struts2文件上传
2011-12-05 11:19
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Struts2 文件上传
2010-04-06 11:16:48| 分类:STRUTS |字号 订阅
前一阵子有些朋友在电子邮件中问关于Struts 2实现文件上传的问题, 所以今天我们就来讨论一下这个问题。
实现原理
Struts 2是通过Commons FileUpload文件上传。Commons FileUpload通过将HTTP的数据保存到临时文件夹,然后Struts使用fileUpload拦截器将文件绑定到Action的实例中。从而我们就能够以本地文件方式的操作浏览器上传的文件。具体实现
前段时间Apache发布了Struts 2.0.6 GA,所以本文的实现是以该版本的Struts作为框架的。以下是例子所依赖类包的列表:清单1 依赖类包的列表
首先,创建文件上传页面FileUpload.jsp,内容如下:
<%
@ page language =
"
java "
contentType =
"
text/html; charset=utf-8
" pageEncoding
=
" utf-8
" %>
<%
@ taglib prefix =
"
s "
uri =
" /struts-tags
"
%>
<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
>
< html
xmlns ="http://www.w3.org/1999/xhtml"
>
< head
>
< title
> Struts 2 File Upload
</ title
>
</ head
>
< body
>
< s:form
action
="fileUpload" method
="POST" enctype
="multipart/form-data" >
< s:file
name ="myFile"
label ="Image File"
/>
< s:textfield
name ="caption"
label ="Caption"
/>
< s:submit
/>
</ s:form
>
</ body
>
</ html
>
清单2 FileUpload.jsp
在FileUpload.jsp中,先将表单的提交方式设为POST,然后将enctype设为multipart/form-data,这并没有什么特别之处。接下来,<s:file/>标志将文件上传控件绑定到Action的myFile属性。
其次是FileUploadAction.java代码:
package tutorial;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Date;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class
FileUploadAction extends
ActionSupport {
private static
final
long serialVersionUID
= 572146812454l
;
private static
final
int BUFFER_SIZE
= 16
*
1024 ;
private File myFile;
private String contentType;
private String fileName;
private String imageFileName;
private String caption;
public void
setMyFileContentType(String contentType) {
this .contentType
= contentType;
}
public void
setMyFileFileName(String fileName) {
this .fileName
= fileName;
}
public void
setMyFile(File myFile) {
this .myFile
= myFile;
}
public String getImageFileName()
{
return imageFileName;
}
public String getCaption()
{
return caption;
}
public void
setCaption(String caption) {
this .caption
= caption;
}
private static
void
copy(File src, File dst) {
try {
InputStream in
= null
;
OutputStream out
= null
;
try {
in
= new
BufferedInputStream(
new FileInputStream(src), BUFFER_SIZE);
out
= new
BufferedOutputStream(
new FileOutputStream(dst), BUFFER_SIZE);
byte [] buffer
= new
byte
[BUFFER_SIZE];
while (in.read(buffer)
> 0
) {
out.write(buffer);
}
}
finally
{
if (
null !=
in) {
in.close();
}
if (
null !=
out) {
out.close();
}
}
}
catch
(Exception e) {
e.printStackTrace();
}
}
private static
String getExtention(String fileName) {
int pos =
fileName.lastIndexOf(
" . "
);
return fileName.substring(pos);
}
@Override
public String execute()
{
imageFileName
= new
Date().getTime() +
getExtention(fileName);
File imageFile
= new
File(ServletActionContext.getServletContext().getRealPath(
" /UploadImages
" ) +
"
/ " +
imageFileName);
copy(myFile, imageFile);
return SUCCESS;
}
}
清单3 tutorial/FileUploadAction.java
在FileUploadAction中我分别写了setMyFileContentType、setMyFileFileName、setMyFile和setCaption四个Setter方法,后两者很容易明白,分别对应FileUpload.jsp中的<s:file/>和<s:textfield/>标志。但是前两者并没有显式地与任何的页面标志绑定,那么它们的值又是从何而来的呢?其实,<s:file/>标志不仅仅是绑定到myFile,还有myFileContentType(上传文件的MIME类型)和myFileFileName(上传文件的文件名,该文件名不包括文件的路径)。因此,<s:file
