javaweb学习总结(五)-文件上传

一.手动实现文件上传

1.指定表单类型为文件上传表单

2.提交方式必须为：POST

<form enctype="multipart/form-data" method="post" action="${pageContext.request.ContextPath}/test">

用户名：<input type="text" name="username"/>文件:<input type="file" name="file">
</form>

3.servlet代码

package com.cx.fileUpload;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * Created by cxspace on 16-7-7.
 */

public class TestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取表单数据
        InputStream in = request.getInputStream();
        //转换流
        InputStreamReader inReader = new InputStreamReader(in);
        //缓冲流
        BufferedReader reader = new BufferedReader(inReader);

        String str = null;

        while ((str=reader.readLine())!=null){
            System.out.println(str);
        }

    }

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

二.使用FileUpload组件

apache提供的开源项目

1.引入.jar包

2.写处理代码

package com.cx.fileUpload;

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * Created by cxspace on 16-7-7.
 */
@WebServlet(name = "FileUpload")
public class FileUpload extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1.创建文件上传工厂类
        FileItemFactory fac = new DiskFileItemFactory();

        //2.创建文件上传核心对象
        ServletFileUpload upload = new ServletFileUpload(fac);

        //3.判断当前是否为文件上传表单
        if (upload.isMultipartContent(request)){
            //把请求数据转换为FileItem集合
            try {
                List<FileItem> list = upload.parseRequest(request);

                for (FileItem item : list){
                    if (item.isFormField())
                    {
                        // 普通表单
                        String fieldName = item.getFieldName();  //文本框名称
                        String content = item.getString(); //文本框值

                    }
                    else
                    {
                        String name = item.getName();  //文件名
                        String contentType = item.getContentType(); //文件类型
                        InputStream in = item.getInputStream();  //文件流

                        System.out.println(name+"-"+contentType);
                        //文件上传表单
                    }
                }

            } catch (FileUploadException e) {
                System.out.println("当前表单不是文件上传表单");
                e.printStackTrace();
            }

        }

    }

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

3.分析api

|-FileItemFactory   文件上传工厂类

    fac.setRepository();  //设置临时目录

|-ServletFileUpload  文件上传核心类，可以获取所有的fileitem  

     List<FileItem> parseRequest(request);  拿到文件对象集合

     isMultipartContent(request); 判断表单类型 

     upload.setFileSizeMax(10);  设置单个文件最大大小

 upload.setSizeMax(100); 设置总文件最大大小

 upload.setHeaderEncoding; 设置上传文件名的编码 

|-FileItem  

      item.getFieldName();   获取上传表单元素名称

      item.getString(); 获取上传数据

      item.getSring("UTF-8")  获取上传文件数据，处理中文

      item.getContentType();  获取上传文件类型[文件项]

      item.getInputStream();  获取文件流[文件项目]

      item.getName();  获取文件名

      item.write(file); 写文件

      item.delete();删除临时文件

文件下载核心代码

String fileName = request.getParameter("filename");
fileName = new String(fileName.getBytes("ISO-8859-1"),"UTF-8");

String basePath = getServletContext().getRealPath("/upload");

InputStream in = new FileInputStream(new FIle(basePath,fileName));
//设置下载相应头response.setHeader("content-disposition","attachment;fileName="+fileName);
OutputStream out = response.getOutputStream();

byte[] b = new byte[1024];
int len = -1;

while ((len = in.read(b))!=-1){

 out.write(b,0,len);

}

out.close();

in.close();