Spring获取上传文件

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 Spring如何获取form中上传的文件呢，Servlet3.0之前的版本，和Servlet3.0是有差别的

 

 

请看这段注释

 

/**
 * 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.
 *
 * @author Juergen Hoeller
 * @since 3.1
 */

 

org.springframework.web.multipart.support.StandardServletMultipartResolver

 Servlet3.0及以后，可以用这个StandardServletMultipartResolver来处理上传文件

 

 

 

org.springframework.web.multipart.commons.CommonsMultipartResolver

 

而3.0之前的版本通常用的是CommonsMultipartResolver来处理

 

这两者有什么区别呢，新版是基于Servlet3.0的API实现的，旧版是基于Apache Commons FileUpload实现的

两者使用的时候配置也是不同的，老版的CommonsMultipartResolver可以在用的时候配置，而新版的StandardServletMultipartResolver必须在注册Servlet的时候就进行配置。

 

 

CommonsMultipartResolver resolver = new CommonsMultipartResolver();
resolver.setMaxInMemorySize(maxInMemorySize);
resolver.setMaxUploadSize(maxUploadSize);
resolver.setDefaultEncoding(defaultEncoding);
resolver.setUploadTempDir(uploadTempDir);

 基于Apache Commons FileUpload的CommonsMultipartResolver的相关配置网上有很多

 通常可以在MultipartResolver的级别进行配置

 

 

 * 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.

 但是基于Servlet3.0的API实现的StandardServletMultipartResolver需要在web.xml或者在配置Servlet的时候进行配置，不允许在MultipartResolver的级别进行配置。

 

你可以在注册Servlet的时候加入一个javax.servlet.MultipartConfigElement来进行配置，或者使用javax.servlet.annotation.MultipartConfig注解在servlet类中进行配置。

 

比如这样：

 

ServletRegistration.Dynamic registration = container.addServlet("dispatcher",	dispatcherServlet);
MultipartConfigElement config = new MultipartConfigElement(BaseConst.UPLOAD_FOLDER, 8000L, 8000L, 0);
registration.setMultipartConfig(config);
registration.setLoadOnStartup(1);
registration.addMapping("/");

 配置了上传文件最大不超过8Kb

 

import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.support.StandardServletMultipartResolver;

 

@Bean
public MultipartResolver multipartResolver(){
	StandardServletMultipartResolver resolver = new StandardServletMultipartResolver();
	return resolver;
}

 配置完后在ApplicationContext中实例化一个StandardServletMultipartResolver就可以了

 

@Service("getUploadFile")
public class GetUploadFile {
	
@Autowired
private MultipartResolver multipartResolver;

public void handleUploadFile(HttpServletRequest request) {

MultipartHttpServletRequest multipartRequest = multipartResolver.resolveMultipart(request);
multipartRequest.getFileNames().forEachRemaining(name -> {
	MultipartFile file = multipartRequest.getFile(name);
	file.getInputStream();//do something
	file.getBytes();//do something
});
}
}

 这是使用的例子，非常方便，新老版本没什么区别。

 

import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;

@Service("getUploadFile")
public class GetUploadFile implements IGetUploadFile {
	
	@Autowired
	private MultipartResolver multipartResolver;

	@Override
	public List getUploadFile(HttpServletRequest request, IMultipartFileHandler handler) {
		MultipartHttpServletRequest multipartRequest = multipartResolver
				.resolveMultipart(request);
		List uploadFiles = new ArrayList<>();
		multipartRequest.getFileNames().forEachRemaining(name -> {
			MultipartFile file = multipartRequest.getFile(name);
			T entity = handler.handle(file);
			uploadFiles.add(entity);
		});
		return uploadFiles;
	}

}

 

import java.util.List;

import javax.servlet.http.HttpServletRequest;

public interface IGetUploadFile {
	
	/**
	 * get upload files and process
	 * return the result list 
	 * as the process method being offered: IMultipartFileHandler
	 * @param request
	 * @param handler
	 * @return
	 */
public List getUploadFile(HttpServletRequest request, IMultipartFileHandler handler);

}

 

import org.springframework.web.multipart.MultipartFile;

@FunctionalInterface
public interface IMultipartFileHandler {
	
	public T handle(MultipartFile file);

}

 

封装成接口来使用，代码更简洁，更易读。

 

@Autowired
private IGetUploadFile iGetUploadFile;

 只需注入一下，就可以复用代码，获取上传的文件了。

 

以上