本文详细介绍了Struts2框架中的文件上传功能，包括配置、基本理论、示例代码及多文件上传处理等内容。
在使用struts处理文件上传的时候往往会遇到一些问题，比如，当上传文件大于2M的时候拦截器不起作用（参见“struts2 common-fileupload上传文件大小限制 ”），多文件上传时file表单不能为空等问题。
下面我简单介绍一下Struts2文件上传的基本理论。，并就我的开发经验提供问题的一些解决方法。
一、enctype属性
关于该属性我就不再赘余了，enctype属性有三个参数。文件上传必须使用muitipart/form-data.这种编码方式会以二进制流的方式处理表单数据，java提供了两个类：URLDecoder和URLEncoder，处理这些二进制。下面看java程序
public class TestURLEncoder
{
public static void main(String[] args) throws Exception
{
String encodeStr = "%CC%E1%BD%BB";
String decodeStr = URLDecoder.decode(encodeStr ,"GBK");
System.out.println(decodeStr);
String rawStr = "课程介绍";
System.out.println(URLEncoder.encode(rawStr , "GBK"));
}
}（3）配置
<?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>
<constant name="struts.custom.i18n.resources" value="globalMessages"/>
<constant name="struts.i18n.encoding" value="GBK"/>
<package name="upload" extends="struts-default">
<action name="upload" class="lee.UploadAction">
<interceptor-ref name="fileUpload">
<param name="allowedTypes">image/bmp,image/png,image/gif,image/jpeg</param>
<param name="maximumSize">2000</param>
</interceptor-ref>
<interceptor-ref name="defaultStack"/>
<param name="savePath">/upload</param>
<result name="input"> /upload.jsp</result>
<result>/succ.jsp</result>
</action>
</package>
</struts>
二、Struts2的文件上传
1、Struts2ti提供的文件上传支持
Struts2的struts.properties配置文件中，配置了上传解析器。默认使用的是Jakarta的Common-FileUpload的文件上传框架。
# struts.multipart.parser=cos
# struts.multipart.parser=pell
struts.multipart.parser=jakarta
2、Struts2文件上传的例子.
（1）页面
<%@ page language="java" contentType="text/html; charset=GBK"%>
<%@taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK" />
<title>利用拦截器实现文件过滤</title>
</head>
<body>
<s:fielderror/>
<form action="upload.action" method="post" enctype="multipart/form-data">
文件标题：<input type="text" name="title" /><br>
选择文件：<input type="file" name="upload" /><br>
<input value="上传" type="submit" />
</form>
</body>
</html>
（2）Action
import com.opensymphony.xwork2.Action;
import org.apache.struts2.ServletActionContext;
import java.io.File;
import java.io.*;
import com.opensymphony.xwork2.ActionSupport;
public class UploadAction extends ActionSupport
{
private String title;
private File upload;
private String uploadContentType;
private String uploadFileName;
//接受依赖注入的属性
private String savePath;
//接受依赖注入的方法
public void setSavePath(String value)
{
this.savePath = value;
}
private String getSavePath() throws Exception
{
return ServletActionContext.getRequest().getRealPath(savePath);
}
public void setTitle(String title) {
this.title = title;
}
public void setUpload(File upload) {
this.upload = upload;
}
public void setUploadContentType(String uploadContentType) {
this.uploadContentType = uploadContentType;
}
public void setUploadFileName(String uploadFileName) {
this.uploadFileName = uploadFileName;
}
public String getTitle() {
return (this.title);
}
public File getUpload() {
return (this.upload);
}
public String getUploadContentType() {
return (this.uploadContentType);
}
public String getUploadFileName() {
return (this.uploadFileName);
}
@Override
public String execute() throws Exception
{
System.out.println("开始上传单个文件-----------------------");
