Spring MVC文件上传示例教程–单个和多个文件
时间：2020-02-23 14:35:55 来源:igfitidea点击:
在任何Web应用程序中，文件上传都是非常常见的任务。
前面我们已经看到了如何在Servlet和Struts2文件上传中上传文件。
今天，我们将学习有关Spring File上传的信息，特别是针对单个和多个文件的Spring MVC File Upload。
Spring MVC文件上传
Spring MVC框架通过集成Apache Commons FileUpload API为上传文件提供支持。
上传文件的过程非常简单，并且需要简单的配置。
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依赖关系
首先，我们需要在pom.xml文件中添加Apache Commons FileUpload依赖项，以便必需的jar文件成为Web应用程序的一部分。
以下是我的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应用程序中上传单个和多个文件。
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HTML文件，为了避免复杂性，我没有使用任何JSP或者Spring标记。
需要注意的重要一点是，表单enctype应该是multipart/form-data，以便Spring Web应用程序知道请求中包含需要处理的文件数据。
还要注意，对于多个文件，格式字段"文件"和"名称"在输入字段中相同，因此数据将以数组形式发送。
我们将采用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
为了利用Apache Commons FileUpload处理多部分请求，我们要做的就是将" multipartResolver" bean配置为" org.springframework.web.multipart.commons.CommonsMultipartResolver"类。
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.theitroad.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DispatcherServlet类的源代码，将会看到在以下方法中定义并初始化了一个名为multipartResolver的MultipartResolver变量。
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，在传递给Controller类之前，multipartResolver将处理enctype为multipart/form-data的任何请求。
Spring文件上传控制器类
控制器类代码非常简单，我们需要为uploadFile和uploadMultipleFile URI定义处理程序方法。
FileUploadController.java代码：
package com.theitroad.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，使用Spring注释使我们的生活更轻松，代码看起来更易读。
" uploadFileHandler"方法用于处理单个文件上传方案，而" uploadMultipleFileHandler"方法用于处理多个文件上传方案。
实际上，我们可以使用一种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。
