瘋狂

struts2 文件上傳 和部分源碼解析，以及一般上傳原理

（1）  單文件上傳 

一.簡介

Struts2并未提供自己的請求解析器，也就是就Struts2不會自己去處理multipart/form-data的請求，它需要調(diào)用其他請求解析器，將HTTP請求中的表單域解析出來。但Struts2在原有的上傳解析器基礎(chǔ)

上做了進(jìn)一步封裝，更進(jìn)一步簡化了文件上傳。
Struts2默認(rèn)使用的是Jakarta的Common-FileUpload框架來上傳文件，因此，要在web應(yīng)用中增加兩個(gè)Jar文件：commons-fileupload-1.2.jar和commons-io-1.3.1.jar。它在原上傳框架上做了進(jìn)一步封裝

，簡化了文件上傳的代碼實(shí)現(xiàn)，取消了不同上傳框架上的編程差異。
如果要改成其它的文件上傳框架，可以修改struts.multipart.parser常量的值為cos/pell，默認(rèn)值是jakata。并在classpath中增加相應(yīng)上傳組件的類庫

例如配置成cos上傳

struts.multipart.parser=cos

struts.multipart.maxSize=1024  指定文件的最大字結(jié)數(shù)

二.原理

不管用common-fileUPload框架，還是用cos，都是通過將HTTP的數(shù)據(jù)保存到臨時(shí)文件夾，然后Struts使用fileUpload攔截器將文件綁定到Action的實(shí)例中。
也就是配置文件的 <interceptor-ref name="fileUpload"/>
我們可以通過源代碼struts2-code-XX.jar的struts-default.xml文件找到
<interceptor name="fileUpload" class="org.apache.struts2.interceptor.FileUploadInterceptor"/>
打開這個(gè)類的源代碼可以看見相關(guān)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/>
也就是說我們需要三個(gè)變量File（表單的name），其他兩個(gè)參數(shù)通過set個(gè)體方法有strtus調(diào)用

接著下面是一些國際化提示的東西：
* 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 表示文件類型錯(cuò)誤：也就是說如果我們給攔截器配置了屬性allowedTypes 例如：
<param name ="allowedTypes">image/bmp,image/png,image/gif,image/jpeg,image/jpg</param>    但是上傳的時(shí)候沒有上傳規(guī)定的類型
struts2就會去我們的資源文件去找key為struts.messages.error.content.type.not.allowed的國際化資源給與提示這時(shí)候我們可以在我們的資源中配置這個(gè)key：
例如：struts.messages.error.content.type.not.allowed=您上傳的文件類型只能為...！請重新選擇！
(當(dāng)然需要<constant name="struts.custom.i18n.resources" value="globalMessages"/>)globalMessages為資源前綴，然后通過：<s:fielderror/>來顯示提示
<!-- 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/>
上面則是攔截器的相關(guān)參數(shù)，一目了然：maximumSize 上傳文件最大多少 默認(rèn)：2MB。allowedTypes容許的上傳類型。allowedExtensions容許的擴(kuò)展名
接著是相關(guān)action的代碼說明：
<!-- 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;
 *       }
 *  }
其實(shí)最主要的是set方法的確定：我們跟蹤到大約238行：
 String contentTypeName = inputName + "ContentType";
 String fileNameName = inputName + "FileName";
最終確定我們的private File file;屬性名稱可以隨便，
但是filenam和contenttype的set方法要有規(guī)定 例如：
如果private File myFile;

則對應(yīng)的其他的兩個(gè)屬性set方法如下：

public void setMyFileContentType(String contentType) {
         this.contentType = contentType;//當(dāng)然contentType可以隨便起名 最終要的是set+MyFile+ContentType方法
    }

public void setMyFileFileName(String filename) {
           this.filename = filename;/當(dāng)然filename可以隨便起名 最終要的是set+MyFile+FileName方法
       }
以下是實(shí)例：
三.需要的jar包(默認(rèn)使用commons-fileupload,如果使用cos，要將jar引進(jìn)來)

