介紹

一些請求引數, 需要解析成某個自定義的類, 而spring boot中並沒有提供這樣自動轉換的註解, 但是,spring boot 預留了擴充套件介面,所以,我們可以自定義實現一個註解.

例如: http://localhost:8999/new/test?a={"name":"aaa", "age":18}&b=123
我們可以通過自定義註解,來把 a 對應的值轉換成我們系統中的類

建立註解

package com.example.demo.conf;

import java.lang.annotation.*;

@Target(ElementType.PARAMETER)
@Retention
 
(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestJson {
    String value();
}

建立請求引數解析實現類

package com.example.demo.conf;

import com.alibaba.fastjson.JSONObject;
import org.springframework.core.MethodParameter;
import org.springframework.stereotype.Component;
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;

public class RequestJsonHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver
 
 {
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(RequestJson.class);
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
                                  NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        RequestJson requestJson = parameter.getParameterAnnotation(RequestJson.class);
        String value = requestJson.value();
        Class clazz = parameter.getParameterType();
        String jsonData = webRequest.getParameter(value);
        if (jsonData == null) {
            return clazz.newInstance();
        }
        Object object = JSONObject.parseObject(jsonData, clazz);
        return object;
    }
}

注入spring boot

package com.example.demo;

import com.example.demo.conf.RequestJsonHandlerMethodArgumentResolver;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import java.util.List;

@SpringBootApplication
public class DemoApplication extends WebMvcConfigurerAdapter{

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        argumentResolvers.add(new RequestJsonHandlerMethodArgumentResolver());
        super.addArgumentResolvers(argumentResolvers);
    }
}

測試

Controller

package com.example.demo.controller;

import com.alibaba.fastjson.JSONObject;
import com.example.demo.conf.RequestJson;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @GetMapping("/new/test")
    public Object newTest(@RequestJson("a") Person person, @RequestParam("b") Integer b) {
        System.out.println("a : " + JSONObject.toJSONString(person));
        System.out.println("b : " + b);
        return "ok";
    }

    public static class Person {
        private String name;
        private Integer age;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }
    }
}

請求

請求url: http://localhost:8999/new/test?a={"name":"aaa", "age":18}&b=123

列印結果:

a : {“age”:18,”name”:”aaa”}
b : 123