使用struts2实现一个文件上传功能并显示进度条

发布时间：2020-11-18 16:16:14 来源：亿速云阅读：154 作者：Leah 栏目：编程语言

本篇文章为大家展示了使用struts2实现一个文件上传功能并显示进度条，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

一. struts2读取进度原理分析

1.　在strut2中控制文件上传信息的类是实现MultiPartRequest接口的JakartaMultiPartRequest

其实第一次看到源文件时我打了个退堂鼓，因为觉得内容太长了，不想看。冷静下来将思路理顺，将分开的各个方法还原到一个方方中中，发现还是很好理解的：

@Override
 public void parse(HttpServletRequest request, String saveDir)
   throws IOException {
  setLocale(request);
　　　 　//规定了File文件的格式（如文件名必须是xxFileName，文件类型xxContentType），并定义了File的保存路径　　　　             DiskFileItemFactory factory = new DiskFileItemFactory(); 
  ServletFileUpload upload = new ServletFileUpload(factory);//处理文件上传的servlet
  upload.setProgressListener(new FileUploadProgressListener(request)); //为文件上传添加监听  factory.setSizeThreshold(0); //if (saveDir != null
   factory.setRepository(new File(saveDir));//临时路径
  }
  try {
   upload.setSizeMax(maxSize);
   List items = upload.parseRequest(createRequestContext(request)); //获取所有请求
   for (Object obItem : items) {
    FileItem item = (FileItem) obItem; //获取每个请求的文件
    if (LOG.isDebugEnabled()) {
     LOG.debug("Found item" + item.getFieldName());
    }
    if (item.isFormField()) { //普通表单提交
     LOG.debug("Item is a normal form field");
     List<String> values;
     if (params.get(item.getFieldName()) != null) {
      values = params.get(item.getFieldName());
     } else {
      values = new ArrayList<String>();
     }
     String charset = request.getCharacterEncoding();
     if (charset != null) {
      values.add(item.getString(charset));
     } else {
      values.add(item.getString());
     }
     params.put(item.getFieldName(), values);
    } else { //文件上传请求
     LOG.debug("Item is a file upload");
     if (item.getName() == null
       || item.getName().trim().length() <= 0) {
      LOG.debug("No file has been uploded for the filed:"
        + item.getFieldName());
      continue;
     }

     List<FileItem> values;
     if (files.get(item.getFieldName()) != null) {
      values = files.get(item.getFieldName());
     } else {
      values = new ArrayList<FileItem>();
     }
     values.add(item);
     files.put(item.getFieldName(), values);
    }
   }

  } catch (FileUploadBase.SizeLimitExceededException e) {
   System.out.println("错误1：" + e);
   if (LOG.isWarnEnabled()) {
    LOG.warn("Request exceeded size limit!", e);
   }
   String errorMessage = buildErrorMessage(e, new Object[]{e.getPermittedSize(), e.getActualSize()});
   if (!errors.contains(errorMessage)) {
    errors.add(errorMessage);
   }
  } catch (Exception e) {
   System.out.println("错误1：" + e);
   if (LOG.isWarnEnabled()) {
    LOG.warn("Unable to parse request", e);
   }
   String errorMessage = buildErrorMessage(e, new Object[]{});
   if (!errors.contains(errorMessage)) {
    errors.add(errorMessage);
   }
  }
 }

2. 文件上传监听文件FileUploadProgressListener.java

public class FileUploadProgressListener implements ProgressListener {
　　private final HttpSession session;
　　private final DecimalFormat format = new DecimalFormat("#00.0");

　　public FileUploadProgressListener(HttpServletRequest request) {
　　　　session = request.getSession();
　　　　FileUploadStatus status = new FileUploadStatus();
　　　　session.setAttribute("uploadStatus", status);
　　}

　　@Override
　　public void update(long pBytesRead, long pContentLength, int pItems) {
　　　　FileUploadStatus uploadStatus = (FileUploadStatus) session.getAttribute("uploadStatus");
　　　　Double uploadRate = (double) (pBytesRead * 100 / pContentLength);
　　　　uploadStatus.setUploadRate(Double.valueOf(format.format(uploadRate)));
　　　　uploadStatus.setReadedBytes(pBytesRead / 1024);
　　　　uploadStatus.setTotalBytes(pContentLength / 1024);
　　　　uploadStatus.setCurrentItems(pItems);
　　}
}

