Spring Controller에서 사용하는 Annotation 분석하기 : @RequestParam

Prologue
Domain
Converter
Example
- Case 1
  - Controller
  - 1. Test Code
  - 1. Log
  - 1. Comment
  - 2. Test Code
  - 2. Log
  - 2. Comment
- Case 2
  - Controller
  - 1. Test Code
  - 1. Log
  - 1. Comment
  - 2. Test Code
  - 2. Log
  - 2. Comment
- Case 3
  - Controller
  - Test Code
  - Log
  - Comment
- Case 4
  - Controller
  - Test Code
  - Log
  - Comment
- Case 5
  - Controller
  - Test Code
  - Log
  - Comment
- Case 6
  - Controller
  - Test Code
  - Log
  - Comment
- Case 7
  - Controller
  - Test Code
  - Log
  - Comment
Summary

Prologue

@RequestParam을 사용하는 예제를
다양한 경우의 수를 통해
분석해보고 이해해보자.

Domain

Person1

@Getter
@Setter
public class Person1 {
    private Long age1_Long; // Age를 뜻하는 필드

    private String name;

    private Boolean isConvert;
}

Person2

@Getter
@Setter
public class Person2 {
    private Long age2_Long; // Age를 뜻하는 필드

    private String name;

    private Boolean isConvert;
}

Person1과 Person2의 차이
- Age를 뜻하는 필드의
- Type은 같지만 필드명이 다름

Person3

@Getter
@Setter
public class Person3 {
    private String age3_String; // Age를 뜻하는 필드

    private String name;

    private Boolean isConvert;
}

Converter

Person1 Converter

public class Person1Converter {

    @Component
    public static class StringToPersonConverter implements Converter<String, Person1> {
        @Override
        public Person1 convert(String s) {
            System.out.println("[Person`1` Converter] StringToPersonConverter Working");
            Person1 person1 = new Person1();
            person1.setIsConvert(true); // Converter 호출했음을 표기하기 위한 값 설정
            return person1;
        }
    }
}

Example

@RequestParam을 사용하는
다양한 Exapmle을 통해
사용법을 분석해본다.

Case 1

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age")
    public Person1 requestParam_Age(@RequestParam("age") Person1 person1) {
        System.out.println("Person1.Age : " + person1.getAge1_Long());
        System.out.println("Person1.Name : " + person1.getName());
        System.out.println("Person1.IsConvert : " + person1.getIsConvert());
        return person1;
    }
}

1. Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Age___Param_Contains_age() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age")
                                              .param("name", "goodgid")
                                              .param("age", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }  
}

1. Log

[Person`1` Converter] StringToPersonConverter Working
Person1.Age : null
Person1.Name : null
Person1.IsConvert : true

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age
       Parameters = {name=[goodgid], age=[1]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 200
    Error message = null
          Headers = [Content-Type:"application/json"]
     Content type = application/json
             Body = {"age1_Long":null,"name":null,"isConvert":true}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

1. Comment

Handler Argument에
@RequestParam(“age”)가 선언이 되어있고
클라이언트 요청 param에
age가 있기 때문에
Converter가 동작한다.

그런데 흥미로운 점은
Person1 객체에는
age라는 필드는 없지만
Converter가 호출된다는 점이다.

여기서 알 수 있는건
Argument Type Class에
필드값 존재 유무가 중요한게 아니라
@RequestParam Annotation에서
선언한 Key값과
(= @RequestParam(“age”)에서 Key는 age)
클라이언트 요청에 담긴
Param의 Key값이
일치한다면
Converter를 호출한다는 점이다.

2. Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;
    
    @Test
    public void requestParam_Age___Param_Contains_age1_Long() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age")
                                              .param("name", "goodgid")
                                              .param("age1_Long", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

2. Log

2020-01-27 20:36:46.113  WARN 46660 --- [     main] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.bind.MissingServletRequestParameterException: 
Required Person1 parameter 'age' is not present]

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age
       Parameters = {name=[goodgid], age1_Long=[1]}
          Headers = []
             Body = null
    Session Attrs = {}
...

MockHttpServletResponse:
           Status = 400
    Error message = Required Person1 parameter 'age' is not present
          Headers = []
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

java.lang.AssertionError: Status expected:<200> but was:<400>
Expected :200
Actual   :400

2. Comment

Handler에서는
age라는 Key값의
Param을 기대한다.

하지만
age라는 key값이 없는 상태로
클라이언트는 요청을 한다.

그렇기 때문에 Exception이 발생한다.
그리고 이유가 발생하는 이유는 다음과 같다.

