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/上一篇：Spring MVC 4 使用常规的fileupload上传文件（带源码）
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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
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;
@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());
}
}
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