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struts2 文件上传和下载,以及部分源码解析

Posted on 2010-06-02 11:37 疯狂 阅读(8304) 评论(5)  编辑  收藏 所属分类: java strutsweb

struts2 文件上传 和部分源码解析,以及一般上传原理

(1)  单文件上传 

一.简介

Struts2并未提供自己的请求解析器,也就是就Struts2不会自己去处理multipart/form-data的请求,它需要调用其他请求解析器,将HTTP请求中的表单域解析出来。但Struts2在原有的上传解析器基础

上做了进一步封装,更进一步简化了文件上传。
Struts2默认使用的是Jakarta的Common-FileUpload框架来上传文件,因此,要在web应用中增加两个Jar文件:commons-fileupload-1.2.jar和commons-io-1.3.1.jar。它在原上传框架上做了进一步封装

,简化了文件上传的代码实现,取消了不同上传框架上的编程差异。
如果要改成其它的文件上传框架,可以修改struts.multipart.parser常量的值为cos/pell,默认值是jakata。并在classpath中增加相应上传组件的类库

例如配置成cos上传

struts.multipart.parser=cos

struts.multipart.maxSize=1024  指定文件的最大字结数

二.原理

不管用common-fileUPload框架,还是用cos,都是通过将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。
也就是配置文件的 <interceptor-ref name="fileUpload"/>
我们可以通过源代码struts2-code-XX.jar的struts-default.xml文件找到
<interceptor name="fileUpload" class="org.apache.struts2.interceptor.FileUploadInterceptor"/>
打开这个类的源代码可以看见相关如下:
/**
 * <!-- START SNIPPET: description -->
 * <p/>
 * Interceptor that is based off of {@link MultiPartRequestWrapper}, which is automatically applied for any request that
 * includes a file. It adds the following parameters, where [File Name] is the name given to the file uploaded by the
 * HTML form:
 * <p/>
 * <ul>
 * <p/>
 * <li>[File Name] : File - the actual File</li>
 * <p/>
 * <li>[File Name]ContentType : String - the content type of the file</li>
 * <p/>
 * <li>[File Name]FileName : String - the actual name of the file uploaded (not the HTML name)</li>
 * <p/>
 * </ul>
 * <p/>
也就是说我们需要三个变量File(表单的name),其他两个参数通过set个体方法有strtus调用

接着下面是一些国际化提示的东西:
* processed for all i18n requests. You can override the text of these messages by providing text for the following
 * keys:
 * <li>struts.messages.error.uploading - a general error that occurs when the file could not be uploaded</li>
 * <p/>
 * <li>struts.messages.error.file.too.large - occurs when the uploaded file is too large</li>
 * <p/>
 * <li>struts.messages.error.content.type.not.allowed - occurs when the uploaded file does not match the expected
 * content types specified</li>
 * <p/>
 * <li>struts.messages.error.file.extension.not.allowed - occurs when the uploaded file does not match the expected
 * file extensions specified</li>
 * <p/>
例如struts.messages.error.content.type.not.allowed 表示文件类型错误:也就是说如果我们给拦截器配置了属性allowedTypes 例如:
<param name ="allowedTypes">image/bmp,image/png,image/gif,image/jpeg,image/jpg</param>    但是上传的时候没有上传规定的类型
struts2就会去我们的资源文件去找key为struts.messages.error.content.type.not.allowed的国际化资源给与提示这时候我们可以在我们的资源中配置这个key:
例如:struts.messages.error.content.type.not.allowed=您上传的文件类型只能为...!请重新选择!
(当然需要<constant name="struts.custom.i18n.resources" value="globalMessages"/>)globalMessages为资源前缀,然后通过:<s:fielderror/>来显示提示
<!-- START SNIPPET: parameters -->
 * <p/>
 * <ul>
 * <p/>
 * <li>maximumSize (optional) - the maximum size (in bytes) that the interceptor will allow a file reference to be set
 * on the action. Note, this is <b>not</b> related to the various properties found in struts.properties.
 * Default to approximately 2MB.</li>
 * <p/>
 * <li>allowedTypes (optional) - a comma separated list of content types (ie: text/html) that the interceptor will allow
 * a file reference to be set on the action. If none is specified allow all types to be uploaded.</li>
 * <p/>
 * <li>allowedExtensions (optional) - a comma separated list of file extensions (ie: .html) that the interceptor will allow
 * a file reference to be set on the action. If none is specified allow all extensions to be uploaded.</li>
 * </ul>
 * <p/>
上面则是拦截器的相关参数,一目了然:maximumSize 上传文件最大多少 默认:2MB。allowedTypes容许的上传类型。allowedExtensions容许的扩展名
接着是相关action的代码说明:
<!-- START SNIPPET: example-action -->
 *    package com.example;
 * <p/>
 *    import java.io.File;
 *    import com.opensymphony.xwork2.ActionSupport;
 * <p/>
 *    public UploadAction extends ActionSupport {
 *       private File file;
 *       private String contentType;
 *       private String filename;
 * <p/>
 *       public void setUpload(File file) {
 *          this.file = file;
 *       }
 * <p/>
 *       public void setUploadContentType(String contentType) {
 *          this.contentType = contentType;
 *       }
 * <p/>
 *       public void setUploadFileName(String filename) {
 *          this.filename = filename;
 *       }
 * <p/>
 *       public String execute() {
 *          //...
 *          return SUCCESS;
 *       }
 *  }
其实最主要的是set方法的确定:我们跟踪到大约238行:
 String contentTypeName = inputName + "ContentType";
 String fileNameName = inputName + "FileName";
最终确定我们的private File file;属性名称可以随便,
但是filenam和contenttype的set方法要有规定 例如:
如果private File myFile;

