得到项目根目录，下载文件相关

1.在开发Web项目中，得到项目根目录有以下几种方式：

 

(1).当可以得到request对象的时候：

  String filePath = request.getRealPath("excels");

 

 @Context

 private org.apache.cxf.jaxrs.ext.MessageContext mc;

 以下在方法内部

 HttpServletRequest req =mc.getHttpServletRequest();

 String filePath = req.getRealPath("excels");

 

(2).当无法得到request对象的时候：(这里需要在jsp中或是继承HttpServlet的类)

  ServletContext context = super.getServletContext();

  String filePath = context.getRealPath("/excels");

 

 

2.生成文件随机名字的方式： fileName =UUID.randomUUID().toString()+".xls";

 

3.生成随机文件下载方式：

  (1)利用SmartUpload

  <%@ page import="com.jspsmart.upload.*"%>

  <%

  try {

  SmartUpload su = new SmartUpload();

  su.initialize(pageContext);

  su.downloadFile(request.getRealPath("excels") + "//"

  + request.getParameter("exportContent"));

  out.clear(); 

  out = pageContext.pushBody();

  } catch (Exception e) {

 

  }

  %> 

(2).<%

request.setCharacterEncoding("UTF-8");

response.setContentType("text/html; charset=UTF-8");

//防止IE缓存        

response.setHeader("pragma","no-cache");        

response.setHeader("cache-control","no-cache");        

response.setDateHeader("Expires",0);    

response.setContentType("APPLICATION/OCTET-STREAM"); 

response.setHeader("Content-Disposition", "attachment;"); 

String objectID = request.getParameter("objectID") == null ? "" : request.getParameter("objectID");

SysModel sysmodel = ModelFactory.getSysmodel();

SysPersistence persistence = PersistenceFactory.getInstance(sysmodel);

String sql="";

sql="select  FILEEXT, Name " +

"from SysComm_FileImg  where Is_del = '0' and FD_OBJECTID="+objectID;

System.out.println(sql);

ArrayList<String[]> list= persistence.getSearchResult(110, sql);

String[] data=(String[])list.get(0);

String filename=data[1]+"."+data[0];

response.setHeader("Content-Disposition", "attachment; filename=/""+java.net.URLEncoder.encode(filename,"UTF-8")+"/""); 

ServletOutputStream sout=null;

try {

SysModel sysmodelimg = ModelFactory.getSysmodel();

SysPersistence persistenceimg = PersistenceFactory.getInstance(sysmodelimg);

sout = response.getOutputStream();

persistenceimg.readBlobToOutputStream(110,objectID,"FileContents",sout);

out.clear();

out = pageContext.pushBody();

}catch (Exception e) {

e.printStackTrace();

System.out.println(e.toString());

}finally{

sout.close();

}

%>

4.文件下载后需要删除临时文件，删除有两种方式

(1)、在下载方法中添加一个线程，下载后立即删除该文件：

 //删除生成的Excel文件

final String filep = filePath + "//" + fileName;

new Thread(new Runnable(){

public void run()

{

try

{

Thread.sleep(50000);

}

catch (InterruptedException e)

{

e.printStackTrace();

}

//System.out.println("文件路径：" + filep);  

File fi = new File(filep);

//System.out.println(fi.getName());

//System.out.println(fi.exists());

//System.out.println(fi.delete());//删除临时文件 

fi.delete();  //删除文件失败，文件存在且路径也正确，删除失败可能是下载该文件的流没有关闭

}

}).start();

(2)、创建一个Servlet，在服务启动的时候删除

 public class DeleteFileServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

public DeleteFileServlet() {

super();

}

/**

* 在服务启动时，删除公路基础数据下载生成的Excel临时文件

*/

public void init(ServletConfig config) throws ServletException {

super.init(config);

ServletContext context = getServletContext();

String filePath = context.getRealPath("/excels");//获得模板文件的路径

File file = new File(filePath);

System.out.println(filePath);

File[] subFiles = file.listFiles(new FileFilter() {

public boolean accept(File pathname) {

if (pathname.getName().endsWith("xls")) {

return true;

}

return false;

}

});

for (File f : subFiles) {

f.delete();

}

}

}

Web.xml中配置文件:

  <servlet>

    <servlet-name>DeleteFileServlet</servlet-name>

    <servlet-class>com.sinosoft.common.printExcel.DeleteFileServlet</servlet-class>

    <load-on-startup>8</load-on-startup>

  </servlet>