name="xxx" />对应Action类里面的xxx、xxxContentType和xxxFileName三个属性。
FileUploadAction作用是将浏览器上传的文件拷贝到WEB应用程序的UploadImages文件夹下,新文件的名称是由系统时间与上传文件的后缀组成,该名称将被赋给imageFileName属性,以便上传成功的跳转页面使用。
下面我们就来看看上传成功的页面:
<%
@ page language =
"
java "
contentType =
"
text/html; charset=utf-8
" pageEncoding
=
" utf-8
" %>
<%
@ taglib prefix =
"
s "
uri =
" /struts-tags
"
%>
<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
>
< html
xmlns ="http://www.w3.org/1999/xhtml"
>
< head
>
< title
> Struts 2 File Upload
</ title
>
</ head
>
< body
>
< div
style ="padding: 3px; border: solid 1px #cccccc; text-align: center"
>
< img
src ='UploadImages/<s:property
value ="imageFileName"
/>
' />
< br
/>
< s:property
value ="caption"
/>
</ div
>
</ body
>
</ html
>
清单4 ShowUpload.jsp
ShowUpload.jsp获得imageFileName,将其UploadImages组成URL,从而将上传的图像显示出来。
然后是Action的配置文件:
<? xml version="1.0" encoding="UTF-8"
?>
<! DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd"
>
< struts
>
< package
name ="fileUploadDemo"
extends ="struts-default"
>
< action
name ="fileUpload"
class ="tutorial.FileUploadAction"
>
<
interceptor-ref name
="fileUploadStack" />
<
result name
="success" >
/ShowUpload.jsp </
result >
</
action >
</ package
>
</ struts
>
清单5 struts.xml
fileUpload Action显式地应用fileUploadStack的拦截器。
最后是web.xml配置文件:
<? xml version="1.0" encoding="UTF-8"
?>
< web-app
id ="WebApp_9"
version ="2.4"
xmlns ="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation ="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
< display-name
> Struts 2 Fileupload
</ display-name
>
< filter
>
< filter-name
> struts-cleanup
</ filter-name
>
< filter-class
>
org.apache.struts2.dispatcher.ActionContextCleanUp
</
filter-class >
</ filter
>
< filter
>
< filter-name
> struts2
</ filter-name
>
< filter-class
>
org.apache.struts2.dispatcher.FilterDispatcher
</
filter-class >
</ filter
>
< filter-mapping
>
< filter-name
> struts-cleanup
</ filter-name
>
< url-pattern
> /*
</ url-pattern
>
</ filter-mapping
>
< filter-mapping
>
< filter-name
> struts2
</ filter-name
>
< url-pattern
> /*
</ url-pattern
>
</ filter-mapping
>
< welcome-file-list
>
< welcome-file
> index.html
</ welcome-file
>
</ welcome-file-list
>
</ web-app
>
清单6 WEB-INF/web.xml
发布运行应用程序,在浏览器地址栏中键入:http://localhost:8080/Struts2_Fileupload/FileUpload.jsp,出现图示页面:
清单7 FileUpload页面
选择图片文件,填写Caption并按下Submit按钮提交,出现图示页面:
清单8 上传成功页面
更多配置
在运行上述例子,如果您留心一点的话,应该会发现服务器控制台有如下输出:Mar 20
, 2007
4
: 08 :
43 PM org.apache.struts2.dispatcher.Dispatcher getSaveDir
INFO: Unable to find 'struts.multipart.saveDir' property setting. Defaulting to javax.servlet.context.tempdir
Mar 20 ,
2007
4 :
08 : 43
PM org.apache.struts2.interceptor.FileUploadInterceptor intercept
INFO: Removing file myFile C:\Program Files\Tomcat 5.5
\work\Catalina\localhost\Struts2_Fileupload\upload_251447c2_1116e355841__7ff7_00000006.tmp
清单9 服务器控制台输出
上述信息告诉我们,struts.multipart.saveDir没有配置。struts.multipart.saveDir用于指定存放临时文件的文件夹,该配置写在struts.properties文件中。例如,如果在struts.properties文件加入如下代码:
