Spring MVC 4使用Servlet 3 MultiPartConfigElement实现文件上传（带源码）

明明如月学长

发布于 2021-08-27 15:28:39

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发布于 2021-08-27 15:28:39

文章被收录于专栏：明明如月的技术专栏

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【翻译 by 明明如月 QQ 605283073】

原文地址：http://websystique.com/springmvc/spring-mvc-4-file-upload-example-using-multipartconfigelement/

上一篇：Spring MVC 4 使用常规的fileupload上传文件（带源码）

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本文在Servlet 3 环境下使用实现了StandardServletMultipartResolver 接口的SpringMultipartResolver类，来实现单个或者多文件上传。

Spring 提供内置的multipart 来支持web应用的文件上传。

概览

前面的文章讲述了用 CommonsMultipartResolver实现文件上传. 在Servlet 3.0 环境下甚至都很好用.本文也将实现同样的上传效果, 但在Servlet 3.0 指定用javax.servlet.MultipartConfigElement

在Servlet 3.0作用要在 Spring 里激活Multipart。需要下面的步骤：

1. 在 Spring配置中添加StandardServletMultipartResolver Bean.它是基于ased on the Servlet 3.0 javax.servlet.http.Part API的MultipartResolver接口的标准实现类,

2. Servlet 3.0环境下启用MultiParsing . 要做到这样,你有很多选择.

选项A. Servlet中设置javax.servlet.MultipartConfigElement . MultipartConfigElement是javax.servlet.annotation.MultipartConfig注解的表示 (和选项 c中类似). 本文中将用此种方法。
选项 B. 如果是基于XML的配置, 在 web.xml中配置multipart-config 节点, 如下:

    SpringDispatcher
    org.springframework.web.servlet.DispatcherServlet
    
        /tmp
        5242880
        20971520
        0

选项C. 你可以通过javax.servlet.annotation.MultipartConfig 注解来自定义Servlet，如下:

@WebServlet(name = "fileUploadServlet", urlPatterns = {"/upload"})
@MultipartConfig(location=/tmp,
                 fileSizeThreshold=0,    
                 maxFileSize=5242880,       // 5 MB
                 maxRequestSize=20971520)   // 20 MB
public class FileUploadServlet extends HttpServlet {
   
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //handle file upload
    }

完整例子

使用的技术和软件

Spring 4.2.0.RELEASE
validation-api 1.1.0.Final
Bootstrap v3.3.2
Maven 3
JDK 1.7
Tomcat 8.0.21
Eclipse JUNO Service Release 2

项目结构

pom.xml里声明依赖

    4.0.0
    com.websystique.springmvc
    Spring4MVCFileUploadMultipartResolverExample
    war
    1.0.0
    Spring4MVCFileUploadMultipartConfigElementExample Maven Webapp
    http://maven.apache.org
 
    
        4.2.0.RELEASE
    
 
    
        
            org.springframework
            spring-webmvc
            ${springframework.version}
        
 
        
            javax.validation
            validation-api
            1.1.0.Final
        
 
        
            javax.servlet
            javax.servlet-api
            3.1.0
        
        
            javax.servlet
            jstl
            1.2
        
    
 
 
    
        
            
                
                    org.apache.maven.plugins
                    maven-compiler-plugin
                    3.2
                    
                        1.7
                        1.7
                    
                
                
                    org.apache.maven.plugins
                    maven-war-plugin
                    2.4
                    
                        src/main/webapp
                        Spring4MVCFileUploadMultipartConfigElementExample
                        false
                    
                
            
        
 
        Spring4MVCFileUploadMultipartConfigElementExample

MultiPartConfigElement注册

注册MultiPartConfigElement提供定制最大文件大小、请求大小等。在上传文件才做时以及存在本地临时文件的位置和入口。

package com.websystique.springmvc.configuration;
 
import javax.servlet.MultipartConfigElement;
import javax.servlet.ServletRegistration;
 
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
 
public class HelloWorldInitializer extends
        AbstractAnnotationConfigDispatcherServletInitializer {
 
    @Override
    protected Class[] getRootConfigClasses() {
        return new Class[] { HelloWorldConfiguration.class };
    }
 
    @Override
    protected Class[] getServletConfigClasses() {
        return null;
    }
 
