SpringMVC中使用CommonsMultipartResolver进行文件上传

概述：

CommonsMultipartResolver是基于Apache的Commons FileUpload来实现文件上传功能的。所以在项目中需要相应的jar文件。

FileUpload版本要求1.2及以上。相应的gradle配置：

"commons-fileupload:commons-fileupload:1.2.2"

上传方法的实现

1. 代码方式

直接在controler中new一个CommonsMultipartResolver。

@Controller @RequestMapping(value = "/file") public class FileController { @RequestMapping(value = "/commUploadA") @ResponseBody public JSONObject commUploadA(HttpServletRequest request) { JSONObject json = new JSONObject(); json.put("succ", false); try { //直接new一个CommonsMultipartResolver CommonsMultipartResolver cmr = new CommonsMultipartResolver(request.getServletContext()); cmr.setDefaultEncoding("utf-8"); cmr.setMaxInMemorySize(40960); cmr.setMaxUploadSize(10485760000L); if (cmr.isMultipart(request)) { MultipartHttpServletRequest multipartRequest = cmr.resolveMultipart(request); MultipartFile file = multipartRequest.getFile("uploadFile");// 与页面input的name相同 File imageFile = new File("d:/upload1.jpg");// 上传后的文件保存目录及名字 file.transferTo(imageFile);// 将上传文件保存到相应位置 json.put("succ", true); return json; } } catch (Exception e) { e.printStackTrace(); } return json; } }

2. Xml方式

通过spring配置一个名为”multipartResolver”的bean。

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> <property name="defaultEncoding" value="utf-8"></property> <property name="maxUploadSize" value="10485760000"></property> <property name="maxInMemorySize" value="40960"></property> </bean>

controller中的方法做相应修改。

@Controller @RequestMapping(value = "/file") public class FileController { @RequestMapping(value = "/commUploadB") @ResponseBody public JSONObject commUploadB(MultipartHttpServletRequest request) {//参数类型不同 JSONObject json = new JSONObject(); json.put("succ", false); try { MultipartFile file = request.getFile("uploadFile");// 与页面input的name相同 File imageFile = new File("d:/upload2.jpg");// 上传后的文件保存目录及名字 file.transferTo(imageFile);// 将上传文件保存到相应位置 json.put("succ", true); return json; } catch (Exception e) { e.printStackTrace(); return json; } } }

两种方法的区别：

将CommonsMultipartResolver的实例化由代码实现改为了xml配置实现。方法中的参数类型由HttpServletRequest变为了MultipartHttpServletRequest。

而上传的获取和保存逻辑没有变化。

注意：

在使用xml方式时，bean的名字必须为：multipartResolver。可在org.springframework.web.servlet.DispatcherServlet中找到原因：

public class DispatcherServlet extends FrameworkServlet { /** Well-known name for the MultipartResolver object in the bean factory for this namespace. */ public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver"; ...... /** * Initialize the MultipartResolver used by this class. * <p>If no bean is defined with the given name in the BeanFactory for this namespace, * no multipart handling is provided. */ private void initMultipartResolver(ApplicationContext context) { try { this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class); if (logger.isDebugEnabled()) { logger.debug("Using MultipartResolver [" + this.multipartResolver + "]"); } } catch (NoSuchBeanDefinitionException ex) { // Default is no multipart resolver. this.multipartResolver = null; if (logger.isDebugEnabled()) { logger.debug("Unable to locate MultipartResolver with name '" + MULTIPART_RESOLVER_BEAN_NAME + "': no multipart request handling provided"); } } } ...... }

简要分析CommonsMultipartResolver

CommonsMultipartResolver实现接口org.springframework.web.multipart.MultipartResolver，主要作用是将HttpSerlvetRequest封装成MultipartHttpServletRequest。

public interface MultipartResolver { ...... MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException; ...... }

具体的封装方法参考CommonsMultipartResolver对resolveMultipart的实现：

org.springframework.web.multipart.commons.CommonsMultipartResolver.resolveMultipart(javax.servlet.http.HttpServletRequest)