Java开发之Spring Webflow实现上传单个文件及多个文件功能实例

介绍

Spring Webflow是Spring框架的扩展模块，可以帮助我们实现基于流程的Web应用程序。在Web应用程序中，文件上传功能是常见需求之一，本文将介绍如何使用Spring Webflow实现上传单个文件及多个文件功能。

上传单个文件

1. Maven依赖

在pom.xml文件中，添加以下依赖：

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webflow</artifactId>
    <version>2.4.5.RELEASE</version>
</dependency>

2. 配置文件

在Spring MVC的配置文件中添加以下内容：

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="5242880"/> // 设置最大上传文件大小5MB
</bean>

3. 文件上传页面

构建上传文件页面upload.jsp，添加如下代码：

<form:form method="post" modelAttribute="fileForm" enctype="multipart/form-data">
    <form:errors path="file" cssClass="error" />
    <form:input type="file" path="file"/>
    <input type="submit" value="Upload"/>
</form:form>

4. 控制器

构建上传文件控制器UploadController.java，添加如下代码：

@Controller
@FlowDefinition(id = "uploadFile", basePath = "/WEB-INF/flows", flowName = "upload-file")
public class UploadController {

    @Autowired
    private ResourceLoader resourceLoader;

    @RequestMapping(value = "/upload", method = RequestMethod.GET)
    public String upload(Model model) {
        model.addAttribute("fileForm", new FileForm());
        return "upload";
    }

    @RequestMapping(value = "/upload", method = RequestMethod.POST)
    public String upload(@ModelAttribute("fileForm") FileForm fileForm, BindingResult result, HttpServletRequest request) {
        if (result.hasErrors()) {
            return null;
        }
        MultipartFile file = fileForm.getFile();
        String fileName = file.getOriginalFilename();
        String filePath = "file:" + request.getSession().getServletContext().getRealPath("/") + "/" + fileName;
        Resource resource = resourceLoader.getResource(filePath);
        try {
            file.transferTo(resource.getFile());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "success";
    }

}

5. 文件上传流程

构建文件上传的流程文件upload-file.xml，添加如下代码：

<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="
      http://www.springframework.org/schema/webflow
      http://www.springframework.org/schema/webflow/spring-webflow-2.4.xsd">

    <var name="fileForm" class="com.example.FileForm"/>

    <view-state id="upload" view="upload">
        <on-entry>
            <evaluate expression="flowScope.fileForm = new com.example.FileForm()"/>
        </on-entry>
        <transition on="submit" to="uploadAction"/>
    </view-state>

    <action-state id="uploadAction">
        <evaluate expression="uploadController.upload(fileForm, messageContext, externalContext.nativeRequest)"/>
        <transition to="success"/>
    </action-state>

    <end-state id="success" view="success"/>

</flow>

6. 文件上传表单数据绑定

构建文件上传表单数据绑定FileForm.java，添加如下代码：

public class FileForm {

    private MultipartFile file;

    // getter and setter

}

上传多个文件

1. Maven依赖

在pom.xml文件中，添加以下依赖：

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>

2. 配置文件

在Spring MVC的配置文件中添加以下内容：

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="5242880"/> // 设置最大上传文件大小5MB
</bean>

3. 文件上传页面

构建上传多个文件页面uploadMultiple.jsp，添加如下代码：

<form:form method="post" modelAttribute="fileForm" enctype="multipart/form-data">
    <form:errors path="files" cssClass="error" />
    <form:input type="file" path="files" multiple="multiple"/>
    <input type="submit" value="Upload"/>
</form:form>

4. 控制器

构建上传多个文件控制器UploadMultipleController.java，添加如下代码：

@Controller
@FlowDefinition(id = "uploadMultipleFiles", basePath = "/WEB-INF/flows", flowName = "upload-multiple-files")
public class UploadMultipleController {

    @RequestMapping(value = "/uploadMultiple", method = RequestMethod.GET)
    public String upload(Model model) {
        model.addAttribute("fileForm", new FileForm());
        return "uploadMultiple";
    }

    @RequestMapping(value = "/uploadMultiple", method = RequestMethod.POST)
    public String upload(@ModelAttribute("fileForm") FileForm fileForm, BindingResult result, HttpServletRequest request) {
        if (result.hasErrors()) {
            return null;
        }
        MultipartFile[] files = fileForm.getFiles();
        String filePath = request.getSession().getServletContext().getRealPath("/") + "/"; // 上传文件保存路径
        for (MultipartFile file : files) {
            String fileName = file.getOriginalFilename();
            File dest = new File(filePath + fileName);
            try {
                file.transferTo(dest);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return "success";
    }

}

5. 文件上传流程

构建文件上传的流程文件upload-multiple-files.xml，添加如下代码：

<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="
      http://www.springframework.org/schema/webflow
      http://www.springframework.org/schema/webflow/spring-webflow-2.4.xsd">

    <var name="fileForm" class="com.example.FileForm"/>

    <view-state id="upload" view="uploadMultiple">
        <on-entry>
            <evaluate expression="flowScope.fileForm = new com.example.FileForm()"/>
        </on-entry>
        <transition on="submit" to="uploadAction"/>
    </view-state>

    <action-state id="uploadAction">
        <evaluate expression="uploadMultipleController.upload(fileForm, messageContext, externalContext.nativeRequest)"/>
        <transition to="success"/>
    </action-state>

    <end-state id="success" view="success"/>

</flow>

6. 文件上传表单数据绑定

构建文件上传表单数据绑定FileForm.java，添加如下代码：

public class FileForm {

    private MultipartFile[] files;

    // getter and setter

}

总结

通过本文的介绍，我们了解了如何使用Spring Webflow实现上传单个文件及多个文件的功能。在实现过程中，关键部分是控制器中的代码逻辑，需要手动处理文件上传的各个步骤。通过Web框架提供的各个模块的帮助，我们可以更加快捷地实现Web应用程序的开发。