文件上传原理实现

文件上传原理实现

客户端浏览器是怎样上传数据的呢？服务器端如何接收上传的文件数据？

级别： 初级

王延成 (王延成), 作者/编者, 

2004 年 9 月 01 日

文章主要描述http表单上传二进制数据流规范的简单实现

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（一）关于Form表单上传文件规范

  总结个人在对新技术、新事物的学习和解决问题的过程，深刻体会到多理解掌握技术基础理论知识再加上相应的实践，的确能帮助我们在解决某些问题的时候起到事半功倍的效果。

以前上传文件类似的功能都是采用第三方组件来做的，真的是基于接口编程了。不出问题还好，真要是出现问题解决起来太不舒服了，往往属于那种拆了西墙补东墙的策略。最近，在做文件上传时学习了一些 关于html>form上传数据的格式规范，依据人家定义的规范做了一些简单的工作。。。算是实现了个小轮子吧。

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（二）实现

1、规则

1.1 上传数据块的分割规则

基于html form表单上传的数据都是以类似-----------------------------7da3c8e180752{0x130x10}这样的分割符来标记一块数据的起止，可不要忘记后面的两个换行符。关于换行符有三种，如下：

操作系统	换行符描述	原始标记	ascii码	十六进制
Window	Window的换行符是两个	//r//n	1310	0x0d0x0a
Unix	Unix的换行符是一个	//n	10	0x0a
Mac OS	Mac OS的换行符是一个	//r	13	0x0d
这块没有对Unix、MacOS上做测试，只在Window上测试了换行是两个(0x0d0x0a)

1.2 注意在后台从request中取得分割串少两个 --，在看下面的原始数据你会发现流的最后是以 --结束的。

1.3 上传的原始数据串，本来中文字符是乱码的。为了清晰一些使用字符集UTF-8转了下码。

-----------------------------7da3c8e180752 Content-Disposition: form-data; name="fileData1"; filename="C:/abcdef.log" Content-Type: application/octet-stream HelloWorld HelloWorld -----------------------------7da3c8e180752 Content-Disposition: form-data; name="fileData2"; filename="C:/deleteThumb.bat" Content-Type: application/octet-stream FOR %%a IN ( C: D: E: F: ) DO DEL /f/s/q/a %%a/Thumbs.db -----------------------------7da3c8e180752 Content-Disposition: form-data; name="textAreaContent" HelloWorld -----------------------------7da3c8e180752 Content-Disposition: form-data; name="id" 文件编码 -----------------------------7da3c8e180752 Content-Disposition: form-data; name="name" 文件名称 -----------------------------7da3c8e180752--

1.4 小结

基于1.3小节可以非常容易总结归纳出html-->form元素内容。有两个文件类型元素，三个text元素(其中一个元素是textarea)

2、操作顺序流程描述

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3、实现代码

需要明确注意的一个问题是关于request.getInputStream();获取请求体数据流不可用的问题，见示例代码： 

/*我是这么认为的在获取流之前，已经通过第三方应用服务器相关对ServletRequest接口实现解析过流了，所以我们再次取请求流内容时会有问题。。在参与.NET设备与JavaWeb交互时也遇到过此类型的问题。*/ /*这就要求我们如果是自己解析request流内容数据，在解析之前不可以调用getParameter(String paramName)相关的需要用到解析流的行为方法。*/ /*以上仅个人理解、个人意见，如有不对请多多指正。*/ request.getParameter("USER_CODE"); InputStream ins = request.getInputStream(); byte[] buff = new byte[1024]; int count = -1; while ((count = ins.read(buff))!=-1) { System.out.println(new String(buff,0, count, "UTF-8")); }

3.1、类图

3.2、代码内容

入口Servlet

package org.ybygjy.web; import java.io.IOException; import java.util.Iterator; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.ybygjy.web.comp.FileItem; import org.ybygjy.web.comp.FileMgrComp; import org.ybygjy.web.utils.WrapperRequest; /** * 处理基于WebHttp的请求/响应 * @author WangYanCheng * @version 2010-1-10 */ public class Servlet extends HttpServlet { /** default serial */ private static final long serialVersionUID = 1L; /** * {@inheritDoc} */ public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); List<FileItem> fileItemArr = null; String contentType = request.getContentType(); if (null != contentType && contentType.startsWith(WrapperRequest.ContentType.FORM_DATA.getType())) { fileItemArr = new FileMgrComp().doAnalyse(WrapperRequest.getInstance(request), response); for (Iterator<FileItem> iterator = fileItemArr.iterator(); iterator.hasNext();) { System.out.println(iterator.next()); } } } }  

