這篇文章將向您展示如何使用Spring MVC4執行文件下載，我們將看到應用程序從文件系統內部以及外部文件下載文件。

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本教程的主要亮點：

下載文件是相當簡單的，涉及以下步驟。

• 創建一個InputStream到文件用于下載。
• 查找MIME類型下載文件的內容。
  –可以是application/pdf, text/html,application/xml,image/png等等。
• 將內容類型與上述發現的MIME類型響應（HttpServletResponse）。
  response.setContentType(mimeType);
• 針對以上找到MIME類型設置內容長度。
  response.setContentLength(file.getLength());//length in bytes
• 為響應設置內容處理標頭。
  response.setHeader(“Content-Disposition”, “attachment; filename=” + fileName);?//隨著“附件”文件將下載?？赡軙@示一個“另存為”基于瀏覽器的設置對話框。

  response.setHeader(“Content-Disposition”, “inline; filename=” + fileName);//通過“內聯”瀏覽器將嘗試顯示內容到瀏覽器中（圖片，PDF，文本，...）。對于其他內容類型，文件將直接下載。

• 從InputStream中復制字節響應到 OutputStream。
• 一旦復制完成后，關閉輸入輸出流。

完整實施例在下面討論。

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使用到以下技術：

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

現在讓我們開始

項目結構

在pom.xml中聲明依賴關系

<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>

創建控制器

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());}}

該控制器包括兩個文件。一個文件是內部應用（內部資源），和其他文件位于外部的應用程序的文件系統。您的項目一定要改變外部文件的路徑。僅用于演示的目的，我們已在路徑一個額外的路徑變量（內部/外部）。我們正在使用Spring FileCopyUtils工具類流從源復制到目的地。

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[] { "/" };}}

添加視圖

<%@ 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>

構建，部署和運行應用程序

現在構建war（在前面的Eclipse教程）或通過Maven的命令行( mvn clean install)。部署 war 到Servlet3.0容器?；?#xff1a;

打開瀏覽器，瀏覽?http://localhost:8080/Spring4MVCFileDownloadExample

點擊第二個鏈接。外部文件應被下載。

點擊第一個鏈接。內部文件[這是一個PDF]應該顯示在瀏覽器中，這是由于?Content-Disposition: inline. 通過內聯，如果內容可以通過瀏覽器顯示，它會顯示它在瀏覽器中。

現在從內聯更改內容處置備注。構建并部署。點擊第一個鏈接。這個時候您應該看到 PDF文件被下載。

就這樣，完成！

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下載代碼：http://pan.baidu.com/s/1c1lmeL6

轉載于:https://www.cnblogs.com/jxldjsn/p/5671582.html

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