spring MVC使用自定义的参数解析器解析参数springboot-springmvc请求参数获取与原理【长文预警，

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编写自定义的参数解析器解析请求参数

项目结构

写在前面

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编写自定义的参数解析器解析请求参数

项目结构

定义注解

import java.lang.annotation.*;

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

实体类

import java.util.Date;

public class Person {

    private String id;
    private String name;
    private Date birthday;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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


    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

controller

import com.cxf.demos.config.MyArgs;
import com.cxf.demos.model.Person;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/test")
public class ArgumentResolverController {

    @RequestMapping("/test")
    public String test(@MyArgs Person person) {
        System.out.println(person);
        return "success value is " + person;
    }
}

定义参数解析器


import com.cxf.demos.model.Person;
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;

import java.text.SimpleDateFormat;
import java.util.Date;

@Component
public class RequestParamMethodArgumentResolver implements HandlerMethodArgumentResolver {

    /**
     * 在这里进行参数的类型转换
     *
     * @param parameter  需要被解析的Controller参数
     * @param mavContainer
     * @param webRequest 当前request
     * @return 转换后的参数值
     * @throws Exception
     */
    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        try {
            MyArgs annotation = parameter.getParameterAnnotation(MyArgs.class);
            String id = webRequest.getParameter("id");
            String name = webRequest.getParameter("name");
            String birthday = webRequest.getParameter("birthday");
            SimpleDateFormat sm = new SimpleDateFormat("yyyyMMdd");
            Date parse = sm.parse(birthday);
            // 返回填充好的对象
            Person person = new Person();
            person.setId(id);
            person.setName(name);
            person.setBirthday(parse);
            System.out.println("Person" + person);
            return person;
        } catch (Exception e) {
            throw new IllegalArgumentException("Date format conversion error", e);
        }
    }

    /**
     * 解析器是否支持当前参数
     *
     * @param methodParameter 需要被解析的Controller参数
     * @return
     */
    @Override
    public boolean supportsParameter(MethodParameter methodParameter) {
        return methodParameter.hasParameterAnnotation(MyArgs.class);
    }

}

注册参数解析器

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
public class ArgumentResolverApplication implements WebMvcConfigurer {

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        // 把自己写的参数解析器放在首位，提高命中率
        if(resolvers.isEmpty()) resolvers.add(0,new RequestParamMethodArgumentResolver());
        else resolvers.set(0,new RequestParamMethodArgumentResolver());
    }
}