springboot文件上传下载简单使用

springboot的文件上传比较简单

一、使用默认的Resolver：StandardServletMultipartResolver

controller

package com.mydemo.webdemo.controller;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/")
public class FileUploadController {

    private Logger logger = LoggerFactory.getLogger(FileUploadController.class);
    @Value("${upload.file.savepath:/tmp}")
    private String savePath;

    @RequestMapping("/toupload")
    public ModelAndView toWelcome() {
        ModelAndView mav = new ModelAndView();
        mav.setViewName("fileupload");
        mav.addObject("time", new Date());
        return mav;
    }

    /**
     * 使用model传值
     *
     * @param uploadFile
     * @param model
     * @return
     */
    @PostMapping("/uploadone")
    public String uploadSingleFile(@RequestParam("uploadFile") MultipartFile uploadFile, Model model) {
        List<MultipartFile> uploadFileList = new ArrayList<>();
        logger.info(uploadFile.toString());
        try {
            uploadFileList.add(uploadFile);
            String result = saveFile(uploadFileList);
            model.addAttribute("msg", result);
        } catch (Exception e) {
            model.addAttribute("msg", "Upload failed");
            e.printStackTrace();
        }
        return "uploadResult";
    }

    /**
     * 使用ModelAndView页面跳转和传值
     *
     * @param uploadFile
     * @return
     */
    @PostMapping("/uploadmore")
    public ModelAndView uploadMoreFile(@RequestParam("uploadFile") MultipartFile[] uploadFile) {
        ModelAndView mav = new ModelAndView();
        List<MultipartFile> uploadFileList = new ArrayList<>();
        try {
            uploadFileList.addAll(Arrays.asList(uploadFile));
            String result = saveFile(uploadFileList);
            mav.addObject("msg", result);
        } catch (Exception e) {
            mav.addObject("msg", "Upload failed");
            e.printStackTrace();
        }
        mav.setViewName("uploadResult");
        return mav;
    }

    private String saveFile(List<MultipartFile> uploadFileList) {
        int successNum = 0;
        for (MultipartFile uploadFile : uploadFileList) {
            InputStream is = null;
            FileOutputStream fos = null;
            try {
                String fileName = uploadFile.getOriginalFilename();
                is = uploadFile.getInputStream();
                fos = new FileOutputStream(savePath + File.separator + fileName);
                int len = 0;
                byte[] b = new byte[1024];
                while ((len = (is.read(b))) != -1) {
                    fos.write(b, 0, len);
                }
                successNum += 1;
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    if (is != null) {
                        is.close();
                    }
                    if (fos != null) {
                        fos.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        if (successNum == 0) {
            return "Upload failed";
        } else if (successNum == uploadFileList.size()) {
            return "Upload success";
        } else {
            return "Partial upload success";
        }

    }
}

src/main/resources/templates/fileupload.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    Current time:<span th:text=${time} /><br />
    <h5>===========================分割线=============================</h5>
    <form id = "uploadone" action="${request}" th:action="@{/uploadone}" method="post" enctype="multipart/form-data">
        <input type="file" name="uploadFile" /><br />
        <input type="submit" value="UploadOne">
    </form>
    <h5>===========================分割线=============================</h5>
    <form id = "uploadmore" action="${request}" th:action="@{/uploadmore}" method="post" enctype="multipart/form-data">
        <input type="file" name="uploadFile" /><br />
        <input type="file" name="uploadFile" /><br />
        <input type="file" name="uploadFile" /><br />
        <input type="submit" value="UploadMore">
    </form>
</body>
</html>

src/main/resources/templates/uploadResult.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <span th:text=${msg}/>
</body>
</html>

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.mydemo.webdemo</groupId>
    <artifactId>fileuploaddemo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>fileuploaddemo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

application.properties

spring.mvc.servlet.load-on-startup=1
server.servlet.context-path=/uploaddemo
upload.file.savepath=D:/upload
## per file size, 500M
spring.servlet.multipart.max-file-size=524288000
## max file size in one request, 600M
spring.servlet.multipart.max-request-size=629145600
## in memory size after write to disk, 10M
spring.servlet.multipart.file-size-threshold=10240

二、使用CommonsMultipartResolver

在第一步操作的基础上，注册multipartResolver的bean为CommonsMultipartResolver

package com.mydemo.webdemo.custombean;

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;

@Component
public class CustomBean {
    @Bean(name = "multipartResolver")
    public CommonsMultipartResolver getMultipartResolver() {
        CommonsMultipartResolver resolver = new CommonsMultipartResolver();
        resolver.setDefaultEncoding("UTF-8");// default ISO-8859-1
        resolver.setMaxInMemorySize(10240);// default 10240 ，单位bytes
        resolver.setMaxUploadSize(1024*1024*600);// default -1 ，无限制，单位bytes
        resolver.setMaxUploadSizePerFile(1024*1024*500);// default -1 ，无限制，单位bytes
        return resolver;
    }

}

pom.xml文件中需要添加commons-fileupload依赖

<dependency>
     <groupId>commons-fileupload</groupId>
     <artifactId>commons-fileupload</artifactId>
     <version>1.4</version>
</dependency>

application.properties配置中去掉上述包含multipart的三个参数，保留如下

spring.mvc.servlet.load-on-startup=1
server.servlet.context-path=/uploaddemo
upload.file.savepath=D:/upload

三、文件下载

在上述基础上，添加下载Controller

package com.mydemo.webdemo.controller;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class DownloadController {
    private Logger logger = LoggerFactory.getLogger(FileUploadController.class);

    @RequestMapping("/download")
    @ResponseBody
    public void download(HttpServletRequest request, HttpServletResponse response) {
        String fileName = request.getParameter("fileName");
        String filePah = "D:/upload" + File.separator + fileName;
        // 自动判断下载文件类型
        response.setContentType("multipart/form-data");
        // 设置文件名称
        response.setHeader("Content-Disposition", "attachment;fileName=" + fileName);
        FileInputStream fis = null;
        OutputStream out = null;
        try {
            fis = new FileInputStream(filePah);
            out = response.getOutputStream();
            byte[] b = new byte[1024];
            int len;
            while ((len = fis.read(b)) != -1) {
                out.write(b, 0, len);
            }
        } catch (IOException e) {
            logger.error("", e);
        } finally {
            try {
                if (fis != null) {
                    fis.close();
                }
                if (out != null) {
                    out.close();
                }
            } catch (IOException e) {
                logger.error("", e);
            }
        }
    }
}

D:\upload\upload.tar文件存在，则可通过如下链接下载该文件

http://localhost:8080/uploaddemo/download?fileName=upload.tar

遗留问题：

1、当上传文件大小超过了文件限制大小后，不能将异常信息传递给前端，比如本例中单个文件大小设置为500M，上传大于500M的单个文件，出现异常，但不能将该异常信息传递给前端正常显示