[SpingBoot guides系列翻译]文件上传

文件上传

这节的任务是做一个文件上传服务。

概况

参考链接

原文

thymeleaf

spring-mvc-flash-attributes

@ControllerAdvice

你构建的内容

分两部分，

服务端，由springboot构建。
客户端，是一个简单的html网页用来测试上传文件。

你需要的东西

大约15min
喜欢的编辑器或IDE(这里用IntelliJ)
jdk1.8+
Maven 3.2+ 或Gradle 4+

如何完成

跟着教程一步一步走。

通过Maven来构建

创建项目结构

mkdir -p src/main/java/hello，其实也就是在IntelliJ里面新建一个空的Java项目，然后添加一个main.java.hellopackage。

添加pom.xml文件。

<?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/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.springframework</groupId>

    <artifactId>gs-uploading-files</artifactId>

    <version>0.1.0</version>

    <parent>

        <groupId>org.springframework</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.4.RELEASE</version>

    </parent>

    <properties>

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

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

            <version>2.1.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-thymeleaf</artifactId>

            <version>2.1.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <version>2.1.4.RELEASE</version>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

spring-boot-starter-thymeleaf 是java的服务端模板引擎。

Spring Boot Maven Plugin 有以下几个作用

把项目打包成一个可执行的jar文件。
搜索并标记public static void main()为可执行类。
使用内置的依赖管理

之前设置的parent和dependency里面的version只指定了RELEASE，这里执行mvn compile的时候报了个错

[ERROR] [ERROR] Some problems were encountered while processing the POMs:

[WARNING] 'parent.version' is either LATEST or RELEASE (both of them are being deprecated) @ line 13, column 18

[WARNING] 'dependencies.dependency.version' for org.springframework.boot:spring-boot-starter-thymeleaf:jar is either LATEST or RELEASE (both of them are being deprecated) @ line 28, column 22

大意就是parent.version的LATEST 和RELEASE的值设置都是已经被废弃，所以，我们这里需要指定一下具体的版本。2.1.4.RELEASE

这个pom.xml配置在后面会报个错，Re-run Spring Boot Configuration Annotation Processor to update generated metadata，需要添加一个dependency
<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-configuration-processor</artifactId>

    <optional>true</optional>

</dependency>

创建一个IStoreService

Controller 里面需要实现一些文件上传或者是读取的逻辑，我们可以在hello.storage包中创建一个IStorageService服务来处理这些。然后在controller中使用它。面向接口编程。

src/main/java/hello/storage/IStorageService.java

package hello.storage;

import org.springframework.core.io.Resource;

import org.springframework.web.multipart.MultipartFile;

import java.nio.file.Path;

import java.util.stream.Stream;

public interface IStorageService {

    void init();

    void store(MultipartFile file);

  	//

    Stream<Path> loadAll();

    Path load(String fileName);

    Resource loadAsResource(String filename);

    void deleteAll();

}

创建一个StorageProperties

package hello.storage;

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

@ConfigurationProperties("storage")

public class StorageProperties {

    /**

     * Folder location for storing files

     */

    private String location = "upload-dir";

    public String getLocation() {

        return location;

    }

    public void setLocation(String location) {

        this.location = location;

    }

}

主要用来配置上传相关的设置，比如文件夹路径。

创建FileSystemStorageService实现这个IStoreService接口

src/main/java/hello/storage/FileSystemStorageService.java

/*

 * Copyright (c) 2019.

 * lou

 */

package hello.storage;

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.FileSystemUtils;

import org.springframework.util.StringUtils;

import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;

import java.io.InputStream;

import java.net.MalformedURLException;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.StandardCopyOption;

import java.util.stream.Stream;

@Service

public class FileSystemStorageService implements IStorageService {

    private final Path rootLocation;

    @Autowired

    public FileSystemStorageService(StorageProperties storageProperties) {

        this.rootLocation = Paths.get(storageProperties.getLocation());

    }

    @Override

    public void init() {

        System.out.println("初始化");

        try {

            Files.createDirectories(rootLocation);

        } catch (IOException e) {

            throw new StorageException("无法初始化", e);

        }

    }

    @Override

    public void store(MultipartFile file) {

        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        try {

            if (file.isEmpty()) {

                throw new StorageException("不能保存空文件" + fileName);

            }

            if (fileName.contains("..")) {

                //相对路径安全检查

                throw new StorageException("不能保存文件" + fileName + "到当前文件夹外");