工具类

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package org.ybygjy.web.utils; import javax.servlet.http.HttpServletRequest; /** * RequestUtils * @author WangYanCheng * @version 2010-1-10 */ public class WrapperRequest { /**ContentType*/ public enum ContentType { /**MIME类型-二进制数据标记*/ FORM_DATA("multipart/form-data"), /**MIME类型-标准编码格式标记*/ FORM_URLENCODE("application/x-www-form-urlencoded"), /**MIME类型-文本格式标记*/ FORM_TEXT("text/plain"); /**inner type*/ private final String type; /** * Constructor * @param str type */ private ContentType(String str) { this.type = str; } /** * getter Type * @return type */ public String getType() { return this.type; } } /**ContentType*/ private String contentType; /**request*/ private HttpServletRequest request = null; /** * Constructor * @param request request */ private WrapperRequest(HttpServletRequest request) { this.request = request; } /** * getInstance * @param request request * @return wrapperRequest */ public static final WrapperRequest getInstance(HttpServletRequest request) { return new WrapperRequest(request); } /** * get no wrapper Request * @return request request/null */ public HttpServletRequest getRequest() { return this.request; } /** * getContentType * @return contentTypeStr/null */ public String getContentType() { if (null == this.contentType) { this.contentType = null == this.request ? null : this.request.getContentType(); } return this.contentType; } /** * 是否二制数据格式 * @return true/false */ public boolean isBinaryData() { boolean rtnBool = false; String tmpStr = getContentType(); if (tmpStr.contains(ContentType.FORM_DATA.getType())) { rtnBool = true; } return rtnBool; } /** * 取得内容界定符 * @return rtnStr/null */ public String getBoundary() { String rtnStr = null; String tmpType = getContentType(); if (null != tmpType) { rtnStr = tmpType.matches("^[//s//S]*boundary=[//s//S]*$") ? tmpType.split("boundary=")[1] : null; } return "--".concat(rtnStr); } /** * 测试入口 * @param args 参数列表 */ public static void main(String[] args) { // WrapperRequest.ContentType[] cts = WrapperRequest.ContentType.values(); // for (WrapperRequest.ContentType ct : cts) { // System.out.println(ct.getType()); // } // System.out.println(WrapperRequest.getInstance(null).getBoundary()); /*Matcher matcher = Pattern.compile("(//s)+").matcher("分/n/r割符"); while (matcher.find()) { int count = matcher.groupCount(); for (int i = 0; i < count; i++) { byte[] tmpByte = matcher.group(i).getBytes(); for (int tmpI : tmpByte) { System.out.print(tmpI); } } }*/ WrapperRequest wpInst = WrapperRequest.getInstance(null); wpInst.getBoundary(); } }  

