页面

<li>
                    <span>当前头像：</span>
                    <!-- <img src="./images/user-lg.png" alt=""> -->
                    <img style="width:100px;height:100px" th:src="@{/headImg?id=} + ${session.member.id}" onerror="defaultImg(this)"/>
                    <!-- <img th:value="${session.member.headImg}" > -->
                    <div style="float:center;margin-left:140px">
                    	<form action="/saveImg" method="post" enctype ="multipart/form-data">
    						<label for="file" class="btn btn-primary" style="float: left;height: 30px;width: 100px;margin-right: 20px">选择照片</label>
    						<input  id="file" name="file" type="file" style="float: left;display:none"/>
    						<input  name="id" type="hidden" th:value="${session.member.id}"/>
    						<input  class="btn btn-primary" type="submit" value="提交" style="float: left">
						</form>
                    </div>
                </li>
<script>
	function defaultImg(img){
		img.src="/images/user-lg.png";
		}
</script>

controller层

@RequestMapping("/saveImg")//its maximum permitted size of 1048576 bytes.
	public String saveUserImg(MultipartFile file,Member member) {
		Map<String,Object> result = new HashMap<String,Object>();
		try {
		// 获取客户端传图图片的输入流
		InputStream ins = file.getInputStream();
		byte[] buffer=new byte[2048];//bit---byte---1k---1m
		int len=0;
		 // 字节输出流
		 ByteArrayOutputStream bos=new ByteArrayOutputStream();
		while((len=ins.read(buffer))!=-1){
			bos.write(buffer,0,len);
		 }
		 bos.flush();
		byte img[] = bos.toByteArray();
		member.setHeadImg(img);
		System.out.println("图片==="+member.getHeadImg());
		int i=memberService.saveImg(member);//修改数据库
		
		result.put("code",i);
			result.put("msg", "保存头像成功");
		} catch (Exception e) {
			result.put("code",0);
			result.put("msg", "保存头像失败");
			return "uploaderror";
		 }				
		return "e-commerce_account";	
	}
	@RequestMapping(value = "/headImg", produces = MediaType.IMAGE_PNG_VALUE)
	public ResponseEntity<byte[]> headImg(String id) throws Exception{

		byte[] imageContent ;
		// 根据id获取当前用户的信息
		Member member = memberService.selectMemberById(id);
				        
		imageContent = member.getHeadImg();
		System.out.println("图片==="+member.getHeadImg());//member.getCzyxm()
				        
		// 设置http头部信息
		final HttpHeaders headers = new HttpHeaders();
		headers.setContentType(MediaType.IMAGE_PNG);
		// 返回响应实体
		return new ResponseEntity<byte[]>(imageContent, headers, HttpStatus.OK);
	}

Service层

	@Override
	public int saveImg(Member member) throws Exception {
		int i = memberMapper.saveUserImg(member);
		if(i!=1) {
			throw new Exception("更新用户头像失败");
		}
		return i;
	}

Mapper层

<update id="saveUserImg" parameterType="com.datangedu.cn.model.Member">
    update member set HEAD_IMG = #{headImg} where id = #{id}
  </update>

另外 上传图片不能过大 修改 Spring Boot工程嵌入的tomcat限制了请求的文件大小（未亲测） 
需要设置以下两个参数

multipart.maxFileSize
multipart.maxRequestSize

Spring Boot 1.3.x或者之前

multipart.maxFileSize=100Mb
multipart.maxRequestSize=1000Mb
Spring Boot 1.4.x

spring.http.multipart.maxFileSize=100Mb
spring.http.multipart.maxRequestSize=1000Mb
很多人设置了multipart.maxFileSize但是不起作用，是因为1.4版本以上的配置改了，详见官方文档：spring boot 1.4

  Spring Boot 2.0之后

spring.servlet.multipart.max-file-size=100MB
spring.servlet.multipart.max-request-size=1000MB