Spring MVC 文件上传示例教程 - 单个和多个文件
文件上传是任何 Web 应用程序中非常常见的任务。我们之前已经了解了如何在 Servlet和Struts2 文件上传中上传文件。今天我们将学习Spring 文件上传，特别是用于单个和多个文件的Spring MVC 文件上传。
Spring MVC 文件上传
Spring MVC 框架通过集成 Apache Commons FileUpload API 提供文件上传支持。文件上传过程非常简单，只需要简单的配置。我们将在 STS 中创建一个简单的Spring MVC项目，如下图所示。
大部分是 STS 工具生成的样板代码，我们将重点介绍利用 Spring 文件上传集成所需的更改。
Apache Commons FileUpload 的 Maven 依赖项
首先，我们需要在 pom.xml 文件中添加 Apache Commons FileUpload 依赖项，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 文件中的依赖项片段。
<!-- Apache Commons FileUpload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.1</version>
</dependency>
<!-- Apache 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 Spring Web 应用程序中进行单个和多个文件上传。upload.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>
uploadMultiple.jsp视图代码：
<%@ 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>
请注意，这些文件是简单的 HTML 文件，我没有使用任何 JSP 或 Spring 标签以避免复杂性。需要注意的重要一点是表单enctype应该是multipart/form-data，以便 Spring Web 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，表单字段“文件”和“名称”在输入字段中是相同的，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 多部分配置
要利用 Apache Commons FileUpload 处理多部分请求，我们需要做的就是将multipartResolver类配置为org.springframework.web.multipart.commons.CommonsMultipartResolver。我们最终的 Spring 配置文件如下所示。servlet-context.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
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<beans:property name="prefix" value="/WEB-INF/views/" />
<beans:property name="suffix" value=".jsp" />
</beans:bean>
<beans:bean id="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- 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，我通过为multipartResolver bean 提供maxUploadSize属性值来设置最大上传大小限制。如果您查看类的源代码，您将看到在下面的方法中定义并初始化了一个名为 multipartResolver 的 MultipartResolver 变量。DispatcherServlet
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");
}
}
通过此配置，任何以 enctype 为 multipart/form-data 的请求都将由 multipartResolver 处理，然后传递给 Controller 类。
Spring 文件上传控制器类
Controller 类代码很简单，我们需要为uploadFile和uploadMultipleFile URI 定义处理程序方法。FileUploadController.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;
}
}
请注意，Spring 注释的使用使我们的生活更轻松，代码看起来更具可读性。uploadFileHandler方法用于处理单个文件上传场景，而uploadMultipleFileHandler方法用于处理多个文件上传场景。实际上，我们可以用一个方法来处理这两种情况。现在将应用程序导出为 WAR 文件并将其部署到 Tomcat servlet 容器中。当我们运行应用程序时，下面的图像向我们展示了请求和响应。
Spring MVC 文件上传示例
您可以检查服务器日志以了解文件的存储位置。从上面的链接下载项目并试用以了解更多信息。
下载 Spring File Upload 项目