|
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 " %>
< 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,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中的和标志。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,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,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 " %>
< 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/ ' /> < 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" ?>
"-//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 与之间加入“”,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,您要做的只是使用与action的属性绑定。这又一次有力地证明了struts 2的简单易用。
|