则对应的其他的两个属性set方法如下:

public void setMyFileContentType(String contentType) {
         this.contentType = contentType;//当然contentType可以随便起名 最终要的是set+MyFile+ContentType方法
    }

public void setMyFileFileName(String filename) {
           this.filename = filename;/当然filename可以随便起名 最终要的是set+MyFile+FileName方法
       }
以下是实例:
三.需要的jar包(默认使用commons-fileupload,如果使用cos,要将jar引进来)

commons-logging-1.1.jar
freemarker-2.3.8.jar
ognl-2.6.11.jar
struts2-core-2.0.6.jar
xwork-2.0.1.jar
commons-io-1.3.1.jar
commons-fileupload-1.2.jar

四.实例

1.首先,创建上传页面

Html代码
1.<%@page language="java" contentType = "text/html; charset=utf-8" pageEncoding = "utf-8"%>   
2.<%@taglib prefix="s" uri ="/struts-tags"%>   
3. 
4.<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
5.<html> 
6.  <head> 
19.  </head> 
20.    
21.  <body> 
22.   <s:form action ="fileUpload" method ="POST" enctype ="multipart/form-data">   
23.                <s:fielderror /> 
24.        <s:file name ="upload"/>     
25.        <s:submit />   
26.    </s:form >   
27. 
28.  </body> 
29.</html> 

2.action


1.package com;     
2.    
3.import java.io.BufferedInputStream;     
4.import java.io.BufferedOutputStream;     
5.import java.io.File;     
6.import java.io.FileInputStream;     
7.import java.io.FileOutputStream;     
8.import java.io.InputStream;     
9.import java.io.OutputStream;     
10.import java.util.Date;     
11.    
12.import org.apache.struts2.ServletActionContext;     
13.    
14.import com.opensymphony.xwork2.ActionSupport;     
15.    
16.public class FileUploadAction extends ActionSupport {     
17.         
18.    private static final long serialVersionUID = 6452146812454l;     
19.    
20.    private File upload;     
21.    
22.    private String uploadContentType;     
23.    
24.    private String uploadFileName;     
25.    
26.    private String imageFileName;     
27.    
28.    public String getUploadContentType() {     
29.        return uploadContentType;     
30.    }     
31.    
32.    public void setUploadContentType(String uploadContentType) {     
33.        this.uploadContentType = uploadContentType;     
34.    }     
35.    
36.    public File getUpload() {     
37.        return upload;     
38.    }     
39.    
40.    public void setUpload(File upload) {     
41.        this.upload = upload;     
42.    }     
43.    
44.    public String getUploadFileName() {     
45.        return uploadFileName;     
46.    }     
47.    
48.    public void setUploadFileName(String uploadFileName) {     
49.        this.uploadFileName = uploadFileName;     
50.    }     
51.    
52.    public void setImageFileName(String imageFileName) {     
53.        this.imageFileName = imageFileName;     
54.    }     
55.    
56.    public String getImageFileName() {     
57.        return imageFileName;     
58.    }     
59.    
60.    private static void copy(File src, File dst) {     
61.        try {     
62.            InputStream in = null;     
63.            OutputStream out = null;     
64.            try {     
65.                in = new BufferedInputStream(new FileInputStream(src));     
66.                out = new BufferedOutputStream(new FileOutputStream(dst));     
67.                byte[] buffer = new byte[1024*10];     
68.                while (in.read(buffer) > 0) {     
69.                    out.write(buffer);     
70.                }     
71.            } finally {     
72.                if (null != in) {     
73.                    in.close();     
74.                }     
75.                if (null != out) {     
76.                    out.close();     
77.                }     
78.            }     
79.        } catch (Exception e) {     
80.            e.printStackTrace();     
81.        }     
82.    }     
83.    
84.    @Override    
85.    public String execute() {     
86.        System.out.println(uploadFileName);     
87.             
88.        imageFileName = System.currentTimeMillis() + uploadFileName.substring(uploadFileName.lastIndexOf("."));     
89.        File imageFile = new File(ServletActionContext.getServletContext()     
90.                .getRealPath("/uploadImages")     
91.                + "/" + imageFileName);     //我们自己重新定义的文件名,也可以直接用 uploadFileName
92.        copy(upload, imageFile);     
93.        return SUCCESS;     
94.    }     
95.    
96.}    
97
表单的enctype ="multipart/form-data,与一般的上传一样.

