1.package元素的abstract属性表示该包是抽象的，不能直接使用，需要由子包继承才能使用。struts-defult这个package就是abstract的，因此需要我们继承这个包来使用。
2.命名空间，package元素的namespace属性起到命名空间分割的作用。通常将namespace的属性值定义成页面所在的目录名。name属性会被子包用到。namespace是路径名。最后的访问链接：http://localhost:8080/struts2/hello/login.jsp
<package name="frist" extend="struts-defult" namespace="/hello">
3.文件上传,进行文件上传时，必须将表单的method属性设置为post（因为GET支持文件大小是有限制的），将enctype属性设为multipart/form-data
private String uploadContentType;//上传文件的类型,(Fileupload拦截器传入的参数)
private File upload;//上传的文件,(Fileupload拦截器传入的参数)
private String uploadFileName;//上传文件的真实文件名，(Fileupload拦截器传入的参数)
4.限制文件大小
1）在struts.xml中配置常量，可以实现对所有<action>文件的大小限制
<constant name="struts.multipart.maxSize" value="5000000"/>
5M大小
2）在action下配置拦截器，可以实现单个<action>文件大小的限制
<interceptor-ref name="fileUpload"> <param name="maximumSize">5000000</param> </interceptor-ref> <interceptor-ref name="defaultStack"></interceptor-ref>
5.限制文件类型
<interceptor-ref name="fileUpload"> <param name="allowedTypes">image/pjpeg,image/jpeg,image/gif,image/png</param> <param name="maximumSize">5000000</param> </interceptor-ref> <interceptor-ref name="defaultStack"></interceptor-ref>
6.在配置文件内指定上传路径，其次，在UploadAction.java中新建一个变量uploadPath,为其设置set方法。同时在uploadMethod方法中将目标文件夹改为uploadPath.
<action name="UploadAction" class="action.UploadAction" method="uploadMethod"> <param name="uploadPath">/home/amosli/develop/struts2_learn/</param> .................
例子：fileload.jsp
<body>
<form action="fileuploadResult.jsp" method="post" enctype="multipart/form-data">
username:<input type="text" name="username" ><br>
file:<input type="file" name="file"><br>
<input type="submit" value="sumbit">
</form>
fileuploadResult.jsp
<body>
<%
InputStream is = request.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));//字符流与字节流的桥接
String buffer = null;
if(null != (buffer=br.readLine()))
{
out.print(buffer+"<br>");
}
br.close();
is.close();
%>
</body>
4.处理文件上传fileupload组件（表单的method属性设为post，将enctype属性设为multipart/form-data）
我们主要使用Commons-fileupload.jar中的类，commons-io是提供流服务用的，我们没有对它进行操作。
- FileItem 类 用来封装表单中的元素和数据。
-
ServletFileUpload类 处理表单数据，将数据封装到 FileItem 对象中。
- DiskFileItemFactory类 设置FileItem 对象的工厂，可以设定缓冲区大小和存放临时文件目录。
-
ServletFileUpload 处理上传的文件的数据，优先保存在缓冲区，如果数据超过了缓冲区大小，则保存到硬盘上，存储在DiskFileItemFactory指定目录下的临时文件。数据都接收完后，它再在从临时文件中将数据写入到上传文件目录下的指定文件中，并删除临时文件。
fileload.jsp
<form action="FileuploadServlet1" method="post" enctype="multipart/form-data"> username:<input type="text" name="username" ><br> file:<input type="file" name="file"><br> file2:<input type="file" name="file2"><br> <input type="submit" value="sumbit"> </form>
FileuploadServlet1
public class FileuploadServlet1 extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); DiskFileItemFactory factory = new DiskFileItemFactory(); String path = request.getRealPath("/fileupload");//设置文件上传的位置 factory.setRepository(new File(path));//设置临时文件目录 factory.setSizeThreshold(1024*1024);//设置默认文件的大小 ServletFileUpload upload = new ServletFileUpload(factory); List<FileItem> list = null; try { list = (List<FileItem>) upload.parseRequest(request);//解析request请求 } catch (FileUploadException e1) { e1.printStackTrace(); } try { for(FileItem item:list)//FileItem包含了文件本身与文本域 { String name = item.getFieldName();//获得name属性的值 if(item.isFormField())//判断是否是文本域 { String value = item.getString();//获得value属性的值 System.out.println(name+":"+value); request.setAttribute(name,value); } else //为文件本身 { String value = item.getName();//对于大部分浏览器获得文件名，个别浏览器获得路径 int strat = value.lastIndexOf("\");//String 在此实例内的最后一个匹配项的索引位置。 String fileName = value.substring(strat+1);//从此实例检索子字符串。子字符串从指定的字符位置开始。 request.setAttribute(name,value); item.write(new File(path,fileName));//写入文件
InputStream is =item.getInputStream();
OutputStream os = new FileOutputStream(new File(path,fileName));
byte[] buffer = new byte[400];
int length = 0;
while(-1 != (length = is.read(buffer)))
{
os.write(buffer);
}
os.close();
is.close();
} } } catch(Exception e) { e.printStackTrace(); } request.getRequestDispatcher("fileloadResult2.jsp").forward(request,response); } }
5.Struts2的文件上传,通过两步实现的：
1）首先将客户端上传的文件保存到struts.multipart.saveDir键所指定的目录中，如果该键所对应的目录不存在，那么久保存到javax.servlet.contexe.tempdir环境变量所指定的目录中。
2）Action中所定义的File类型的成员变量file实际上指向的是临时目录中的临时文件，然后在服务器端通过io的方式将临时文件写入到指定的服务器目录中。
(1)单个文件上传
fileupload.jsp
<form action="FileUploadAction" method="post" enctype="multipart/form-data"> username:<input type="text" name="username"><br> file:<input type="file" name="file"><br> <input type="submit" value="submit"> </form>
FileUploadAction
