commons-fileupload上传组件学习记录
????? 最近在用commons-fileupload做文件上传的时候遇到了一点小的麻烦，不过最终在学友的帮助下解决，在写之前先说明一下几个错误，在群里面问了上传页面中file选择框的name是否可以相同，很多人说name是不能相同的，不然就不知道是哪个上传的了，这种理解是错误的：
普通表单项name可以相同，在后台接收的时候就用String[]，而且在Struts2中我们也看到，在页面中相同名字的file框name在Action中用File[] 接收，通过这两点分析，以及之后的实验发现，name完全可以相同，下面的FileItem分析也可以说明这一点
?先贴一下FileUpload的工具类，这是做了一个封装：
import java.io.File;import java.io.UnsupportedEncodingException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.TreeMap;import javax.servlet.http.HttpServletRequest;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUpload;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;public class FileUploadUtil {private Map fileField = new TreeMap(); private Map formField = new TreeMap(); private List<FileItem> list=new ArrayList<FileItem>();private int memoryBlock = 2048; private File tempFolder = null; private boolean multipart = false; private HttpServletRequest request = null; private final int maxSize = (int) Common.getByteSizeByBKMG(JavaCenterHome.jchConfig.get("upload_max_filesize")); public FileUploadUtil(File tempFolder, int memeoryBlock) {this.tempFolder = tempFolder;this.memoryBlock = memeoryBlock;}public FileUploadUtil() {}public void parse(HttpServletRequest request, String charset) throws FileUploadException {this.request = request;multipart = FileUpload.isMultipartContent(request);if (multipart) {DiskFileItemFactory factory = new DiskFileItemFactory();factory.setSizeThreshold(memoryBlock);factory.setRepository(tempFolder);ServletFileUpload upload = new ServletFileUpload(factory);upload.setSizeMax(maxSize);List items;items = upload.parseRequest(request);Iterator iterator = items.iterator();while (iterator.hasNext()) {FileItem item = (FileItem) iterator.next();if (item.isFormField()) {processFormField(item, charset);} else {processUploadedFile(item);}}}}private void processFormField(FileItem item, String charset) {try {String name = item.getFieldName();String value = item.getString(charset);Object objv = formField.get(name);if (objv == null) {formField.put(name, value);} else {List values = null;if (objv instanceof List) {values = (List) objv;values.add(value);} else {String strv = (String) objv;values = new ArrayList();values.add(strv);values.add(value);}formField.put(name, values);}} catch (UnsupportedEncodingException e) {throw new IllegalArgumentException("the argument "charset" missing!");}}private void processUploadedFile(FileItem item) {String name = item.getFieldName();long size=item.getSize();if(size>0)list.add(item);fileField.put(name, list);}public static boolean write2file(FileItem item, File file) {boolean flag = false;try {item.write(file);flag = true;} catch (Exception e) {}return flag;}public List<FileItem> getFileItemList(String name) {if (multipart) {return (List<FileItem>) fileField.get(name);} else {return null;}}public String getParameter(String name) {String value = null;if (multipart) {Object obj = formField.get(name);if (obj != null && obj instanceof String) {value = (String) obj;}} else if (request != null) {value = request.getParameter(name);}return value;}public String[] getParameterValues(String name) {String[] values = null;if (multipart) {Object obj = formField.get(name);if (obj != null) {if (obj instanceof List) {values = (String[]) ((List) obj).toArray(new String[0]);} else {values = new String[] {(String) obj};}}} else if (request != null) {values = request.getParameterValues(name);}return values;}public File getRepository() {return this.tempFolder;}public int getSizeThreshold() {return this.memoryBlock;}public boolean isMultipart() {return this.multipart;}public int getMaxSize() {return maxSize;}}?
这个工具类有改动，之前没考虑到多文件上传，在Map只是这样存：
String name = item.getFieldName();fileField.put(name, item);
这样有二点缺点：
1、如果name相同的话，前面上传的文件就会被后面上传的文件覆盖
2、如果上传文件的size为0，并且在最后面，那么最终fileFiled存放的是一个size为0的FilteItem这显然是无效的
?
上面最后改进后，对于多文件上传也可以起作用了。
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下面来分析一下，这句话后,items中存的东西是怎样的：
List items;items = upload.parseRequest(request);
?上面的意思是解析request，下面来看在我项目中一个表单提交后得到的装有FileItem的List
[name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000054.tmp, size=1bytes, isFormField=true, FieldName=productcategory_id, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000055.tmp, size=0bytes, isFormField=true, FieldName=self_type_id, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000056.tmp, size=0bytes, isFormField=true, FieldName=brand_id, name=null,StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000057.tmp, size=18bytes, isFormField=true, FieldName=name, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000058.tmp, size=2bytes, isFormField=true, FieldName=productsn, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000059.tmp, size=1bytes, isFormField=true, FieldName=price, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000060.tmp, size=1bytes, isFormField=true, FieldName=marketprice, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000061.tmp, size=1bytes, isFormField=true, FieldName=weight, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000062.tmp, size=1bytes, isFormField=true, FieldName=weightunit, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000063.tmp, size=1bytes, isFormField=true, FieldName=base_sale_num, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000064.tmp, size=1bytes, isFormField=true, FieldName=product_unit, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000065.tmp, size=1bytes, isFormField=true, FieldName=store, name=http_imgloadCAEP58ES.jpg, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000066.tmp, size=141869bytes, isFormField=false, FieldName=productImages, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000067.tmp, size=16bytes, isFormField=true, FieldName=productImageParameterTypes, name=http_imgloadCAFH1MHX.jpg, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000068.tmp, size=70138bytes, isFormField=false, FieldName=productImages, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000069.tmp, size=16bytes, isFormField=true, FieldName=productImageParameterTypes, name=, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000070.tmp, size=0bytes, isFormField=false, FieldName=productImages, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000071.tmp, size=44bytes, isFormField=true, FieldName=description, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000072.tmp, size=0bytes, isFormField=true, FieldName=producttype_id, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000073.tmp, size=1bytes, isFormField=true, FieldName=valid_date, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000074.tmp, size=1bytes, isFormField=true, FieldName=ismarketable, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000075.tmp, size=1bytes, isFormField=true, FieldName=isbest, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000076.tmp, size=1bytes, isFormField=true, FieldName=isnew, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000077.tmp, size=1bytes, isFormField=true, FieldName=ishot, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000078.tmp, size=0bytes, isFormField=true, FieldName=metakeywords, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000079.tmp, size=0bytes, isFormField=true, FieldName=metadescription, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000080.tmp, size=8bytes, isFormField=true, FieldName=formhash, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000081.tmp, size=0bytes, isFormField=true, FieldName=id, name=null, StoreLocation=D:\Tomcat 6.0.20\webapps\JavaCenterHome\.\data\temp\upload_365228b4_12f048b1396__8000_00000082.tmp, size=1bytes, isFormField=true, FieldName=productsubmit]
?上面每一行就是一个FiteItem中的内容，也就是说使用commons-fileupload上传组件后，对于表单中的每一项它都会解析后构造成一个个的FileItem，我们只要操作这写FileItem就行了。
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