文章HTML代码翻译于地址:https://www.cnblogs.com/linyihai/p/7040786.html
文件MD5有啥用？
文件上传时会上传文件的信息此时将文件的md5上传，服务器中存储这个md5值，并存储这个md5值所对应的已上传字节长度，比如未上传对应为0，已上传对应为-1，已上传200字节就对应200，这个上传的时候可以匹配到这个文件在服务器中的状态，方便做断点续传，只要源文件没有更改，即使换个名字，换个账户都可以在服务器找到对应的文件，所以当服务器中有已经上传完毕的此文件时，别人再上传这个文件就可以实现秒传。
下面代码实现HTML选择文件获取MD5值、JAVA根据文件地址获取文件MD5值。
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <form id="fileupload" action="" method="POST" enctype="multipart/form-data"> <div> <div> 添加文件 <input type="file" name="" id="fileinput"> </div> <progress class='progressbar' value="0" max="100" style='500px;margin-top:20px'></progress> <div style='margin-top:20px'> <span id="handler_info" ></span> </div> </div> </form> <!-- https://github.com/satazor/js-spark-md5 --> <script src="spark-md5.min.js" type="text/javascript"></script> <script> function get_filemd5sum(ofile) { var file = ofile; var tmp_md5; var blobSlice = File.prototype.slice || File.prototype.mozSlice || File.prototype.webkitSlice, // file = this.files[0], chunkSize = 8097152, // Read in chunks of 2MB chunks = Math.ceil(file.size / chunkSize), currentChunk = 0, spark = new SparkMD5.ArrayBuffer(), fileReader = new FileReader(); fileReader.onload = function(e) { // console.log('read chunk nr', currentChunk + 1, 'of', chunks); spark.append(e.target.result); // Append array buffer currentChunk++; var md5_progress = Math.floor((currentChunk / chunks) * 100); console.log(file.name + " 正在处理，请稍等," + "已完成" + md5_progress + "%"); var handler_info = document.getElementById("handler_info"); var progressbar = document.getElementsByClassName("progressbar")[0]; handler_info.innerHTML=file.name + " 正在处理，请稍等," + "已完成" + md5_progress + "%" progressbar.value =md5_progress; if (currentChunk < chunks) { loadNext(); } else { tmp_md5 = spark.end(); console.log(tmp_md5) handler_info.innerHTML = file.name + "的MD5值是：" + tmp_md5; } }; fileReader.onerror = function() { console.warn('oops, something went wrong.'); }; function loadNext() { var start = currentChunk * chunkSize, end = ((start + chunkSize) >= file.size) ? file.size : start + chunkSize; fileReader.readAsArrayBuffer(blobSlice.call(file, start, end)); } loadNext(); } var uploadfile = document.getElementById('fileinput') uploadfile.onchange = function(e){ var file = this.files[0]; if(!file) { alert('请选择文件！'); return false; } get_filemd5sum(file) } </script> </body> </html>
/** * 获取文件的md5 * @param filePath 文件地址 * @param fileName 文件名 * @return */ public static String getFileMd5Value(String filePath, String fileName){ File file = new File(filePath + File.separator + fileName); if(!file.exists() || !file.isFile()){ return ""; } byte[] buffer = new byte[2048]; try { MessageDigest digest = MessageDigest.getInstance("MD5"); FileInputStream in = new FileInputStream(file); while(true){ int len = in.read(buffer,0,2048); if(len != -1){ digest.update(buffer, 0, len); }else{ break; } } in.close(); byte[] md5Bytes = digest.digest(); StringBuffer hexValue = new StringBuffer(); for (int i = 0; i < md5Bytes.length; i++) { int val = ((int) md5Bytes[i]) & 0xff; if (val < 16) { hexValue.append("0"); } hexValue.append(Integer.toHexString(val)); } return hexValue.toString(); } catch (Exception e) { e.printStackTrace(); return ""; } } public static void main(String[] args) { System.out.println(Snippet.getFileMd5Value("C:\Users\Administrator\Desktop", "test.txt")); }