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {

	/**
	 * Whether the parameter is required.
	 * <p>Defaults to {@code true}, leading to an exception being thrown
	 * if the parameter is missing in the request. Switch this to
	 * {@code false} if you prefer a {@code null} value if the parameter is
	 * not present in the request.
	 * <p>Alternatively, provide a {@link #defaultValue}, which implicitly
	 * sets this flag to {@code false}.
	 */
	boolean required() default true;

}

기본적으로 required가 true이기 때문에
Exception이 발생한다.

만약 required를 false로
명시적 선언을 해준다면
Exception은 발생하지 않는다.

public Person1 requestParam_Age(@RequestParam(value = "age", required = false) Person1 person1) {

하지만 person1에는 어떠한 값도
Binding되어 있지 않기 때문에
null인 상태가 된다.

Case 2

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age1_Long")
    public Person1 requestParam_Age1_Long(@RequestParam("age1_Long") Person1 person1) {
        System.out.println("Person1.Age : " + person1.getAge1_Long());
        System.out.println("Person1.Name : " + person1.getName());
        System.out.println("Person1.IsConvert : " + person1.getIsConvert());
        return person1;
    }
}

1. Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Age1_Long___Param_Contains_age() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age1_Long")
                                              .param("name", "goodgid")
                                              .param("age", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }

}

1. Log

2020-02-02 20:37:27.964  WARN 19790 --- [      main] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.bind.MissingServletRequestParameterException: 
Required Person1 parameter 'age1_Long' is not present]

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age1_Long
       Parameters = {name=[goodgid], age=[1]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 400
    Error message = Required Person1 parameter 'age1_Long' is not present
          Headers = []
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []


java.lang.AssertionError: Status expected:<200> but was:<400>
Expected :200
Actual   :400
<Click to see difference>

1. Comment

Case 1 -> Test Case 2st과 같은 원리로
동일한 결과를 확인할 수 있다.

Handler에서는
age1_Long라는 Key값의
Param을 기대한다.

하지만
age1_Long라는 key값이 없는 상태로
클라이언트는 요청을 한다.
그렇기 때문에 Exception이 발생한다.

2. Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;
    
    @Test
    public void requestParam_Age1_Long___Param_Contains_age1_Long() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age1_Long")
                                              .param("name", "goodgid")
                                              .param("age1_Long", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

2. Log

[Person`1` Converter] StringToPersonConverter Working
Person1.Age : null
Person1.Name : null
Person1.IsConvert : true

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age1_Long
       Parameters = {name=[goodgid], age1_Long=[1]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 200
    Error message = null
          Headers = [Content-Type:"application/json"]
     Content type = application/json
             Body = {"age1_Long":null,"name":null,"isConvert":true}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

2. Comment

Hnadler Argument에서
age1_Long 값을 기대하고
클라이언트 요청에서
Key값이
age1_Long인
Param을 보내기 때문에
테스트는 성공한다.

Case 3

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age/not/converter")
    public Person3 requestParam_Age_Not_Converter(@RequestParam("age") Person3 person3) {
        System.out.println("Person3.Age : " + person3.getAge3_String());
        System.out.println("Person3.Name : " + person3.getName());
        System.out.println("Person3.IsConvert : " + person3.getIsConvert());
        return person3;
    }
}

Argument Type의 변화가 있다.
Person1 -> Person3

그런데 Person3을
Conversion할 수 있는
Converter가 없는 상황이다.

Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Age_Not_Converter___Param_Contains_age() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age/not/converter")
                                              .param("name", "goodgid")
                                              .param("age", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

Log

2020-02-02 20:54:09.601  WARN 20322 --- [      main] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException:
Failed to convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3'; 
nested exception is java.lang.IllegalStateException: 
Cannot convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3': 
no matching editors or conversion strategy found]

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age/not/converter
       Parameters = {name=[goodgid], age=[1]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 500
    Error message = null
          Headers = []
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

java.lang.AssertionError: Status expected:<200> but was:<500>
Expected :200
Actual   :500
<Click to see difference>

Comment

Person3 Type으로
Conversion 할 수 있는
Converter가 없기 때문에
Exception이 발생한다.

그리고 이 경우엔
클라이언트의 잘못이 아닌
서버의 잘못이기 때문에
Response Status는
500 서버 Error가 된다.

Case 4

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age3_String/not/converter")
    public Person3 requestParam_Age1_Long_Not_Converter(@RequestParam("age3_String") Person3 person3) {
        System.out.println("Person3.Age : " + person3.getAge3_String());
        System.out.println("Person3.Name : " + person3.getName());
        System.out.println("Person3.IsConvert : " + person3.getIsConvert());
        return person3;
    }
}

Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Age_Not_Converter___Param_Contains_age3_String() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age1_Long/not/converter")
                                              .param("name", "goodgid")
                                              .param("age3_String", "3"))
               .andDo(print())
               .andExpect(status().isOk());
    }

}

Log

2020-02-02 21:12:45.971  WARN 20892 --- [        main] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException:
Failed to convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3';
nested exception is java.lang.IllegalStateException: 
Cannot convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3': 
no matching editors or conversion strategy found]

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age1_Long/not/converter
       Parameters = {name=[goodgid], age3_String=[3]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 500
    Error message = null
          Headers = []
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

java.lang.AssertionError: Status expected:<200> but was:<500>
Expected :200
Actual   :500
<Click to see difference>

Comment

결과를 보면
Case 3과 같다.