System.out.println(getSavePath());
System.out.println("==========" + getUploadFileName());
System.out.println("==========" + getUploadContentType());
System.out.println("==========" + getUpload());
//以服务器的文件保存地址和原文件名建立上传文件输出流
FileOutputStream fos = new FileOutputStream(getSavePath() + "\\" + getUploadFileName());
FileInputStream fis = new FileInputStream(getUpload());
byte[] buffer = new byte[1024];
int len = 0;
while ((len = fis.read(buffer)) > 0)
{
fos.write(buffer , 0 , len);
}
return SUCCESS;
}
}
3、根据Struts2上传的例子分析得出：
如果表单中包含一个name属性为xxx的文件域，对应的action需要3个属性来封装该文件
类型为File的xxx属性封装了该文件域对应的文件内容。
类型为String的xxxFileName属性封装了该文件域对应的文件的文件名。
类型为String的xxxContentType属性封装了该文件域对应的文件的文件类型。
4、拦截器实现文件过滤
Struts2中文件上传过滤器是fileUpload。配置fileUpload是可指定两个参数：
allowedTypes:指定允许上传的文件类型，多文件类型用逗号分隔。
maximumSize:指定允许上传的文件大小，单位字节。
当文件过滤失败后，系统自动转入input视图，因此action必须配置input的逻辑视图。除此之外，还必须显示的为改Action配置defaultStack的拦截器引用。
5、输出出错信息<s:fielderror/>
如果你觉得这通过该方法输出的出错信息太刺眼，可以通过国际化信息替换它。
三、同时上传多个文件
上传的例子参看附件
如果你用Struts2做过同时上传多个文件就会知道，你上传时，多个file表单必不为null，否则返回文件类型错误的提示。
maximumSize参数控制的是单次请求允许上传的最大限制，而不是某个文件的最大限制。
这时我们就不能再用Struts2上传过滤器fileUpload了，我们需要手动实现文件过滤。下面提供一个简单的例子。
import com.opensymphony.xwork2.*;
import org.apache.struts2.ServletActionContext;
import java.io.File;
import java.io.*;
public class UploadAction extends ActionSupport
{
private String title;
private File upload;
private String uploadContentType;
private String uploadFileName;
//接受依赖注入的属性
private String savePath;
//接受依赖注入的方法
public void setSavePath(String value)
{
this.savePath = value;
}
private String getSavePath() throws Exception
{
return ServletActionContext.getRequest().getRealPath(savePath);
}
private String allowTypes;
public String getAllowTypes()
{
return allowTypes;
}
public void setAllowTypes(String allowTypes)
{
this.allowTypes = allowTypes;
}
public void setTitle(String title) {
this.title = title;
}
public void setUpload(File upload) {
this.upload = upload;
}
public void setUploadContentType(String uploadContentType) {
this.uploadContentType = uploadContentType;
}
public void setUploadFileName(String uploadFileName) {
this.uploadFileName = uploadFileName;
}
public String getTitle() {
return (this.title);
}
public File getUpload() {
return (this.upload);
}
public String getUploadContentType() {
return (this.uploadContentType);
}
public String getUploadFileName() {
return (this.uploadFileName);
}
public String filterType(String[] types)
{
String fileType = getUploadContentType();
for (String type : types)
{
if (type.equals(fileType))
{
return null;
}
}
return INPUT;
}
@Override
public String execute() throws Exception
{
String filterResult = filterType(getAllowTypes().split(","));
if (filterResult != null)
{
ActionContext.getContext().put("typeError" , "您要上传的文件类型不正确！");
return filterResult;
}
System.out.println("文件大小---------------------------" + getUpload().length());
//以服务器的文件保存地址和原文件名建立上传文件输出流
FileOutputStream fos = new FileOutputStream(getSavePath() + "\\" + getUploadFileName());
FileInputStream fis = new FileInputStream(getUpload());
byte[] buffer = new byte[1024];
int len = 0;
while ((len = fis.read(buffer)) > 0)
{
fos.write(buffer , 0 , len);
}
return SUCCESS;
}
}
附:contentType类型.
