文件上传原理
来个例子
客户端
<form role="form" th:action="@{/upload}" method="post" enctype="multipart/form-data"> <div class="form-group"> <label for="exampleInputEmail1">邮箱</label> <input type="email" name="email" class="form-control" id="exampleInputEmail1" placeholder="Enter email"> </div> <div class="form-group"> <label for="exampleInputPassword1">名字</label> <input type="text" name="userName" class="form-control" id="exampleInputPassword1" placeholder="Password"> </div> <div class="form-group"> <label for="headImage">头像</label> <input type="file" name="headImage" id="headImage"> <p class="help-block">Example block-level help text here.</p> </div> <div class="form-group"> <label for="photos">File input</label> <input type="file" name="photos" id="photos" multiple> <p class="help-block">Example block-level help text here.</p> </div> <div class="checkbox"> <label> <input type="checkbox"> Check me out </label> </div> <button type="submit" class="btn btn-primary">Submit</button> </form>
服务端
@Log4j2 @Controller public class UpLoadController { @PostMapping("/upload") public String upLoad(@RequestParam("email") String email, @RequestParam("userName") String userName, @RequestPart("headImage") MultipartFile headImage, @RequestPart("photos") MultipartFile[] photos) { log.info("上传信息:email:{},userName:{},headImage:{},photos:{}", email, userName, headImage.getSize(), photos.length); return "form/form_layouts"; } }
设置单个文件大小限制、总体文件大小限制
spring.servlet.multipart.max-file-size=10MB spring.servlet.multipart.max-file-size=100MB
原理
在SpringBoot启动的时候,会通过MultipartAutoConfiguration向IOC中注入一个文件解析器:StandardServletMultipartResolver,就是它负责判断和解析的
判断当前的请求是否是文件上传
请求来到DispatcherServlet中的doDispatch方法,然后在调用checkMultipart方法实现判断:就是判断当前的请示是否以"multipart/"开头,所有以我们在请求端的时候标注的enctype="multipart/form-data"是很重要的。
@Override public boolean isMultipart(HttpServletRequest request) { return StringUtils.startsWithIgnoreCase(request.getContentType(), "multipart/"); }
然后调用StandardServletMultipartResolver的resolveMultipart方法将请求封装成MultipartHttpServletRequest返回
根据客户端的参数和服务端接收的参数找到对应的参数解析器
得到MultipartHttpServletRequest之后,会去HandlerMapping中获取对应的HandlerExecutionChain(里面包含的了HandlerAdapter和拦截器),在调用HandlerAdapter的handle( )方法获取参数解析器。匹配对应的参数解析器的代在:HandlerMethodArgumentResolverComposite类中的getArgumentResolver( )方法,最后得到的解析文件上传的解析器叫做RequestPartMethodArgumentResolver,判断方法就是看你参数上是否标注了RequestPart注解
//拿到系统内置的参数解析器,用单个参数挨个的匹配使用哪个文件解析器(第一次查找到之后会缓存起来) @Nullable private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) { HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter); if (result == null) { for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) { if (resolver.supportsParameter(parameter)) { result = resolver; this.argumentResolverCache.put(parameter, result); break; } } } return result; }
解析文件
最后使用的是MultipartResolutionDelegate类中的静态方法resolveMultipartArgument获取到客户端上传的文件
@Override @Nullable public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer, NativeWebRequest request, @Nullable WebDataBinderFactory binderFactory) throws Exception { ......省略很多..... Object mpArg = MultipartResolutionDelegate.resolveMultipartArgument(name, parameter, servletRequest); ......省略很多..... }
MultipartFile获取方式
获取方式
在spring-config配置了 之后
后台的获取有两种方法:
1、指定@RequestParam MultipartFile file 例如:public Map logsUpload(@RequestParam MultipartFile file,@RequestParam(value="key") String key)参数;
2、将request转化为MultipartHttpServletRequest multiRequest = (MultipartHttpServletRequest)(request);
