
下面，我们提供两个示例代码，一个是前端页面的html代码，另一个是后端的java代码。
html代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>大文件上传</title>
</head>
<body>
<input id="fileupload" type="file" name="uploadFile" multiple accept="" />
<button id="upload_button" onclick="startUpload()">上传</button>
</body>
<script>
function startUpload() {
var file = document.getElementById("fileupload").files[0];
var fileSize = file.size;
var chunkSize = 1024 * 1024; // 每个文件块的大小为1MB
var chunks = Math.ceil(fileSize / chunkSize);
for (var i = 0; i < chunks; i++) {
var start = i * chunkSize;
var end = start + chunkSize;
if (end > fileSize) end = fileSize;
var chunk = file.slice(start, end);
var formData = new FormData();
formData.append('file', chunk);
formData.append('filename', file.name);
formData.append('total_chunks', chunks);
formData.append('chunk_index', i);
$.ajax({
url: '/uploadChunk',
type: 'POST',
cache: false,
async: true,
data: formData,
processData: false,
contentType: false,
success: function (data) {
console.log(data);
if (i === chunks - 1) { //最后一块
$.ajax({
url: '/mergeChunks',
type: 'POST',
data: {filename: file.name, total_chunks: chunks},
success: function (data) {
alert('上传成功');
}
});
}
},
error: function (xhr, textStatus, errorThrown) {
console.log('Upload failed!');
}
});
}
}
</script>
</html>
java代码：
@RequestMapping(value = "/uploadChunk", method = RequestMethod.POST)
public ResponseEntity uploadChunk(@RequestParam("chunk") MultipartFile file, HttpServletRequest request) {
String realPath = request.getSession().getServletContext().getRealPath("/");
String fileName = request.getParameter("filename");
int totalChunks = Integer.parseInt(request.getParameter("total_chunks"));
int chunkIndex = Integer.parseInt(request.getParameter("chunk_index"));
String chunkName = fileName + "_part_" + chunkIndex;
try {
File tempFile = new File(realPath, chunkName);
file.transferTo(tempFile);
} catch (Exception e) {
e.printStackTrace();
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("upload failed!");
}
return ResponseEntity.ok("upload success!");
}
@RequestMapping(value = "/mergeChunks", method = RequestMethod.POST)
public ResponseEntity mergeChunks(HttpServletRequest request) {
String realPath = request.getSession().getServletContext().getRealPath("/");
String fileName = request.getParameter("filename");
int totalChunks = Integer.parseInt(request.getParameter("total_chunks"));
try {
File targetFile = new File(realPath, fileName);
FileOutputStream outputStream = new FileOutputStream(targetFile);
for (int i = 0; i < totalChunks; i++) {
String chunkName = fileName + "_part_" + i;
File chunkFile = new File(realPath, chunkName);
FileInputStream inputStream = new FileInputStream(chunkFile);
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, len);
}
inputStream.close();
chunkFile.delete();
}
} catch (Exception e) {
e.printStackTrace();
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("merge failed!");
}
return ResponseEntity.ok("merge success!");
}
总结：
以上就是基于html5+java实现大文件上传的完整攻略和示例程序。希望对大家有所帮助！
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