    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    }
 
    @Override
    protected void customizeRegistration(ServletRegistration.Dynamic registration) {
        registration.setMultipartConfig(getMultipartConfigElement());
    }
 
    private MultipartConfigElement getMultipartConfigElement() {
        MultipartConfigElement multipartConfigElement = new MultipartConfigElement( LOCATION, MAX_FILE_SIZE, MAX_REQUEST_SIZE, FILE_SIZE_THRESHOLD);
        return multipartConfigElement;
    }
 
    private static final String LOCATION = "C:/temp/"; // Temporary location where files will be stored
 
    private static final long MAX_FILE_SIZE = 5242880; // 5MB : Max file size.
                                                        // Beyond that size spring will throw exception.
    private static final long MAX_REQUEST_SIZE = 20971520; // 20MB : Total request size containing Multi part.
     
    private static final int FILE_SIZE_THRESHOLD = 0; // Size threshold after which files will be written to disk
}

注意，我们重写了customizeRegistration 方法将MultiPartConfigElement注册到DispatcherServletin。

创建配置

创建 StandardServletMultipartResolver Bean。

它是基于 Servlet 3.0 javax.servlet.http.Part API的MultipartResolver 接口的实现类。

package com.websystique.springmvc.configuration;
 
import org.springframework.context.MessageSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.ResourceBundleMessageSource;
import org.springframework.web.multipart.support.StandardServletMultipartResolver;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;
 
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.websystique.springmvc")
public class HelloWorldConfiguration extends WebMvcConfigurerAdapter {
 
    @Bean(name = "multipartResolver")
    public StandardServletMultipartResolver resolver() {
        return new StandardServletMultipartResolver();
    }
 
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setViewClass(JstlView.class);
        viewResolver.setPrefix("/WEB-INF/views/");
        viewResolver.setSuffix(".jsp");
        registry.viewResolver(viewResolver);
    }
 
    @Bean
    public MessageSource messageSource() {
        ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
        messageSource.setBasename("messages");
        return messageSource;
    }
 
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/static/**").addResourceLocations( "/static/");
    }
 
}

对应的XML配置：

            messages
        
    
 
 
    
        
            /WEB-INF/views/
        
        
            .jsp

创建Model（模型）类

package com.websystique.springmvc.model;
 
import org.springframework.web.multipart.MultipartFile;
 
public class FileBucket {
 
    MultipartFile file;
     
    public MultipartFile getFile() {
        return file;
    }
 
    public void setFile(MultipartFile file) {
        this.file = file;
    }
}

包装类：

package com.websystique.springmvc.model;
 
import java.util.ArrayList;
import java.util.List;
 
public class MultiFileBucket {
 
    List files = new ArrayList();
     
    public MultiFileBucket(){
        files.add(new FileBucket());
        files.add(new FileBucket());
        files.add(new FileBucket());
    }
     
    public List getFiles() {
        return files;
    }
 
    public void setFiles(List files) {
        this.files = files;
    }
}

此类最多可以处理3个文件上传

创建控制器

package com.websystique.springmvc.controller;
 
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
 
import javax.validation.Valid;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.util.FileCopyUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.multipart.MultipartFile;
 
import com.websystique.springmvc.model.FileBucket;
import com.websystique.springmvc.model.MultiFileBucket;
import com.websystique.springmvc.util.FileValidator;
import com.websystique.springmvc.util.MultiFileValidator;
 
@Controller
public class FileUploadController {
 
    private static String UPLOAD_LOCATION="C:/mytemp/";
 
    @Autowired
    FileValidator fileValidator;
 
    @Autowired
    MultiFileValidator multiFileValidator;
 
    @InitBinder("fileBucket")
    protected void initBinderFileBucket(WebDataBinder binder) {
        binder.setValidator(fileValidator);
    }
 
    @InitBinder("multiFileBucket")
    protected void initBinderMultiFileBucket(WebDataBinder binder) {
        binder.setValidator(multiFileValidator);
    }
 
    @RequestMapping(value = { "/", "/welcome" }, method = RequestMethod.GET)
    public String getHomePage(ModelMap model) {
        return "welcome";
    }
 
    @RequestMapping(value = "/singleUpload", method = RequestMethod.GET)
    public String getSingleUploadPage(ModelMap model) {
        FileBucket fileModel = new FileBucket();
        model.addAttribute("fileBucket", fileModel);
        return "singleFileUploader";
    }
 