'ez' => 'application/andrew-inset',
'hqx' => 'application/mac-binhex40',
'cpt' => 'application/mac-compactpro',
'doc' => 'application/msword',
'bin' => 'application/octet-stream',
'dms' => 'application/octet-stream',
'lha' => 'application/octet-stream',
'lzh' => 'application/octet-stream',
'exe' => 'application/octet-stream',
'class' => 'application/octet-stream',
'so' => 'application/octet-stream',
'dll' => 'application/octet-stream',
'oda' => 'application/oda',
'pdf' => 'application/pdf',
'ai' => 'application/postscript',
'eps' => 'application/postscript',
'ps' => 'application/postscript',
'smi' => 'application/smil',
'smil' => 'application/smil',
'mif' => 'application/vnd.mif',
'xls' => 'application/vnd.ms-excel',
'ppt' => 'application/vnd.ms-powerpoint',
'wbxml' => 'application/vnd.wap.wbxml',
'wmlc' => 'application/vnd.wap.wmlc',
'wmlsc' => 'application/vnd.wap.wmlscriptc',
'bcpio' => 'application/x-bcpio',
'vcd' => 'application/x-cdlink',
'pgn' => 'application/x-chess-pgn',
'cpio' => 'application/x-cpio',
'csh' => 'application/x-csh',
'dcr' => 'application/x-director',
'dir' => 'application/x-director',
'dxr' => 'application/x-director',
'dvi' => 'application/x-dvi',
'spl' => 'application/x-futuresplash',
'gtar' => 'application/x-gtar',
'hdf' => 'application/x-hdf',
'js' => 'application/x-javas
cript',
'skp' => 'application/x-koan',
'skd' => 'application/x-koan',
'skt' => 'application/x-koan',
'skm' => 'application/x-koan',
'latex' => 'application/x-latex',
'nc' => 'application/x-netcdf',
'cdf' => 'application/x-netcdf',
'sh' => 'application/x-sh',
'shar' => 'application/x-shar',
'swf' => 'application/x-shockwave-flash',
'sit' => 'application/x-stuffit',
'sv4cpio' => 'application/x-sv4cpio',
'sv4crc' => 'application/x-sv4crc',
'tar' => 'application/x-tar',
'tcl' => 'application/x-tcl',
'tex' => 'application/x-tex',
'texinfo' => 'application/x-texinfo',
'texi' => 'application/x-texinfo',
't' => 'application/x-troff',
'tr' => 'application/x-troff',
'roff' => 'application/x-troff',
'man' => 'application/x-troff-man',
'me' => 'application/x-troff-me',
'ms' => 'application/x-troff-ms',
'ustar' => 'application/x-ustar',
'src' => 'application/x-wais-source',
'xhtml' => 'application/xhtml+xml',
'xht' => 'application/xhtml+xml',
'zip' => 'application/zip',
'au' => 'audio/basic',
'snd' => 'audio/basic',
'mid' => 'audio/midi',
'midi' => 'audio/midi',
'kar' => 'audio/midi',
'mpga' => 'audio/mpeg',
'mp2' => 'audio/mpeg',
'mp3' => 'audio/mpeg',
'aif' => 'audio/x-aiff',
'aiff' => 'audio/x-aiff',
'aifc' => 'audio/x-aiff',
'm3u' => 'audio/x-mpegurl',
'ram' => 'audio/x-pn-realaudio',
'rm' => 'audio/x-pn-realaudio',
'rpm' => 'audio/x-pn-realaudio-plugin',
'ra' => 'audio/x-realaudio',
'wav' => 'audio/x-wav',
'pdb' => 'chemical/x-pdb',
'xyz' => 'chemical/x-xyz',
'bmp' => 'image/bmp',
'gif' => 'image/gif',
'ief' => 'image/ief',
'jpeg' => 'image/jpeg',
'jpg' => 'image/jpeg',
'jpe' => 'image/jpeg',
'png' => 'image/png',
'tiff' => 'image/tiff',
'tif' => 'image/tiff',
'djvu' => 'image/vnd.djvu',
'djv' => 'image/vnd.djvu',
'wbmp' => 'image/vnd.wap.wbmp',
'ras' => 'image/x-cmu-raster',
'pnm' => 'image/x-portable-anymap',
'pbm' => 'image/x-portable-bitmap',
'pgm' => 'image/x-portable-graymap',
'ppm' => 'image/x-portable-pixmap',
'rgb' => 'image/x-rgb',
'xbm' => 'image/x-xbitmap',
'xpm' => 'image/x-xpixmap',
'xwd' => 'image/x-xwindowdump',
'igs' => 'model/iges',
'iges' => 'model/iges',
'msh' => 'model/mesh',
'mesh' => 'model/mesh',
'silo' => 'model/mesh',
'wrl' => 'model/vrml',
'vrml' => 'model/vrml',
'css' => 'text/css',
'html' => 'text/html',
'htm' => 'text/html',
'asc' => 'text/plain',
'txt' => 'text/plain',
'rtx' => 'text/richtext',
'rtf' => 'text/rtf',
'sgml' => 'text/sgml',
'sgm' => 'text/sgml',
'tsv' => 'text/tab-separated-values',
'wml' => 'text/vnd.wap.wml',
'wmls' => 'text/vnd.wap.wmlscript',
'etx' => 'text/x-setext',
'xsl' => 'text/xml',
'xml' => 'text/xml',
'mpeg' => 'video/mpeg',
'mpg' => 'video/mpeg',
'mpe' => 'video/mpeg',
'qt' => 'video/quicktime',
'mov' => 'video/quicktime',
'mxu' => 'video/vnd.mpegurl',
'avi' => 'video/x-msvideo',
'movie' => 'video/x-sgi-movie',
'ice' => 'x-conference/x-cooltalk'
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