3. 添加状态文件：FileUploadStatus.java

public class FileUploadStatus {
 private Double uploadRate = 0.0;
 private Long readedBytes = 0L;
 private Long totalBytes = 0L;
 private int currentItems = 0;
 private Long uploadSpeed = 0L;
 private Long startTime = System.currentTimeMillis();
 private Long readedTimes = 0L;
 private Long totalTimes = 0L;
 // "-1" 错误 "0" 正常 "1" 完成
 private String error = "0";

 ...
  setter getter方法
 ...  
}

4. Action类（如果是多文件上传，则将File FileName ContentType定义成数组形式即可）

/**
 * 利用io流上传文件
 */
public class FileStreamUploadAction extends ActionSupport {
 /**
  * serialVersionUID作用： ---相当于类的身份证。 序列化时为了保持版本的兼容性，即在版本升级时反序列化仍保持对象的唯一性。
  * 有两种生成方式： 一个是默认的1L，比如：private static final long serialVersionUID = 1L;
  * 一个是根据类名、接口名、成员方法及属性等来生成一个64位的哈希字段，比如： private static final long
  * serialVersionUID = xxxxL;
  */
 private static final long serialVersionUID = 1L;
 private File image;
 private String imageFileName;
 private String imageContentType;
 private String message;
 public String uploadFile() {
  FileInputStream in = null;
  FileOutputStream out = null;
  System.out.println("文件名：" + imageFileName);
  try {
   this.setNewFileName(imageFileName);
   String realPath = ServletActionContext.getServletContext()
     .getRealPath("/file");
   File filePath = new File(realPath);
   if (!filePath.exists()) { // 如果保存的路径不存在则创建
    filePath.mkdir();
   }
   if (image == null) {
    message = "上传文件为空";
    System.out.println(message);
   } else {
    File saveFile = new File(filePath, this.getNewFileName());
    out = new FileOutputStream(saveFile);
   }
   in = new FileInputStream(image);
   byte[] byt = new byte[1024];
   int length = 0;
   while ((length = in.read(byt)) > 0) {
    out.write(byt, 0, length);
    out.flush();
   }
   message = "上传成功";
   System.out.println(message);
  } catch (FileNotFoundException e) {
   message = "找不到文件！";
   e.printStackTrace();
  } catch (IOException e) {
   message = "文件读取失败！";
   e.printStackTrace();
  } finally {
   closeStream(in, out);
  }
  return "uploadSucc";
 }
 public void closeStream(FileInputStream in, FileOutputStream out) {
  try {
   if (in != null) {
    in.close();
   }
   if (out != null) {
    out.close();
   }
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
  ...
  setter() getter()
  ...  
}

获取进度的Action

public class FileProgressAction extends ActionSupport {
　　private static final long serialVersionUID = 1L;
　　private FileUploadStatus uploadStatus;

　　public String uploadPercent() {
　　　　HttpSession session = ServletActionContext.getRequest().getSession();
　　　　this.uploadStatus = (FileUploadStatus) session.getAttribute("uploadStatus");
　　　　if (uploadStatus == null) {
　　　　　　System.out.println("action is null");
　　　　　　uploadStatus = new FileUploadStatus();
　　　　　　uploadStatus.setCurrentItems(0);
　　　　}
　　　　return "getPercent";
　　}

　　public FileUploadStatus getUploadStatus() {
　　　　return uploadStatus;
　　}

　　public void setUploadStatus(FileUploadStatus uploadStatus) {
　　　　this.uploadStatus = uploadStatus;
　　}
}

5.struts.xml中

<struts>
  <constant name="struts.multipart.maxSize" value="2147483648"/><!-- 默认值为2M,设置为2G -->
  <constant name="struts.custom.i18n.resources" value="messageResource" />
  <constant name="struts.i18n.encoding" value="utf-8" />
  <constant name="struts.multipart.saveDir" value="e:/fileUpload"/><!-- 临时路径 -->
 
