如果我们做一个小型的web站，而且刚好选择的kotlin 和Spring Boot技术栈，那么上传文件的必不可少了，当然，如果你做一个中大型的web站，那建议你使用云存储，能省不少事情。
这篇文章就介绍怎么使用kotlin 和Spring Boot上传文件
构建工程
如果对于构建工程还不是很熟悉的可以参考《我的第一个Kotlin应用》
完整 build.gradle 文件
group 'name.quanke.kotlin'version '1.0-SNAPSHOT'buildscript { ext.kotlin_version = '1.2.10' ext.spring_boot_version = '1.5.4.RELEASE' repositories { mavenCentral() } dependencies { classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version" classpath("org.springframework.boot:spring-boot-gradle-plugin:$spring_boot_version")// Kotlin整合SpringBoot的默认无参构造函数，默认把所有的类设置open类插件 classpath("org.jetbrains.kotlin:kotlin-noarg:$kotlin_version") classpath("org.jetbrains.kotlin:kotlin-allopen:$kotlin_version") }}apply plugin: 'kotlin'apply plugin: "kotlin-spring" // See https://kotlinlang.org/docs/reference/compiler-plugins.html#kotlin-spring-compiler-pluginapply plugin: 'org.springframework.boot'jar { baseName = 'chapter11-5-6-service' version = '0.1.0'}repositories { mavenCentral()}dependencies { compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlin_version" compile "org.springframework.boot:spring-boot-starter-web:$spring_boot_version" compile "org.springframework.boot:spring-boot-starter-thymeleaf:$spring_boot_version" testCompile "org.springframework.boot:spring-boot-starter-test:$spring_boot_version" testCompile "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"}compileKotlin { kotlinOptions.jvmTarget = "1.8"}compileTestKotlin { kotlinOptions.jvmTarget = "1.8"}创建文件上传controller
import name.quanke.kotlin.chaper11_5_6.storage.StorageFileNotFoundExceptionimport name.quanke.kotlin.chaper11_5_6.storage.StorageServiceimport org.springframework.beans.factory.annotation.Autowiredimport org.springframework.core.io.Resourceimport org.springframework.http.HttpHeadersimport org.springframework.http.ResponseEntityimport org.springframework.stereotype.Controllerimport org.springframework.ui.Modelimport org.springframework.web.bind.annotation.*import org.springframework.web.multipart.MultipartFileimport org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilderimport org.springframework.web.servlet.mvc.support.RedirectAttributesimport java.io.IOExceptionimport java.util.stream.Collectors/** * 文件上传控制器 * Created by http://quanke.name on 2018/1/12. */@Controllerclass FileUploadController @Autowiredconstructor(private val storageService: StorageService) { @GetMapping("/") @Throws(IOException::class) fun listUploadedFiles(model: Model): String { model.addAttribute("files", storageService .loadAll() .map { path -> MvcUriComponentsBuilder .fromMethodName(FileUploadController::class.java, "serveFile", path.fileName.toString()) .build().toString() } .collect(Collectors.toList())) return "uploadForm" } @GetMapping("/files/{filename:.+}") @ResponseBody fun serveFile(@PathVariable filename: String): ResponseEntity<Resource> { val file = storageService.loadAsResource(filename) return ResponseEntity .ok() .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=/"" + file.filename + "/"") .body(file) } @PostMapping("/") fun handleFileUpload(@RequestParam("file") file: MultipartFile, redirectAttributes: RedirectAttributes): String { storageService.store(file) redirectAttributes.addFlashAttribute("message", "You successfully uploaded " + file.originalFilename + "!") return "redirect:/" } @ExceptionHandler(StorageFileNotFoundException::class) fun handleStorageFileNotFound(exc: StorageFileNotFoundException): ResponseEntity<*> { return ResponseEntity.notFound().build<Any>() }}上传文件服务的接口
import org.springframework.core.io.Resourceimport org.springframework.web.multipart.MultipartFileimport java.nio.file.Pathimport java.util.stream.Streaminterface StorageService { fun init() fun store(file: MultipartFile) fun loadAll(): Stream<Path> fun load(filename: String): Path fun loadAsResource(filename: String): Resource fun deleteAll()}上传文件服务