<s:file name="upload">会将upload绑定到action的upload,其次他还会将上传记文件的MIME类型绑定到uploadContentType,文件名绑定到uploadFileName中,他们是通过

setUploadContentType和setUploadFileName进行绑定的,下面进行的多文件上传也是同个道理,不过要用数组或者是list来进行绑定,然后多个文件的MIME类型也会绑定到以数组

名字加ContentType和FileName的字符串数组中。   比如说上传的文件的数组名为:File[] uploads,则它们的MIME类型绑定的对应的数组是uploadsFileName和uploadsContentType.

3.struts.xml的配置

Xml代码

Xml代码
1.<?xml version="1.0" encoding="UTF-8" ?>    
2.<!DOCTYPE struts PUBLIC     
3.    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"     
4.    "http://struts.apache.org/dtds/struts-2.0.dtd">    
5.    
6.<struts>    
7.    <constant name="struts.multipart.saveDir" value="/tmp" />    
8.    <package name="fileUploadDemo" extends="struts-default">    
9.        <action name ="fileUpload" class ="com.FileUploadAction">      
10.              
11.            <interceptor-ref name ="fileUpload">      
12.                <param name ="allowedTypes">image/bmp,image/png,image/gif,image/jpeg,image/jpg</param>      
13.            </interceptor-ref>      
14.            <interceptor-ref name ="defaultStack"/>      
15.              
16.            <result name ="input" >/fileUpload.jsp</result>    
17.            <result name ="success">/showUpload.jsp </result>      
18.        </action>      
19.    </package>    
20.</struts>    

4.最后是web.xml的配置

Xml代码
1.<?xml version="1.0" encoding="UTF-8"?>    
2.<web-app version="2.4"      
3.    xmlns="http://java.sun.com/xml/ns/j2ee"      
4.    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"      
5.    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee      
6.    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">    
7.         
8.    <filter>      
9.        <filter-name>struts-cleanup</filter-name>      
10.        <filter-class>      
11.            org.apache.struts2.dispatcher.ActionContextCleanUp     
12.        </filter-class>      
13.    </filter>      
14.         
15.    <filter>      
16.        <filter-name>struts2</filter-name >      
17.        <filter-class>      
18.            org.apache.struts2.dispatcher.FilterDispatcher     
19.        </filter-class >      
20.    </filter>      
21.         
22.    <filter-mapping>      
23.        <filter-name>struts-cleanup</filter-name >      
24.        <url-pattern>/*</url-pattern>      
25.    </filter-mapping>      
26.    
27.    <filter-mapping>      
28.        <filter-name>struts2</filter-name >      
29.        <url-pattern>/*</url-pattern >      
30.    </filter-mapping>      
31.         
32.  <welcome-file-list>    
33.    <welcome-file>index.jsp</welcome-file>    
34.  </welcome-file-list>    
35.</web-app>  

