场景：

通常会遇到写接口时仅需要传入单个参数的情况，但是spring自带的参数解析器不支持解析这种传参，导致接收到的参数始终为null。

解决方案：

1、使用JSONObject与@RequestBody注解配合接收参数； 

 @PostMapping("/getSingleParam")
 public void getSingleParam(@RequestBody JSONObject object){
     System.out.println(object.getString("name"));

2、使用Map与@RequestBody注解配合接收参数；
 

 @PostMapping("/getSingleParam")
 public void getSingleParam(@RequestBody Map<String, Object> map){
     System.out.println(map.get("name").toString());

3、以json字符串形式接收参数再通过JSONObject将json字符串转为对象，与方案1类似；
 

 @PostMapping("/getSingleParam")
 public void getSingleParam(@RequestBody String name){
     JSONObject object = JSONObject.parseObject(name);
     System.out.println(object.getString("name"));

最佳解决方案：
 

4、模仿@RequestParam自定义@RequestSingleParam注解来解析参数，@RequestParam从请求路径获取参数，自定义注解从request body中获取参数；
 

第一步：自定义@RequestSingleParam注解
 

 package com.blog.utils.aop;
 import org.springframework.web.bind.annotation.ValueConstants;
 import java.lang.annotation.*;
  * 自定义注解接收单个参数
  * @author created by wutong li on 2021/04/29
 @Target(ElementType.PARAMETER)
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 public @interface RequestSingleParam {
     String value();
     boolean required() default true;
     String defaultValue() default ValueConstants.DEFAULT_NONE;

第二步：实现HandlerMethodArgumentResolver接口，配置参数解析器
 

 package com.blog.utils.aop;
 import com.alibaba.fastjson.JSONObject;
 import org.springframework.core.MethodParameter;
 import org.springframework.web.bind.support.WebDataBinderFactory;
 import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.method.support.ModelAndViewContainer;
 import javax.servlet.http.HttpServletRequest;
 import java.io.BufferedReader;
  * RequestStringParam参数解析器 实现 HandlerMethodArgumentResolver 接口
  * @author created by wutong li on 2021/04/29
 public class RequestStringParamHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {
     @Override
     public boolean supportsParameter(MethodParameter parameter) {
         return parameter.hasParameterAnnotation(RequestSingleParam.class);
     @Override
     public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
                                   NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
         RequestSingleParam requestSingleParam = parameter.getParameterAnnotation(RequestSingleParam.class);
         HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
         BufferedReader reader = request.getReader();
         StringBuilder sb = new StringBuilder();
         char[] buf = new char[1024];
         int rd;
         while ((rd = reader.read(buf)) != -1) {
             sb.append(buf, 0, rd);
         JSONObject jsonObject = JSONObject.parseObject(sb.toString());
         String value = requestSingleParam.value();
         return jsonObject.get(value);

第三步：配置WebMvcConfigurer注册自定义的参数解析器
 

 package com.blog.config;
 import com.blog.utils.aop.RequestStringParamHandlerMethodArgumentResolver;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 import java.util.List;
  * 配置WebMvcConfigurer
  * @author created by wutong li on 2021/04/29
 @Configuration
 public class WebMvcConfig implements WebMvcConfigurer {
      * 注册自定义的参数解析器
     @Override
     public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers){
         argumentResolvers.add(new RequestStringParamHandlerMethodArgumentResolver());
         WebMvcConfigurer.super.addArgumentResolvers(argumentResolvers);

第四步：在Controller中接收参数处加上@RequestSingleParam注解，再调一下接口就可以接收到单个的入参了
 

 @PostMapping("/getSingleParam")
 public void getSingleParam(@RequestSingleParam(value = "name") String name){
     System.out.println(name);
        # spring
        # java
Logo
华为云开发者联盟

为开发者提供学习成长、分享交流、生态实践、资源工具等服务，帮助开发者快速成长。

  • 浏览量 1.2w
  • 收藏 1
  • 0

所有评论(0)

加载更多

`送你一朵小红花

@llwutong