Spring4 MVC檔案下載執行個體

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這篇文章將向您展示如何使用Spring MVC4執行檔案下載，我們將看到應用程式從檔案系統內部以及外部檔案下載檔案。

 

本教程的主要亮點：

下載檔案是相當簡單的，涉及以下步驟。

• 建立一個InputStream到檔案用於下載。
• 尋找MIME類型下載檔案的內容。
  –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類型設定內容長度。
  response.setContentLength(file.getLength());//length in bytes
• 為響應設定內容處理標題。
  response.setHeader(“Content-Disposition”, “attachment; filename=” + fileName); //隨著“附件”檔案將下載。可能會顯示一個“另存新檔”基於瀏覽器的設定對話方塊。

  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，...）。對於其他內容類型，檔案將直接下載。

• 從InputStream中複製位元組響應到 OutputStream。
• 一旦複製完成後，關閉輸入輸出資料流。

完整實施例在下面討論。

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中聲明依賴關係

<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> 

建立控制器

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;@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());}}

該控制器包括兩個檔案。一個檔案是內部應用（內部資源），和其他檔案位於外部的應用程式的檔案系統。您的項目一定要改變外部檔案的路徑。僅用於示範的目的，我們已在路徑一個額外的路徑變數（內部/外部）。我們正在使用Spring FileCopyUtils工具類流從源複製到目的地。

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{@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.yiibai.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[] { "/" };    }  }

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，部署和運行應用程式

現在構建war（在前面的Eclipse教程）或通過Maven的命令列( mvn clean install)。部署 war 到Servlet3.0容器。或：

開啟瀏覽器，瀏覽 http://localhost:8080/Spring4MVCFileDownloadExample

點擊第二個連結。外部檔案應被下載。

點擊第一個連結。內部檔案[這是一個PDF]應該顯示在瀏覽器中，這是由於 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忘。構建並部署。點擊第一個連結。這個時候您應該看到 PDF檔案被下載。

 

就這樣，完

Spring4 MVC檔案下載執行個體