如何为普通用户和管理员配置不同maxUploadSize的MultipartResolver？

为普通用户和管理员配置不同maxUploadSize的MultipartResolver，可以通过以下步骤实现：

在Spring Boot应用中，创建一个名为MultipartConfig.java的配置文件，并添加以下代码：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;
import org.springframework.web.multipart.support.StandardServletMultipartResolver;

@Configuration
public class MultipartConfig {

    @Bean
    public CommonsMultipartResolver commonsMultipartResolver() {
        CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
        commonsMultipartResolver.setMaxUploadSize(1000000); // 设置普通用户上传文件的最大大小为1MB
        return commonsMultipartResolver;
    }

    @Bean
    public StandardServletMultipartResolver standardServletMultipartResolver() {
        StandardServletMultipartResolver standardServletMultipartResolver = new StandardServletMultipartResolver();
        standardServletMultipartResolver.setMaxUploadSize(10000000); // 设置管理员上传文件的最大大小为10MB
        return standardServletMultipartResolver;
    }
}

在Spring Boot应用中，创建一个名为WebMvcConfig.java的配置文件，并添加以下代码：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Autowired
    private CommonsMultipartResolver commonsMultipartResolver;

    @Autowired
    private StandardServletMultipartResolver standardServletMultipartResolver;

    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
        resolvers.add(new MultipartExceptionResolver());
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/uploads/**").addResourceLocations("file:./uploads/");
    }

    @Bean
    public CommonsMultipartResolver multipartResolver() {
        return commonsMultipartResolver;
    }

    @Bean
    public StandardServletMultipartResolver standardMultipartResolver() {
        return standardServletMultipartResolver;
    }
}

在Spring Boot应用中，创建一个名为MultipartExceptionResolver.java的异常处理类，并添加以下代码：

import javax.servlet.http.HttpServletRequest;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.SimpleMappingExceptionResolver;

public class MultipartExceptionResolver extends SimpleMappingExceptionResolver {

    @Override
    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response, Object handler,
            Exception ex) {
        if (ex instanceof MultipartException) {
            return new ModelAndView("error").addObject("message", "上传文件大小超出限制");
        }
        return super.doResolveException(request, response, handler, ex);
    }
}

在Spring Boot应用中，创建一个名为UserController.java的控制器类，并添加以下代码：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private CommonsMultipartResolver commonsMultipartResolver;

    @Autowired
    private StandardServletMultipartResolver standardServletMultipartResolver;

    @PostMapping("/upload")
    public String upload(MultipartFile file) {
        // 在这里处理普通用户上传的文件
        return "上传成功";
    }

    @PostMapping("/admin/upload")
    public String adminUpload(MultipartFile file) {
        // 在这里处理管理员上传的文件
        return "上传成功";
    }
}

通过以上代码，可以为普通用户和管理员配置不同的maxUploadSize的MultipartResolver。普通用户上传文件的最大大小为1MB，管理员上传文件的最大大小为10MB。