轉 [JAVA] 使用 common-fileupload 實現文件上傳

就在前段時間，還在苦於找到不到合適的上傳組件，雖然很早就知道了 common-fileupload，但當時卻因為沒有找到如何獲取表單參數的方法而使用 jspSmartUpload，歷盡艱辛終於找到了它的 jar，可是使用后才發現此東西對中文參數支持奇差，甚至需要修改源代碼才能解決問題，可是jspSmartUpload並不是開源的項目，而且開發團隊也不再對它進行更新，連官方網站都關門大吉了，情急之下使用JadClipse 反編譯了它的jar包，原以為問題算是得到解決了，誰知道后來卻發現獲取到的參數經常出現部分中文亂碼，而且還不是固定的漢字出現亂碼，仔細研究加Google后才找出了規律，原來是奇數字數的中文會出現亂碼，而偶數字數的則正常，閱讀了源代碼，終於還是沒耐心閱讀下去，而且看到網上還有評論說該組件有內存泄露的問題，於是才下定決定搞定common-fileupload。

於是從 http://jakarta.apache.org/commons/fileupload/ 下載到了最新版的 FileUpload 1.2，閱讀了部分文檔跟例子，終於找到了獲取表單中參數的方法並對該組件做了進一點封裝，使其更容易使用，並支持單文件上傳和多文件上傳兩種方式，首先定義一個基類放置公共屬性：

FileUploadBase.java

import java.io.File;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;

publicabstractclass FileUploadBase {
protected Map<String, String> parameters =new HashMap<String, String>();// 保存普通form表單域

protected String encoding ="utf-8"; // 字符編碼，當讀取上傳表單的各部分時會用到該encoding

protected UploadFileFilter filter =null; // 文件過濾器, 默認為NULL 不過濾

/** *//**
* The directory in which uploaded files will be stored, if stored on disk.
*/
protectedint sizeThreshold = DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD;

/** *//**
*
* The maximum size permitted for the complete request, as opposed to
*
* {@link #fileSizeMax}. A value of -1 indicates no maximum.
*
*/
protectedlong sizeMax =-1;

/** *//**
* The directory in which uploaded files will be stored, if stored on disk.
*/
protected File repository;

public String getParameter(String key) {
return parameters.get(key);
}

public String getEncoding() {
return encoding;
}

publicvoid setEncoding(String encoding) {
this.encoding = encoding;
}

/** *//**
* 獲取上傳文件最大的大小，單位為Byte(字節），為-1時表示無限制
* @return
*/
publiclong getSizeMax() {
return sizeMax;
}

/** *//**
* 設置上傳文件最大的大小，單位為Byte(字節），為-1時表示無限制
* @param sizeMax
*/
publicvoid setSizeMax(long sizeMax) {
this.sizeMax = sizeMax;
}

publicint getSizeThreshold() {
return sizeThreshold;
}

publicvoid setSizeThreshold(int sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}

/** *//**
* Returns the directory used to temporarily store files that are larger
* than the configured size threshold.
*
* @return The directory in which temporary files will be located.
*
* @see #setRepository(java.io.File)
*
*/
public File getRepository() {
return repository;
}

/** *//**
* Sets the directory used to temporarily store files that are larger than
* the configured size threshold.
*
* @param repository
* The directory in which temporary files will be located.
*
* @see #getRepository()
*
*/
publicvoid setRepository(File repository) {
this.repository = repository;
}

/** *//**
* 獲取參數列表
* @return
*/
public Map<String, String> getParameters() {
return parameters;
}

/** *//**
* 獲取過濾器
* @return
*/
public UploadFileFilter getFilter() {
return filter;
}

/** *//**
* 設置文件過濾器，不符合過濾器規則的將不被上傳
* @param filter
*/
publicvoid setFilter(UploadFileFilter filter) {
this.filter = filter;
}

/** *//**
* 驗證文件是否有效
* @param item
* @return
*/
protectedboolean isValidFile(FileItem item){
return item ==null|| item.getName() ==""|| item.getSize() ==0|| (filter !=null&&!filter.accept(item.getName())) ?false : true;
}
}

支持單文件上傳的 SingleFileUpload 類：
SingleFileUpload.java

import java.io.File;
import java.io.UnsupportedEncodingException;
import java.util.List;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

publicclass SingleFileUpload extends FileUploadBase {
private FileItem fileItem;

/** *//**
*
* @param request
* @throws UnsupportedEncodingException
*/
publicvoid parseRequest(HttpServletRequest request)
throws UnsupportedEncodingException {

DiskFileItemFactory factory =new DiskFileItemFactory();

factory.setSizeThreshold(sizeThreshold);

if (repository !=null)
factory.setRepository(repository);

