Java怎么实现根据文件路径找到excel表格，从浏览器下载？

Question

项目部署在服务器上，我做的一个生成excel表格保存在服务器文件路径中，java怎么实现根据服务器上的文件路径得到excel，下载到客户端浏览器上？

Answer 1

在实际应用中，经常会遇到上传Excel或者下载Excel的情况，比如导入数据、下载统计数据等等场景。针对这个问题，我写了个基于SpringMVC的简单上传下载示例，其中Excel的处理使用Apache的POI组件。

主要依赖的包如下：

<dependency> 
  <groupId>commons-io</groupId> 
  <artifactId>commons-io</artifactId> 
  <version>2.4</version> 
 </dependency> 
 <dependency> 
  <groupId>commons-fileupload</groupId> 
  <artifactId>commons-fileupload</artifactId> 
  <version>1.3.1</version> 
 </dependency> 
 <dependency> 
  <groupId>org.springframework</groupId> 
  <artifactId>spring-web</artifactId> 
  <version>4.0.0.RELEASE</version> 
 </dependency> 
 <dependency> 
  <groupId>org.springframework</groupId> 
  <artifactId>spring-webmvc</artifactId> 
  <version>4.0.0.RELEASE</version> 
 </dependency> 
 <dependency> 
  <groupId>org.apache.poi</groupId> 
  <artifactId>poi</artifactId> 
  <version>3.10.1</version> 
 </dependency> 

相关处理类：

（一）Controller类

package com.research.spring.controller; 
 
import java.io.IOException; 
import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 
 
import org.apache.poi.hssf.usermodel.HSSFWorkbook; 
import org.apache.poi.ss.usermodel.Row; 
import org.apache.poi.ss.usermodel.Sheet; 
import org.apache.poi.ss.usermodel.Workbook; 
import org.springframework.stereotype.Controller; 
import org.springframework.web.bind.annotation.RequestMapping; 
import org.springframework.web.bind.annotation.RequestParam; 
import org.springframework.web.multipart.MultipartFile; 
import org.springframework.web.servlet.ModelAndView; 
 
import com.research.spring.model.UserInfo; 
import com.research.spring.view.ExcelView; 
 
@Controller 
@RequestMapping("/file") 
public class FileController { 
 
 /** 
 * Excel文件上传处理 
 * @param file 
 * @return 
 */ 
 @RequestMapping("/upload") 
 public ModelAndView uploadExcel(@RequestParam("file") MultipartFile file){ 
 List<UserInfo> list = new ArrayList<UserInfo>(); 
  //这里只处理文件名包括“用户”的文件，模板使用下载模板 
 if( file.getOriginalFilename().contains("用户") ){ 
  try { 
  Workbook wb = new HSSFWorkbook(file.getInputStream()); 
  Sheet sheet = wb.getSheetAt(0); 
  for( int i = 1; i <= sheet.getLastRowNum(); i++ ){ 
   Row row = sheet.getRow(i); 
   UserInfo info = new UserInfo(); 
   info.setUserName(row.getCell(0).getStringCellValue()); 
   info.setPassword(row.getCell(1).getStringCellValue()); 
   list.add(info); 
  } 
  } catch (IOException e) { 
  e.printStackTrace(); 
  } 
 } 
 ModelAndView mav = new ModelAndView("content"); 
 mav.addObject("content",list.toString()); 
 return mav; 
 } 
 
 /** 
 * Excel文件下载处理 
 */ 
 @RequestMapping("/download") 
 public ModelAndView downloanExcel(){ 
 List<UserInfo> list = new ArrayList<UserInfo>(); 
 UserInfo userInfo = new UserInfo(); 
 userInfo.setPassword("0000"); 
 userInfo.setUserName("sdfas"); 
 list.add(userInfo); 
 list.add(userInfo); 
 list.add(userInfo); 
 list.add(userInfo); 
 Map<String,List<UserInfo>> map = new HashMap<String, List<UserInfo>>(); 
 map.put("infoList", list); 
 ExcelView ve = new ExcelView(); 
 return new ModelAndView(ve,map); 
 } 
} 

（二）实体类

package com.research.spring.model; 
 
public class UserInfo { 
 
 private String userName; 
 
 private String password; 
 
 public String getUserName() { 
 return userName; 
 } 
 
 public void setUserName(String userName) { 
 this.userName = userName; 
 } 
 
 public String getPassword() { 
 return password; 
 } 
 
 public void setPassword(String password) { 
 this.password = password; 
 } 
 
 @Override 
 public String toString() { 
 return "UserInfo [userName=" + userName + ", password=" + password 
  + "]"; 
 } 
} 

