在任何web应用程序中，文件上传都是一项非常常见的任务。我们之前已经知道如何在Servlet中上载文件和Struts2文件上传. 今天我们将了解Spring文件上传，特别是Spring MVC文件上传对于单个和多个文件。
目录
Spring MVC文件上传
SpringMVC框架通过集成阿帕奇CommonsFileUpload API提供了对上传文件的支持。上传文件的过程非常简单，需要简单的配置。我们将创建一个简单的SpringMVC项目在STS将看起来像下图。
大部分的部分是由STS工具生成的锅炉板代码，我们将重点介绍利用Spring文件上传集成所需的更改。
阿帕奇 Commons FileUpload的Maven依赖项
首先，我们需要在pom.xml文件文件，以便所需的jar文件成为web应用程序的一部分。下面是我的pom.xml文件文件。
<!-- 阿帕奇 Commons FileUpload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.1</version>
</dependency>
<!-- 阿帕奇 Commons IO -->
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.4</version>
</dependency>
Spring文件上传表单视图
我们将创建两个JSP页面，以允许在springweb应用程序中上载单个和多个文件。
上传.jsp查看代码：
<%@ taglib uri="https://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page session="false" %>
<html>
<head>
<title>Upload File Request Page</title>
</head>
<body>
<form method="POST" action="uploadFile" enctype="multipart/form-data">
File to upload: <input type="file" name="file"><br />
Name: <input type="text" name="name"><br /> <br />
<input type="submit" value="Upload"> Press here to upload the file!
</form>
</body>
</html>
上传多个.jsp查看代码：
<%@ taglib uri="https://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page session="false" %>
<html>
<head>
<title>Upload Multiple File Request Page</title>
</head>
<body>
<form method="POST" action="uploadMultipleFile" enctype="multipart/form-data">
File1 to upload: <input type="file" name="file"><br />
Name1: <input type="text" name="name"><br /> <br />
File2 to upload: <input type="file" name="file"><br />
Name2: <input type="text" name="name"><br /> <br />
<input type="submit" value="Upload"> Press here to upload the file!
</form>
</body>
</html>
注意，这些文件是简单的HTML文件，为了避免复杂性，我没有使用任何JSP或Spring标记。重要的一点是要注意的形式编码方式应该是多部分/表单数据，以便springweb应用程序知道请求包含需要处理的文件数据。
还要注意，对于多个文件，输入字段中的表单字段“；文件”；和“；名称”；是相同的，因此数据将以数组的形式发送。我们将获取输入数组并解析文件数据并将其存储在给定的文件名中。
Spring MVC多部件配置
要利用apachecommons FileUpload处理多部分请求，我们只需配置multipartResolver bean with class as org.springframework.web.multipart.commons.CommonsMultipartResolver.
最后的Spring配置文件如下所示。
servlet-上下文.xml代码：
<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="https://www.springframework.org/schema/mvc"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xmlns:beans="https://www.springframework.org/schema/beans"
xmlns:context="https://www.springframework.org/schema/context"
xsi:schemaLocation="https://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd
https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
https://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
<!-- DispatcherServlet Context: defines this servlet"s request-processing
infrastructure -->
<!-- Enables the Spring MVC @Controller programming model -->
<annotation-driven />
<!-- Handles HTTP GET requests for /resources/** by efficiently serving
up static resources in the ${webappRoot}/resources directory -->
<resources mapping="/**" location="/" />
<!-- Resolves views selected for rendering by @Controllers to .jsp resources
in the /WEB-INF/views directory -->
<beans:bean
>
<beans:property name="prefix" value="/WEB-INF/views/" />
<beans:property name="suffix" value=".jsp" />
</beans:bean>
<beans:bean id="multipartResolver"
>
<!-- setting maximum upload size -->
<beans:property name="maxUploadSize" value="100000" />
</beans:bean>
<context:component-scan base-package="com.journaldev.spring.controller" />
</beans:beans>
请注意，我通过提供最大上传大小的属性值多部分解器比恩。如果你想看看DispatcherServlet class, you will see that a MultipartResolver variable with name multipartResolver is defined and initialized in below method.
