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文件上传原理实现

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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

（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。

（二）实现

1、规则: 1.1 上传数据块的分割规则; 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。; 1.4 小结

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); } }

（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

【上篇】4英寸触摸屏诺基亚MeeGo手机平板曝光
【下篇】关于MFC中回车关闭对话框的问题的解决

作者: conveying

该日志由 conveying 于11年前发表在综合分类下，最后更新于 2013年08月05日.
转载请注明: 文件上传原理实现 | 学步园 +复制链接

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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)

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