spring boot 图片上传与显示功能实例详解

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 

如果大家对spring boot不是很了解，大家可以参考下面两篇文章。

spring boot 快速入门教程

spring boot 快速入门指南

以上所述是小编给大家介绍的spring boot 图片上传与显示功能实例详解，希望对大家有所帮助