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Spring boot 自定义参数解析器

1. 应用场景

从token解析出来的信息想放到controller层的参数对象中。此处用到java反射，不会的自行学习。

2. 代码

创建Spring boot项目

创建@Zkq注解

import java.lang.annotation.*;

/**
 * @Description 自定义参数解析器注解
 * @Author 张凯强
 * @Date Created in 2021/5/19
 * @E-mail 862166318@qq.com
 */
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Zkq {}

创建参数解析器

import org.springframework.core.MethodParameter;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;
import java.lang.reflect.Field;

/**
 * @Description 参数解析器,利用反射创建对象并从nativeWebRequest取出我们在filter中的值
 * @Author 张凯强
 * @Date Created in 2021/5/19
 * @E-mail 862166318@qq.com
 */
public class ZkqParameterHandler implements HandlerMethodArgumentResolver {
    public boolean supportsParameter(MethodParameter methodParameter) {
        return methodParameter.hasParameterAnnotation(Zkq.class);
    }

    public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {
        // 得到反射对象的类
        Class<?> nestedParameterType = methodParameter.getNestedParameterType();
        // 利用反射创建当前注解的实体类
        Object o = nestedParameterType.getConstructor().newInstance();
        // 利用反射获取当前类的所有私有属性
        Field[] fields = nestedParameterType.getDeclaredFields();
        // 利用反射给创建的类赋值
        for (Field field:fields) {
            // 开启私有属性的赋值功能
            field.setAccessible(true);
            field.set(o,nativeWebRequest.getAttribute(field.getName(), RequestAttributes.SCOPE_REQUEST));
        }
        return o;
    }
}

把解析器添加到Spring 容器中

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
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;

/**
 * @Description 接口WebMvcConfigurer 添加参数解析器
 * @Author 张凯强
 * @Date Created in 2021/5/19
 * @E-mail 862166318@qq.com
 */
@Configuration
public class MvcConfig implements WebMvcConfigurer {
    // 添加参数解析器
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        resolvers.add(new ZkqParameterHandler());
    }

    // 添加 filter 向servletRequest 中放值，这里我写死的，可以从token或数据库中那动态数据
    @Bean
    public FilterRegistrationBean zkqFilter(){
        return new FilterRegistrationBean((servletRequest,servletResponse,filterChain) ->{
            servletRequest.setAttribute("id",1L);
            servletRequest.setAttribute("name","张凯强");
            servletRequest.setAttribute("age",25);
            servletRequest.setAttribute("sex","男");
            servletRequest.setAttribute("email","862166318@qq.com");
            filterChain.doFilter(servletRequest,servletResponse);
        }){{
            setOrder(1);
            setName("zkq");
            setEnabled(true);
            addUrlPatterns("/*");
        }};
    }
}

3. 测试代码

创建实体类User

import lombok.Data;

/**
 * @Description 用户信息
 * @Author 张凯强
 * @Date Created in 2021/5/19
 * @E-mail 862166318@qq.com
 */
@Data
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String sex;
    private String email;
}

创建测试Controller API接口

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Description test
 * @Author 张凯强
 * @Date Created in 2021/5/19
 * @E-mail 862166318@qq.com
 */

@RestController
public class ZkqController {

    @RequestMapping("zkq")
    public User zkq(@Zkq User user){
        return user;
    }
}