转载

SpringMVC文件上传

来自 org.springframework.web.multipart 包下的 MultipartResolver 提供解析包括文件上传在内的多部分请求策略。一种实现方式是基于 Commons FileUpload ,另外则基于 Servlet 3.0 的多部分请求解析。

启用多部分处理，需要在 DispatcherServlet Spring配置中声明一个名为 multipartResolver 的 MultipartResolver bean。 DispatcherServlet 检测到它并将其应用于传入的请求。当接收到一个 content-type 是 multipart/form-data 的POST请求时，解析程序将解析内容并将当前 HttpServletRequest 包装为 MultipartHttpServletRequest ，以提供对已解析部分的访问权限，此外将其作为请求参数公开。

Apache Commons `FileUpload`

使用Apache Commons FileUpload ,需要配置名称为 multipartResolver 的 CommonsMultipartResolver 类型的Bean。还需要引入 commons-fileupload 的依赖。

Servlet 3.0

启用Servlet 3.0多部分解析需要通过Servlet容器配置。操作如下：

MultipartConfigElement
<multipart-config>

代码实现

Spring MVC环境配置

通过MAVEN构建一个 maven-archetypeweb-app 项目，通过Java代码形式配置SpringMVC，具体配置方式如下。

pom.xml,引入依赖

<properties>
    ...
    <spring.version>5.2.2.RELEASE</spring.version>
    <tomcat.version>8.5.5</tomcat.version>
</properties>

<dependencies>
    <!--spring -core-->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <!--web-->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
</dependencies>
复制代码

Spring MVC配置

AppConfig.java

@Configuration
@ComponentScan("io.github.nirvanafire")
public class AppConfig implements WebMvcConfigurer {
    ...
}
复制代码

MyWebApplicationInitializer.java

public class MyWebApplicationInitializer implements WebApplicationInitializer {

    private int MAX_UPLOAD_SIZE = 5 * 1024 * 1024;

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        System.out.println("---MyApplicationInitializer onStartup---");

        // 加载Spring Web应用配置
        AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext ();
        ac.register(AppConfig.class);
        ac.refresh();

        // 创建并注册DispatcherServlet(前端控制器)
        DispatcherServlet ds = new DispatcherServlet(ac);
        ServletRegistration.Dynamic registration = servletContext.addServlet("dispatchServlet", ds);
        registration.setLoadOnStartup(1);
        registration.addMapping("*.do");
    }
}
复制代码

文件上传Controller实现

@RestController
public class UploadController {

    @PostMapping("/upload_commons")
    public String uploadCommons(@RequestPart("file") MultipartFile file) {

        System.out.println("---Run Upload Commons---");
        storeFile(file);
        return "success";
    }

    private void storeFile(MultipartFile file) {
        try {

            String originalFilename = file.getOriginalFilename();
            System.out.println("----File Name: " + originalFilename + "----");

            File tmpFolder = new File("tmp");
            if (!tmpFolder.exists()) {
                tmpFolder.mkdir();
            }

            File tmp = new File("tmp/" + originalFilename);
            FileOutputStream fos = new FileOutputStream(tmp);
            FileCopyUtils.copy(file.getInputStream(), fos);
        } catch (IOException e) {
            System.out.println("Upload File Error: " + e.getMessage());
        }
    }
}
复制代码

页面代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>SpringMVC-UploadFile</title>
</head>
<body>
    <h1>SpringMVC-UploadFile</h1>

    <hr>
    <h2>Apache Commons FileUpload</h2>
    <form action="/upload_commons.do" enctype="multipart/form-data" method="post">
        <input type="file" name="file">
        <input type="submit" value="Submit">
    </form>
 
</body>
</html>
复制代码

Apache Commons `FileUpload`

在pom.xml文件中引入依赖Apache Commons FileUpload依赖：

<!-- commons-fileupload -->
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>
复制代码

在 AppConfig.java 中声明一个名称为 multipartResolver 的 CommonsMultipartResolver Bean。

@Configuration
@ComponentScan("io.github.nirvanafire")
public class AppConfig implements WebMvcConfigurer {
    ...
    @Bean("multipartResolver")
    public CommonsMultipartResolver commonsMultipartResolver() {
        CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
        return commonsMultipartResolver;
    }
}
复制代码

Servlet 3.0

在Servlet注册器中设置一个 MultipartConfigElement ，即在 MyWebApplicationInitializer.java 中添加如下代码:

private int MAX_UPLOAD_SIZE = 5 * 1024 * 1024;
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
    ...
    System.out.println("---tmpdir: "  + System.getProperty("java.io.tmpdir") + "---");
    File uploadDirectory = new File(System.getProperty("java.io.tmpdir"));

    /**
     * MultipartConfigElement参数含义
     * @param location the directory location where files will be stored (上传文件存储目录)
     * @param maxFileSize the maximum size allowed for uploaded files(单文件上传大小限制)
     * @param maxRequestSize the maximum size allowed for multipart/form-data requests(一个请求上传大小限制)
     * @param fileSizeThreshold the size threshold after which files will (文件写入磁盘的阈值，可理解为每次读取文件大小)
     */
    MultipartConfigElement multipartConfigElement = new MultipartConfigElement(uploadDirectory.getAbsolutePath(),
            MAX_UPLOAD_SIZE, MAX_UPLOAD_SIZE * 2, MAX_UPLOAD_SIZE / 2);
    registration.setMultipartConfig(multipartConfigElement);
}
复制代码

在 AppConfig.java 中声明一个名称为 multipartResolver 的 StandardServletMultipartResolver Bean。

@Configuration
@ComponentScan("io.github.nirvanafire")
public class AppConfig implements WebMvcConfigurer {
    ...
    @Bean("multipartResolver")
    public StandardServletMultipartResolver standardServletMultipartResolver() {
        StandardServletMultipartResolver standardServletMultipartResolver = new StandardServletMultipartResolver();
        return standardServletMultipartResolver;
    }
}
复制代码

原文 https://juejin.im/post/5dfb025cf265da33d7442dba

正文到此结束