import org.springframework.beans.factory.annotation.Autowiredimport org.springframework.core.io.Resourceimport org.springframework.core.io.UrlResourceimport org.springframework.stereotype.Serviceimport org.springframework.util.FileSystemUtilsimport org.springframework.util.StringUtilsimport org.springframework.web.multipart.MultipartFileimport java.io.IOExceptionimport java.net.MalformedURLExceptionimport java.nio.file.Filesimport java.nio.file.Pathimport java.nio.file.Pathsimport java.nio.file.StandardCopyOptionimport java.util.stream.Stream@Serviceclass FileSystemStorageService @Autowiredconstructor(properties: StorageProperties) : StorageService { private val rootLocation: Path init { this.rootLocation = Paths.get(properties.location) } override fun store(file: MultipartFile) { val filename = StringUtils.cleanPath(file.originalFilename) try { if (file.isEmpty) { throw StorageException("Failed to store empty file " + filename) } if (filename.contains("..")) { // This is a security check throw StorageException( "Cannot store file with relative path outside current directory " + filename) } Files.copy(file.inputStream, this.rootLocation.resolve(filename), StandardCopyOption.REPLACE_EXISTING) } catch (e: IOException) { throw StorageException("Failed to store file " + filename, e) } } override fun loadAll(): Stream<Path> { try { return Files.walk(this.rootLocation, 1) .filter { path -> path != this.rootLocation } .map { path -> this.rootLocation.relativize(path) } } catch (e: IOException) { throw StorageException("Failed to read stored files", e) } } override fun load(filename: String): Path { return rootLocation.resolve(filename) } override fun loadAsResource(filename: String): Resource { try { val file = load(filename) val resource = UrlResource(file.toUri()) return if (resource.exists() || resource.isReadable) { resource } else { throw StorageFileNotFoundException( "Could not read file: " + filename) } } catch (e: MalformedURLException) { throw StorageFileNotFoundException("Could not read file: " + filename, e) } } override fun deleteAll() { FileSystemUtils.deleteRecursively(rootLocation.toFile()) } override fun init() { try { Files.createDirectories(rootLocation) } catch (e: IOException) { throw StorageException("Could not initialize storage", e) } }}自定义异常
open class StorageException : RuntimeException { constructor(message: String) : super(message) constructor(message: String, cause: Throwable) : super(message, cause)}class StorageFileNotFoundException : StorageException { constructor(message: String) : super(message) constructor(message: String, cause: Throwable) : super(message, cause)}配置文件上传目录
import org.springframework.boot.context.properties.ConfigurationProperties@ConfigurationProperties("storage")class StorageProperties { /** * Folder location for storing files */ var location = "upload-dir"}启动Spring Boot
/** * Created by http://quanke.name on 2018/1/9. */@SpringBootApplication@EnableConfigurationProperties(StorageProperties::class)class Application { @Bean internal fun init(storageService: StorageService) = CommandLineRunner { storageService.deleteAll() storageService.init() } companion object { @Throws(Exception::class) @JvmStatic fun main(args: Array<String>) { SpringApplication.run(Application::class.java, *args) } }}创建一个简单的 html模板 src/main/resources/templates/uploadForm.html
<html xmlns:th="http://www.thymeleaf.org"><body><div th:if="${message}"> <h2 th:text="${message}"/></div><div> <form method="POST" enctype="multipart/form-data" action="/"> <table> <tr> <td>File to upload:</td> <td><input type="file" name="file"/></td> </tr> <tr> <td></td> <td><input type="submit" value="Upload"/></td> </tr> </table> </form></div><div> <ul> <li th:each="file : ${files}"> <a th:href="${file}" rel="external nofollow" th:text="${file}"/> </li> </ul></div></body></html>配置文件 application.yml
spring: http: multipart: max-file-size: 128KB max-request-size: 128KB
更多Spring Boot 和 kotlin相关内容，欢迎关注 《Spring Boot 与 kotlin 实战》
源码：
https://github.com/quanke/spring-boot-with-kotlin-in-action/
参考:
https://spring.io/guides/gs/uploading-files/
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。