JSP 文件上传下载.docx
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JSP文件上传下载
MyEclipse6实战开发讲解视频入门10JSP文件上传下载
2007-12-2
本视频讲解了如何使用最新版本开源的ApacheCommonsFileUpload来上传文件以及如何编写文件下载代码.
视频部分代码屏幕出现闪烁,错位,不便之处请参考本文中的源码和文档中绿色部分的注释:
//Setfactoryconstraints
factory.setSizeThreshold（yourMaxMemorySize）;//设置最多只允许在内存中存储的数据,单位:
字节
factory.setRepository（yourTempDirectory）;//设置一旦文件大小超过getSizeThreshold（）的值时数据存放在硬盘的目录（默认可以不用设置）
//Createanewfileuploadhandler
ServletFileUploadupload=newServletFileUpload（factory）;
//Setoverallrequestsizeconstraint
//设置允许用户上传文件大小,单位:
字节
upload.setSizeMax（yourMaxRequestSize）;
友情提示:
下载微软网盘文件时关闭下载工具, 否则你将得到错误的文件,双击EXE会出来DOS窗口.正确操作是点击文件名后能看到显示下载链接和文件大小等信息.
代码:
http:
//cid- 132KB
视频:
http:
//cid-16分31秒6.0MB
内容包括:
1.ApacheCommonsFileUpload项目介绍
2.下载并增加必要的类库
3.编写文件上传表单HTML
4.编写文件上传处理JSP
5.编写文件下载JSP
6.发布并测试
视频截图:
代码:
upload.htm
Login: |
|
Password: |
|
附件:
|
upload.jsp
<%@pagelanguage="java"import="java.util.*"pageEncoding="GBK"%>
<%@pageimport="mons.fileupload.servlet.ServletFileUpload"%>
<%@pageimport="mons.fileupload.disk.DiskFileItemFactory"%>
<%!
/**
*得到文件的短路径,不包括目录.
*@date2005-10-18
*
*@paramfileName
* 需要处理的文件的名字.
*@returntheshortversionofthefile'sname.
*/
publicstaticStringgetShortFileName（StringfileName）{
if（fileName!
=null）{
StringoldFileName=newString（fileName）;
fileName=fileName.replace（'\\','/'）;
//Handledir
if（fileName.endsWith（"/"））{
intidx=fileName.indexOf（'/'）;
if（idx==-1||idx==fileName.length（）-1）{
returnoldFileName;
}else{
returnoldFileName
.substring（idx+1,fileName.length（）-1）;
}
}
if（fileName.lastIndexOf（"/"）>0）{
fileName=fileName.substring（fileName.lastIndexOf（"/"）+1,
fileName.length（））;
}
returnfileName;
}
return"";
}%>
<%
//Checkthatwehaveafileuploadrequest
booleanisMultipart=ServletFileUpload.isMultipartContent（request）;
if（isMultipart）{
//Createafactoryfordisk-basedfileitems
mons.fileupload.FileItemFactoryfactory=newDiskFileItemFactory（）;
//Createanewfileuploadhandler
ServletFileUploadupload=newServletFileUpload（factory）;
//Parsetherequest
List/*FileItem*/items=upload.parseRequest（request）;
//Processtheuploadeditems
Iteratoriter=items.iterator（）;
while（iter.hasNext（））{
mons.fileupload.FileItemitem=（mons.fileupload.FileItem）iter
.next（）;
if（item.isFormField（））{
Stringname=item.getFieldName（）;
Stringvalue=item.getString（"GBK"）;
out.println（name+"="+value）;
}else{
StringfieldName=item.getFieldName（）;//file
StringfileName=item.getName（）;
StringcontentType=item.getContentType（）;
booleanisInMemory=item.isInMemory（）;
longsizeInBytes=item.getSize（）;
out.println（"上传的文件名是:
"+fileName）;
if（fileName==null||fileName.length（）==0）{
out.println（"请选择一个文件来上传"）;
}else{
java.io.FileOutputStreamfout=newjava.io.FileOutputStream（
application.getRealPath（"upload/"
+getShortFileName（fileName）））;
fout.write（item.get（））;
fout.close（）;
}
}
}
}else{
out.println（"请用文件上传表单来访问这个页面"）;
}
%>
相关资料:
下载地址
http:
//commons.apache.org/fileupload/
http:
//commons.apache.org/io/
用法文档:
http:
//commons.apache.org/fileupload/using.html
UsingFileUpload
FileUploadcanbeusedinanumberofdifferentways,dependingupontherequirementsofyourapplication.Inthesimplestcase,youwillcallasinglemethodtoparsetheservletrequest,andthenprocessthelistofitemsastheyapplytoyourapplication.Attheotherendofthescale,youmightdecidetocustomizeFileUploadtotakefullcontrolofthewayinwhichindividualitemsarestored;forexample,youmightdecidetostreamthecontentintoadatabase.
