java如何实现文件上传和下载的功能
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希望高手可以详解一下input type=file的用法，其属性的含义，以及如何限制上传文件大小、下载文件的方法，谢谢了！！
对不起，我说错了，应该是在jsp中，谢谢！
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.jspsmart.upload.*;
import net.sf.json.JSONObject;
import action.StudentAction;
public class UploadServlet extends HttpServlet
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
this.doPost(request, response);
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
boolean result=true;
SmartUpload mySmartUpload=new SmartUpload();
mySmartUpload.initialize(this.getServletConfig(), request,response);
mySmartUpload.setTotalMaxFileSize(50*1024*1024);//大小限制
mySmartUpload.setAllowedFilesList("doc,docx");//后缀名限制
try
mySmartUpload.upload();
com.jspsmart.upload.File myFile = mySmartUpload.getFiles().getFile(0);
myFile.saveAs("/file/"+1+".doc");//保存目录
catch (SmartUploadException e)
e.printStackTrace();result=false;
//*****************************//
response.setContentType("text/html;charset=UTF-8");
response.setHeader("Cache-Control","no-cache");
PrintWriter out = response.getWriter();
out.print(result);
out.flush();
out.close();
//我这是ajax方式的，不想这样,把//**********************//以下部分修改就行了
//需要SmartUpload组件，去网上下个就行了，也有介绍的 参考技术A 自定义一个http请求。把文件内容包在http中发送想服务器即可！
Java：SpringBoot使用EasyExcel实现Excel文件的导出下载和上传导入功能
SpringBoot使用EasyExcel实现Excel文件的导出下载和上传导入功能
文件目录
$ tree -I target
.
├── README.md
├── pom.xml
└── src
└── main
├── java
│ └── com
│ └── example
│ └── demo
│ ├── DemoApplication.java
│ ├── controller
│ │ └── EasyExcelController.java
│ ├── converter
│ │ └── GenderConverter.java
│ └── excel
│ └── Member.java
└── resources
├── application.properties
└── json
└── members.json
依赖 pom.xml
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.11</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!--EasyExcel相关依赖-->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>3.0.5</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.68</version>
</dependency>
<dependency>
<groupId>cn.hutool</groupId>
<artifactId>hutool-json</artifactId>
<version>5.8.10</version>
</dependency>
</dependencies>
Member.java
package com.example.demo.excel;
import com.alibaba.excel.annotation.ExcelIgnore;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.format.DateTimeFormat;
import com.alibaba.excel.annotation.write.style.ColumnWidth;
import com.example.demo.converter.GenderConverter;
import lombok.Data;
import lombok.EqualsAndHashCode;
import java.util.Date;
/**
* 购物会员
* Created by macro on 2021/10/12.
*/
@Data
@EqualsAndHashCode(callSuper = false)
public class Member
@ExcelProperty("ID")
@ColumnWidth(10)
private Long id;
@ExcelProperty("用户名")
@ColumnWidth(20)
private String username;
@ExcelIgnore
private String password;
@ExcelProperty("昵称")
@ColumnWidth(20)
private String nickname;
@ExcelProperty("出生日期")
@ColumnWidth(20)
@DateTimeFormat("yyyy-MM-dd")
private Date birthday;
@ExcelProperty("手机号")
@ColumnWidth(20)
private String phone;
@ExcelIgnore
private String icon;
@ExcelProperty(value = "性别", converter = GenderConverter.class)
@ColumnWidth(10)
private Integer gender;
GenderConverter.java
package com.example.demo.converter;
import com.alibaba.excel.converters.Converter;
import com.alibaba.excel.converters.ReadConverterContext;
import com.alibaba.excel.converters.WriteConverterContext;
import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.data.WriteCellData;
import com.alibaba.excel.util.StringUtils;
/**
* excel性别转换器
* Created by macro on 2021/12/29.
