自定义方法限制上传图片（文件）的格式

import org.apache.catalina.core.ApplicationPart;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.IOException;
import java.util.Collection;
import java.util.List;

/**
 * @author zlw
 * @date 2018/11/13
 * @description
 */
public class UploadFileInterceptor implements HandlerInterceptor {

    /** 允许上传的图片格式 */
    private static final String[] PERMITTED_IMAGE_TYPE = {"jpg", "png"};

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        //在请求处理之前进行调用（Controller方法调用之前）
        // 只有返回true才会继续向下执行，返回false取消当前请求
        return isImageQuealified(httpServletRequest);
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        //请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        //在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）
    }

    /**
     * 注意：此方法不具有普适性，只适用于http的post请求，且第一个参数为MultipartFile类型的
     * 校验所拦截的请求中上传的图片的格式是否合格
     */
    private boolean isImageQuealified (HttpServletRequest httpServletRequest) throws IOException, ServletException {

        Collection parts =  httpServletRequest.getParts();
        String fileType = "";

        if (null != parts && parts.size() > 0) {
            List list = (List) parts;
            ApplicationPart partZero = (ApplicationPart) list.get(0);
            String zeroName = partZero.getSubmittedFileName();
            String trimedName = zeroName.trim();
            int lastDotIndex = trimedName.lastIndexOf(".");
            fileType = trimedName.substring(lastDotIndex + 1, trimedName.length());
        }

        for (String s : PERMITTED_IMAGE_TYPE) {
            if (fileType.equalsIgnoreCase(s)) {
                return true;
            }
        }
        return false;

    }


}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;



/**
 * 拦截器注册配置
 */
@Configuration
public class WebMvcConfig extends WebMvcConfigurerAdapter {



    /**
     * 上传的图片校验拦截器，将拦截器作为bean写入配置中，不能直接new,否则拦截器无法注入服务
     */
    @Bean
    public UploadFileInterceptor uploadFileInterceptor() {
        return new UploadFileInterceptor();
    }

    /**
     * 拦截器注册
     *
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 多个拦截器组成一个拦截器链
        // addPathPatterns 用于添加拦截规则
        // excludePathPatterns 用户排除拦截
        registry.addInterceptor(loginInterceptor());
        registry.addInterceptor(uploadFileInterceptor()).addPathPatterns("/pacs/uploadScreenShot");//对上传图片接口拦截，做图片格式校验
    }
}