Here,wewilldescribethebasicprinciplesofFileUpload,andillustratesomeofthesimpler-andmostcommon-usagepatterns.CustomizationofFileUploadisdescribedelsewhere.
FileUploaddependsonCommonsIO,somakesureyouhavetheversionmentionedonthedependenciespageinyourclasspathbeforecontinuing.
Howitworks
AfileuploadrequestcomprisesanorderedlistofitemsthatareencodedaccordingtoRFC1867,"Form-basedFileUploadinHTML".FileUploadcanparsesucharequestandprovideyourapplicationwithalistoftheindividualuploadeditems.EachsuchitemimplementstheFileIteminterface,regardlessofitsunderlyingimplementation.
ThispagedescribesthetraditionalAPIofthecommonsfileuploadlibrary.ThetraditionalAPIisaconvenientapproach.However,forultimateperformance,youmightpreferthefasterStreamingAPI.
Eachfileitemhasanumberofpropertiesthatmightbeofinterestforyourapplication.Forexample,everyitemhasanameandacontenttype,andcanprovideanInputStreamtoaccessitsdata.Ontheotherhand,youmayneedtoprocessitemsdifferently,dependinguponwhethertheitemisaregularformfield-thatis,thedatacamefromanordinarytextboxorsimilarHTMLfield-oranuploadedfile.TheFileIteminterfaceprovidesthemethodstomakesuchadetermination,andtoaccessthedatainthemostappropriatemanner.
FileUploadcreatesnewfileitemsusingaFileItemFactory.ThisiswhatgivesFileUploadmostofitsflexibility.Thefactoryhasultimatecontroloverhoweachitemiscreated.ThefactoryimplementationthatcurrentlyshipswithFileUploadstorestheitem'sdatainmemoryorondisk,dependingonthesizeoftheitem（i.e.bytesofdata）.However,thisbehaviorcanbecustomizedtosuityourapplication.
ServletsandPortlets
Startingwithversion1.1,FileUploadsupportsfileuploadrequestsinbothservletandportletenvironments.Theusageisalmostidenticalinthetwoenvironments,sotheremainderofthisdocumentrefersonlytotheservletenvironment.
Ifyouarebuildingaportletapplication,thefollowingarethetwodistinctionsyoushouldmakeasyoureadthisdocument:
∙WhereyouseereferencestotheServletFileUploadclass,substitutethePortletFileUploadclass.
∙WhereyouseereferencestotheHttpServletRequestclass,substitutetheActionRequestclass.
Parsingtherequest
Beforeyoucanworkwiththeuploadeditems,ofcourse,youneedtoparsetherequestitself.Ensuringthattherequestisactuallyafileuploadrequestisstraightforward,butFileUploadmakesitsimplicityitself,byprovidingastaticmethodtodojustthat.
//Checkthatwehaveafileuploadrequest
booleanisMultipart=ServletFileUpload.isMultipartContent（request）;
Nowwearereadytoparsetherequestintoitsconstituentitems.
Thesimplestcase
Thesimplestusagescenarioisthefollowing:
∙Uploadeditemsshouldberetainedinmemoryaslongastheyarereasonablysmall.
∙Largeritemsshouldbewrittentoatemporaryfileondisk.
∙Verylargeuploadrequestsshouldnotbepermitted.
∙Thebuilt-indefaultsforthemaximumsizeofanitemtoberetainedinmemory,themaximumpermittedsizeofanuploadrequest,andthelocationoftemporaryfilesareacceptable.
Handlingarequestinthisscenariocouldn'tbemuchsimpler:
//Createafactoryfordisk-basedfileitems
FileItemFactoryfactory=newDiskFileItemFactory（）;
//Createanewfileuploadhandler
ServletFileUploadupload=newServletFileUpload（factory）;
//Parsetherequest
List/*FileItem*/items=upload.parseRequest（request）;
That'sallthat'sneeded.Really!
TheresultoftheparseisaListoffileitems,eachofwhichimplementstheFileIteminterface.Processingtheseitemsisdiscussedbelow.
Exercisingmorecontrol
Ifyourusagescenarioisclosetothesimplestcase,describedabove,butyouneedalittlemorecontrol,youcaneasilycustomizethebehavioroftheuploadhandlerorthefileitemfactoryorboth.Thefollowingexampleshowsseveralconfigurationoptions:
//Createafactoryfordisk-basedfileitems
DiskFileItemFactoryfactory=newDiskFileItemFactory（）;
//Setfactoryconstraints
factory.setSizeThreshold（yourMaxMemorySize）;//设置最多只允许在内存中存储的数据,单位:
字节
factory.setRepository（yourTempDirectory）;//设置一旦文件大小超过getSizeThreshold（）的值时数据存放在硬盘的目录（默认可以不用设置）
//Createanewfileuploadhandler
ServletFileUploadupload=newServletFileUpload（factory）;
//Setoverallrequestsizeconstraint
//设置允许用户上传文件大小,单位:
字
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