1. commons-fileupload框架源碼解析(一)--實例
2. commons-fileupload框架源碼解析(二)--HTTP
3. commons-fileupload框架源碼解析（三）--ParseRequest
4. commons-fileupload框架源碼解析（四）--FileItemIterator
5. commons-fileupload框架源碼解析（五）--MultipartStream
6. commons-fileupload框架源碼解析（六）--ParameterParser
7. commons-fileupload框架源碼解析（七）--FileCleaningTracker
8. commons-fileupload框架源碼解析（八）--DeferredFileOutputStream

前言

commons-fileupload雖然我經(jīng)常會在項目里用的弄贿，它有非常強大的文件上傳功能翎承，雖然經(jīng)常用响鹃，卻不曾了解過其源碼的實現(xiàn)亮垫，為了讓自己更加牛B，更好的掌握文件上傳的原理和具體實現(xiàn)方式谍倦，我開始了長達一個月的解析該框架源碼的工作瘦锹，總算將框架的實現(xiàn)原理給摸清悉患。是時候?qū)懸幌盗胁┛蛠硌bB,comons-fileupload的版本是1.4

第一章簡介

第一章的我并不是馬上講起原理季俩，而是直接我的用例展現(xiàn)出來，我打算通過該用例去解析其原理翎卓。

用例

只是一個普通的JavaWeb項目，代碼的實現(xiàn)都在FileUploadServlet里

目錄結(jié)構(gòu)截圖

項目目錄結(jié)構(gòu).png

pom.xml

  <dependency>
          <groupId>commons-fileupload</groupId>
          <artifactId>commons-fileupload</artifactId>
          <version>1.4</version>
      </dependency>

FileUploadServlet

package bin.study;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.Iterator;
import java.util.List;

/**
 * 實現(xiàn)文件上傳的Servlet
 * @author Administrator
 *
 */
public class FileUploadServlet extends HttpServlet {


    //上傳路徑
    private File uploadPath;


    //當文件過大時偶房，需要設置一個臨時路徑
    private File tempPath;


    public void doPost(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {

        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 內(nèi)存存儲的最大值
        factory.setSizeThreshold(4096);

        factory.setRepository(tempPath);

        ServletFileUpload upload = new ServletFileUpload(factory);
        //設置文件上傳大小
        upload.setSizeMax(1000000 * 20);
        try {
            List fileItems = upload.parseRequest(req);
            String itemNo = "";
            for (Iterator iter = fileItems.iterator(); iter.hasNext(); ) {
                FileItem item = (FileItem) iter.next();

                //是普通的表單輸入域
                if (item.isFormField()) {
                    if ("itemNo".equals(item.getFieldName())) {
                        itemNo = item.getString();
                    }
                }
                //是否為input="type"輸入域
                if (!item.isFormField()) {
                    String fileName = item.getName();
                    long size = item.getSize();
                    if ((fileName == null || fileName.equals("")) && size == 0) {
                        continue;
                    }
                    //截取字符串 如：C:\WINDOWS\Debug\PASSWD.LOG
                    fileName = fileName.substring(fileName.lastIndexOf("\\") + 1, fileName.length());
                    //item.write(new File(uploadPath + itemNo + ".gif"));
                    item.write(new File(uploadPath, itemNo + ".gif"));
                }
            }
            //重定向頁面
            res.sendRedirect(req.getContextPath() + "/servlet/item/SearchItemServlet");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 初始化方法趁曼，設定目錄
     */
    public void init() throws ServletException {
        uploadPath = new File(getServletContext().getRealPath("upload"));
        //System.out.println("uploadPath=====" + uploadPath);
        //如果目錄不存在
        if (!uploadPath.exists()) {
            //創(chuàng)建目錄
            uploadPath.mkdir();
        }

        //臨時目錄
        tempPath = new File(getServletContext().getRealPath("temp"));
        if (!tempPath.exists()) {
            tempPath.mkdir();
        }
    }
}

web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <servlet>
    <servlet-name>fileUploadServlet</servlet-name>
    <servlet-class>bin.study.FileUploadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>fileUploadServlet</servlet-name>
    <url-pattern>/fileUploadServlet</url-pattern>
  </servlet-mapping>
</web-app>