public class FileUploadAction extends ActionSupport { private String username; private File file; private String fileFileName; private String fileContentType; public String getFileFileName() { return fileFileName; } public void setFileFileName(String fileFileName) { this.fileFileName = fileFileName; } public String getFileContentType() { return fileContentType; } public void setFileContentType(String fileContentType) { this.fileContentType = fileContentType; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public File getFile() { return file; } public void setFile(File file) { this.file = file; } @Override public String execute() throws Exception { InputStream is = new FileInputStream(file); String path = ServletActionContext.getRequest().getRealPath("/fileupload"); System.out.println(fileFileName); OutputStream os = new FileOutputStream(new File(path,fileFileName)); byte[] buffer = new byte[400]; int length = 0; while(-1 != (length = is.read(buffer))) { os.write(buffer,0,length); } os.close(); is.close(); return SUCCESS; } }
struts.xml
<action name="FileUploadAction" class="com.liule.action.FileUploadAction"> <result name="success">/fileuploadResult.jsp</result> </action>
fileuploadResult.jsp
<body> username:<s:property value="username"/><br> file:<s:property value="fileFileName"/> </body>
(2)多个文件上传
fileupload2.jsp
<form action="FileUploadAction2" method="post" enctype="multipart/form-data"> username:<input type="text" name="username"><br> file:<input type="file" name="file"><br> file:<input type="file" name="file"><br> file:<input type="file" name="file"><br> <input type="submit" value="submit"> </form>
FileUploadAction2
public class FileUploadAction2 extends ActionSupport { private String username; private List<File> file; private List<String> fileFileName; private List<String> fileContentType; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public List<File> getFile() { return file; } public void setFile(List<File> file) { this.file = file; } public List<String> getFileFileName() { return fileFileName; } public void setFileFileName(List<String> fileFileName) { this.fileFileName = fileFileName; } public List<String> getFileContentType() { return fileContentType; } public void setFileContentType(List<String> fileContentType) { this.fileContentType = fileContentType; } @Override public String execute() throws Exception { for(int i = 0 ;i <file.size();i++) { String path = ServletActionContext.getRequest().getRealPath("/fileupload"); OutputStream os = new FileOutputStream(new File(path,fileFileName.get(i))); InputStream is = new FileInputStream(file.get(i)); byte[] buffer = new byte[400]; int length =0; while(-1 != (length=is.read(buffer))) { os.write(buffer,0,length); } is.close(); os.close(); } return SUCCESS; } }
fileupload2Result.jsp
<body> username:<s:property value="username"/><br> <s:iterator value="fileFileName" id="f"> file:<s:property value="#f"/><br> </s:iterator> </body>
6.文件下载
fileDownload.jsp
<body>
<a href="DownloadFile.action">文件下载</a>
</body>
DownloadAction
public class DownloadAction extends ActionSupport { public InputStream getDownloadFile() { return ServletActionContext.getServletContext().getResourceAsStream("/fileupload/新建文本文档 (2).zip"); } @Override public String execute() throws Exception { return SUCCESS; } }
struts.xml
<action name="DownloadFile" class="com.liule.action.DownloadAction"> <result type="stream"> <param name="contextDisPosition">attachment;filename="新建文本文档 (2).zip"</param> <param name="inputName">downloadFile</param> </result> </action>
灵活下载：
downloadFile.jsp
<body>
<a href="DownloadFile.action?number=1">下载</a>
</body>
DownloadFile
public class DownloadFile extends ActionSupport { private int number; private String filename; public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } public String getFilename() { return filename; } public void setFilename(String filename) { this.filename = filename; } public InputStream getDownloadFile() { if(1 == number) { this.filename="新建文本文档 (2).txt"; try { this.filename = new String(this.filename.getBytes("gbk"), "8859_1"); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } ServletActionContext.getServletContext().getResourceAsStream("/file/新建文本文档 (2).txt"); } else { this.filename="新建文本文档 (2).zip"; try { this.filename = new String(this.filename.getBytes("gbk"), "8859_1"); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } ServletActionContext.getServletContext().getResourceAsStream("/file/新建文本文档 (2).zip"); } return null; } @Override public String execute() throws Exception { return SUCCESS; } }
struts.xml
<action name="DownloadFile" class="com.liule.action.DownloadFile"> <result type="stream"> <param name="contentDisposition">attachment;filename=${filename}</param> <param name="inputName">downloadFile</param> </result> </action>
http://www.cnblogs.com/liunanjava/p/4389661.html