struts2 文件上传 和部分源代码解析，以及一般上传原理
（1） 单文件上传
一.简单介绍
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，它须要调用其它请求解析器，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应用中添加两个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。
假设要改成其他的文件上传框架，能够改动struts.multipart.parser常量的值为cos/pell，默认值是jakata。并在classpath中添加对应上传组件的类库
比如配置成cos上传
struts.multipart.parser=cos
struts.multipart.maxSize=1024 指定文件的最大字结数
二.原理
无论用common-fileUPload框架，还是用cos，都是通过将HTTP的数据保存到暂时目录。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
我们能够通过源码struts2-code-XX.jar的struts-default.xml文件找到
打开这个类的源码能够看见相关例如以下：
/**
*
*
* 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:
*
*
- *
*
- [File Name] : File - the actual File
*
*
- [File Name]ContentType : String - the content type of the file
*
*
- [File Name]FileName : String - the actual name of the file uploaded (not the HTML name)
*
*
*
也就是说我们须要三个变量File（表单的name）。其它两个參数通过set个体方法有strtus调用
接着以下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:
*
- struts.messages.error.uploading - a general error that occurs when the file could not be uploaded
*
*
- struts.messages.error.file.too.large - occurs when the uploaded file is too large
*
*
- struts.messages.error.content.type.not.allowed - occurs when the uploaded file does not match the expected
* content types specified
*
*
- struts.messages.error.file.extension.not.allowed - occurs when the uploaded file does not match the expected
* file extensions specified
*
比如struts.messages.error.content.type.not.allowed 表示文件类型错误：也就是说假设我们给拦截器配置了属性allowedTypes 比如：
image/bmp,image/png,image/gif,image/jpeg,image/jpg 可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能够在我们的资源中配置这个key：
比如：struts.messages.error.content.type.not.allowed=您上传的文件类型仅仅能为...。请又一次选择！
(当然须要)globalMessages为资源前缀，然后通过：来显示提示
*
*
- *
*
- maximumSize (optional) - the maximum size (in bytes) that the interceptor will allow a file reference to be set
* on the action. Note, this is not related to the various properties found in struts.properties.
* Default to approximately 2MB.
*
*
- 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.
*
*
- 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.
*
*
上面则是拦截器的相关參数，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：
* package com.example;
*
* import java.io.File;
* import com.opensymphony.xwork2.ActionSupport;
*
* public UploadAction extends ActionSupport {
* private File file;
* private String contentType;
* private String filename;
*
* public void setUpload(File file) {
* this.file = file;
* }
*
* public void setUploadContentType(String contentType) {
* this.contentType = contentType;
* }
*
* public void setUploadFileName(String filename) {
* this.filename = filename;
* }
*
* public String execute() {
* //...
* return SUCCESS;
* }
* }
事实上最基本的是set方法的确定：我们跟踪到大约238行：
String contentTypeName = inputName + "ContentType";
String fileNameName = inputName + "FileName";
终于确定我们的private File file;属性名称能够随便，
可是filenam和contenttype的set方法要有规定 比如：
假设private File myFile;
则相应的其它的两个属性set方法例如以下：
public void setMyFileContentType(String contentType) {
this.contentType = contentType;//当然contentType能够随便起名 终于要的是set+MyFile+ContentType方法
}
public void setMyFileFileName(String filename) {
this.filename = filename;/当然filename能够随便起名 终于要的是set+MyFile+FileName方法
}
下面是实例：
三.须要的jar包(默认使用commons-fileupload,假设使用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
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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); //我们自己又一次定义的文件名称。也能够直接用 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．
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,文件名称绑定到uploadFileName中。他们是通过
setUploadContentType和setUploadFileName进行绑定的,以下进行的多文件上传也是同个道理，只是要用数组或者是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。 比方说上传的文件的数组名为：File[] uploads,则它们的MIME类型绑定的相应的数组是uploadsFileName和uploadsContentType.
3.struts.xml的配置
Xml代码
Xml代码
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12. image/bmp,image/png,image/gif,image/jpeg,image/jpg
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16. /fileUpload.jsp
17. /showUpload.jsp
18.
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4.最后是web.xml的配置
Xml代码
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9. struts-cleanup
10.
11. org.apache.struts2.dispatcher.ActionContextCleanUp
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16. struts2
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18. org.apache.struts2.dispatcher.FilterDispatcher
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23. struts-cleanup
24. /*
25.
26.
27.
28. struts2
29. /*
30.
31.
32.
33. index.jsp
34.
35.
（2） 多文件上传
多文件上传
与单文件上传相似，实现多文件你能够将多个绑定Action的数组或列表。
例如以下例所看到的。
假设你希望绑定到数组，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
假设你想绑定到列表，则应类似：
private List uploads ;
private List uploadSFileName ;
private List 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：当然详细能够看http协议的rfc文档：
关于multipart/form-data 相关资料能够看;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：
我们通过下面代码看到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參数
out.println(buffer + "
");
}
out.flush();
out.close();
比如：我上传一个文件D:\apache-tomcat-6018\bin\version.sh （tomcat版本号文件）
终于页面显示：
-----------------------------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
因此我们能够通过下面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)
{
//假设读到的内容以-----------------------------開始。
//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;
}
//假设读到的内容以-----------------------------開始，表明開始了一个表单域
if(buffer.startsWith("-----------------------------"))
{
//假设下一行内容中有filename字符串。表明这是一个文件域
if (br.readLine().indexOf("filename") > 1)
{
//跳过两行，開始处理上传的文件内容
br.readLine();
br.readLine();
//以系统时间为文件名称，创建一个新文件
File file = new File(request.getRealPath("/")
+ System.currentTimeMillis());
//当然我们能够读取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;
//接着開始读取文件内容
while( (content = br.readLine()) != null)
{
//假设读取的内容以-----------------------------開始。
//表明開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里
ps.println(content);
}
//关闭输出
ps.flush();
ps.close();
}
}
}
br.close();
关于strtus2下载:
下载终于是通过contentType和数据流将数据输出到client来实现。在struts中也是通过InputStream和相关的配置来实现：
相同终于到strtus的下载相关的源码：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;
当然这些參数都能够在 中配置 比如;
\uploads\document.pdf
Application/pdf
targetFile
attachment;filename="document.pdf"
2048
当中：
contentType：指定被下载文件的文件类型。 application/octet-stream 默认值，能够下载全部类型
inputName：指定被下载文件的入口输入流, 和DownloadAction中的getInputStream()相应,主要是获得实际资源文件
contentDisposition：指定下载的文件名称和显示方式,一般和文件名称一致，可是要注意中文件名称保存时乱码问题，解决的方法就是进行编码处理
targetFile
是下载的入口 我们不须要在我们的action里面配置targetFile变量 但须要getTargetFile方法。默认须要getInputStream()方法 也就是：inputName參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里面的代码例如以下：
private String inputPath;//通过strtus获取文件地址 也能够直接写比如：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);
}
假设报下面错误：
Can not find a java.io.InputStream with the name [targetFile] in the invocation stack. Check the 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？我们看一部分源码代码就非常明确了：
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();
}
//-----------
非常easy。就像曾经在servlet中一样通过getOutputStream 和配置content type ，content-disposition，cache control。content length这些參数的来实现。
这样就非常easy的实现了下载功能。
以上是自己工作之余写的下面总结，不正确的地方希望大家指点，谢谢，转载。请说明地址
很多其它详情