spring boot 图片的上传与显示

http://blog.csdn.net/a625013/article/details/52414470

首先描述一下问题，spring boot 使用的是内嵌的tomcat， 所以不清楚文件上传到哪里去了， 而且spring boot 把静态的文件全部在启动的时候都会加载到classpath的目录下的，所以上传的文件不知相对于应用目录在哪，也不知怎么写访问路径合适，对于新手的自己真的一头雾水。

后面想起了官方的例子，没想到一开始被自己找到的官方例子，后面太依赖百度谷歌了，结果发现只有官方的例子能帮上忙，而且帮上大忙，直接上密码的代码

package hello;

import static org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo;
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.methodOn;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Collectors;

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.ResourceLoader;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
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;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@Controller
public class FileUploadController {

    private static final Logger log = LoggerFactory.getLogger(FileUploadController.class);

    public static final String ROOT = "upload-dir";

    private final ResourceLoader resourceLoader;

    @Autowired
    public FileUploadController(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    @RequestMapping(method = RequestMethod.GET, value = "/")
    public String provideUploadInfo(Model model) throws IOException {

        model.addAttribute("files", Files.walk(Paths.get(ROOT))
                .filter(path -> !path.equals(Paths.get(ROOT)))
                .map(path -> Paths.get(ROOT).relativize(path))
                .map(path -> linkTo(methodOn(FileUploadController.class).getFile(path.toString())).withRel(path.toString()))
                .collect(Collectors.toList()));

        return "uploadForm";
    }

//显示图片的方法关键 匹配路径像 localhost:8080/b7c76eb3-5a67-4d41-ae5c-1642af3f8746.png
    @RequestMapping(method = RequestMethod.GET, value = "/{filename:.+}")
    @ResponseBody
    public ResponseEntity<?> getFile(@PathVariable String filename) {

        try {
            return ResponseEntity.ok(resourceLoader.getResource("file:" + Paths.get(ROOT, filename).toString()));
        } catch (Exception e) {
            return ResponseEntity.notFound().build();
        }
    }

<strong>//上传的方法</strong>
    @RequestMapping(method = RequestMethod.POST, value = "/")
    public String handleFileUpload(@RequestParam("file") MultipartFile file,
                                   RedirectAttributes redirectAttributes, HttpServletRequest request) {
        System.out.println(request.getParameter("member"));
        if (!file.isEmpty()) {
            try {
                Files.copy(file.getInputStream(), Paths.get(ROOT, file.getOriginalFilename()));
                redirectAttributes.addFlashAttribute("message",
                        "You successfully uploaded " + file.getOriginalFilename() + "!");
            } catch (IOException|RuntimeException e) {
                redirectAttributes.addFlashAttribute("message", "Failued to upload " + file.getOriginalFilename() + " => " + e.getMessage());
            }
        } else {
            redirectAttributes.addFlashAttribute("message", "Failed to upload " + file.getOriginalFilename() + " because it was empty");
        }

        return "redirect:/";
    }

}

看完上面的代码可以理解到spring boot 的存取文件思路了，存的时候的路径为

Paths.get(ROOT, filename).toString()))

这个路径会在本地的工程根目录上创建，不应用部署里的目录，所以一般的访问http访问不可能 ，所以它提供了ResourceLoader,利于这个类可以加载非应用目录的里文件然后返回

所以就可以读取文件，所以就要写getFIle方法来显示图片

 

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