            }

            try (InputStream inputStream = file.getInputStream()) {

                Files.copy(inputStream, this.rootLocation.resolve(fileName), StandardCopyOption.REPLACE_EXISTING);

            }

        } catch (IOException e) {

            new StorageException("保存文件失败:" + fileName, e);

        }

    }

    @Override

    public Stream<Path> loadAll() {

        System.out.println("获取所有");

        try {

            return Files.walk(this.rootLocation, 1)

                    .filter(path -> !path.equals(this.rootLocation))

//                    .map(path -> rootLocation.relativize(path));

                    //::表示一个委托

                    .map(this.rootLocation::relativize);

        } catch (IOException e) {

            throw new StorageException("读取保存的文件失败", e);

        }

    }

    @Override

    public Path load(String fileName) {

        System.out.println("加载单个文件" + fileName + "路径");

        return rootLocation.resolve(fileName);

    }

    @Override

    public Resource loadAsResource(String filename) {

        System.out.println("返回" + filename + "Resource类型的内容");

        try {

            Path file = load(filename);

            Resource resource = new UrlResource(file.toUri());

            if (resource.exists() || resource.isReadable()) {

                return resource;

            }

            throw new StorageFileNotFoundException("文件" + filename + "不存在");

        } catch (MalformedURLException e) {

            throw new StorageException("无法读取文件" + filename, e);

        }

    }

    @Override

    public void deleteAll() {

        System.out.println("删除所有");

        FileSystemUtils.deleteRecursively(rootLocation.toFile());

    }

}

这里需要把实现类加上@Service注解，。

定义一个StorageFileNotFound Exception

src/main/java/hello/storage/StorageFileNotFoundException.java

/*

 * Copyright (c) 2019.

 * lou

 */

package hello.storage;

public class StorageFileNotFoundException extends RuntimeException {

    public StorageFileNotFoundException(String message) {

        super(message);

    }

    public StorageFileNotFoundException(String message, Throwable cause) {

        super(message, cause);

    }

}

创建一个文件上传controller

有了上面的IStorageService，下面就可以开始创建FileUploadController了。

src/main/java/hello/FileUploadController.java

/*

 * Copyright (c) 2019.

 * lou

 */

package hello;

import hello.storage.IStorageService;

import hello.storage.StorageFileNotFoundException;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.core.io.Resource;

import org.springframework.http.HttpHeaders;

import org.springframework.http.ResponseEntity;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

import org.springframework.web.bind.annotation.*;

import org.springframework.web.multipart.MultipartFile;

import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;

import org.springframework.web.servlet.mvc.support.RedirectAttributes;

import java.util.stream.Collectors;

@Controller

public class FileUploadController {

    private final IStorageService storageService;

    @Autowired

    public FileUploadController(IStorageService storageService) {

        this.storageService = storageService;

    }

    @GetMapping("/")

    public String listUploadedFiles(Model model) {

        model.addAttribute("files", storageService.loadAll().map(

                path -> MvcUriComponentsBuilder.fromMethodName(

                        FileUploadController.class,

                        "serveFile",

                        path.getFileName().toString())

                        .build().toString())

                .collect(Collectors.toList()));

        return "uploadForm";

    }

    @GetMapping("/files/{filename:.+}")

    @ResponseBody

    public ResponseEntity<Resource> serveFile(@PathVariable String filename) {

        Resource file = storageService.loadAsResource(filename);

        return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=\"" + file.getFilename() + "\"").body(file);

    }

    @PostMapping("/")

    public String handleFileUpload(MultipartFile file, RedirectAttributes redirectAttributes) {

        storageService.store(file);

        redirectAttributes.addFlashAttribute("message", "you successfuly uploaded " + file.getOriginalFilename() + "!");

        return "redirect:/";

    }

    @ExceptionHandler(StorageFileNotFoundException.class)

    public ResponseEntity<?> handleStorageFileNotFound(StorageFileNotFoundException exc) {

        return ResponseEntity.notFound().build();

    }

}

@Controller注解要加上。构造函数上加上@AutoWired注解，Spring就会自动装配，因为构造函数上有IStorageService，Spring会去找实现这个类的@Service bean。然后定义几个方法，以及对应的路由。handleStorageFileNotFound方法用来处理当前controller出现的StorageFileNotFound异常。

