Spring Boot 文件上傳與下載

時間 2019-11-17

原文原文鏈接

文件的上傳及下載功能是開發人員在平常應用及編程開發中常常會遇到的。正好最近開發須要用到此功能，雖然本人是 Android 開發人員，但仍是業餘客串了一下後臺開發。javascript

在本文中，您將學習如何使用 Spring Boot 實現 Web 服務中的文件上傳和下載功能。首先會構建一個 REST APIs 實現上傳及下載的功能，而後使用 Postman 工具來測試這些接口，最後建立一個 Web 界面使用 JavaScript 調用接口演示完整的功能。最終界面及功能以下：css

項目環境

- Spring Boot : 2.1.3.RELEASE
- Gredle : 5.2.1
- Java : 1.8
- Intellij IDEA : 2018.3.3
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項目建立

開發環境爲 Intellij IDEA，項目建立很簡單，按照下面的步驟建立便可：html

File -> New -> Project...
選擇 Spring Initializr，點擊 Next
填寫 Group (項目域名) 和 Artifact (項目別名)
構建類型能夠選擇 Maven 或 Gradle，看我的習慣
添加 Web 依賴
輸入項目名稱及保存路徑，完成建立

項目建立完畢以後就能夠進行開發，項目的完整結構以下圖所示：前端

參數配置

項目建立完成以後，須要設置一些必要的參數，打開項目resources目錄下配置文件application.properties，在其中添加如下參數：java

server.port=80

## MULTIPART (MultipartProperties)
# 開啓 multipart 上傳功能
spring.servlet.multipart.enabled=true
# 文件寫入磁盤的閾值
spring.servlet.multipart.file-size-threshold=2KB
# 最大文件大小
spring.servlet.multipart.max-file-size=200MB
# 最大請求大小
spring.servlet.multipart.max-request-size=215MB

## 文件存儲所需參數
# 全部經過 REST APIs 上傳的文件都將存儲在此目錄下
file.upload-dir=./uploads
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其中file.upload-dir=./uploads參數爲自定義的參數，建立FileProperties.javaPOJO類，使配置參數能夠自動綁定到POJO類。git

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "file")
public class FileProperties {
    private String uploadDir;

    public String getUploadDir() {
        return uploadDir;
    }
    public void setUploadDir(String uploadDir) {
        this.uploadDir = uploadDir;
    }
}
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而後在@SpringBootApplication註解的類中添加@EnableConfigurationProperties註解以開啓ConfigurationProperties功能。github

SpringBootFileApplication.javaweb

@SpringBootApplication
@EnableConfigurationProperties({
        FileProperties.class
})
public class SpringBootFileApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootFileApplication.class, args);
    }
}
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配置完成，之後如有file前綴開頭的參數須要配置，可直接在application.properties配置文件中配置並更新FileProperties.java便可。spring

另外再建立一個上傳文件成功以後的Response響應實體類UploadFileResponse.java及異常類FileException.java來處理異常信息。數據庫

UploadFileResponse.java

public class UploadFileResponse {
    private String fileName;
    private String fileDownloadUri;
    private String fileType;
    private long size;

    public UploadFileResponse(String fileName, String fileDownloadUri, String fileType, long size) {
        this.fileName = fileName;
        this.fileDownloadUri = fileDownloadUri;
        this.fileType = fileType;
        this.size = size;
    }
    // getter and setter ...
}
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FileException.java

public class FileException extends RuntimeException{
    public FileException(String message) {
        super(message);
    }

    public FileException(String message, Throwable cause) {
        super(message, cause);
    }
}
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建立接口

下面須要建立文件上傳下載所需的 REST APIs 接口。建立文件FileController.java。

import com.james.sample.file.dto.UploadFileResponse;
import com.james.sample.file.service.FileService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;

import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

@RestController
public class FileController {

    private static final Logger logger = LoggerFactory.getLogger(FileController.class);

    @Autowired
    private FileService fileService;

    @PostMapping("/uploadFile")
    public UploadFileResponse uploadFile(@RequestParam("file") MultipartFile file){
        String fileName = fileService.storeFile(file);

        String fileDownloadUri = ServletUriComponentsBuilder.fromCurrentContextPath()
                .path("/downloadFile/")
                .path(fileName)
                .toUriString();

        return new UploadFileResponse(fileName, fileDownloadUri,
                file.getContentType(), file.getSize());
    }


    @PostMapping("/uploadMultipleFiles")
    public List<UploadFileResponse> uploadMultipleFiles(@RequestParam("files") MultipartFile[] files) {
        return Arrays.stream(files)
                .map(this::uploadFile)
                .collect(Collectors.toList());
    }

    @GetMapping("/downloadFile/{fileName:.+}")
    public ResponseEntity<Resource> downloadFile(@PathVariable String fileName, HttpServletRequest request) {
        // Load file as Resource
        Resource resource = fileService.loadFileAsResource(fileName);