*/
public class GenderConverter implements Converter<Integer>
@Override
public Class<?> supportJavaTypeKey()
//对象属性类型
return Integer.class;
@Override
public CellDataTypeEnum supportExcelTypeKey()
//CellData属性类型
return CellDataTypeEnum.STRING;
@Override
public Integer convertToJavaData(ReadConverterContext<?> context) throws Exception
//CellData转对象属性
String cellStr = context.getReadCellData().getStringValue();
if (StringUtils.isEmpty(cellStr)) return null;
if ("男".equals(cellStr))
return 0;
else if ("女".equals(cellStr))
return 1;
else
return null;
@Override
public WriteCellData<?> convertToExcelData(WriteConverterContext<Integer> context) throws Exception
//对象属性转CellData
Integer cellValue = context.getValue();
if (cellValue == null)
return new WriteCellData<>("");
if (cellValue == 0)
return new WriteCellData<>("男");
else if (cellValue == 1)
return new WriteCellData<>("女");
else
return new WriteCellData<>("");
EasyExcelController.java
package com.example.demo.controller;
import cn.hutool.json.JSONArray;
import cn.hutool.json.JSONUtil;
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.support.ExcelTypeEnum;
import com.example.demo.excel.Member;
import lombok.SneakyThrows;
import org.springframework.core.io.ClassPathResource;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.util.List;
/**
* EasyExcel导入导出测试Controller
* Created by macro on 2021/10/12.
*/
@Controller
@RequestMapping("/easyExcel")
public class EasyExcelController
/**
* 下载地址：http://localhost:8080/easyExcel/exportMemberList
*
* @param response
*/
@SneakyThrows(IOException.class)
@RequestMapping(value = "/exportMemberList", method = RequestMethod.GET)
public void exportMemberList(HttpServletResponse response)
this.setExcelResponseHeader(response, "会员列表");
// List<Member> memberList = LocalJsonUtil.getListFromJson("json/members.json", Member.class);
// https://blog.csdn.net/qq6420529/article/details/125215520
ClassPathResource classPathResource = new ClassPathResource("/json/members.json");
JSONArray objects = JSONUtil.readJSONArray(classPathResource.getFile(), Charset.forName("utf-8"));
List<Member> memberList = objects.toList(Member.class);
EasyExcel.write(response.getOutputStream())
.head(Member.class)
.excelType(ExcelTypeEnum.XLSX)
.sheet("会员列表")
.doWrite(memberList);
/**
* 从Excel导入会员列表
* <p>
* http://localhost:8080/easyExcel/importMemberList
*
* @param file
* @return
*/
@SneakyThrows
@RequestMapping(value = "/importMemberList", method = RequestMethod.POST)
@ResponseBody
public List<Member> importMemberList(@RequestPart("file") MultipartFile file)
List<Member> memberList = EasyExcel.read(file.getInputStream())
.head(Member.class)
.sheet()
.doReadSync();
return memberList;
/**
* 设置excel下载响应头属性
*/
private void setExcelResponseHeader(HttpServletResponse response, String rawFileName) throws UnsupportedEncodingException
response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.setCharacterEncoding("utf-8");
String fileName = URLEncoder.encode(rawFileName, "UTF-8").replaceAll("\\\\+", "%20");
response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
members.json
[
"id": 1,
"username": "刘备",
"password": "123456",
"nickname": "刘玄德",
"birthday": "2000-10-10",
"phone": "1234567890",
"icon": "icon",
"gender": "1"
,
"id": 2,
"username": "关于",
"password": "234567",
"nickname": "关云长",
"birthday": "2000-10-10",
"phone": "1234567890",
"icon": "icon",
"gender": "1"
,
"id": 3,
"username": "用户名",
"password": "password",
"nickname": "昵称",
"birthday": "2000-10-10",
"phone": "1234567890",
"icon": "icon",
"gender": "0"
]
下载的文件 会员列表.xlsx
上传文件
[
"id": 1,
"username": "刘备",
"password": null,
"nickname": "刘玄德",
"birthday": "2000-10-09T16:00:00.000+00:00",
"phone": "1234567890",
"icon": null,
"gender": 1
,
"id": 2,
"username": "关于",
"password": null,
"nickname": "关云长",
"birthday": "2000-10-09T16:00:00.000+00:00",
"phone": "1234567890",
"icon": null,
"gender": 1
,
"id": 3,
"username": "用户名",
"password": null,
"nickname": "昵称",
"birthday": "2000-10-09T16:00:00.000+00:00",
"phone": "1234567890",
"icon": null,
"gender": 0
]
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