Overview

When you want to get headers, parameters, etc. from "HttpServeletRequest" For the time being

public Oject sample(HttpServletRequest request) {
    //processing
}

If you do, you can do it in the controller class, Since the responsibility of the controller class increases, I wanted to bind and receive only the required values to the appropriate objects.

Method

You should use HandlerMethodArgumentResolver!

Details

I just want to understand how to use HandlerMethodArgumentResolver Try to easily receive the value of the request parameter in your own class instead of String

Class that receives parameters

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.ToString;

@Getter
@AllArgsConstructor
@ToString
public class SampleArgument {
    private String value;

    public static SampleArgument of(String value) {
        return new SampleArgument(value);
    }
}

For my personal taste, instantiation is possible with the ʻofmethod. A simple class that holds the string received as an argument invalue`.

HandlerMethodArgumentResolver A class for binding to any class in the subject

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;

@Component
public class SampleResolver implements HandlerMethodArgumentResolver {

    //Details are omitted. .. ResolveArgument is executed only if true
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return true;
    }

    //The object returned here will be available as an argument
    @Override
    public Object resolveArgument(
            MethodParameter       parameter,
            ModelAndViewContainer mavContainer,
            NativeWebRequest      webRequest,
            WebDataBinderFactory  binderFactory
    ) throws Exception {

        String value = webRequest.getParameter("value");
        return SampleArgument.of(value);
    }
}

Implements the HandlerMethodArgumentResolver interface. Here, @Component is added to register as a bean.

Enable the implemented HandlerMethodArgumentResolver

import lombok.AllArgsConstructor;
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
@AllArgsConstructor
public class HandlerMethodArgumentResolverConfiguration implements WebMvcConfigurer {
    private SampleResolver sampleResolver;

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

Since I added @Component earlier, Resolver receives it in the constructor (self-propelled generation with @AllArgsConstructor) The point is -Implementing the WebMvcConfigurer interface -Give @Configuration to the class After that, add the Resolver implemented in the list with the implementation method of ʻaddArgumentResolvers` and it's OK!

Operation check

We have prepared the following controllers.

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping("/HandlerMethodArgumentResolver")
@Slf4j
public class HandlerMethodArgumentResolverController {
    @GetMapping("/sample")
    @ResponseBody
    public SampleArgument sample(SampleArgument sampleArgument) {
        log.info("sampleArgument: {}", sampleArgument);
        return sampleArgument;
    }
}

http://localhost:8080/HandlerMethodArgumentResolver/sample?value=HelloWorld When you access

sampleArgument: SampleArgument(value=HelloWorld)

I was able to confirm that I was able to bind to my own class! !!