基础实现

package org.ybygjy.web.comp; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import org.ybygjy.web.utils.FileUtils; /** * 负责文件的存储解析 * @author WangYanCheng * @version 2010-08-31 */ public class FileItem { /** 源文件路径 */ private String srcFilePath; /** 源文件全名称 */ private String srcFileFullName; /** 源文件名称 */ private String srcFileName; /** 文件转储路径 */ private String filePath; /** 文件名称 */ private String fileName; /** 文件全名称 */ private String fileFullName; /** 上传文件参数名称 */ private String paramName; /** MIME Type */ private String mimeType; /** 分割串 */ private String boundaryStr; /** * Constructor * @param paramStr 参数名称 * @param fileStr 源文件地址串 * @param mimeType MIMEType * @param boundaryStr 分割约束 */ public FileItem(String paramStr, String fileStr, String mimeType, String boundaryStr) { String[] tmpStrArr = paramStr.split("="); this.setParamName(tmpStrArr[1].substring(1, tmpStrArr[1].length() - 1)); tmpStrArr = fileStr.split("="); this.setSrcFilePath(tmpStrArr[1].substring(1, tmpStrArr[1].length() - 1)); this.setMIME(mimeType); this.setBoundaryStr(boundaryStr); } /** * setFilePath * @param filePath filePath */ public void setSrcFilePath(String filePath) { this.srcFilePath = filePath; if (this.srcFilePath != null && filePath.length() > 0) { this.srcFileFullName = new File(this.srcFilePath).getName(); this.srcFileName = this.srcFileFullName.substring(0, this.srcFileFullName.indexOf('.')); } } /** * setMIME * @param mimeType mimeType */ public void setMIME(String mimeType) { this.mimeType = mimeType; } /** * getMIME * @return mimeType mimeType */ public String getMIME() { return this.mimeType; } /** * setBoundary * @param boundaryStr the boundaryStr to set */ public void setBoundaryStr(String boundaryStr) { this.boundaryStr = boundaryStr; } /** * setParamName * @param paramName paramName */ public void setParamName(String paramName) { this.paramName = paramName; } /** * getParamName * @return paramName */ public String getParamName() { return this.paramName; } /** * 源上传文件全名称 * @return the srcFileName */ public String getSrcFileFullName() { return srcFileFullName == null ? null : srcFileFullName.length() == 0 ? null : this.srcFileFullName; } /** * 源上传文件名称 * @return the srcFileName */ public String getSrcFileName() { return srcFileName; } /** * 文件存储路径 * @return the filePath */ public String getFilePath() { return filePath; } /** * 取文件名称 * @return the fileName */ public String getFileName() { return fileName; } /** * 取文件全名称 * @return the fileFullName */ public String getFileFullName() { return fileFullName; } /** * 转储文件 * @param ins ins * @throws IOException IOException */ public void doStoreFile(InputStream ins) throws IOException { String id = String.valueOf(System.currentTimeMillis()); File tmpFile = new File(FileUtils.getTmpFilePath(), id); this.filePath = tmpFile.getPath(); this.fileFullName = tmpFile.getName(); this.fileName = id; BufferedOutputStream bos = null; try { bos = new BufferedOutputStream(new FileOutputStream(tmpFile)); this.doStoreFile(ins, bos); } catch (IOException ioe) { throw ioe; } finally { try { bos.close(); } catch (IOException ioe) { ioe.printStackTrace(); } } } /** * 存储文件 * @param ins ins * @param bos bos * @throws IOException IOException */ private void doStoreFile(InputStream ins, OutputStream bos) throws IOException { byte[] byteArr = new byte[this.boundaryStr.getBytes().length]; try { int tmpI = -1; int tmpL = -1; ins.skip(2); while (((tmpI = ins.read()) != -1)) { if (13 == tmpI) { tmpL = ins.read(); if (10 == tmpL && isBoundary(ins, byteArr)) { break; } else { bos.write(tmpI); bos.write(tmpL); if (10 == tmpL) { bos.write(byteArr); } continue; } } bos.write(tmpI); } bos.flush(); } catch (IOException ioe) { throw ioe; } } /** * 检验是否边界 * @param ins ins * @param byteArr byteArr * @return true/false * @throws IOException IOException */ private boolean isBoundary(InputStream ins, byte[] byteArr) throws IOException { if (null == this.boundaryStr) { return false; } boolean rtnFlag = false; int count = ins.read(byteArr); if (count != -1) { String str = new String(byteArr, 0, count); if (this.boundaryStr.equals(str)) { rtnFlag = true; } byteArr = str.getBytes(); } return rtnFlag; } @Override public String toString() { StringBuilder builder = new StringBuilder(); builder.append("FileItem [boundaryStr="); builder.append(boundaryStr); builder.append(", fileFullName="); builder.append(fileFullName); builder.append(", fileName="); builder.append(fileName); builder.append(", filePath="); builder.append(filePath); builder.append(", mimeType="); builder.append(mimeType); builder.append(", paramName="); builder.append(paramName); builder.append(", srcFileName="); builder.append(srcFileFullName); builder.append(", srcFilePath="); builder.append(srcFilePath); builder.append("]"); return builder.toString(); } }  