Case 4에서 확인해 보고 싶었던 부분은
Person3 Class에서 필드명과
(= private String age3_String )
클라이언트 요청 Param의 Key값이 동일하다면
Case 3과 다른 결과가 나오지 않을까?란 궁금증이였다.

하지만 Case 4를 통해
@RequestParam Annotation의 Key와
(= @RequestParam(“age3_String” )
Argument Type Class에 필드명과의
(= private String age3_String )
상관 관계는 없다는 점이다.

Case 5

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/not/request/param/annotation")
    public Person1 requestParam_Not_Request_Param_Annotation(Person1 person1) {
        System.out.println("Person1.Age : " + person1.getAge1_Long());
        System.out.println("Person1.Name : " + person1.getName());
        System.out.println("Person1.IsConvert : " + person1.getIsConvert());
        return person1;
    }
}

Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Not_Request_Param_Annotation___Param_Contains_ALL() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/not/request/param/annotation")
                                              .param("name", "goodgid")
                                              .param("age1_Long", "1")
                                              .param("age2_Long", "2")
                                              .param("age3_String", "3")
                                              .param("age4_String", "4"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

Log

Person1.Age : 1
Person1.Name : goodgid
Person1.IsConvert : null

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/not/request/param/annotation
       Parameters = {name=[goodgid], age1_Long=[1], age2_Long=[2], age3_String=[3], age4_String=[4]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 200
    Error message = null
          Headers = [Content-Type:"application/json"]
     Content type = application/json
             Body = {"age1_Long":1,"name":"goodgid","isConvert":null}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

Comment

@RequestParam Annotation이 없는 상황이다.
그렇기 때문에
ModelAttribute 방법으로
Data Binding이 이뤄졌다.

Case 6

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age1_Long/name")
    public Person1 requestParam_Age1_Long_Name(@RequestParam("age1_Long") Person1 person1,
                                               @RequestParam("name") Person1 person1_2,
                                               @RequestParam("name") Person2 person2,
                                               Person2 person2_2) {
        System.out.println("Person1.Age : " + person1.getAge1_Long());
        System.out.println("Person1.Name : " + person1.getName());
        System.out.println("Person1.IsConvert : " + person1.getIsConvert());

        System.out.println("Person1_2.Age : " + person1_2.getAge1_Long());
        System.out.println("Person1_2.Name : " + person1_2.getName());
        System.out.println("Person1_2.IsConvert : " + person1_2.getIsConvert());

        System.out.println("Person2.Age : " + person2.getAge2_Long());
        System.out.println("Person2.Name : " + person2.getName());
        System.out.println("Person2.IsConvert : " + person2.getIsConvert());

        System.out.println("Person2_2.Age : " + person2_2.getAge2_Long());
        System.out.println("Person2_2.Name : " + person2_2.getName());
        System.out.println("Person2_2.IsConvert : " + person2_2.getIsConvert());
        return person1;
    }
}

Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Age_Not_Converter___Param_Contains_age1_Long() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/age1_Long/not/converter")
                                              .param("name", "goodgid")
                                              .param("age1_Long", "1"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

Log

[Person`1` Converter] StringToPersonConverter Working
[Person`1` Converter] StringToPersonConverter Working
[Person`2` Converter] StringToPersonConverter Working
Person1.Age : null
Person1.Name : null
Person1.IsConvert : true
Person1_2.Age : null
Person1_2.Name : null
Person1_2.IsConvert : true
Person2.Age : null
Person2.Name : null
Person2.IsConvert : true
Person2_2.Age : 2
Person2_2.Name : goodgid
Person2_2.IsConvert : null

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age1_Long/name
       Parameters = {name=[goodgid], age1_Long=[1], age2_Long=[2]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 200
    Error message = null
          Headers = [Content-Type:"application/json"]
     Content type = application/json
             Body = {"age1_Long":null,"name":null,"isConvert":true}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

Comment

public Person1 requestParam_Age1_Long_Name(@RequestParam("age1_Long") Person1 person1,
                                           @RequestParam("name") Person1 person1_2,
                                           @RequestParam("name") Person2 person2,
                                            Person2 person2_2) {

Handler를 보면
3개의 @RequestParam Annotation을 사용한 Arguments와
@RequestParam Annotation을 사용하지 않은 Argument가 있다.

