Spring Boot文件上傳示例

本文介紹如何在Spring Boot Web應用程序中上傳文件。

使用的工具：

Spring Boot 1.4.3.RELEASE
Spring 4.3.5.RELEASE
Thymeleaf
Maven 3
Embedded Tomcat 8.5.6

1. 項目結構

標準項目結構如下圖所示 -

Spring

2. 項目依賴

Spring boot依賴關係，無需額外的文件上傳庫。

<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>com.yiibai</groupId>
    <artifactId>spring-boot-file-upload</artifactId>
    <packaging>jar</packaging>
    <version>1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.3.RELEASE</version>
    </parent>

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

    <dependencies>

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

        <!-- hot swapping, disable cache for template, enable live reload -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <!-- Package as an executable jar/war -->
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3.文件上傳示例

Spring Boot文件上傳，不需要什麼特別的配置。在Controller中，將上傳的文件映射到MultipartFile。
文件：UploadController.java -

package com.yiibai.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@Controller
public class UploadController {

    //Save the uploaded file to this folder
    private static String UPLOADED_FOLDER = "D://temp//";

    @GetMapping("/")
    public String index() {
        return "upload";
    }

    @PostMapping("/upload") // //new annotation since 4.3
    public String singleFileUpload(@RequestParam("file") MultipartFile file,
                                   RedirectAttributes redirectAttributes) {

        if (file.isEmpty()) {
            redirectAttributes.addFlashAttribute("message", "Please select a file to upload");
            return "redirect:uploadStatus";
        }

        try {

            // Get the file and save it somewhere
            byte[] bytes = file.getBytes();
            Path path = Paths.get(UPLOADED_FOLDER + file.getOriginalFilename());
            Files.write(path, bytes);

            redirectAttributes.addFlashAttribute("message",
                    "You successfully uploaded '" + file.getOriginalFilename() + "'");

        } catch (IOException e) {
            e.printStackTrace();
        }

        return "redirect:/uploadStatus";
    }

    @GetMapping("/uploadStatus")
    public String uploadStatus() {
        return "uploadStatus";
    }

}

在thymeleaf，只是一些普通的HTML文件標籤。文件：upload.html -

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<body>

<h1>Spring Boot文件上傳示例</h1>

<form method="POST" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file" /><br/><br/>
    <input type="submit" value="提交" />
</form>

</body>
</html>

另外一個頁面，用爲顯示文件上傳的狀態。文件：uploadStatus.html -

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<body>

<h1>Spring Boot文件上傳狀態</h1>

<div th:if="${message}">
    <h2 th:text="${message}"/>
</div>

</body>
</html>

4. 超過最大上傳大小

要處理最大上傳大小超出異常，請聲明一個[@ControllerAdvice](https://github.com/ControllerAdvice "@ControllerAdvice")並捕獲MultipartException。
文件：GlobalExceptionHandler.java

package com.yiibai.controller;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@ControllerAdvice
public class GlobalExceptionHandler {

    //http://jira.spring.io/browse/SPR-14651
    //4.3.5 supports RedirectAttributes redirectAttributes
    @ExceptionHandler(MultipartException.class)
    public String handleError1(MultipartException e, RedirectAttributes redirectAttributes) {

        redirectAttributes.addFlashAttribute("message", e.getCause().getMessage());
        return "redirect:/uploadStatus";

    }

}

5. Tomcat連接重置

如果部署到Tomcat，請配置maxSwallowSize以避免此Tomcat連接重置問題。對於嵌入式Tomcat，聲明一個TomcatEmbeddedServletContainerFactory，如下所示, SpringBootWebApplication.java -

package com.yiibai;

import org.apache.coyote.http11.AbstractHttp11Protocol;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.embedded.tomcat.TomcatConnectorCustomizer;
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
import org.springframework.context.annotation.Bean;

//http://www.agilegroup.co.jp/technote/springboot-fileupload-error-handling.html
@SpringBootApplication
public class SpringBootWebApplication {

    private int maxUploadSizeInMb = 10 * 1024 * 1024; // 10 MB

    public static void main(String[] args) throws Exception {
        SpringApplication.run(SpringBootWebApplication.class, args);
    }

    //Tomcat large file upload connection reset

    @Bean
    public TomcatEmbeddedServletContainerFactory tomcatEmbedded() {

        TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();

        tomcat.addConnectorCustomizers((TomcatConnectorCustomizer) connector -> {
            if ((connector.getProtocolHandler() instanceof AbstractHttp11Protocol<?>)) {
                //-1 means unlimited
                ((AbstractHttp11Protocol<?>) connector.getProtocolHandler()).setMaxSwallowSize(-1);
            }
        });

        return tomcat;

    }

}

6. Multipart文件大小

默認情況下，Spring Boot max文件上傳大小爲1MB，可以通過以下應用程序屬性來配置它的值，application.properties -

#http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#common-application-properties
#search multipart
spring.http.multipart.max-file-size=10MB
spring.http.multipart.max-request-size=10MB

7. 運行示例

使用默認的嵌入式Tomcat啓動Spring Boot的命令如下： mvn spring-boot:run ，運行結果如下 -

23:40:03,238 |-INFO in ch.qos.logback.classic.joran.JoranConfigurator@5a39699c - Registering current configuration as safe fallback point


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
::Spring Boot::       (v1.4.3.RELEASE)

2017-03-30 23:40:04 INFO  com.yiibai.SpringBootWebApplication - Starting SpringBootWebApplication on MY-PC with PID 880 (F:\worksp\springboot\file-upload\target\classes started by Administrator in F:\worksp\springboot\file-upload)
2017-03-30 23:40:04 DEBUG com.yiibai.SpringBootWebApplication - Running with Spring Boot v1.4.3.RELEASE, Spring v4.3.5.RELEASE
2017-03-30 23:40:04 INFO  com.yiibai.SpringBootWebApplication - No active profile set, falling back to default profiles: default
2017-03-30 23:40:08 INFO  com.yiibai.SpringBootWebApplication - Started SpringBootWebApplication in 5.359 seconds (JVM running for 6.355)

打開瀏覽器，訪問： http://localhost:8080/ 輸出結果如下 -
Spring

選擇一個文件並將其上傳，選擇大於10mb的文件，將會看到頁面提示如下 -