【SpringMVC】实现文件下载功能

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * ResponseEntity：可以作为控制器方法的返回值，表示响应到浏览器的完整的响应报文
 */
@Controller
public class FileUpAndDownController {
    @RequestMapping("/test/down")
    public ResponseEntity testResponseEntity(HttpSession session) throws IOException {
        //获取ServletContext对象
        ServletContext servletContext = session.getServletContext();
        //获取服务器中文件的真实路径
        String realPath = servletContext.getRealPath("img");
        realPath = realPath + File.separator + "1.jpg";
        //System.out.println(realPath);
        //创建输入流
        InputStream is = new FileInputStream(realPath);
        //创建字节数组is.available():获取输入流对应文件的字节数
        byte[] bytes = new byte[is.available()];
        //将流读到字节数组中
        is.read(bytes);
        //创建HttpHeaders对象设置响应头信息，map集合
        MultiValueMap headers = new HttpHeaders();
        //设置要下载方式以及下载文件的名字，以下都是固定格式，除了文件名字，，attachment：下载方式
        headers.add("Content-Disposition", "attachment;filename=1.jpg");
        //设置响应状态码
        HttpStatus statusCode = HttpStatus.OK;
        //创建ResponseEntity对象    响应体  响应头  响应状态码
        ResponseEntity responseEntity = new ResponseEntity<>(bytes, headers,statusCode);
        //关闭输入流
        is.close();
        return responseEntity;
    }
}