ServletFileUpload upload =new ServletFileUpload(factory);

upload.setHeaderEncoding(encoding);

try{
List<FileItem> items = upload.parseRequest(request);

for (FileItem item : items) {
if (item.isFormField()) {
String fieldName = item.getFieldName();
String value = item.getString(encoding);
parameters.put(fieldName, value);
}else{

if (!super.isValidFile(item)) {
continue;
}

if (fileItem ==null)
fileItem = item;
}
}

}catch (FileUploadException e) {
e.printStackTrace();
}
}

/** *//**
* 上傳文件, 調用該方法之前必須先調用 parseRequest(HttpServletRequest request)
* @param fileName 完整文件路徑
* @throws Exception
*/
publicvoid upload(String fileName) throws Exception {
File file =new File(fileName);
uploadFile(file);
}

/** *//**
* 上傳文件, 調用該方法之前必須先調用 parseRequest(HttpServletRequest request)
* @param parent 存儲的目錄
* @throws Exception
*/
publicvoid upload(File parent) throws Exception {
if (fileItem ==null)
return;

String name = fileItem.getName();
File file =new File(parent, name);
uploadFile(file);
}

privatevoid uploadFile(File file) throws Exception{
if (fileItem ==null)
return;

long fileSize = fileItem.getSize();
if (sizeMax >-1&& fileSize >super.sizeMax){
String message = String.format("the request was rejected because its size (%1$s) exceeds the configured maximum (%2$s)", fileSize, super.sizeMax);

thrownew org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException(message, fileSize, super.sizeMax);
}

String name = fileItem.getName();
fileItem.write(file);
}

/** *//**
* 獲取文件信息
* 必須先調用 parseRequest(HttpServletRequest request)
* @return
*/
public FileItem getFileItem() {
return fileItem;
}
}

支持多文件上傳的 MutiFileUpload 類：
MutiFileUpload.java

import java.io.File;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.fileupload.FileItem;
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;

publicclass MutiFileUpload extends FileUploadBase {

private Map<String, FileItem> files;// 保存上傳的文件
privatelong filesSize =0; // 所有文件的總大小


publicvoid parseRequest(HttpServletRequest request)
throws UnsupportedEncodingException {

files =new HashMap<String, FileItem>();

// Create a factory for disk-based file items

DiskFileItemFactory factory =new DiskFileItemFactory();

factory.setSizeThreshold(sizeThreshold);

if (repository !=null)
factory.setRepository(repository);

ServletFileUpload upload =new ServletFileUpload(factory);

upload.setHeaderEncoding(encoding);

try{
List<FileItem> items = upload.parseRequest(request);

for (FileItem item : items) {
if (item.isFormField()) {
String fieldName = item.getFieldName();
String value = item.getString(encoding);
parameters.put(fieldName, value);
}else{

if (super.isValidFile(item)) {
continue;
}

String fieldName = item.getFieldName();

files.put(fieldName, item);
filesSize += item.getSize();
}
}

}catch (FileUploadException e) {
e.printStackTrace();
}
}

/** *//**
* 上傳文件, 調用該方法之前必須先調用 parseRequest(HttpServletRequest request)
* @param parent 文件存儲的目錄
* @throws Exception
*/
publicvoid upload(File parent) throws Exception {
if (files.isEmpty())
return;

if (sizeMax >-1&& filesSize >super.sizeMax){
String message = String.format("the request was rejected because its size (%1$s) exceeds the configured maximum (%2$s)", filesSize, super.sizeMax);

thrownew SizeLimitExceededException(message, filesSize, super.sizeMax);
}

for (String key : files.keySet()) {
FileItem item = files.get(key);
String name = item.getName();

File file =new File(parent, name);
item.write(file);
}
}

public Map<String, FileItem> getFiles() {
return files;
}

}

當然還少不了過濾器 UploadFileFilter：
UploadFileFilter.java

publicinterface UploadFileFilter {
/** *//**
* 通過文件名后綴判斷文件是否被接受
* @param filename 文件名，不包括路徑
* @return
*/
publicboolean accept(String filename);
}

這樣在 Servlet 中我們就可以通過簡單的代碼實現文件的上傳了：

SingleFileUpload upload =new SingleFileUpload();
upload.parseRequest(request);
File parent =new File("C:\\upload\\");

try{
upload.upload(parent);
}
catch(org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException e){
// 文件大小超出最大值
e.printStackTrace();
}catch (Exception e) {
e.printStackTrace();
}

相比 jspSmartUpload 我覺得 common-fileupload 有如下的優點：
1、開源；
2、Jakarta項目組的支持，開發十分活躍，而 jspSmartUpload 則已經停止開發了；
3、不需要寫入文件之前即可獲取到參數和文件信息，jspSmartUpload 則需要在獲取之前調用 upload 方法；
4、對中文支持友好。

轉自：http://www.cnblogs.com/yyw84/archive/2007/06/27/797652.html