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Spring Boot入门——文件上传与下载

1、在pom.xml文件中添加依赖

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.wyl</groupId>
  <artifactId>SpringBootFile</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>SpringBootFile</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <java.version>1.7</java.version>
  </properties>
  
  <parent>
      <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.3.RELEASE</version>
  </parent>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    
    <!-- thymeleaf模板插件 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    
    <!-- devtools插件，热部署 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
        <scope>true</scope>
    </dependency>
    
  </dependencies>
</project>

2、application.properties文件中取消模板文件缓存

spring.thymeleaf.cache=false

3、编写模板文件

file.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org"  
      xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
<head>
<meta charset="UTF-8" />
<title>Insert title here</title>
</head>
<body>
    <h1 th:inlines="text">文件上传</h1>
    <form action="fileUpload" method="post" enctype="multipart/form-data">
        <p>选择文件: <input type="file" name="fileName"/></p>
        <p><input type="submit" value="提交"/></p>
    </form>
</body>
</html>


multifile.html
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org"  
      xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
<head>
<meta charset="UTF-8" />
<title>Insert title here</title>
</head>
<body>
    <h1 th:inlines="text">文件上传</h1>
    <form action="multifileUpload" method="post" enctype="multipart/form-data" >
        <p>选择文件1: <input type="file" name="fileName"/></p>
        <p>选择文件2: <input type="file" name="fileName"/></p>
        <p>选择文件3: <input type="file" name="fileName"/></p>
        <p><input type="submit" value="提交"/></p>
    </form>
</body>
</html>

4、编写Controller

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class FileUploadController {

    /*
     * 获取file.html页面
     */
    @RequestMapping("file")
    public String file(){
        return "/file";
    }
    
    /**
     * 实现文件上传
     * */
    @RequestMapping("fileUpload")
    @ResponseBody 
    public String fileUpload(@RequestParam("fileName") MultipartFile file){
        if(file.isEmpty()){
            return "false";
        }
        String fileName = file.getOriginalFilename();
        int size = (int) file.getSize();
        System.out.println(fileName + "-->" + size);
        
        String path = "F:/test" ;
        File dest = new File(path + "/" + fileName);
        if(!dest.getParentFile().exists()){ //判断文件父目录是否存在
            dest.getParentFile().mkdir();
        }
        try {
            file.transferTo(dest); //保存文件
            return "true";
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "false";
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "false";
        }
    }

　　/*
     * 获取multifile.html页面
     */
    @RequestMapping("multifile")
    public String multifile(){
        return "/multifile";
    }
    
    /**
     * 实现多文件上传
     * */
    @RequestMapping(value="multifileUpload",method=RequestMethod.POST)

　　/**public @ResponseBody String multifileUpload(@RequestParam("fileName")List<MultipartFile> files) */
    public @ResponseBody String multifileUpload(HttpServletRequest request){
        
        List<MultipartFile> files = ((MultipartHttpServletRequest)request).getFiles("fileName");
        
        if(files.isEmpty()){
            return "false";
        }

        String path = "F:/test" ;
        
        for(MultipartFile file:files){
            String fileName = file.getOriginalFilename();
            int size = (int) file.getSize();
            System.out.println(fileName + "-->" + size);
            
            if(file.isEmpty()){
                return "false";
            }else{        
                File dest = new File(path + "/" + fileName);
                if(!dest.getParentFile().exists()){ //判断文件父目录是否存在
                    dest.getParentFile().mkdir();
                }
                try {
                    file.transferTo(dest);
                }catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    return "false";
                } 
            }
        }
        return "true";
    }
}

5、测试

6、多文件上传中遇到的问题

org.apache.tomcat.util.http.fileupload.FileUploadBase$FileSizeLimitExceededException: The field fileName exceeds its maximum permitted size of 1048576 bytes.

Spring Boot默认文件上传大小为2M，多文档上传中总是出现文件大小超出限度

解决方法：

a、在application.properties文件中设置文件大小

# Single file max size  
multipart.maxFileSize=50Mb
# All files max size  
multipart.maxRequestSize=50Mb

　　但是，事实证明此种方法不能够解决以上问题

b、在启动类App.class文件中配置Bean来设置文件大小

import javax.servlet.MultipartConfigElement;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@Configuration
public class App 
{
    public static void main( String[] args )
    {
        System.out.println( "Hello World!" );
        SpringApplication.run(App.class, args);
    }
    
    /**  
     * 文件上传配置  
     * @return  
     */  
    @Bean  
    public MultipartConfigElement multipartConfigElement() {  
        MultipartConfigFactory factory = new MultipartConfigFactory();  
        //单个文件最大  
        factory.setMaxFileSize("10240KB"); //KB,MB  
        /// 设置总上传数据总大小  
        factory.setMaxRequestSize("102400KB");  
        return factory.createMultipartConfig();  
    }

7、文件下载

@RequestMapping("download")
    public String downLoad(HttpServletResponse response){
        String filename="2.jpg";
        String filePath = "F:/test" ;
        File file = new File(filePath + "/" + filename);
        if(file.exists()){ //判断文件父目录是否存在
            response.setContentType("application/force-download");
            response.setHeader("Content-Disposition", "attachment;fileName=" + filename);
            
            byte[] buffer = new byte[1024];
            FileInputStream fis = null; //文件输入流
            BufferedInputStream bis = null;
            
            OutputStream os = null; //输出流
            try {
                os = response.getOutputStream();
                fis = new FileInputStream(file); 
                bis = new BufferedInputStream(fis);
                int i = bis.read(buffer);
                while(i != -1){
                    os.write(buffer);
                    i = bis.read(buffer);
                }
                
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println("----------file download" + filename);
            try {
                bis.close();
                fis.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return null;
    }

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原文地址：https://www.cnblogs.com/studyDetail/p/7003253.html