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package org.ybygjy.web.comp; import java.io.BufferedInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.UnsupportedEncodingException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.ybygjy.web.utils.WrapperRequest; /** * 负责对文件实体进行的操作 * @author WangYanCheng * @version 2010-8-27 */ public class FileMgrComp { /** serialNumber */ private static final long serialVersionUID = 5563862601527965192L; /** boundaryStr */ private String boundaryStr; /** ifcArray */ private List<FileItem> ifcArray; /** * Constructor */ public FileMgrComp() { ifcArray = new ArrayList<FileItem>(); } /** * doService * @param wrRequest wrRequest * @param response response * @return rtnList rtnList/null * @throws IOException IOException */ public List<FileItem> doAnalyse(WrapperRequest wrRequest, HttpServletResponse response) throws IOException { doInnerTest(wrRequest.getRequest()); List<FileItem> fileArr = null; if (wrRequest.isBinaryData()) { this.boundaryStr = wrRequest.getBoundary(); if (null != boundaryStr) { fileArr = doAnalyseBinaryData(wrRequest); } } return fileArr; } /** * 分析存储二进制数据 * @param wrRequest wrRequest * @return fileItemArr fileItemArr */ private List<FileItem> doAnalyseBinaryData(WrapperRequest wrRequest) { BufferedInputStream bins = null; ByteArrayOutputStream baos = new ByteArrayOutputStream(); try { bins = new BufferedInputStream(wrRequest.getRequest().getInputStream()); int tmpI = -1; int tmpL = -1; while ((tmpI = bins.read()) != -1) { if (tmpI == 13) { tmpL = (bins.read()); if (tmpL == 10) { if (baos.size() == 0) { continue; } FileItem fi = analyseFileInput(baos, bins); if (fi != null) { ifcArray.add(fi); } baos.reset(); continue; } baos.write(tmpI); baos.write(tmpL); } baos.write(tmpI); } } catch (IOException ioe) { ioe.printStackTrace(); } finally { if (null != bins) { try { baos.close(); bins.close(); } catch (IOException e) { e.printStackTrace(); } } } return this.getIfcArray(); } /** * 解析验证上传内容是否文件类型 * @param os outStream * @param ins insStream * @return ifcInst ifcInst/null */ private FileItem analyseFileInput(ByteArrayOutputStream os, InputStream ins) { String tmpStr = null; try { tmpStr = os.toString("UTF-8"); } catch (UnsupportedEncodingException e1) { e1.printStackTrace(); } FileItem ifcIns = null; if (tmpStr.indexOf("filename") != -1) { String[] tmpStrArr = tmpStr.split(";"); if (tmpStrArr.length > 2) { // 取MIME文件类型 ByteArrayOutputStream baos = new ByteArrayOutputStream(); try { doRead(ins, baos); tmpStr = baos.toString(); if (tmpStr.startsWith("Content-Type:")) { ifcIns = new FileItem(tmpStrArr[1].trim(), tmpStrArr[2].trim(), tmpStr.split(":")[1].trim(), this.boundaryStr); if (ifcIns.getSrcFileFullName() != null) { ifcIns.doStoreFile(ins); } } } catch (IOException e) { e.printStackTrace(); } finally { try { baos.close(); } catch (IOException ioe) { ioe.printStackTrace(); } } } } return ifcIns; } /** * doRead * @param ins ins * @param baos baos * @throws IOException IOException */ private void doRead(InputStream ins, ByteArrayOutputStream baos) throws IOException { int tmpI = -1; while ((tmpI = ins.read()) != -1) { if (tmpI == 13) { tmpI = ins.read(); if (tmpI == 10) { break; } else { baos.write(13); baos.write(tmpI); continue; } } baos.write(tmpI); } } /** * getIfcArray * @return the ifcArray */ public List<FileItem> getIfcArray() { return ifcArray; } /** * innerTest * @param request request */ private void doInnerTest(HttpServletRequest request) { Map<String, Object> testInfo = new HashMap<String, Object>(); testInfo.put("AuthType", request.getAuthType()); testInfo.put("CharacterEncoding", request.getCharacterEncoding()); testInfo.put("ContentLength", request.getContentLength()); testInfo.put("ContentType", request.getContentType()); testInfo.put("ContextPath", request.getContextPath()); testInfo.put("HeaderNames", request.getHeaderNames()); testInfo.put("LocalAddr", request.getLocalAddr()); testInfo.put("LocalName", request.getLocalName()); testInfo.put("PathInfo", request.getPathInfo()); testInfo.put("RequestedSessionId", request.getRequestedSessionId()); testInfo.put("UserPrincipal", request.getUserPrincipal()); org.ybygjy.test.TestUtils.doPrint(testInfo); } } 

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（三）资源

示例代码下载

下载示例代码

资料

搜集文件上传原理

表单规范

1、http://www.ietf.org:80/rfc/rfc1867.txt

2、http://www.ietf.org:80/rfc/rfc2045.txt

3、http://www.iana.org:80/assignments/character-sets

4、http://www.htmlhelp.com/reference/html40/forms/form.html

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