（三）View类

这个类在下载时用到，在Spring渲染页面时使用自定义的View类进行Excel的相关处理。

package com.research.spring.view; 
 
import java.io.OutputStream; 
import java.net.URLEncoder; 
import java.util.List; 
import java.util.Map; 
 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
import org.apache.poi.hssf.usermodel.HSSFWorkbook; 
import org.apache.poi.ss.usermodel.Cell; 
import org.apache.poi.ss.usermodel.Row; 
import org.apache.poi.ss.usermodel.Sheet; 
import org.springframework.web.servlet.view.document.AbstractExcelView; 
 
import com.research.spring.model.UserInfo; 
 
/** 
 * 下载Excel视图 
 * 
 * @author wdmcygah 
 * 
 */ 
public class ExcelView extends AbstractExcelView { 
 
 @Override 
 protected void buildExcelDocument(Map<String, Object> model, 
  HSSFWorkbook workbook, HttpServletRequest request, 
  HttpServletResponse response) throws Exception { 
 @SuppressWarnings("unchecked") 
 List<UserInfo> list = (List<UserInfo>) model.get("infoList"); 
 if (list != null && list.size() != 0) { 
  int len = list.size(); 
  Sheet sheet = workbook.createSheet(); 
  // 第一行文字说明 
  Row row = sheet.createRow(0); 
  Cell cell = row.createCell(0, Cell.CELL_TYPE_STRING); 
  cell.setCellValue("用户名"); 
  cell = row.createCell(1, Cell.CELL_TYPE_STRING); 
  cell.setCellValue("密码"); 
 
  //下面是具体内容 
  for (int i = 0; i < len; i++) { 
  row = sheet.createRow(i + 1); 
  cell = row.createCell(0, Cell.CELL_TYPE_STRING); 
  cell.setCellValue(list.get(i).getUserName()); 
  cell = row.createCell(1, Cell.CELL_TYPE_STRING); 
  cell.setCellValue(list.get(i).getPassword()); 
  } 
 } 
 
 response.setContentType("application/vnd.ms-excel"); 
 response.setCharacterEncoding("utf-8"); 
 //这里对文件名进行编码，保证下载时汉字显示正常 
 String fileName = URLEncoder.encode("用户.xls", "utf-8"); 
 //Content-disposition属性设置成以附件方式进行下载 
 response.setHeader("Content-disposition", "attachment;filename=" 
  + fileName); 
 OutputStream os = response.getOutputStream(); 
 workbook.write(os); 
 os.flush(); 
 os.close(); 
 } 
} 

（四）主要配置文件

上传文件时需要在配置文件中配置MultipartResolver类，配置后Spring会自动将文件传成MultipartFile对象，然后就可以进行相应的处理。示例看Controller类。

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" 
 xmlns:context="http://www.springframework.org/schema/context" 
 xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util" 
 xsi:schemaLocation="http://www.springframework.org/schema/beans 
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
 http://www.springframework.org/schema/context 
 http://www.springframework.org/schema/context/spring-context-3.0.xsd 
 http://www.springframework.org/schema/mvc 
 http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd 
 http://www.springframework.org/schema/util 
 http://www.springframework.org/schema/util/spring-util-3.0.xsd"> 
 
 <context:component-scan base-package="com.research" /> 
 
 <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
 <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /> 
 <property name="prefix" value="/WEB-INF/" /> 
 <property name="suffix" value=".jsp" /> 
 </bean> 
 
 <!-- 上传文件解析器配置 --> 
 <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> 
 <property name="defaultEncoding" value="UTF-8"></property> 
 <!-- 上传文件的大小限制 ，单位是字节--> 
 <property name="maxUploadSize" value="5242880000000"></property> 
 <!-- 上传文件的临时路径，上传完成后会自动删除 --> 
 <property name="uploadTempDir" value="upload/temp"></property> 
 </bean> 
</beans> 

（五）测试页面

<html> 
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
</head> 
<body> 
<h3>测试下载Excel功能</h3> 
<form action="file/download.htm" enctype="multipart/form-data" method="post"> 
 <input type="submit" value="下载Excel"></input> 
</form> 
 
<h3>测试上传Excel功能</h3> 
<form action="file/upload.htm" enctype="multipart/form-data" method="post"> 
 <input type="file" name="file"></input> 
 <input type="submit" value="上传Excel"></input> 
</form> 
</body> 
</html> 

如果想看完整源码，可以到我的Github仓库查看。 其中，上传文件只处理符合下载模板的文件。若要处理其它文件需要自实现。代码测试通过无误。