        // Try to determine file's content type
        String contentType = null;
        try {
            contentType = request.getServletContext().getMimeType(resource.getFile().getAbsolutePath());
        } catch (IOException ex) {
            logger.info("Could not determine file type.");
        }

        // Fallback to the default content type if type could not be determined
        if(contentType == null) {
            contentType = "application/octet-stream";
        }

        return ResponseEntity.ok()
                .contentType(MediaType.parseMediaType(contentType))
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
                .body(resource);
    }
}
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FileController類在接收到用戶的請求後，使用FileService類提供的storeFile()方法將文件寫入到系統中進行存儲，其存儲目錄就是以前在application.properties配置文件中的file.upload-dir參數的值./uploads。

下載接口downloadFile()在接收到用戶請求以後，使用FileService類提供的loadFileAsResource()方法獲取存儲在系統中文件並返回文件供用戶下載。

FileService.java

import com.james.sample.file.exception.FileException;
import com.james.sample.file.property.FileProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.net.MalformedURLException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;

@Service
public class FileService {

    private final Path fileStorageLocation; // 文件在本地存儲的地址

    @Autowired
    public FileService(FileProperties fileProperties) {
        this.fileStorageLocation = Paths.get(fileProperties.getUploadDir()).toAbsolutePath().normalize();
        try {
            Files.createDirectories(this.fileStorageLocation);
        } catch (Exception ex) {
            throw new FileException("Could not create the directory where the uploaded files will be stored.", ex);
        }
    }

    /** * 存儲文件到系統 * * @param file 文件 * @return 文件名 */
    public String storeFile(MultipartFile file) {
        // Normalize file name
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        try {
            // Check if the file's name contains invalid characters
            if(fileName.contains("..")) {
                throw new FileException("Sorry! Filename contains invalid path sequence " + fileName);
            }

            // Copy file to the target location (Replacing existing file with the same name)
            Path targetLocation = this.fileStorageLocation.resolve(fileName);
            Files.copy(file.getInputStream(), targetLocation, StandardCopyOption.REPLACE_EXISTING);

            return fileName;
        } catch (IOException ex) {
            throw new FileException("Could not store file " + fileName + ". Please try again!", ex);
        }
    }

    /** * 加載文件 * @param fileName 文件名 * @return 文件 */
    public Resource loadFileAsResource(String fileName) {
        try {
            Path filePath = this.fileStorageLocation.resolve(fileName).normalize();
            Resource resource = new UrlResource(filePath.toUri());
            if(resource.exists()) {
                return resource;
            } else {
                throw new FileException("File not found " + fileName);
            }
        } catch (MalformedURLException ex) {
            throw new FileException("File not found " + fileName, ex);
        }
    }
}
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接口測試

在完成上述的代碼以後，打開SpringBootFileApplication.java並運行，運行完成以後就可使用 Postman 進行測試了。

單個文件上傳結果：

多個文件上傳結果：

文件下載結果：

Web 前端開發

index.html

<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <!-- Required meta tags -->
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <title>Spring Boot File Upload / Download Rest API Example</title>

    <!-- Bootstrap CSS -->
    <link href="/css/main.css" rel="stylesheet"/>
</head>
<body>

<noscript>
    <h2>Sorry! Your browser doesn't support Javascript</h2>
</noscript>

<div class="upload-container">
    <div class="upload-header">
        <h2>Spring Boot File Upload / Download Rest API Example</h2>
    </div>
    <div class="upload-content">
        <div class="single-upload">
            <h3>Upload Single File</h3>
            <form id="singleUploadForm" name="singleUploadForm">
                <input id="singleFileUploadInput" type="file" name="file" class="file-input" required/>
                <button type="submit" class="primary submit-btn">Submit</button>
            </form>
            <div class="upload-response">
                <div id="singleFileUploadError"></div>
                <div id="singleFileUploadSuccess"></div>
            </div>
        </div>
        <div class="multiple-upload">
            <h3>Upload Multiple Files</h3>
            <form id="multipleUploadForm" name="multipleUploadForm">
                <input id="multipleFileUploadInput" type="file" name="files" class="file-input" multiple required/>
                <button type="submit" class="primary submit-btn">Submit</button>
            </form>
            <div class="upload-response">
                <div id="multipleFileUploadError"></div>
                <div id="multipleFileUploadSuccess"></div>
            </div>
        </div>
    </div>
</div>

<!-- Optional JavaScript -->
<script src="/js/main.js"></script>
</body>
</html>
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main.css

* {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 0;
    font-weight: 400;
    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size: 1rem;
    line-height: 1.58;
    color: #333;
    background-color: #f4f4f4;
}

body:before {
    height: 50%;
    width: 100%;
    position: absolute;
    top: 0;
    left: 0;
    background: #128ff2;
    content: "";
    z-index: 0;
}

