Spring MVC 4 文件下载实例（带源码）

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原文地址：http://websystique.com/springmvc/spring-mvc-4-file-download-example/

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本文将为你展示通过Spring MVC 4实现文件下载。

下载一个文件比较简单，主要包括下面几个步骤.

• 创建下载文件的InputStream（输入流）
• 找到下载文件类型的MIME type .
  – 可能是 application/pdf, text/html,application/xml,image/png, ..或者其他类型.
• 在response(HttpServletResponse)中设置  Content-Type 为上面的值.
  response.setContentType(mimeType);
• 设置Content length 文件长度.
  response.setContentLength(file.getLength());//字节长度
• 在响应中设置Content-Disposition HEADER 
  response.setHeader(“Content-Disposition”, “attachment; filename=” + fileName); //With ‘attachement’ File will be downloaded as is. 可能会显示基于浏览器的 ‘文件另存为’对话框.

  response.setHeader(“Content-Disposition”, “inline; filename=” + fileName);//With ‘inline’ browser will try to display content right into broswer for certain contents(imgages,PDF,text,..). 其他内容文件将直接被下载

• 拷贝 InputStream(输入流)的字节到 response的OutputStream（输出流） .
•  一旦拷贝完成，关闭输入输出流

下面是完整的例子

---

所用的技术或者软件：

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

让我们开始吧

项目结构

 pom.xml文件声明依赖

<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.websystique.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-compiler-plugin</artifactId><version>3.2</version><configuration><source>1.7</source><target>1.7</target></configuration></plugin><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.websystique.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;@Controllerpublic 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());}}

配置

package com.websystique.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.websystique.springmvc")public class HelloWorldConfiguration extends WebMvcConfigurerAdapter{          @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);    }         @Override    public void addResourceHandlers(ResourceHandlerRegistry registry) {        registry.addResourceHandler("/static/**").addResourceLocations("/static/");    } }

初始化

package com.websystique.springmvc.configuration; 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[] { "/" };    }   }

创建视图

<%@ 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>

构建发布和运行

在tomcat里面发布运行

浏览器输入 http://localhost:8080/Spring4MVCFileDownloadExample

点击第二个超链接 将下载外部（项目外）文件

点击第一个超链接. 内部（项目内部）文件 [一个 PDF] 将在浏览器中显示, 如果能在浏览器能够显示就会被显示在浏览器里面。

把Content-Disposition 从inline设置为 attachment.构建并重新发布 点第一个链接，PDF将被下载下来。

项目下载：http://websystique.com/?smd_process_download=1&download_id=1769