GET /路由通过StorageService获取所有上传的文件列表，然后装载到Thymeleaf模板引擎中。通过MvcUriComponentsBuilder来计算得到实际的链接。
GET /files/{filename}加载资源，如果存在的话通过Content-Disposition头返回给浏览器用于下载。
POST /用于接收file，然后传递给storageService处理。

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="${file}" th:text="${file}" />

        </li>

    </ul>

</div>

</body>

</html>

有3点：

第一个div中是可选的message参数，用来展示spring mvc设置的flash-scoped message
第二个div用来给用户添加上传文件。
第三个div显示所有的文件。

调节上传文件的相关限制

一般来说，我们会设置上传的文件大小。设想一下如果让spring去处理一个5G的文件上传。可以通过如下方法设置。

添加application.properties文件。

src/main/resources/application.properties

# Copyright (c) 2019.

# lou

#

spring.servlet.multipart.max-file-size=128KB

spring.servlet.multipart.max-request-size=128KB

设置了最大文件大小和最大的请求大小，这样如果上传的文件太大，会获取到异常。

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Mon May 06 17:46:51 CST 2019

There was an unexpected error (type=Internal Server Error, status=500).

Maximum upload size exceeded; nested exception is java.lang.IllegalStateException: org.apache.tomcat.util.http.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (727520) exceeds the configured maximum (131072)

max-request-size里面包括所有input的内容，也就是说request-size≥file-size。

定义一个FileUploadExceptionAdvice来处理MaxUploadSizeExceededException

这个org.springframework.web.multipart.MaxUploadSizeExceededException在是无法在控制器里面获取到的，所以可以通过@ControllerAdvice来处理。

src/main/java/hello/storage/FileUploadExceptionAdvice.java

/*

 * Copyright (c) 2019.

 * lou

 */

package hello.storage;

import org.apache.tomcat.util.http.fileupload.FileUploadBase;

import org.springframework.http.ResponseEntity;

import org.springframework.web.bind.annotation.ControllerAdvice;

import org.springframework.web.bind.annotation.ExceptionHandler;

import org.springframework.web.multipart.MaxUploadSizeExceededException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@ControllerAdvice

public class FileUploadExceptionAdvice {

    @ExceptionHandler(MaxUploadSizeExceededException.class)

    public ResponseEntity<ResponseResult> handleMaxSizeException(

            MaxUploadSizeExceededException ex,

            HttpServletRequest request,

            HttpServletResponse response) {

        long actual = request.getContentLengthLong();

        long permitted = -1L;

        if (ex.getCause() != null && ex.getCause().getCause() instanceof FileUploadBase.SizeLimitExceededException) {

            FileUploadBase.SizeLimitExceededException causeEx = (FileUploadBase.SizeLimitExceededException) ex.getCause().getCause();

            permitted = causeEx.getPermittedSize();

        }

        return ResponseEntity.ok(new ResponseResult("上传文件大小："+actual + "，超过了最大:" + permitted, false));

    }

}

通过MaxUploadSizeExceededException.getCause()获取内部的SizeLimitExceededException异常详细信息，再通过ResponseEntity.ok()返回json数据。

构建可执行程序

下面就到了写Application.java 的时候了。

src/main/java/hello/Application.java

/*

 * Copyright (c) 2019.

 * lou

 */

package hello;

import hello.storage.IStorageService;

import hello.storage.StorageProperties;

import org.springframework.boot.CommandLineRunner;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

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

import org.springframework.context.annotation.Bean;

@SpringBootApplication

@EnableConfigurationProperties({StorageProperties.class})

public class Application {

    public static void main(String[] args) {

        SpringApplication.run(Application.class, args);

    }

    @Bean

    CommandLineRunner run(IStorageService storageService) {

        System.out.println("进入run方法");

        return args -> {

            storageService.deleteAll();

            storageService.init();

        };

    }

}

CommandLineRunner+@Bean确保程序启动的时候会运行。

@SpringBootApplication提供一下几点：

表名这个configuration 类里面声明了一些@Bean方法。
触发 auto-configuration
开启 component 扫描.
等于同时定义了 @Configuration, @EnableAutoConfiguration and @ComponentScan.

@EnableConfigurationProperties使得StorageProperties可以作为配置类。

运行输入 mvn spring-boot:run。

打包输入mvn package。然后生成jar就可以用java -jar xxx.jar运行了。

巴特西