先看歧義現(xiàn)象

值為null

未傳遞此屬性


所以此時(shí)如何區(qū)分null 時(shí)傳遞進(jìn)來的的null，還是屬性的默認(rèn)值null?

引入方案

引入過濾器，中間截獲requestBodyData并保存到HttpServletRequest，業(yè)務(wù)層從HttpServletRequest 獲取到requestBodyData輔助判斷此屬性為未傳遞還是值為null

第1步：定義并注冊過濾器

自定義過濾器截獲requestBodyData并保存到HttpServletRequest

import com.practisesvr.utils.http.FilterHttpServletRequest;
import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpServletRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.GenericFilterBean;

import java.io.IOException;

@Component
public class RequestCheckFilter extends GenericFilterBean {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.err.println("***RequestHeaderCheckFilter.doFilter.start***");

        if (!(request instanceof HttpServletRequest)) {
            throw new IllegalStateException("Expected HttpServletRequest");
        }

        HttpServletRequest httpRequest = (HttpServletRequest) request;
        FilterHttpServletRequest filterHttpRequest = new FilterHttpServletRequest(httpRequest);
        String body = filterHttpRequest.getBody();
        filterHttpRequest.setAttribute("requestBodyData", body);
        
        // 繼續(xù)執(zhí)行filter鏈
        chain.doFilter(filterHttpRequest, response);

        System.err.println("***RequestHeaderCheckFilter.doFilter.end***");
    }
}

[Ref： 過濾器使用到 HttpServletRequestWrapper 參考如下 ] What is HttpServletRequestWrapper does?

注冊過濾器

@Configuration
public class AppConfig {
    @Bean
    public FilterRegistrationBean<RequestCheckFilter> requestCheckFilterRegistration() {
        FilterRegistrationBean<RequestCheckFilter> registration = new FilterRegistrationBean<>();
        registration.setFilter(new RequestCheckFilter());
        // 可以設(shè)置過濾器名稱
        registration.setName("requestCheckFilter");
        // 設(shè)置攔截規(guī)則
        registration.addUrlPatterns("/*"); // 攔截所有請求
        // 設(shè)置過濾器執(zhí)行順序，默認(rèn)為0，數(shù)值越小優(yōu)先級越高
        registration.setOrder(2);
        return registration;
    }
}

第2步：從HttpServletRequest 獲取到requestBodyData

public class RequestIUtils {
    /**
     * 從當(dāng)前請求上下文中獲取并解析請求體數(shù)據(jù)，將其轉(zhuǎn)換為Map類型對象.
     *
     * @return 如果成功獲取到請求體數(shù)據(jù)并轉(zhuǎn)換成功，則返回一個(gè)包含請求體內(nèi)容的Map對象；
     * 若RequestAttributes不存在或請求體數(shù)據(jù)為空，則返回一個(gè)新的空HashMap對象。
     */
    public static Map<String, Object> getRequestBodyBody() {
        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        if (requestAttributes == null) {
            return new HashMap<>();
        }
        HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();

        Object requestBody = request.getAttribute("requestBodyData");
        if (requestBody == null) {
            return new HashMap<>();
        }
        return JsonUtils.jsonToT(requestBody.toString(), Map.class);
    }
}    

第3步：業(yè)務(wù)層使用requestBodyData輔助判斷

@Override
public Student update(Student student) {
    Map<String, Object> requestBody = RequestIUtils.getRequestBodyBody();
    
    Student stu = new Student();
    stu.setId(student.getId());
    stu.setUsername(student.getUsername());
    stu.setPassword(student.getPassword());
    stu.setAge(student.getAge());
    stu.setHeight(student.getHeight());
    stu.setGender(student.getGender());
    // 使用方式
    if (requestBody.containsKey("classId")){
        stu.setClassId(student.getClassId());
    }
    stu.setIsDelete(student.getIsDelete());
    
    this.studentsMapper.update(student);
    return this.queryById(student.getId());
}

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