SpringMVC__简单文件上传与下载

一、文件上传
1、要用的基本两个包：

2、简单的表单：

<form action="/SpringDemo08/upLoad" method="post" enctype="multipart/form-data">
		账号:<input type="text" name="userName"><br>
		头像:<input type="file" name="file"><br>
		<input type="submit" value="提交">
	</form>

这里重点是：
method="post"
enctype="multipart/form-data"

必须是post方式提交，也必须设置enctype为
multipart/form-data，

controller

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class UploadFile {
	/**
	 * 文件上传
	 * @param file
	 * @return
	 * @throws IllegalStateException
	 * @throws IOException
	 */
	@RequestMapping("/upLoad")
	@ResponseBody
	public String upLoad(MultipartFile file) throws IllegalStateException, IOException {
		// TODO Auto-generated method stub
		// getOriginalFilename()获取原始文件名(在客户端时的文件名)
		//getFileName() 在服务器上的文件名.
		String filename = file.getOriginalFilename();
		File file2 = new File("D:/imgs/"+filename);
		//这里你可以进行重命名也可以把路径入库
     //这里我就不做其他业务操作了

		//MultipartFile中的transferTo不能使用两次
		//因为http post文件流只可以接收读取一次，传输完毕则关闭流。
		//可以把流保存为文件1，然后对文件1进行复制，移动等操作
		//transferTo转存文件到指定路径
		file.transferTo(file2);
		return "上传成功";
	}
}

applicationContext.xml配置：

<!-- 配置文件上传的处理器 -->
	<bean class="org.springframework.web.multipart.commons.CommonsMultipartResolver" id="multipartResolver">
		<property name="maxUploadSize" value="5242880"/>
	</bean>

CommonsMultipartResolver这个Bean的id必须为multipartResolver，
原因：CommonsMultipartResolver Bean是在中央控制器DispatcherServlet中加载的，而DispatcherServlet是通过名字来查找这个Bean的。而其他的，则是按照类型查找。

二、文件下载

1. 方式一:基于ResponseEntity实现

@RequestMapping("/download ")
public ResponseEntity<byte[]> download(HttpServletRequest request) throws IOException {
    // 需要下载的文件
	File file = new File("C:\Users\Administrator\Pictures\Saved Pictures\2.jpg");
    byte[] body = null;
    InputStream is = new FileInputStream(file);
    body = new byte[is.available()];
    is.read(body);
    HttpHeaders headers = new HttpHeaders();
    headers.add("Content-Disposition", "attchement;filename=" + file.getName());
    HttpStatus statusCode = HttpStatus.OK;
    ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(body, headers, statusCode);
    return entity;
}

2. 方式二：通用下载实现

/**
	 * 文件下载
	 * @param req
	 * @param resp
	 * @throws IOException
	 */
	@RequestMapping("/downLoad")
	@SuppressWarnings("resource")
	public void downLoad(HttpServletRequest req,HttpServletResponse resp) throws IOException {
		// TODO Auto-generated method stub
		File file = new File("C:\Users\Administrator\Pictures\Saved Pictures\2.jpg");
		req.setCharacterEncoding("utf-8");
		resp.setContentType("multipart/form-data");
	    resp.setHeader("Content-Disposition", "attachment;fileName="+file.getName() );
	    FileInputStream inputStream = new FileInputStream(file);
	    ServletOutputStream outputStream = resp.getOutputStream();
	    int num = 0;
	    byte[] b = new byte[1024]; 
	    while ((num = inputStream.read(b)) != -1) {
	    	outputStream.write(b, 0, num);
		}
	    outputStream.flush();
	    outputStream.close();
	    inputStream.close();
	}