    @RequestMapping(value = "/singleUpload", method = RequestMethod.POST)
    public String singleFileUpload(@Valid FileBucket fileBucket,
            BindingResult result, ModelMap model) throws IOException {
 
        if (result.hasErrors()) {
            System.out.println("validation errors");
            return "singleFileUploader";
        } else {
            System.out.println("Fetching file");
            MultipartFile multipartFile = fileBucket.getFile();
 
            // Now do something with file...
            FileCopyUtils.copy(fileBucket.getFile().getBytes(), new File( UPLOAD_LOCATION + fileBucket.getFile().getOriginalFilename()));
            String fileName = multipartFile.getOriginalFilename();
            model.addAttribute("fileName", fileName);
            return "success";
        }
    }
 
    @RequestMapping(value = "/multiUpload", method = RequestMethod.GET)
    public String getMultiUploadPage(ModelMap model) {
        MultiFileBucket filesModel = new MultiFileBucket();
        model.addAttribute("multiFileBucket", filesModel);
        return "multiFileUploader";
    }
 
    @RequestMapping(value = "/multiUpload", method = RequestMethod.POST)
    public String multiFileUpload(@Valid MultiFileBucket multiFileBucket,
            BindingResult result, ModelMap model) throws IOException {
 
        if (result.hasErrors()) {
            System.out.println("validation errors in multi upload");
            return "multiFileUploader";
        } else {
            System.out.println("Fetching files");
            List fileNames = new ArrayList();
            // Now do something with file...
            for (FileBucket bucket : multiFileBucket.getFiles()) {
                FileCopyUtils.copy(bucket.getFile().getBytes(), new File(UPLOAD_LOCATION + bucket.getFile().getOriginalFilename()));
                fileNames.add(bucket.getFile().getOriginalFilename());
            }
 
            model.addAttribute("fileNames", fileNames);
            return "multiSuccess";
        }
    }
 
}

将宝存在 C:/mytemp文件夹。

创建Validators （验证器）类

package com.websystique.springmvc.util;
 
import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;
 
import com.websystique.springmvc.model.FileBucket;
 
@Component
public class FileValidator implements Validator {
     
    public boolean supports(Class clazz) {
        return FileBucket.class.isAssignableFrom(clazz);
    }
 
    public void validate(Object obj, Errors errors) {
        FileBucket file = (FileBucket) obj;
         
        if(file.getFile()!=null){
            if (file.getFile().getSize() == 0) {
                errors.rejectValue("file", "missing.file");
            }
        }
    }
}

package com.websystique.springmvc.util;
 
import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;
 
import com.websystique.springmvc.model.FileBucket;
import com.websystique.springmvc.model.MultiFileBucket;
 
@Component
public class MultiFileValidator implements Validator {
     
    public boolean supports(Class clazz) {
        return MultiFileBucket.class.isAssignableFrom(clazz);
    }
 
    public void validate(Object obj, Errors errors) {
        MultiFileBucket multiBucket = (MultiFileBucket) obj;
         
        int index=0;
         
        for(FileBucket file : multiBucket.getFiles()){
            if(file.getFile()!=null){
                if (file.getFile().getSize() == 0) {
                    errors.rejectValue("files["+index+"].file", "missing.file");
                }
            }
            index++;
        }
         
    }
}

messages.properties

missing.file= Please select a file.

创建视图

singleFileUploader.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

 

    
    Spring 4 MVC File Upload Example
    
    

 
 
    
        Spring 4 MVC File Upload Example 
        
         
            
                
                    Upload a file
                    
                        
                        
                            
                        
                    
                
            
     
            
                
                    
                
            
        
        Home

success.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>


    
    File Upload Success
    
    


    
        File  ${fileName} uploaded successfully.
        


        Home

multiFileUploader.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

 

    
    Spring 4 MVC File Multi Upload Example
    
    

 
 
    
        Spring 4 MVC Multi File Upload Example 
        
         
            
                
                
                    
                
            
            

            
                
                    
                
            
        
         
        

        Home

multiSuccess.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>


    
    File Upload Success
    
    


    
            
                File  ${fileName} uploaded successfully

            
            

        Home

welcome.jsp

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

 

    
    Spring 4 MVC File Upload Example
    
    


    
        Welcome to FileUploader Example
         
        Click on below links to see FileUpload in action.


         
        Single File Upload  OR  Multi File Upload