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.實(shí)例

1.首先，創(chuàng)建上傳頁面

Html代碼
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);     //我們自己重新定義的文件名，也可以直接用 uploadFileName
92.        copy(upload, imageFile);     
93.        return SUCCESS;     
94.    }     
95.    
96.}    
97
表單的enctype ="multipart/form-data，與一般的上傳一樣．

<s:file name="upload">會將upload綁定到action的upload,其次他還會將上傳記文件的MIME類型綁定到uploadContentType,文件名綁定到uploadFileName中，他們是通過

setUploadContentType和setUploadFileName進(jìn)行綁定的,下面進(jìn)行的多文件上傳也是同個(gè)道理，不過要用數(shù)組或者是list來進(jìn)行綁定，然后多個(gè)文件的MIME類型也會綁定到以數(shù)組

名字加ContentType和FileName的字符串?dāng)?shù)組中。   比如說上傳的文件的數(shù)組名為：File[] uploads,則它們的MIME類型綁定的對應(yīng)的數(shù)組是uploadsFileName和uploadsContentType.

3.struts.xml的配置

Xml代碼

Xml代碼
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代碼
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） 多文件上傳

多文件上傳
與單文件上傳相似，實(shí)現(xiàn)多文件你可以將多個(gè)<s:file />綁定Action的數(shù)組或列表。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 > 清單14 多文件上傳JSP代碼片段
如果你希望綁定到數(shù)組，Action的代碼應(yīng)類似：

     private File[] uploads;
     private String[] uploadSFileName;
     private String[] uploadSContentType;

多文件上傳數(shù)組綁定Action代碼片段
如果你想綁定到列表，則應(yīng)類似：

     private List < File > uploads ;
     private List < String > uploadSFileName ;
     private List < String > uploadSContentType ;
多文件上傳列表綁定Action代碼片段

另外是一般上傳文件的原理：當(dāng)然具體可以看http協(xié)議的rfc文檔：
關(guān)于multipart/form-data 相關(guān)資料可以看;http://www.ietf.org/rfc/rfc1867.txt 大約在[Page 1]的地方有介紹
 表單配置multipart/form-data 說明以二進(jìn)制流的方式傳輸表單字段的數(shù)據(jù)：
我們通過以下代碼看到request數(shù)據(jù)流中的內(nèi)容：

 PrintWriter out = response.getWriter();
  InputStream is = request.getInputStream();
  
  BufferedReader br = new BufferedReader(
   new InputStreamReader(is));
  String buffer = null;
  while( (buffer = br.readLine()) != null)
  {
   //在頁面中顯示讀取到的請求參數(shù)
   out.println(buffer + "<br />");
  }
out.flush();
out.close();
例如：我上傳一個(gè)文件D:\apache-tomcat-6018\bin\version.sh （tomcat版本文件）
最終頁面顯示：
-----------------------------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--
我們發(fā)現(xiàn)我們上傳的內(nèi)容在
-----------------------------7da1052ec05fe
Content-Disposition: form-data; name="ff"; filename="D:\apache-tomcat-6018\bin\version.sh"
Content-Type: text/plain和-----------------------------7da1052ec05fe--中間
因此我們可以通過以下代碼來獲取上傳內(nèi)容并保存：

