SpringBoot开发（5）——自定义参数实现

//在需要获得解析参数前加上注解，例如@CurrentUserId
public ResponseResult findAll(@CurrentUserId String userId){
        System.out.println(userId);
}

package com.cxsbg.resolver;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.PARAMETER) //定义注解可以用在哪里，例如方法参数上
@Retention(RetentionPolicy.RUNTIME)//定义注解可以用在什么时候，比如runtime
public @interface CurrentUserId {
}

package com.cxsbg.config;

import com.cxsbg.resolver.UserIdArgumentResolver;
import org.springframework.beans.factory.annotation.Autowired;
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;

@Configuration //表示这是配置
public class ArgumentResolverConfig implements WebMvcConfigurer {
    @Autowired
    private UserIdArgumentResolver userIdArgumentResolver;
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        resolvers.add(userIdArgumentResolver);
    }
}

package com.cxsbg.resolver;

import com.cxsbg.utils.JwtUtil;
import io.jsonwebtoken.Claims;
import org.springframework.core.MethodParameter;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;


@Component
public class UserIdArgumentResolver implements HandlerMethodArgumentResolver {
    //判断方法参数有没有加上CurrentUserId注解，如果有就会进行解析
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(CurrentUserId.class);
    }

    //自定义的参数解析方法，解析后的结果返回，会赋值到加了CurrentUserId注解的参数上
    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        //获取请求头的token
        String token = webRequest.getHeader("token");
        if(StringUtils.hasText(token)){
            //解析token，获得userId
            Claims claims = JwtUtil.parseJWT(token);
            String userId = claims.getSubject();
            return userId;
        }
        return null;
    }
}