实践Spring MVC之文件上传下载

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Spring MVC文件上传基于MultipartResolver实现，参考实现包括如下两种：

Apache Commons FileUpload

CommonsMultipartResolver

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<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
	<property name="maxUploadSize" value="2000000"/>
</bean>

Serlvet 3

StandardServletMultipartResolver，定义beanmultipartResolver，例如：

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<bean id="multipartResolver" class="org.springframework.web.multipart.support.StandardServletMultipartResolver">
</bean>

同时还需要对相应Servlet进行文件上传相关配置，有下面几种方式：

web.xml中Servlet新增<multipart-config/>

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<servlet>
	<servlet-name>springmvc</servlet-name>
	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
	<init-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB-INF/config/springmvc-config.xml</param-value>
	</init-param>
	<multipart-config>
		<location>/app/upload</location>
		<max-file-size>20848820</max-file-size>
		<max-request-size>418018841</max-request-size>
		<file-size-threshold>1048576</file-size-threshold>
	</multipart-config>
</servlet>

​

编程式Servlet注册方式下，注入MultipartConfigElement实例

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//代替web.xml
public class WebInitializer implements WebApplicationInitializer {//1

	@Override
	public void onStartup(ServletContext servletContext)
			throws ServletException {
		AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        ctx.register(MyMvcConfig.class);
        ctx.setServletContext(servletContext); //2
        
        Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(ctx)); //3
        servlet.addMapping("/");
        servlet.setMultipartConfig(new MultipartConfigElement("/app/upload",20848820,418018841,1048576));
        servlet.setLoadOnStartup(1);
        servlet.setAsyncSupported(true);//1
	}
}

​

在注解式Servlet上使用MultipartConfig注解

在spring boot中，定义MultipartConfigElement的bean即可。

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	@Bean
    public MultipartConfigElement multipartConfigElement() {
        MultipartConfigFactory factory = new MultipartConfigFactory();
        // 设置文件大小限制 ,超出设置页面会抛出异常信息，
        // 这样在文件上传的地方就需要进行异常信息的处理了;
        factory.setMaxFileSize("256KB"); // KB,MB
        /// 设置总上传数据总大小
        factory.setMaxRequestSize("512KB");
        // Sets the directory location where files will be stored.
        factory.setLocation("路径地址");
        return factory.createMultipartConfig();
    }

Form设置

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<form enctype="multipart/form-data"> 
</form>