  <!-- 加载自定义的文件读取配置文件 -->
  <bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="Refactor" class="com.nova.core.RefactorMultiPartRequest" scope="default" />
  <constant name="struts.multipart.handler" value="Refactor" />
  <!-- 这里配置struts.multipart.handler -->
  <package name="ajaxUpload" extends="json-default"> <!-- json-default需要struts2-json-plugin-2.3.3.jar -->
   <action name="ajaxUploadFile_*" class="com.nova.action.FileStreamUploadAction" method="{1}">
    <result type="json" name="uploadSucc">
     <param name="root">newFileName</param>
     <param name="contentType"> 
      text/html
     </param> 
    </result> 
   </action>
   <action name="uploadPercent_*" class="com.nova.action.FileProgressAction" method="{1}">
    <result name="getPercent" type="json">
     <param name="root">uploadStatus</param>
    </result>
   </action>
  </package>
 </struts>

二. 进度条显示

View页面设置，利用ajaxfileupload.js来获取文件并进行异步上传，bootstrap中的进度条效果显示进度（利用setInterval间断的获取进度信息来形式一种进度的前进显示）

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<link rel="stylesheet" type="text/css" href="bootstrap/css/bootstrap.css" rel="external nofollow" >
<link rel="stylesheet" type="text/css" href="bootstrap/css/bootstrap-responsive.css" rel="external nofollow" >
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript" src="js/ajaxfileupload.js"></script>
<script type="text/javascript" src="<%=request.getContextPath() %>/bootstrap/js/bootstrap.js"></script>
<script type="text/javascript" src="<%=request.getContextPath() %>/bootstrap/js/jquery.showLoading.min.js"></script>
<script type="text/javascript">
 var setinterval;
 $(document).ready(function(){
  $("#upload").click(function(){
   $("#upload").addClass("disabled");
   $("#upload").attr("disabled" ,true);
   $("#upload").attr("title" ,"文件上传中...");
   uploadFile();
   setinterval = setInterval(uploadProgress,200);
  });
 });
 //文件上传
 function uploadFile(){
  $.ajaxFileUpload({
   url:'ajaxUploadFile_uploadFile.action', 
   secureuri:false, //是否采用安全协议，默认为false
   fileElementId:'image',
   dataType: 'json',
   success: function (data){
    $("#showImage").attr("src","/FileUpLoadTest/file/"+data);
   }
  });
 }
 //上传进度
 function uploadProgress(){
  $.get("uploadPercent_uploadPercent.action","",function(data){
   $("#ProgressRate").html("上传速度：" + data.uploadRate + "%");
   $("#readBytes").html("以读取：" + data.readedBytes + " KB");
   $("#totalBytes").html("总大小：" + data.totalBytes + " KB");
   $("#progress").attr("style","width:" + data.uploadRate + "%;");
   $("#progress").html(data.uploadRate + "%");
   if(data.uploadRate == 100){
    clearInterval(setinterval);
    $("#progress").html("上传成功");
    $("#upload").removeClass("disabled");
    $("#upload").attr("disabled" ,false);
   }
  });
 }
</script>
</head>
<body>
 <div class="navbar navbar-inverse navbar-fixed-top">
  <div class="navbar-inner">
  <div class="container">
   <button type="button" class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
   <span class="icon-bar"></span>
   <span class="icon-bar"></span>
   <span class="icon-bar"></span>
   </button>
   <a class="brand" href="#" rel="external nofollow" >文件异步上传+进度条</a>
  </div>
  </div>
 </div>
 <br><br><br>
 <div class="container">
  <input type="file" name="image" id="image"/><br/> //file的name属性必须设置的与后台Action中file的名称是相同的，否则ajaxFileUpload获取不到文件信息
  <input type="button" id="upload" value="上传" class="btn btn-info" title=""/><br/>
  <img alt="" src="" id="showImage">
  <div id="ProgressRate"></div>
  <div id="readBytes"></div>
  <div id="totalBytes"></div>
  <div id="uploadTimes"></div>
  <div class="progress progress-striped span4">
    <div id="progress" class="bar">
    </div>
  </div>
 </div>
</body>
</html>

三、总结

　　用这种方法获取上传进度有一个缺点：读取进度阶段是文件从指定目录开始在临时文件中存储的过程，而文件上传则是重临时路径下将文件转移到目标路径下，这样就造成了一个时间差，就是读取进度总会比上传文件快，上传的文件越大这个缺点越是明显。

上述内容就是使用struts2实现一个文件上传功能并显示进度条，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注亿速云行业资讯频道。

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