Spring Boot 上传下载



  • 上传下载

    在本章中,您将学习如何使用Web服务上载和下载文件。
  • 上传文件

    要上传文件,您可以将MultipartFile用作请求参数,并且此API应该使用Multi-Part表单数据值。遵守下面给出的代码
    
    @RequestMapping(value = "/upload", method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    
    public String fileUpload(@RequestParam("file") MultipartFile file) {
       return null;
    }
    
    
    相同的完整代码如下-
    
    package com.jc2182.demo.controller;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    import org.springframework.http.MediaType;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.multipart.MultipartFile;
    
    @RestController
    public class FileUploadController {
       @RequestMapping(value = "/upload", method = RequestMethod.POST, 
          consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
       
       public String fileUpload(@RequestParam("file") MultipartFile file) throws IOException {
          File convertFile = new File("/var/tmp/"+file.getOriginalFilename());
          convertFile.createNewFile();
          FileOutputStream fout = new FileOutputStream(convertFile);
          fout.write(file.getBytes());
          fout.close();
          return "File is upload successfully";
       }
    }
    
    
  • 下载文件

    对于文件下载,应使用InputStreamResource下载文件。我们需要在Response中设置HttpHeader Content-Disposition,并需要指定应用程序的响应媒体类型。
    注 –在以下示例中,文件应在应用程序运行所在的指定路径上可用。
    
    @RequestMapping(value = "/download", method = RequestMethod.GET) 
    public ResponseEntity<Object> downloadFile() throws IOException  {
       String filename = "/var/tmp/mysql.png";
       File file = new File(filename);
       InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
       HttpHeaders headers = new HttpHeaders();
          
       headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
       headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
       headers.add("Pragma", "no-cache");
       headers.add("Expires", "0");
          
       ResponseEntity<Object> 
       responseEntity = ResponseEntity.ok().headers(headers).contentLength(file.length()).contentType(
          MediaType.parseMediaType("application/txt")).body(resource);
          
       return responseEntity;
    }
    
    
    相同的完整代码如下-
    
    package com.jc2182.demo.controller;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    
    import org.springframework.core.io.InputStreamResource;
    import org.springframework.http.HttpHeaders;
    import org.springframework.http.MediaType;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class FileDownloadController {
       @RequestMapping(value = "/download", method = RequestMethod.GET) 
       public ResponseEntity<Object> downloadFile() throws IOException  {
          String filename = "/var/tmp/mysql.png";
          File file = new File(filename);
          InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
          HttpHeaders headers = new HttpHeaders();
          
          headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
          headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
          headers.add("Pragma", "no-cache");
          headers.add("Expires", "0");
          
          ResponseEntity<Object> 
          responseEntity = ResponseEntity.ok().headers(headers).contentLength(
             file.length()).contentType(MediaType.parseMediaType("application/txt")).body(resource);
          
          return responseEntity;
       }
    }
    
    
    下面给出了主要的Spring Boot应用程序-
    
    package com.jc2182.demo;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class DemoApplication {
       public static void main(String[] args) {
          SpringApplication.run(DemoApplication.class, args);
       }
    }
    
    
    Maven构建的代码– pom.xml如下所示-
    
    <?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 https://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>2.3.0.BUILD-SNAPSHOT</version>
            <relativePath/> <!-- lookup parent from repository -->
        </parent>
        <groupId>com.jc2182</groupId>
        <artifactId>demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>demo</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-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
            </repository>
            <repository>
                <id>spring-snapshots</id>
                <name>Spring Snapshots</name>
                <url>https://repo.spring.io/snapshot</url>
                <snapshots>
                    <enabled>true</enabled>
                </snapshots>
            </repository>
        </repositories>
        <pluginRepositories>
            <pluginRepository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
            </pluginRepository>
            <pluginRepository>
                <id>spring-snapshots</id>
                <name>Spring Snapshots</name>
                <url>https://repo.spring.io/snapshot</url>
                <snapshots>
                    <enabled>true</enabled>
                </snapshots>
            </pluginRepository>
        </pluginRepositories>
    
    </project>
    
    
    下面给出了Gradle Build – build.gradle的代码-
    
    plugins {
        id 'org.springframework.boot' version '2.3.0.BUILD-SNAPSHOT'
        id 'io.spring.dependency-management' version '1.0.9.RELEASE'
        id 'java'
    }
    
    group = 'com.jc2182'
    version = '0.0.1-SNAPSHOT'
    sourceCompatibility = '1.8'
    
    repositories {
        mavenCentral()
        maven { url 'https://repo.spring.io/milestone' }
        maven { url 'https://repo.spring.io/snapshot' }
    }
    
    dependencies {
        implementation 'org.springframework.boot:spring-boot-starter-web'
        testImplementation('org.springframework.boot:spring-boot-starter-test') {
            exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
        }
    }
    
    test {
        useJUnitPlatform()
    }    
    
    
    您可以创建一个可执行的JAR文件,并使用Maven或Gradle命令运行Spring Boot应用程序-
    对于Maven,您可以使用以下命令-
    
    mvn clean install
    
    
    在“BUILD SUCCESS”之后,您可以在target目录下找到JAR文件。
    对于Gradle,您可以使用以下命令-
    
    gradle clean build
    
    
    在“BUILD SUCCESSFUL”之后,您可以在build/libs目录下找到JAR文件。
    您可以使用以下命令运行JAR文件-
    
    java –jar <JARFILE>
    
    
    在Tomcat端口8080上启动应用程序
    文件上传 - http://localhost:8080/upload
    文件下载 - http://localhost:8080/download