그리고 @RequestParam의 Key값은
name과 age1_Long이다.

클라이언트 요청에 담겨있는
Param에있는 Key값 또한
name과 age1_Long이다.

그렇기 때문에
결과적으로
3번의 Converter 호출이 이뤄진다.
Person1 : 2번 / Person2 : 1번

그리고 @RequestParam Annotation을 사용하지 않은
4st Argument는
ModelAttribute 방식으로
Data Binding이 이뤄진다.

그렇기 때문에
Log를 보면
Person2_2에 대해서는
Age와 Name 값이 존재한다.
물론 Converter와 관련이 없기 때문에
IsConvert 값은 null이다.

[Person`1` Converter] StringToPersonConverter Working
[Person`1` Converter] StringToPersonConverter Working
[Person`2` Converter] StringToPersonConverter Working
Person1.Age : null
Person1.Name : null
Person1.IsConvert : true
Person1_2.Age : null
Person1_2.Name : null
Person1_2.IsConvert : true
Person2.Age : null
Person2.Name : null
Person2.IsConvert : true
Person2_2.Age : 2
Person2_2.Name : goodgid
Person2_2.IsConvert : null

Case 7

Controller

@RestController
public class SpringController {

    @GetMapping("/request/param/age1_Long/name/binding/result")
    public Person1 requestParam_Age1_Long_Name_Binding_Result(
                            @RequestParam("age1_Long") Person1 person1,
                            @RequestParam("name") Person2 person2,
                            @RequestParam("name") Person3 person3,
                            BindingResult bindingResult) {
        if (bindingResult.hasErrors()) {
            bindingResult.getAllErrors().forEach(c -> {
                System.out.println(c);
            });
        }
        System.out.println("Person1.Age : " + person1.getAge1_Long());
        System.out.println("Person1.Name : " + person1.getName());
        System.out.println("Person1.IsConvert : " + person1.getIsConvert());

        System.out.println("Person2.Age : " + person2.getAge2_Long());
        System.out.println("Person2.Name : " + person2.getName());
        System.out.println("Person2.IsConvert : " + person2.getIsConvert());

        System.out.println("Person3.Age : " + person3.getAge3_String());
        System.out.println("Person3.Name : " + person3.getName());
        System.out.println("Person3.IsConvert : " + person3.getIsConvert());

        return person1;
    }
}

Test Code

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
class SpringControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    ObjectMapper objectMapper;

    @Test
    public void requestParam_Not_Request_Param_Annotation___Param_Contains_ALL() 
    throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/request/param/not/request/param/annotation")
                                              .param("name", "goodgid")
                                              .param("age1_Long", "1")
                                              .param("age2_Long", "2")
                                              .param("age3_String", "3")
                                              .param("age4_String", "4"))
               .andDo(print())
               .andExpect(status().isOk());
    }
}

Log

[Person`1` Converter] StringToPersonConverter Working
[Person`2` Converter] StringToPersonConverter Working

2020-02-02 22:35:24.992  WARN 23513 --- [    main] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException:
Failed to convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3'; 
nested exception is java.lang.IllegalStateException: 
Cannot convert value of type 'java.lang.String' to required type 'goodgid.gidhub.Person3': 
no matching editors or conversion strategy found]

MockHttpServletRequest:
      HTTP Method = GET
      Request URI = /request/param/age1_Long/name/binding/result
       Parameters = {name=[goodgid], age1_Long=[1], age2_Long=[2]}
          Headers = []
             Body = null
    Session Attrs = {}

...

MockHttpServletResponse:
           Status = 500
    Error message = null
          Headers = []
     Content type = null
             Body = 
    Forwarded URL = null
   Redirected URL = null
          Cookies = []


java.lang.AssertionError: Status expected:<200> but was:<500>
Expected :200
Actual   :500
<Click to see difference>

Comment

BindingResult bindingResult을 선언하였고
bindingResult에 Error가 담기지 않을까하는 궁금증으로
테스트를 진행하였다.

결과는 다음과 같았다.
Log를 보면
Person1과 Person2 Converter가 호출된 후
Person3 Converter를 호출하려고하는데
등록된 Converter가 없어
Exception이 발생한다.

즉 bindingResult에 담기지 않았고
Exception을 Throw하였다.

Summary

@RequestParam을 사용하는
다양한 예제를 통해 이해도를 높혔다.

추가적으로 더 궁금한 점이 있다면
반드시 학습을 하도록하자.

혹시 필자의 글이 틀리거나
궁금증이 있다면
연락을 주었으면 좋겠다.

끝으로
한 번에 다 보고 이해하기엔
다소 부담스러운 양이라고 생각한다.

그렇기 때문에
충분한 여유를 갖고
글을 읽고
이해하며 확실하게
학습하도록 하자.