javaweb文件上传详解

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package com.yangfei.servlet;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.IOUtils;

/**
 * @author yangfei
 */
public class FileUploadServlet2 extends HttpServlet {

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        try {

            //1、创建磁盘文件项工厂
            //作用：设置缓存文件的大小  设置临时文件存储的位置
            String path_temp = this.getServletContext().getRealPath("temp");
            //DiskFileItemFactory factory = new DiskFileItemFactory(1024*1024, new File(path_temp));
            DiskFileItemFactory factory = new DiskFileItemFactory();
            factory.setSizeThreshold(1024*1024);
            factory.setRepository(new File(path_temp));
            //2、创建文件上传的核心类
            ServletFileUpload upload = new ServletFileUpload(factory);
            //设置上传文件的名称的编码
            upload.setHeaderEncoding("UTF-8");
            //ServletFileUpload的API
            //判断表单是否是文件上传的表单
            boolean multipartContent = ServletFileUpload.isMultipartContent(request);
            if(multipartContent){
                //是文件上传的表单
                //***解析request获得文件项集合
                List<FileItem> parseRequest = upload.parseRequest(request);
                if(parseRequest!=null){
                    for(FileItem item : parseRequest){
                        //判断是不是一个普通表单项
                        boolean formField = item.isFormField();
                        if(formField){
                            //username=zhangsan
                            String fieldName = item.getFieldName();
                            //对普通表单项的内容进行编码
                            String fieldValue = item.getString("UTF-8");

                            System.out.println(fieldName+"----"+fieldValue);

                            //当表单是enctype="multipart/form-data"时 request.getParameter相关的方法
                            //String parameter = request.getParameter("username");

                        }else{
                            //文件上传项
                            //文件的名
                            String fileName = item.getName();
                            //获得上传文件的内容
                            InputStream in = item.getInputStream();
                            String path_store = this.getServletContext().getRealPath("upload");
                            OutputStream out = new FileOutputStream(path_store+"/"+fileName);
                            IOUtils.copy(in, out);
                            in.close();
                            out.close();

                            //删除临时文件
                            item.delete();

                        }
                    }
                }

            }else{
                //不是文件上传表单
                //使用原始的表单数据的获得方式 request.getParameter();
            }
        } catch (FileUploadException e) {
            e.printStackTrace();
        }


    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}