//取得HttpServletRequest的InputStream輸入流
InputStream is = request.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String buffer = null;
//循環(huán)讀取請求內(nèi)容的每一行內(nèi)容
while( (buffer = br.readLine()) != null)
{
 //如果讀到的內(nèi)容以-----------------------------開始，
 //且以--結(jié)束，表明已到請求內(nèi)容尾
 if(buffer.endsWith("--") && buffer
  .startsWith("-----------------------------"))//length為29
 {
  //跳出循環(huán)
  break;
 }
 //如果讀到的內(nèi)容以-----------------------------開始，表明開始了一個(gè)表單域
 if(buffer.startsWith("-----------------------------"))
 {
  //如果下一行內(nèi)容中有filename字符串，表明這是一個(gè)文件域
  if (br.readLine().indexOf("filename") > 1)
  {
   //跳過兩行，開始處理上傳的文件內(nèi)容
   br.readLine();
   br.readLine();
   //以系統(tǒng)時(shí)間為文件名，創(chuàng)建一個(gè)新文件
   File file = new File(request.getRealPath("/")
    + System.currentTimeMillis());
                         //當(dāng)然我們可以讀取filenam來保存這里簡化
   //創(chuàng)建一個(gè)文件輸出流
   PrintStream ps = new PrintStream(new FileOutputStream(file));
   String content = null;
   //接著開始讀取文件內(nèi)容
   while( (content = br.readLine()) != null)
   {
    //如果讀取的內(nèi)容以-----------------------------開始，
    //表明開始了下一個(gè)表單域內(nèi)容
    if(content.startsWith("-----------------------------"))length為29
    {
     //跳出處理
     break;
    }
    //將讀到的內(nèi)容輸出到文件中
    ps.println(content);
   }
   //關(guān)閉輸出
   ps.flush();
   ps.close();
  }
 }
}
br.close();

關(guān)于strtus2下載:
下載最終是通過contentType和數(shù)據(jù)流將數(shù)據(jù)輸出到客戶端來實(shí)現(xiàn)，在struts中也是通過InputStream和相關(guān)的配置來實(shí)現(xiàn)：
同樣最終到strtus的下載相關(guān)的源代碼：org.apache.struts2.dispatcher.StreamResult我們看到
 
     public static final String DEFAULT_PARAM = "inputName";

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

當(dāng)然這些參數(shù)都可以在 <result  type="stream">中配置 例如;
<param name="inputPath">\uploads\document.pdf</param>
<!-- 指定下載文件的文件類型 -->
<param name="contentType">Application/pdf</param>
<!-- 指定由getTargetFile()方法返回被下載文件的InputStream -->
<param name="inputName">targetFile</param>
<param name="contentDisposition">attachment;filename="document.pdf"</param>
<!-- 指定下載文件的緩沖大小 -->
<param name="bufferSize">2048</param>
其中：
    contentType：指定被下載文件的文件類型。 application/octet-stream 默認(rèn)值，可以下載所有類型
      inputName：指定被下載文件的入口輸入流, 和DownloadAction中的getInputStream()對應(yīng),主要是獲得實(shí)際資源文件
      contentDisposition：指定下載的文件名和顯示方式,一般和文件名一致，但是要注意中文件名保存時(shí)亂碼問題，解決辦法就是進(jìn)行編碼處理
<!-- 指定由getTargetFile()方法返回被下載文件的InputStream -->
<param name="inputName">targetFile</param>
是下載的入口 我們不需要在我們的action里面配置targetFile變量 但需要getTargetFile方法，默認(rèn)需要getInputStream()方法 也就是：inputName參數(shù)的值就是入口方法去掉get前綴、首字母小寫的

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我們的action里面的代碼如下：

 private String inputPath;//通過strtus獲取文件地址 也可以直接寫例如：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);
 }
如果報(bào)以下錯(cuò)誤：
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.

實(shí)際問題是ServletActionContext.getServletContext().getResourceAsStream(inputPath);找不到資源，請檢查你的path是否正確。
而關(guān)于下載實(shí)際struts做了什么呢？我們看一部分源代碼代碼就很明白了：

  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();
        }
//-----------
很簡單，就像以前在servlet中一樣通過getOutputStream 和配置content type ，content-disposition，cache control，content length這些參數(shù)的來實(shí)現(xiàn)。

這樣就很簡單的實(shí)現(xiàn)了下載功能。
以上是自己工作之余寫的以下總結(jié)，不對的地方希望大家指點(diǎn)，謝謝，轉(zhuǎn)載，請說明地址