Spring4 MVC文件下载实例

这篇文章将向您展示如何使用Spring MVC4执行文件下载，我们将看到应用程序从文件系统内部以及外部文件下载文件。

本教程的主要亮点：

下载文件是相当简单的，涉及以下步骤。

创建一个InputStream到文件用于下载。
查找MIME类型下载文件的内容。
–可以是application/pdf, text/html,application/xml,image/png等等。
将内容类型与上述发现的MIME类型响应（HttpServletResponse）。
response.setContentType(mimeType);
针对以上找到MIME类型设置内容长度。
response.setContentLength(file.getLength());//length in bytes
为响应设置内容处理标头。
response.setHeader(“Content-Disposition”, “attachment; filename=” + fileName); //随着“附件”文件将下载。可能会显示一个“另存为”基于浏览器的设置对话框。
response.setHeader(“Content-Disposition”, “inline; filename=” + fileName);//通过“内联”浏览器将尝试显示内容到浏览器中（图片，PDF，文本，...）。对于其他内容类型，文件将直接下载。
从InputStream中复制字节响应到 OutputStream。
一旦复制完成后，关闭输入输出流。

完整实施例在下面讨论。

使用到以下技术：

Spring 4.2.0.RELEASE
Bootstrap v3.3.2
Maven 3
JDK 1.7
Tomcat 8.0.21
Eclipse JUNO Service Release 2

现在让我们开始

项目结构

在pom.xml中声明依赖关系

<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>Spring4MVCFileDownloadExample</artifactId><packaging>war</packaging><version>1.0.0</version><name>Spring4MVCFileDownloadExample Maven Webapp</name><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.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>Spring4MVCFileDownloadExample</warName><failOnMissingWebXml>false</failOnMissingWebXml></configuration></plugin></plugins></pluginManagement><finalName>Spring4MVCFileDownloadExample</finalName></build>
</project>

创建控制器

package com.yiibai.springmvc.controller;import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLConnection;
import java.nio.charset.Charset;import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;@Controller
public class FileDownloadController {private static final String INTERNAL_FILE="irregular-verbs-list.pdf";private static final String EXTERNAL_FILE_PATH="C:/mytemp/SpringMVCHibernateManyToManyCRUDExample.zip";@RequestMapping(value={"/","/welcome"}, method = RequestMethod.GET)public String getHomePage(ModelMap model) {return "welcome";}/** Download a file from *   - inside project, located in resources folder.*   - outside project, located in File system somewhere. */@RequestMapping(value="/download/{type}", method = RequestMethod.GET)public void downloadFile(HttpServletResponse response, @PathVariable("type") String type) throws IOException {File file = null;if(type.equalsIgnoreCase("internal")){ClassLoader classloader = Thread.currentThread().getContextClassLoader();file = new File(classloader.getResource(INTERNAL_FILE).getFile());}else{file = new File(EXTERNAL_FILE_PATH);}if(!file.exists()){String errorMessage = "Sorry. The file you are looking for does not exist";System.out.println(errorMessage);OutputStream outputStream = response.getOutputStream();outputStream.write(errorMessage.getBytes(Charset.forName("UTF-8")));outputStream.close();return;}String mimeType= URLConnection.guessContentTypeFromName(file.getName());if(mimeType==null){System.out.println("mimetype is not detectable, will take default");mimeType = "application/octet-stream";}System.out.println("mimetype : "+mimeType);response.setContentType(mimeType);/* "Content-Disposition : inline" will show viewable types [like images/text/pdf/anything viewable by browser] right on browser while others(zip e.g) will be directly downloaded [may provide save as popup, based on your browser setting.]*/response.setHeader("Content-Disposition", String.format("inline; filename=\"" + file.getName() +"\""));/* "Content-Disposition : attachment" will be directly download, may provide save as popup, based on your browser setting*///response.setHeader("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));response.setContentLength((int)file.length());InputStream inputStream = new BufferedInputStream(new FileInputStream(file));//Copy bytes from source to destination(outputstream in this example), closes both streams.FileCopyUtils.copy(inputStream, response.getOutputStream());}}

该控制器包括两个文件。一个文件是内部应用（内部资源），和其他文件位于外部的应用程序的文件系统。您的项目一定要改变外部文件的路径。仅用于演示的目的，我们已在路径一个额外的路径变量（内部/外部）。我们正在使用Spring FileCopyUtils工具类流从源复制到目的地。

配置

package com.yiibai.springmvc.configuration;import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
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{@Overridepublic void configureViewResolvers(ViewResolverRegistry registry) {InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();viewResolver.setViewClass(JstlView.class);viewResolver.setPrefix("/WEB-INF/views/");viewResolver.setSuffix(".jsp");registry.viewResolver(viewResolver);}@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {registry.addResourceHandler("/static/**").addResourceLocations("/static/");}}

初始化

package com.yiibai.springmvc.configuration;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;public class HelloWorldInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {@Overrideprotected Class<?>[] getRootConfigClasses() {return new Class[] { HelloWorldConfiguration.class };}@Overrideprotected Class<?>[] getServletConfigClasses() {return null;}@Overrideprotected String[] getServletMappings() {return new String[] { "/" };}}

添加视图

<%@ 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 Download 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 FileDownloader Example</h1>Click on below links to see FileDownload in action.<br/><br/><a href="<c:url value='/download/internal' />">Download This File (located inside project)</a>  <br/><a href="<c:url value='/download/external' />">Download This File (located outside project, on file system)</a></div> 
</body>
</html>