.clearfix:after {
    display: block;
    content: "";
    clear: both;
}


h1, h2, h3, h4, h5, h6 {
    margin-top: 20px;
    margin-bottom: 20px;
}

h1 {
    font-size: 1.7em;
}

a {
    color: #128ff2;
}

button {
    box-shadow: none;
    border: 1px solid transparent;
    font-size: 14px;
    outline: none;
    line-height: 100%;
    white-space: nowrap;
    vertical-align: middle;
    padding: 0.6rem 1rem;
    border-radius: 2px;
    transition: all 0.2s ease-in-out;
    cursor: pointer;
    min-height: 38px;
}

button.primary {
    background-color: #128ff2;
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.12);
    color: #fff;
}

input {
    font-size: 1rem;
}

input[type="file"] {
    border: 1px solid #128ff2;
    padding: 6px;
    max-width: 100%;
}

.file-input {
    width: 100%;
}

.submit-btn {
    display: block;
    margin-top: 15px;
    min-width: 100px;
}

@media screen and (min-width: 500px) {
    .file-input {
        width: calc(100% - 115px);
    }

    .submit-btn {
        display: inline-block;
        margin-top: 0;
        margin-left: 10px;
    }
}

.upload-container {
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    background-color: #fff;
    box-shadow: 0 1px 11px rgba(0, 0, 0, 0.27);
    margin-top: 60px;
    min-height: 400px;
    position: relative;
    padding: 20px;
}

.upload-header {
    border-bottom: 1px solid #ececec;
}

.upload-header h2 {
    font-weight: 500;
}

.single-upload {
    padding-bottom: 20px;
    margin-bottom: 20px;
    border-bottom: 1px solid #e8e8e8;
}

.upload-response {
    overflow-x: hidden;
    word-break: break-all;
}
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main.js

'use strict';

var singleUploadForm = document.querySelector('#singleUploadForm');
var singleFileUploadInput = document.querySelector('#singleFileUploadInput');
var singleFileUploadError = document.querySelector('#singleFileUploadError');
var singleFileUploadSuccess = document.querySelector('#singleFileUploadSuccess');

var multipleUploadForm = document.querySelector('#multipleUploadForm');
var multipleFileUploadInput = document.querySelector('#multipleFileUploadInput');
var multipleFileUploadError = document.querySelector('#multipleFileUploadError');
var multipleFileUploadSuccess = document.querySelector('#multipleFileUploadSuccess');

function uploadSingleFile(file) {
    var formData = new FormData();
    formData.append("file", file);

    var xhr = new XMLHttpRequest();
    xhr.open("POST", "/uploadFile");

    xhr.onload = function() {
        console.log(xhr.responseText);
        var response = JSON.parse(xhr.responseText);
        if(xhr.status == 200) {
            singleFileUploadError.style.display = "none";
            singleFileUploadSuccess.innerHTML = "<p>File Uploaded Successfully.</p><p>DownloadUrl : <a href='" + response.fileDownloadUri + "' target='_blank'>" + response.fileDownloadUri + "</a></p>";
            singleFileUploadSuccess.style.display = "block";
        } else {
            singleFileUploadSuccess.style.display = "none";
            singleFileUploadError.innerHTML = (response && response.message) || "Some Error Occurred";
        }
    }

    xhr.send(formData);
}

function uploadMultipleFiles(files) {
    var formData = new FormData();
    for(var index = 0; index < files.length; index++) {
        formData.append("files", files[index]);
    }

    var xhr = new XMLHttpRequest();
    xhr.open("POST", "/uploadMultipleFiles");

    xhr.onload = function() {
        console.log(xhr.responseText);
        var response = JSON.parse(xhr.responseText);
        if(xhr.status == 200) {
            multipleFileUploadError.style.display = "none";
            var content = "<p>All Files Uploaded Successfully</p>";
            for(var i = 0; i < response.length; i++) {
                content += "<p>DownloadUrl : <a href='" + response[i].fileDownloadUri + "' target='_blank'>" + response[i].fileDownloadUri + "</a></p>";
            }
            multipleFileUploadSuccess.innerHTML = content;
            multipleFileUploadSuccess.style.display = "block";
        } else {
            multipleFileUploadSuccess.style.display = "none";
            multipleFileUploadError.innerHTML = (response && response.message) || "Some Error Occurred";
        }
    }

    xhr.send(formData);
}

singleUploadForm.addEventListener('submit', function(event){
    var files = singleFileUploadInput.files;
    if(files.length === 0) {
        singleFileUploadError.innerHTML = "Please select a file";
        singleFileUploadError.style.display = "block";
    }
    uploadSingleFile(files[0]);
    event.preventDefault();
}, true);

multipleUploadForm.addEventListener('submit', function(event){
    var files = multipleFileUploadInput.files;
    if(files.length === 0) {
        multipleFileUploadError.innerHTML = "Please select at least one file";
        multipleFileUploadError.style.display = "block";
    }
    uploadMultipleFiles(files);
    event.preventDefault();
}, true);
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