(2) 多文件上传

多文件上传
与单文件上传相似,实现多文件你可以将多个<s:file />绑定Action的数组或列表。如下例所示。

< s:form action ="uploadList" 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[] uploadSFileName;
     private String[] uploadSContentType;

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 ;
     private List < String > uploadSFileName ;
     private List < String > uploadSContentType ;
多文件上传列表绑定Action代码片段

另外是一般上传文件的原理:当然具体可以看http协议的rfc文档:
关于multipart/form-data 相关资料可以看;http://www.ietf.org/rfc/rfc1867.txt 大约在[Page 1]的地方有介绍
 表单配置multipart/form-data 说明以二进制流的方式传输表单字段的数据:
我们通过以下代码看到request数据流中的内容:

 PrintWriter out = response.getWriter();
  InputStream is = request.getInputStream();
  
  BufferedReader br = new BufferedReader(
   new InputStreamReader(is));
  String buffer = null;
  while( (buffer = br.readLine()) != null)
  {
   //在页面中显示读取到的请求参数
   out.println(buffer + "<br />");
  }
out.flush();
out.close();
例如:我上传一个文件D:\apache-tomcat-6018\bin\version.sh (tomcat版本文件)
最终页面显示:
-----------------------------7da1052ec05fe
Content-Disposition: form-data; name="ff"; filename="D:\apache-tomcat-6018\bin\version.sh"
Content-Type: text/plain

#!/bin/sh

# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# resolve links - $0 may be a softlink
PRG="$0"

while [ -h "$PRG" ] ; do
ls=`ls -ld "$PRG"`
link=`expr "$ls" : '.*-> \(.*\)$'`
if expr "$link" : '/.*' > /dev/null; then
PRG="$link"
else
PRG=`dirname "$PRG"`/"$link"
fi
done

PRGDIR=`dirname "$PRG"`
EXECUTABLE=catalina.sh

# Check that target executable exists
if [ ! -x "$PRGDIR"/"$EXECUTABLE" ]; then
echo "Cannot find $PRGDIR/$EXECUTABLE"
echo "This file is needed to run this program"
exit 1
fi

exec "$PRGDIR"/"$EXECUTABLE" version "$@"

-----------------------------7da1052ec05fe--
我们发现我们上传的内容在
-----------------------------7da1052ec05fe
Content-Disposition: form-data; name="ff"; filename="D:\apache-tomcat-6018\bin\version.sh"
Content-Type: text/plain和-----------------------------7da1052ec05fe--中间
因此我们可以通过以下代码来获取上传内容并保存:

//取得HttpServletRequest的InputStream输入流
InputStream is = request.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String buffer = null;
//循环读取请求内容的每一行内容
while( (buffer = br.readLine()) != null)
{
 //如果读到的内容以-----------------------------开始,
 //且以--结束,表明已到请求内容尾
 if(buffer.endsWith("--") && buffer
  .startsWith("-----------------------------"))//length为29
 {
  //跳出循环
  break;
 }
 //如果读到的内容以-----------------------------开始,表明开始了一个表单域
 if(buffer.startsWith("-----------------------------"))
 {
  //如果下一行内容中有filename字符串,表明这是一个文件域
  if (br.readLine().indexOf("filename") > 1)
  {
   //跳过两行,开始处理上传的文件内容
   br.readLine();
   br.readLine();
   //以系统时间为文件名,创建一个新文件
   File file = new File(request.getRealPath("/")
    + System.currentTimeMillis());
                         //当然我们可以读取filenam来保存这里简化
   //创建一个文件输出流
   PrintStream ps = new PrintStream(new FileOutputStream(file));
   String content = null;
   //接着开始读取文件内容
   while( (content = br.readLine()) != null)
   {
    //如果读取的内容以-----------------------------开始,
    //表明开始了下一个表单域内容
    if(content.startsWith("-----------------------------"))length为29
    {
     //跳出处理
     break;
    }
    //将读到的内容输出到文件中
    ps.println(content);
   }
   //关闭输出
   ps.flush();
   ps.close();
  }
 }
}
br.close();

关于strtus2下载:
下载最终是通过contentType和数据流将数据输出到客户端来实现,在struts中也是通过InputStream和相关的配置来实现:
同样最终到strtus的下载相关的源代码:org.apache.struts2.dispatcher.StreamResult我们看到
 
     public static final String DEFAULT_PARAM = "inputName";

    protected String contentType = "text/plain";
    protected String contentLength;
    protected String contentDisposition = "inline";//在线
    protected String contentCharSet ;
    protected String inputName = "inputStream";
    protected InputStream inputStream;
    protected int bufferSize = 1024;
    protected boolean allowCaching = true;

