Spring 文件上传功能

2015-11-28 20:56:17 分类：编程

本篇文章，我们要来做一个Spring的文件上传功能：

1. 创建一个Maven的web工程，然后配置pom.xml文件，增加依赖：

      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-web</artifactId>
          <version>1.0.2.RELEASE</version>
      </dependency>

2.在webapp目录下的index.jsp文件中输入一个表单：

<html>
<body>
<form method="POST" enctype="multipart/form-data"
      action="/upload">
    File to upload: <input type="file" name="file"><br /> Name: <input
        type="text" name="name"><br /> <br /> <input type="submit"
                                                     value="Upload"> Press here to upload the file!
</form>
</body>
</html>

这个表单就是我们模拟的上传页面。

3. 编写处理这个表单的Controller：

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;

import org.springframework.stereotype.Controller;
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.ResponseBody;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class FileUploadController {

    @RequestMapping(value="/upload", method=RequestMethod.GET)
    public @ResponseBody String provideUploadInfo() {
        return "You can upload a file by posting to this same URL.";
    }

    @RequestMapping(value="/upload", method=RequestMethod.POST)
    public @ResponseBody String handleFileUpload(@RequestParam("name") String name,
            @RequestParam("file") MultipartFile file){
        if (!file.isEmpty()) {
            try {
                byte[] bytes = file.getBytes();
                BufferedOutputStream stream =
                        new BufferedOutputStream(new FileOutputStream(new File(name + "-uploaded")));
                stream.write(bytes);
                stream.close();
                return "You successfully uploaded " + name + " into " + name + "-uploaded !";
            } catch (Exception e) {
                return "You failed to upload " + name + " => " + e.getMessage();
            }
        } else {
            return "You failed to upload " + name + " because the file was empty.";
        }
    }

}

4. 然后我们对上传的文件做一些限制，同时编写main方法来启动这个web ：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.context.embedded.MultiPartConfigFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import javax.servlet.MultipartConfigElement;

@Configuration
@ComponentScan
@EnableAutoConfiguration
public class Application {

    @Bean
    public MultipartConfigElement multipartConfigElement() {
        MultiPartConfigFactory factory = new MultiPartConfigFactory();
        factory.setMaxFileSize("128KB");
        factory.setMaxRequestSize("128KB");
        return factory.createMultipartConfig();
    }

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

　　5. 然后访问http://localhost:8080/upload就可以看到页面了。

上面的例子是实现的是单个文件上传的功能，假定我们现在要实现文件批量上传的功能的话，我们只需要简单的修改一下上面的代码就行，考虑到篇幅的问题，下面只是贴出和上面不同的代码，没有贴出的说明和上面一样。：

1.　　新增batchUpload.jsp文件

<html>
<body>
<form method="POST" enctype="multipart/form-data"
      action="/batch/upload">
    File to upload: <input type="file" name="file"><br />
    File to upload: <input type="file" name="file"><br />
    <input type="submit" value="Upload"> Press here to upload the file!
</form>
</body>
</html>

2. 新增BatchFileUploadController.java文件：

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;

import javax.servlet.http.HttpServletRequest;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.util.List;

/**
 * Created by wenchao.ren on 2014/4/26.
 */

@Controller
public class BatchFileUploadController {

    @RequestMapping(value="/batch/upload", method= RequestMethod.POST)
    public @ResponseBody
    String handleFileUpload(HttpServletRequest request){
        List<MultipartFile> files = ((MultipartHttpServletRequest)request).getFiles("file");
        for (int i =0; i< files.size(); ++i) {
            MultipartFile file = files.get(i);
            String name = file.getName();
            if (!file.isEmpty()) {
                try {
                    byte[] bytes = file.getBytes();
                    BufferedOutputStream stream =
                            new BufferedOutputStream(new FileOutputStream(new File(name + i)));
                    stream.write(bytes);
                    stream.close();
                } catch (Exception e) {
                    return "You failed to upload " + name + " => " + e.getMessage();
                }
            } else {
                return "You failed to upload " + name + " because the file was empty.";
            }
        }
        return "upload successful";
    }
}

　　这样一个简单的批量上传文件的功能就ok了，是不是很简单啊。

注意：上面的代码只是为了演示而已，所以编码风格上采取了随性的方式，不建议大家模仿。

参考资料：

1. MultipartResolver也可以实现文件上传功能。参考文章：http://mylfd.iteye.com/blog/1893648

Spring 文件上传功能

在线测试

参考手册