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。
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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 values;
if (params.get(item.getFieldName()) != null) {
values = params.get(item.getFieldName());
} else {
values = new ArrayList();
}
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 values;
if (files.get(item.getFieldName()) != null) {
values = files.get(item.getFieldName());
} else {
values = new ArrayList();
}
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
newFileName text/html uploadStatus
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）
Insert title here
//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
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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，欢迎关注创新互联行业资讯频道。