原理是:使用spring的CommosMultipartResolver 配置MultipartResolver 用于文件上传,DispatcherServlet 将调用 MultipartResolver 的 isMultipart(request) 方法检查当前 Web 请求是否为 multipart类型。如果是,DispatcherServlet 将调用 MultipartResolver 的 resolveMultipart(request) 方法,对原始 request 进行装饰,并返回一个 MultipartHttpServletRequest 供后继处理流程使用(最初的 HttpServletRequest 被偷梁换柱成了 MultipartHttpServletRequest),否则,直接返回最初的 HttpServletRequest。也就是说请求一旦被 MultipartResolver 接手,它就会解析请求中的文件,而不必等待后续 controller 主动从 MultipartRequest 中 getFile,所以在配置了MultipartResolver后,再通过这样的方法
MultipartResolver resolver = new CommonsMultipartResolver(request.getSession().getServletContext());
MultipartHttpServletRequest multipartRequest = resolver.resolveMultipart(request);
是获取不到file的,因为控制器已经帮我们进行了转换 直接获取即可。
如果你使用该方法发觉获取没有问题,你可以看看给这个方法是不是配置了servlet,如果配置了servlet是不走这个 MultipartResolver控制,是能获取成功的。
无需进行spring-config的配置,直接在后台获取进行转换即可
MultipartResolver resolver = new CommonsMultipartResolver(request.getSession().getServletContext());
MultipartHttpServletRequest multipartRequest = resolver.resolveMultipart(request);
MultipartFile file = multipartRequest.getFile("file");
String key = multipartRequest.getParameter("key");
然后项目具体需要什么样的修改,自己结合业务斟酌即可。
java实现Multipart/form-data
新的maven和先前的版本的API不同
<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpmime</artifactId> <version>4.5.3</version> </dependency>
上传
package uploadTest; import java.io.File; import java.io.IOException; import java.nio.charset.Charset; import java.util.HashMap; import java.util.Map; import java.util.Set; import org.apache.http.Consts; import org.apache.http.HttpEntity; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.ContentType; import org.apache.http.entity.mime.MultipartEntityBuilder; import org.apache.http.entity.mime.content.FileBody; import org.apache.http.entity.mime.content.StringBody; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class UploadTest { public static Map<String,Object> uploadFileByHTTP(File postFile,String postUrl,Map<String,String> postParam){ Logger log = LoggerFactory.getLogger(UploadTest.class); Map<String,Object> resultMap = new HashMap<String,Object>(); CloseableHttpClient httpClient = HttpClients.createDefault(); try{ //把一个普通参数和文件上传给下面这个地址 是一个servlet HttpPost httpPost = new HttpPost(postUrl); //把文件转换成流对象FileBody FileBody fundFileBin = new FileBody(postFile); //设置传输参数 MultipartEntityBuilder multipartEntity = MultipartEntityBuilder.create(); multipartEntity.addPart(postFile.getName(), fundFileBin);//相当于<input type="file" name="media"/> //设计文件以外的参数 Set<String> keySet = postParam.keySet(); for (String key : keySet) { //相当于<input type="text" name="name" value=name> multipartEntity.addPart(key, new StringBody(postParam.get(key), ContentType.create("text/plain", Consts.UTF_8))); } HttpEntity reqEntity = multipartEntity.build(); httpPost.setEntity(reqEntity); log.info("发起请求的页面地址 " + httpPost.getRequestLine()); //发起请求 并返回请求的响应 CloseableHttpResponse response = httpClient.execute(httpPost); try { log.info("----------------------------------------"); //打印响应状态 //log.info(response.getStatusLine()); resultMap.put("statusCode", response.getStatusLine().getStatusCode()); //获取响应对象 HttpEntity resEntity = response.getEntity(); if (resEntity != null) { //打印响应长度 log.info("Response content length: " + resEntity.getContentLength()); //打印响应内容 resultMap.put("data", EntityUtils.toString(resEntity,Charset.forName("UTF-8"))); } //销毁 EntityUtils.consume(resEntity); } catch (Exception e) { e.printStackTrace(); } finally { response.close(); } } catch (ClientProtocolException e1) { e1.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } finally{ try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } log.info("uploadFileByHTTP result:"+resultMap); return resultMap; } //测试 public static void main(String args[]) throws Exception { //要上传的文件的路径 String filePath = "d:/test0.jpg"; String postUrl = "http://localhost:8080/v1/contract/addContract.do"; Map<String,String> postParam = new HashMap<String,String>(); postParam.put("shopId", "15"); File postFile = new File(filePath); Map<String,Object> resultMap = uploadFileByHTTP(postFile,postUrl,postParam); System.out.println(resultMap); } }
