Spring MVC4使用Servlet3 MultiPartConfigElement文件上传实例

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在这篇文章中，我们将使用Spring MultipartResolver 实现 StandardServletMultipartResolver在Servlet3环境中实现单点和多文件上传功能。Spring提供了内置的multipart支持来处理Web应用程序文件上传。

简短的概述

在这篇文章中，我们将使用Servlet3.0以及javax.servlet.MultipartConfigElement，为了激活 Servlet3.0环境和Spring 的Multipart支持，你需要做以下：

1.添加 StandardServletMultipartResolver Bean 在 Spring 配置。这是一个标准实现 MultipartResolver 接口，基于Servlet3.0 javax.servlet.http.Part API。

2. 启用在Servlet3.0环境的多解析(MultiParsing)。要做到这一点，你有多种方案可供选择。

方案A. 对方案性 Servlet 注册设置 javax.servlet.MultipartConfigElement。MultipartConfigElement是javax.servlet.annotation.MultipartConfig 的注释值(如选择C所述)的简单Java类表示。这篇文章将特别侧重于这个选择。
方案B. 如果您使用基于XML的配置，可以在web.xml中在servlet配置声明 multipart-configsection 部分，如下图所示：
<servlet>
<servlet-name>SpringDispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<multipart-config>
<location>/tmp</location>
<max-file-size>5242880</max-file-size>
<max-request-size>20971520</max-request-size>
<file-size-threshold>0</file-size-threshold>
</multipart-config>
</servlet>
方案C. 可以创建一个自定义 Servlet 和 javax.servlet.annotation.MultipartConfig 标注其标注，如下图所示：
@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
}

话虽这么说，我们将专注于在这个例子中选择。

完整的例子

使用以下技术：

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

Let’s begin.

项目结构

在pom.xml声明依赖关系

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.yiibai.springmvc</groupId>
<artifactId>Spring4MVCFileUploadMultipartFile</artifactId>
<packaging>war</packaging>
<version>1.0.0</version>
<name>Spring4MVCFileUploadMultipartFile Maven Webapp</name>
<url>http://maven.apache.org</url><properties>
<springframework.version>4.2.0.RELEASE</springframework.version>
</properties><dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${springframework.version}</version>
</dependency><dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.1.0.Final</version>
</dependency><dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
</dependencies><build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.4</version>
<configuration>
<warSourceDirectory>src/main/webapp</warSourceDirectory>
<warName>Spring4MVCFileUploadMultipartFile</warName>
<failOnMissingWebXml>false</failOnMissingWebXml>
</configuration>
</plugin>
</plugins>
</pluginManagement><finalName>Spring4MVCFileUploadMultipartFile</finalName>
</build>
</project>

MultiPartConfigElement的编程注册

这个注册提供一个配置，以设置像最大文件大小，请求大小，位置和门限值。文件上传操作期间暂时存储在磁盘上的特定属性。

package com.yiibai.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 storedprivate 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
}

请注意，我们如何才能注册所需的 MultiPartConfigElement 到 DispatcherServlet 的重写函数 customizeRegistration。

创建配置

配置StandardServletMultipartResolver Bean。这是一个标准实现MultipartResolver接口，基于Servlet3.0 javax.servlet.http.Part API。

package com.yiibai.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.yiibai.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/");
}}

以XML格式配置类将是：

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> <context:component-scan base-package="com.yiibai.springmvc" />
<mvc:annotation-driven /> <bean id="multipartResolver" class="org.springframework.web.multipart.support.StandardServletMultipartResolver"/> <mvc:resources mapping="/static/**" location="/static/" />
<mvc:default-servlet-handler /> <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
<property name="basename">
<value>messages</value>
</property>
</bean> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix">
<value>/WEB-INF/views/</value>
</property>
<property name="suffix">
<value>.jsp</value>
</property>
</bean>
</beans>

创建模型类

Spring提供 org.springframework.web.multipart.MultipartFile，这是一个 multipart 请求获得上传文件的表示。它提供了方便的方法，如getName()，getContentType()，GetBytes()，getInputStream()等。这让我们处理更容易一点，同时检索有关被上传文件的信息。

让我们写一个包装类，进一步简化我们应用程序的使用。

package com.yiibai.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;
}
}

为了展示Multiple上传的例子，让我们再创建一个包装类。

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

这个类可以处理多达3个文件上传。

创建控制器

package com.yiibai.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.yiibai.springmvc.model.FileBucket;
import com.yiibai.springmvc.model.MultiFileBucket;
import com.yiibai.springmvc.util.FileValidator;
import com.yiibai.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<String> fileNames = new ArrayList<String>();
// 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";
}
}}