private void initMultipartResolver(ApplicationContext context)
{
try
{
this.multipartResolver = ((MultipartResolver)context.getBean("multipartResolver", MultipartResolver.class));
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using MultipartResolver [" + this.multipartResolver + "]");
}
}
catch (NoSuchBeanDefinitionException ex)
{
this.multipartResolver = null;
if (this.logger.isDebugEnabled())
this.logger.debug("Unable to locate MultipartResolver with name "multipartResolver": no multipart request handling provided");
}
}
使用此配置，任何enctype为multipart/form数据的请求都将在传递到Controller类之前由multipartResolver处理。
Spring文件上传控制器类
控制器类代码非常简单，我们需要为上传文件和上载多文件URI。
文件上传控制器.java代码：
package com.journaldev.spring.controller;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
/**
* Handles requests for the application file upload requests
*/
@Controller
public class FileUploadController {
private static final Logger logger = LoggerFactory
.getLogger(FileUploadController.class);
/**
* Upload single file using Spring Controller
*/
@RequestMapping(value = "/uploadFile", method = RequestMethod.POST)
public @ResponseBody
String uploadFileHandler(@RequestParam("name") String name,
@RequestParam("file") MultipartFile file) {
if (!file.isEmpty()) {
try {
byte[] bytes = file.getBytes();
// Creating the directory to store file
String rootPath = System.getProperty("catalina.home");
File dir = new File(rootPath + File.separator + "tmpFiles");
if (!dir.exists())
dir.mkdirs();
// Create the file on server
File serverFile = new File(dir.getAbsolutePath()
+ File.separator + name);
BufferedOutputStream stream = new BufferedOutputStream(
new FileOutputStream(serverFile));
stream.write(bytes);
stream.close();
logger.info("Server File Location="
+ serverFile.getAbsolutePath());
return "You successfully uploaded file=" + name;
} catch (Exception e) {
return "You failed to upload " + name + " => " + e.getMessage();
}
} else {
return "You failed to upload " + name
+ " because the file was empty.";
}
}
/**
* Upload multiple file using Spring Controller
*/
@RequestMapping(value = "/uploadMultipleFile", method = RequestMethod.POST)
public @ResponseBody
String uploadMultipleFileHandler(@RequestParam("name") String[] names,
@RequestParam("file") MultipartFile[] files) {
if (files.length != names.length)
return "Mandatory information missing";
String message = "";
for (int i = 0; i < files.length; i++) {
MultipartFile file = files[i];
String name = names[i];
try {
byte[] bytes = file.getBytes();
// Creating the directory to store file
String rootPath = System.getProperty("catalina.home");
File dir = new File(rootPath + File.separator + "tmpFiles");
if (!dir.exists())
dir.mkdirs();
// Create the file on server
File serverFile = new File(dir.getAbsolutePath()
+ File.separator + name);
BufferedOutputStream stream = new BufferedOutputStream(
new FileOutputStream(serverFile));
stream.write(bytes);
stream.close();
logger.info("Server File Location="
+ serverFile.getAbsolutePath());
message = message + "You successfully uploaded file=" + name
+ "<br />";
} catch (Exception e) {
return "You failed to upload " + name + " => " + e.getMessage();
}
}
return message;
}
}
注意Spring注解的使用使我们的生活更轻松，代码看起来更可读。
uploadFileHandler method is used to handle single file upload scenario whereas uploadMultipleFileHandler method is used to handle multiple files upload scenario. Actually we could have a single method to handle both the scenarios.
现在将应用程序导出为WAR文件并将其部署到tomcatservlet容器中。
当我们运行应用程序时，下面的图片显示了请求和响应。
