SpringBoot我们大多数的时候是当做服务提供者来使用的，但是在一些场景中还是要用到一些文件上传下载这种"非常规"操作的。那么怎么在SpringBoot中实现文件的上传下载功能呢？想象一些我们在SpringMVC中是怎么做的。我们需要在SpringMVC的配置文件中增加文件上传的Bean的配置，如下：
有时候我们可能还要进行一些文件类型的现在，那么这个怎么做呢？我们可以通过自定的Interceptor来实现这样的功能。代码示例如下：
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
然后在后台对应的处理方法中就可以直接获取到文件的输入流了。而对于SpringBoot来说，我们不需要配置文件上传的解析类了，因为SpringBoot已经帮我们注册好了。下面我们来看一下具体的开发。
增加thymeleaf的依赖
这里我们用thymeleaf来作为页面的呈现，所以我们这里需要引入thymeleaf的相关依赖：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
文件上传下载页面：
接着我们需要写一个文件的上传下载的页面，我简单的写了下面这个页面
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8"/>
<title>Title</title>
<script th:src="@{/js/jquery-2.1.4.min.js}"></script>
</head>
<body>
<form id="upload" enctype="multipart/form-data" method="post" action="/uploadAndDownload/uploadFileAction">
<input type="file" name="uploadFile"/>
<input type="hidden" name="id" value="12"/>
<input type="button" value="文件上传" onclick="doUpload()"/>
</form>
<input type="button" value="下载文件" onclick="doDownload()"/>
<form id="download" method="post" action="/uploadAndDownload/downloadFileAction">
</form>
<script type="text/javascript">
function doUpload() {
var upl = document.getElementById("upload");
upl.submit();
}
function doDownload() {
var upl = document.getElementById("download");
upl.submit();
}
</script>
</body>
</html>
后台处理类：
接着我们写一个处理文件上传和下载的控制类：
访问页面的方法：
@Controller
@RequestMapping("/uploadAndDownload")
public class UploadAndDownloadFileController {
@RequestMapping("/index")
public String index() {
return "uploadAndDownload";
}
}
上传文件的处理方法：
@RequestMapping(value = "/uploadFileAction", method = RequestMethod.POST)
public ModelAndView uploadFileAction(@RequestParam("uploadFile") MultipartFile uploadFile, @RequestParam("id") Long id) {
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("uploadAndDownload");
InputStream fis = null;
OutputStream outputStream = null;
try {
fis = uploadFile.getInputStream();
outputStream = new FileOutputStream("G:\\uploadfile\\"+uploadFile.getOriginalFilename());
IOUtils.copy(fis,outputStream);
modelAndView.addObject("sucess", "上传成功");
return modelAndView;
} catch (IOException e) {
e.printStackTrace();
}finally {
if(fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(outputStream != null){
try {
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
modelAndView.addObject("sucess", "上传失败!");
return modelAndView;
}
下载文件的处理方法：
@RequestMapping("downloadFileAction")
public void downloadFileAction(HttpServletRequest request, HttpServletResponse response) {
response.setCharacterEncoding(request.getCharacterEncoding());
response.setContentType("application/octet-stream");
FileInputStream fis = null;
try {
File file = new File("G:\\config.ini");
fis = new FileInputStream(file);
response.setHeader("Content-Disposition", "attachment; filename="+file.getName());
IOUtils.copy(fis,response.getOutputStream());
response.flushBuffer();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}当我们发送请求为：http://localhost:8003/uploadAndDownload/index，会看到如下的页面(没有做排版处理)：
当我们上传文件时，会调用uploadFileAction这个方法，然后将上传的文件信息存放到一个地方，根据个人的需求去做。
当我们下载文件时：
有时候我们可能需要限制上传文件的大小，可以这样设置上传文件的大小：
@Configuration
public class UploadFileConfiguration {
@Bean
public MultipartConfigElement multipartConfigElement() {
MultipartConfigFactory factory = new MultipartConfigFactory();
factory.setMaxFileSize("256KB");
factory.setMaxRequestSize("512KB");
return factory.createMultipartConfig();
}
}
有时候我们可能还要进行一些文件类型的现在，那么这个怎么做呢？我们可以通过自定的Interceptor来实现这样的功能。代码示例如下：
自定义的拦截器
package com.zkn.learnspringboot.aop;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
/**
* Created by zkn
*/
@Component("fileUploadInterceptor")
@ConfigurationProperties(prefix = "fileupload")
public class FileUploadInterceptor extends HandlerInterceptorAdapter {
private List<String> allowFileTypeList;
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
//文件上传的Servlet
if (request instanceof MultipartHttpServletRequest) {
//允许所有的文件类型
if (allowFileTypeList == null) {
return super.preHandle(request, response, handler);
}
MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
Iterator<String> it = multipartRequest.getFileNames();
if (it != null) {
while (it.hasNext()) {
String fileParameter = it.next();
List<MultipartFile> listFile = multipartRequest.getFiles(fileParameter);
if (!CollectionUtils.isEmpty(listFile)) {
MultipartFile multipartFile = null;
String fileName = "";
for (int i = 0; i < listFile.size(); i++) {
multipartFile = listFile.get(i);
fileName = multipartFile.getOriginalFilename();
int flag = 0;
if ((flag = fileName.lastIndexOf(".")) > 0) {
fileName = fileName.substring(flag+1);
}
//不被允许的后缀名
if (!allowFileTypeList.contains(fileName)) {
this.outputStream(request, response);
return false;
}
}
}
}
}
}
return super.preHandle(request, response, handler);
}
private void outputStream(HttpServletRequest request, HttpServletResponse response) {
response.setCharacterEncoding(request.getCharacterEncoding());
ServletOutputStream output = null;
try {
output = response.getOutputStream();
output.write(("所传入的文件类型是不被允许的，允许的文件类型是：" + Arrays.toString(allowFileTypeList.toArray())).getBytes(request.getCharacterEncoding()));
} catch (IOException e) {
e.printStackTrace();
} finally {
if (output != null) {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public void setAllowFileType(String allowFileType) {
//默认运行所有的类型
if (StringUtils.isEmpty(allowFileType)) {
allowFileTypeList = null;
return;
}
allowFileTypeList = Arrays.asList(allowFileType.split(","));
}
}
注册拦截器：
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
@Autowired
private FileUploadInterceptor fileUploadInterceptor;
//注册拦截器
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(fileUploadInterceptor);
}
//配置加载静态资源
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/templates/**").addResourceLocations(ResourceUtils.CLASSPATH_URL_PREFIX+"/templates/");
registry.addResourceHandler("/static/**").addResourceLocations(ResourceUtils.CLASSPATH_URL_PREFIX+"/static/");
super.addResourceHandlers(registry);
}
}新增配置信息：
fileupload.allowFileType=txt,docs这样我们的程序在运行的时候就会把不是txt或者docs文件类型的文件给过滤掉。