当然这些参数都可以在 <result  type="stream">中配置 例如;
<param name="inputPath">\uploads\document.pdf</param>
<!-- 指定下载文件的文件类型 -->
<param name="contentType">Application/pdf</param>
<!-- 指定由getTargetFile()方法返回被下载文件的InputStream -->
<param name="inputName">targetFile</param>
<param name="contentDisposition">attachment;filename="document.pdf"</param>
<!-- 指定下载文件的缓冲大小 -->
<param name="bufferSize">2048</param>
其中:
    contentType:指定被下载文件的文件类型。 application/octet-stream 默认值,可以下载所有类型
      inputName:指定被下载文件的入口输入流, 和DownloadAction中的getInputStream()对应,主要是获得实际资源文件
      contentDisposition:指定下载的文件名和显示方式,一般和文件名一致,但是要注意中文件名保存时乱码问题,解决办法就是进行编码处理
<!-- 指定由getTargetFile()方法返回被下载文件的InputStream -->
<param name="inputName">targetFile</param>
是下载的入口 我们不需要在我们的action里面配置targetFile变量 但需要getTargetFile方法,默认需要getInputStream()方法 也就是:inputName参数的值就是入口方法去掉get前缀、首字母小写的

字符串

我们的action里面的代码如下:


 private String inputPath;//通过strtus获取文件地址 也可以直接写例如:String inputPath = ServletActionContext.getRequest().getRealPath("\uploads\document.pdf");
 
 public void setInputPath(String value)
 {
  inputPath = value;
 }
public InputStream getTargetFile() throws Exception
 { 
  return ServletActionContext.getServletContext().getResourceAsStream(inputPath);
 }
如果报以下错误:
Can not find a java.io.InputStream with the name [targetFile] in the invocation stack. Check the <param name="inputName"> tag specified for this action.

实际问题是ServletActionContext.getServletContext().getResourceAsStream(inputPath);找不到资源,请检查你的path是否正确。
而关于下载实际struts做了什么呢?我们看一部分源代码代码就很明白了:

  HttpServletResponse oResponse = (HttpServletResponse) invocation.getInvocationContext().get(HTTP_RESPONSE);
 // Set the content type
...
 //Set the content length
...
 // Set the content-disposition
...
 // Set the cache control headers if neccessary
...
// Get the outputstream
//------------
            oOutput = oResponse.getOutputStream();

            if (LOG.isDebugEnabled()) {
                LOG.debug("Streaming result [" + inputName + "] type=[" + contentType + "] length=[" + contentLength +
                    "] content-disposition=[" + contentDisposition + "] charset=[" + contentCharSet + "]");
            }

            // Copy input to output
            LOG.debug("Streaming to output buffer +++ START +++");
            byte[] oBuff = new byte[bufferSize];
            int iSize;
            while (-1 != (iSize = inputStream.read(oBuff))) {
                oOutput.write(oBuff, 0, iSize);
            }
            LOG.debug("Streaming to output buffer +++ END +++");

            // Flush
            oOutput.flush();
        }
        finally {
            if (inputStream != null) inputStream.close();
            if (oOutput != null) oOutput.close();
        }
//-----------
很简单,就像以前在servlet中一样通过getOutputStream 和配置content type ,content-disposition,cache control,content length这些参数的来实现。

这样就很简单的实现了下载功能。
以上是自己工作之余写的以下总结,不对的地方希望大家指点,谢谢,转载,请说明地址


评论

# re: struts2 文件上传和下载,以及部分源码解析  回复  更多评论   

2011-12-27 22:55 by 热太热让他热天
热太热儿童热天热天热天

# re: struts2 文件上传和下载,以及部分源码解析  回复  更多评论   

2012-07-13 08:25 by 33
frsfrefgr

# re: struts2 文件上传和下载,以及部分源码解析  回复  更多评论   

2012-09-04 13:41 by 33
@33
fdfdfd

# re:  回复  更多评论   

2012-09-04 13:42 by 33
kjkj

# re: struts2 文件上传和下载,以及部分源码解析  回复  更多评论   

2013-07-13 11:16 by @张小梅
看看,没试,不知道好用不

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