以上控制器是相当微不足道。它处理上传视图的GET和POST请求的文件。当文件从文件选择器，用户选择点击上传，我们只是创建具有相同的名称和字节的内容作为原始文件的新文件，从原始复制文件的字节数。为此，我们正在使用Spring FileCopyUtils工具类流从源复制到目的地。在这个例子中，我们指定的目的地是 C:/mytemp 文件夹，所有文件将存在这个文件夹中。

创建验证类

我们使用的是一些验证，以验证用户确实选择了要上传的文件。它们如下所示。

package com.yiibai.springmvc.util;import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;import com.yiibai.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.yiibai.springmvc.util;import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;import com.yiibai.springmvc.model.FileBucket;
import com.yiibai.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"%>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Spring 4 MVC File Upload Example</title>
<link href="<c:url value='/static/css/bootstrap.css' />" rel="stylesheet" type="text/css"></link>
<link href="<c:url value='/static/css/app.css' />" rel="stylesheet" type="text/css"></link>
</head>
<body> <div class="form-container">
<h1>Spring 4 MVC File Upload Example </h1>
<form:form method="POST" modelAttribute="fileBucket" enctype="multipart/form-data" class="form-horizontal"><div class="row">
<div class="form-group col-md-12">
<label class="col-md-3 control-lable" for="file">Upload a file</label>
<div class="col-md-7">
<form:input type="file" path="file" id="file" class="form-control input-sm"/>
<div class="has-error">
<form:errors path="file" class="help-inline"/>
</div>
</div>
</div>
</div><div class="row">
<div class="form-actions floatRight">
<input type="submit" value="Upload" class="btn btn-primary btn-sm">
</div>
</div>
</form:form>
<a href="<c:url value='/welcome' />">Home</a>
</div>
</body>
</html>

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" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>File Upload Success</title>
<link href="<c:url value='/static/css/bootstrap.css' />" rel="stylesheet"></link>
<link href="<c:url value='/static/css/app.css' />" rel="stylesheet"></link>
</head>
<body>
<div class="success">
File <strong>${fileName}</strong> uploaded successfully.
<br/><br/>
<a href="<c:url value='/welcome' />">Home</a>
</div>
</body>
</html>

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"%>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Spring 4 MVC File Multi Upload Example</title>
<link href="<c:url value='/static/css/bootstrap.css' />" rel="stylesheet" type="text/css"></link>
<link href="<c:url value='/static/css/app.css' />" rel="stylesheet" type="text/css"></link>
</head>
<body> <div class="form-container">
<h1>Spring 4 MVC Multi File Upload Example </h1>
<form:form method="POST" modelAttribute="multiFileBucket" enctype="multipart/form-data" class="form-horizontal"><c:forEach var="v" varStatus="vs" items="${multiFileBucket.files}">
<form:input type="file" path="files[${vs.index}].file" id="files[${vs.index}].file" class="form-control input-sm"/>
<div class="has-error">
<form:errors path="files[${vs.index}].file" class="help-inline"/>
</div>
</c:forEach>
<br/>
<div class="row">
<div class="form-actions floatRight">
<input type="submit" value="Upload" class="btn btn-primary btn-sm">
</div>
</div>
</form:form><br/>
<a href="<c:url value='/welcome' />">Home</a>
</div>
</body>
</html>

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" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>File Upload Success</title>
<link href="<c:url value='/static/css/bootstrap.css' />" rel="stylesheet"></link>
<link href="<c:url value='/static/css/app.css' />" rel="stylesheet"></link>
</head>
<body>
<div class="success">
<c:forEach var="fileName" items="${fileNames}">
File <strong>${fileName}</strong> uploaded successfully<br/>
</c:forEach>
<br/>
<a href="<c:url value='/welcome' />">Home</a>
</div>
</body>
</html>

welcome.jsp

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Spring 4 MVC File Upload Example</title>
<link href="<c:url value='/static/css/bootstrap.css' />" rel="stylesheet"></link>
<link href="<c:url value='/static/css/app.css' />" rel="stylesheet"></link>
</head>
<body>
<div class="form-container">
<h1>Welcome to FileUploader Example</h1>Click on below links to see FileUpload in action.<br/><br/><a href="<c:url value='/singleUpload' />">Single File Upload</a> OR <a href="<c:url value='multiUpload' />">Multi File Upload</a>
</div>
</body>
</html>

构建，部署和运行应用程序

现在构建 war(前面的Eclipse教程)或通过Maven的命令行( mvn clean install).部署 war 到Servlet3.0容器。

打开浏览器，浏览 http://localhost:8080/Spring4MVCFileUploadMultipart/