接收
@Path("addContract.do") @Consumes(MediaType.MULTIPART_FORM_DATA) @Produces(MediaType.TEXT_HTML) public String addContract(@Context HttpServletRequest request, @Context HttpServletResponse response){ try{ //这里根据业务做修改 Contract contract = new Contract(); //重点是调用saveFile方法 UploadResult uploadResult = saveFile(request); contract.setShopId(Integer.valueOf(uploadResult.getParamMap().get("shopId"))); contract.setContractUrl(uploadResult.getFilePath()); Boolean success = contractService.addContract(contract); return JSON.toJSONString(RespApi.buildResp(200, "success", success)); } catch (ContractExeption contractExeption) { log.warn(ExceptionUtils.getStackTrace(contractExeption)); return JSON.toJSONString(RespApi.buildResp(400, "fail to add contract", false)); } } public UploadResult saveFile(HttpServletRequest request) { Map<String,String> resultMap = new HashMap<>(); String fileName = ""; try { if (ServletFileUpload.isMultipartContent(request)) { FileItemFactory factory = new DiskFileItemFactory(); //如果没以下两行设置的话,上传大的 文件 会占用 很多内存, //设置暂时存放的 存储室 , 这个存储室,可以和 最终存储文件 的目录不同 /** * 原理 它是先存到 暂时存储室,然后在真正写到 对应目录的硬盘上, * 按理来说 当上传一个文件时,其实是上传了两份,第一个是以 .tem 格式的 * 然后再将其真正写到 对应目录的硬盘上 */ //这个tempDir需要自己设置 File tempF = new File(tempDir); if (!tempF.exists()) { tempF.mkdirs(); } factory.setRepository(tempF); //设置 缓存的大小,当上传文件的容量超过该缓存时,直接放到 暂时存储室 factory.setSizeThreshold(1024 * 1024); //高水平的API文件上传处理 ServletFileUpload upload = new ServletFileUpload(factory); List<FileItem> items = null; try { items = upload.parseRequest(request); } catch (FileUploadException e) { e.printStackTrace(); } if (items != null) { Iterator<FileItem> iter = items.iterator(); while (iter.hasNext()) { FileItem item = iter.next(); //属性字段 if (item.isFormField()) { //获取表单的属性名字 String name = item.getFieldName(); String value = item.getString(); resultMap.put(name,value); } //文件 if (!item.isFormField() && item.getSize() > 0) { //可以得到流 InputStream in = item.getInputStream(); fileName = processFileName(item.getName()); try { String basePath = getRootPath(); String types = "pic"; String date = DateUtil.getNowDateStr(DateUtil.TO_DAY); String realPath = basePath + File.separator + types + File.separator + date + File.separator; //String realPath = basePath + File.separator + types + File.separator + date // + File.separator; System.out.println(realPath); File file1 = new File(realPath); if (!file1.exists()) { file1.mkdirs(); } String name = UUID.randomUUID().toString() + ".jpg"; fileName = types + File.separator + date + File.separator + name; File files = new File(realPath + name); item.write(files); } catch (Exception e) { e.printStackTrace(); } } } } } } catch (Exception e) { } UploadResult uploadResult = new UploadResult(); uploadResult.setFilePath(fileName); uploadResult.setParamMap(resultMap); return uploadResult; } //返回结果的包装类 public class UploadResult { private String filePath; private Map<String,String> paramMap; public String getFilePath() { return filePath; } public void setFilePath(String filePath) { this.filePath = filePath; } public Map<String, String> getParamMap() { return paramMap; } public void setParamMap(Map<String, String> paramMap) { this.paramMap = paramMap; } }
参考:
https://www.cnblogs.com/wonyun/p/7966967.html
https://blog.csdn.net/qq_27062249/article/details/118305016
https://blog.csdn.net/weixin_39849479/article/details/114132147
标签:SpringBoot,request,new,File,import,原理,上传,public,String From: https://www.cnblogs.com/fnlingnzb-learner/p/16625553.html