struts.multipart.saveDir
= /tmp
清单10 struts配置
这样上传的文件就会临时保存到你根目录下的tmp文件夹中(一般为c:\tmp),如果此文件夹不存在,Struts 2会自动创建一个。
错误处理
上述例子实现的图片上传的功能,所以应该阻止用户上传非图片类型的文件。在Struts 2中如何实现这点呢?其实这也很简单,对上述例子作如下修改即可。首先修改FileUpload.jsp,在<body>与<s:form>之间加入“<s:fielderror />”,用于在页面上输出错误信息。
然后修改struts.xml文件,将Action fileUpload的定义改为如下所示:
<
action name
="fileUpload" class
="tutorial.FileUploadAction" >
<
interceptor-ref name
="fileUpload" >
<
param name
="allowedTypes" >
image/bmp,image/png,image/gif,image/jpeg
</
param >
</
interceptor-ref >
<
interceptor-ref name
="defaultStack" />
<
result name
="input" >
/FileUpload.jsp </
result >
<
result name
="success" >
/ShowUpload.jsp </
result >
</
action >
清单11 修改后的配置文件
显而易见,起作用就是fileUpload拦截器的allowTypes参数。另外,配置还引入defaultStack它会帮我们添加验证等功能,所以在出错之后会跳转到名称为“input”的结果,也即是FileUpload.jsp。
发布运行应用程序,出错时,页面如下图所示:
清单12 出错提示页面
上面的出错提示是Struts 2默认的,大多数情况下,我们都需要自定义和国际化这些信息。通过在全局的国际资源文件中加入“struts.messages.error.content.type.not.allowed=The file you uploaded is not a image”,可以实现以上提及的需求。对此有疑问的朋友可以参考我之前的文章《在Struts
2.0中国际化(i18n)您的应用程序》。
实现之后的出错页面如下图所示:
清单13 自定义出错提示页面
同样的做法,你可以使用参数“maximumSize”来限制上传文件的大小,它对应的字符资源名为:“struts.messages.error.file.too.large”。
字符资源“struts.messages.error.uploading”用提示一般的上传出错信息。
多文件上传
与单文件上传相似,Struts 2实现多文件上传也很简单。你可以将多个<s:file />绑定Action的数组或列表。如下例所示。< s:form action
="doMultipleUploadUsingList"
method ="POST"
enctype ="multipart/form-data"
>
< s:file
label ="File (1)"
name ="upload"
/>
< s:file
label ="File (2)"
name ="upload"
/>
< s:file
label ="FIle (3)"
name ="upload"
/>
< s:submit
/>
</ s:form
>
清单14 多文件上传JSP代码片段
如果你希望绑定到数组,Action的代码应类似:
private
File[] uploads;
private String[] uploadFileNames;
private String[] uploadContentTypes;
public File[] getUpload()
{ return
this
.uploads; }
public void
setUpload(File[] upload) {
this .uploads
= upload; }
public String[] getUploadFileName()
{ return
this
.uploadFileNames; }
public void
setUploadFileName(String[] uploadFileName) {
this .uploadFileNames
= uploadFileName; }
public String[] getUploadContentType()
{ return
this
.uploadContentTypes; }
public void
setUploadContentType(String[] uploadContentType)
{ this
.uploadContentTypes =
uploadContentType; }
清单15 多文件上传数组绑定Action代码片段
如果你想绑定到列表,则应类似:
private
List <
File > uploads
= new
ArrayList <
File >
();
private List
< String
> uploadFileNames =
new
ArrayList <
String > ();
private List
< String
> uploadContentTypes =
new
ArrayList <
String > ();
public List
< File
> getUpload() {
return this
.uploads;
}
public void
setUpload(List <
File >
uploads) {
this .uploads
= uploads;
}
public List
< String
> getUploadFileName() {
return this
.uploadFileNames;
}
public void
setUploadFileName(List
< String >
uploadFileNames) {
this .uploadFileNames
= uploadFileNames;
}
public List
< String
> getUploadContentType() {
return this
.uploadContentTypes;
}
public void
setUploadContentType(List
< String >
contentTypes) {
this .uploadContentTypes
= contentTypes;
}
清单16 多文件上传列表绑定Action代码片段
总结
在Struts 2中实现文件上传的确是轻而易举,您要做的只是使用<s:file />与Action的属性绑定。这又一次有力地证明了Struts 2的简单易用。相关文章推荐
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