Spring MVC之MultipartResolver

超、凢脫俗 2022-05-07 00:58 153阅读 0赞

`MultipartResolver`是`spring`提供的文件上传解析器的接口，该接口有两个实现类：`StandardServletMultipartResolver`、`CommonsMultipartResolver`，`MultipartResolver#isMultipart`是判断是否文件上传的请求，`post`请求、`contentType`是否是以`multipart/`开头这两个是先决条件。

**在`spring`上下文中，有且只有一个该实例。** `spring`容器启动时初始化文件上传解析器：

DispatcherServlet#initStrategies(ApplicationContext context) {
    	initMultipartResolver(context);
    }

* **StandardServletMultipartResolver** 
 基于`Servlet3.0 API`实现，不需要引入额外的`jar`包，在`spring`的配置文件中注入此`Bean`时，不需要配置上传文件大小等参数，但是在`web.xml`中配置`DispatcherServlet`时，需要添加`multipart-config`配置。
 
 <servlet>
 <servlet-name>springmvc</servlet-name>
 <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
 <init-param>
 <param-name>contextConfigLocation</param-name>
 <param-value>classpath:Spring_mvc.xml</param-value>
 </init-param>
 <load-on-startup>1</load-on-startup>
 <multipart-config>
 
 <location>d:/</location>
 
 <max-file-size>5242880</max-file-size>
 
 <max-request-size>10485760</max-request-size>
 
 <file-size-threshold>0</file-size-threshold>
 </multipart-config>
 </servlet>
 <servlet-mapping>
 <servlet-name>springmvc</servlet-name>
 <url-pattern>/</url-pattern>
 </servlet-mapping>
 
 Standard implementation of the {@link MultipartResolver} interface,
 based on the Servlet 3.0 {@link javax.servlet.http.Part} API.
 To be added as "multipartResolver" bean to a Spring DispatcherServlet context,
 without any extra configuration at the bean level (see below).
 
 Note: In order to use Servlet 3.0 based multipart parsing,
 you need to mark the affected servlet with a "multipart-config" section in
 {@code web.xml}, or with a {@link javax.servlet.MultipartConfigElement}
 in programmatic servlet registration, or (in case of a custom servlet class)
 possibly with a {@link javax.servlet.annotation.MultipartConfig} annotation
 on your servlet class. Configuration settings such as maximum sizes or
 storage locations need to be applied at that servlet registration level;
 Servlet 3.0 does not allow for them to be set at the MultipartResolver level.
 * **CommonsMultipartResolver** 
 基于`Apache Commons FileUpload`实现，继承自`apache`的`CommonsFileUploadSupport`。在spring中注入`CommonsMultipartResolver`时，可以配置`"maxUploadSize", "maxInMemorySize" and "defaultEncoding"`等属性。需要依赖`jar`：`commons-fileupload、commons-io`。
 
 <bean id="multipartResolver"
 		class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
 		
 		<property name="defaultEncoding" value="UTF-8" />
 		<property name="maxUploadSize" value="5242880" />
 		<property name="maxInMemorySize" value="40960" />
 	</bean>
 
 Servlet-based {@link MultipartResolver} implementation for
 <a href="http://commons.apache.org/proper/commons-fileupload">Apache Commons FileUpload</a>
 1.2 or above.
 
 Provides "maxUploadSize", "maxInMemorySize" and "defaultEncoding" settings as
 bean properties (inherited from {@link CommonsFileUploadSupport}). See corresponding
 ServletFileUpload / DiskFileItemFactory properties ("sizeMax", "sizeThreshold",
 "headerEncoding") for details in terms of defaults and accepted values.
 Saves temporary files to the servlet container's temporary directory.
 Needs to be initialized either by an application context or
 via the constructor that takes a ServletContext (for standalone usage).

**在controller中用MultipartFile和MultipartHttpServletRequest接收参数即可，具体可以尝试解析这两种方式有什么API**