文件上传（JavaScript实现）

设计思路：

form实现文件上传

内在也是通过form实现，

在Js中创建一个form 对象，点击按钮，触发事件（模拟form被点击），得到文件-》通过构造的form对象上传文件

前端代码：

 
   
    
    
    
    
   
 
     
 选择上传文件 
 
   
 
    
  

后端代码：

package my; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.text.SimpleDateFormat; import java.util.Date; import java.util.UUID; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.fileupload.FileItemIterator; import org.apache.commons.fileupload.FileItemStream; import org.apache.commons.fileupload.servlet.ServletFileUpload; import org.apache.commons.fileupload.util.Streams; import org.json.JSONObject; / * Servlet implementation class FileUploadService */ @WebServlet("/FileUploadService") public class FileUploadService extends HttpServlet { //文件上传的临时目录 File tmpDir; @Override public void init() throws ServletException { File webRoot = new File(getServletContext().getRealPath("/")); tmpDir = new File(webRoot, "upload"); tmpDir.mkdirs(); //上传进来的文件存放在 WebRoot/upload/ 下 } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { JSONObject jresp = new JSONObject(); try { Object data = doUpload(request, response); jresp.put("error", 0); jresp.put("reason", "OK"); if(data != null) jresp.put("data", data); } catch (Exception e) { jresp.put("error", -1); jresp.put("reason", e.getMessage()); } response.setCharacterEncoding("UTF-8"); response.setContentType("text/plain"); PrintWriter out = response.getWriter(); out.write(jresp.toString(2)); out.close(); } private Object doUpload(HttpServletRequest request, HttpServletResponse response) throws Exception { boolean isMultipart = ServletFileUpload.isMultipartContent(request); if(!isMultipart) throw new Exception("请求编码必须为：multipart/form-data!"); request.setCharacterEncoding("utf-8"); // ServletFileUpload ： commons包里提供的工具类 ServletFileUpload upload = new ServletFileUpload(); AfFileUploadInfo info = new AfFileUploadInfo(); FileItemIterator iter = upload.getItemIterator(request); while(iter.hasNext()) { //表单域 FileItemStream item = iter.next(); String fieldName = item.getFieldName(); InputStream fieldStream = item.openStream(); if(item.isFormField()) { // 普通表单域: 直接读取值 // 指的是,,输入控件的值, 字符串类型 String fieldValue = Streams.asString(fieldStream, "utf-8"); printLog("表单域:" + fieldName + "=" + fieldValue); } else { // 文件域, 指 <file> 控件的值，指文件的数据 // 生成唯一的文件名 info.realName = item.getName(); // 原始文件名 info.suffix = fileSuffix(info.realName); // 后缀 info.tmpFileName = createTmpFileName(info.suffix); // 服务器临时文件名 info.tmpFile = new File(tmpDir, info.tmpFileName); info.fileSize = 0; // 文件大小 printLog("文件上传开始:" + info.realName + " >> " + info.tmpFile); // 从FieldStream读取数据, 保存到目标文件 info.tmpFile.getParentFile().mkdirs(); FileOutputStream fileStream = new FileOutputStream(info.tmpFile); try{ // 从请求里读取文件数据，保存到本地文件 info.fileSize = copy(fieldStream, fileStream); }finally{ try{ fileStream.close();}catch(Exception e){} try{ fieldStream.close();}catch(Exception e){} } printLog("文件上传完成:" + info.realName + ", 大小: " + info.fileSize); } } return info.tmpFileName; } private long copy(InputStream in, OutputStream out) throws Exception { long count = 0; byte[] buf = new byte[8192]; while(true) { int n = in.read(buf); if(n < 0) break; if(n == 0) continue; out.write(buf, 0, n); count +=n; } return count; } // private void printLog(String message) { System.out.println(message); } //生成唯一的ID private String createUUID() { String s = UUID.randomUUID().toString(); String s2 = s.substring(0,8)+s.substring(9,13)+s.substring(14,18)+s.substring(19,23)+s.substring(24); return s2.toUpperCase(); } // 得到一个保证不重复的临时文件名 private String createTmpFileName(String suffix) { SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd-HHmmss"); String datestr = sdf.format(new Date()); String name = datestr + "-" + createUUID() + "." + suffix; return name; } // 得到文件的后缀名 public String fileSuffix(String fileName) { int p = fileName.lastIndexOf('.'); if(p >= 0) { return fileName.substring(p+1).toLowerCase(); //转换成小写 } return ""; } } </file>

package my; import java.io.File; public class AfFileUploadInfo { public String realName; //原始文件名 public String suffix; //后缀 public String tmpFileName; //服务器临时文件名 public File tmpFile; public long fileSize; //文件大小 }