web.xmlを残しつつjavaConfigで設定

web.xmlに以下を追加

web.xml

<!-- windows-31j を適用するフィルター -->
<filter>
    <filter-name>sjisEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>windows-31j</param-value>
    </init-param>
    <init-param>
        <param-name>forceEncoding</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>sjisEncodingFilter</filter-name>
    <url-pattern>/api/v1/396_x/*</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>sjisEncodingFilter</filter-name>
    <url-pattern>/api/v1/1321_x/*</url-pattern>
</filter-mapping>

javaConfigのクラス追加

AppInitializer.java

import java.util.EnumSet;
import java.util.List;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import jakarta.servlet.DispatcherType;
import jakarta.servlet.FilterRegistration;
import jakarta.servlet.ServletContext;

@Configuration
public class AppInitializer implements WebMvcConfigurer {
	
    public void onStartup(ServletContext servletContext) {
        // UTF-8 を適用するフィルター
        CharacterEncodingFilter utf8Filter = new CharacterEncodingFilter();
        utf8Filter.setEncoding("UTF-8");
        utf8Filter.setForceEncoding(true);

        FilterRegistration.Dynamic utf8FilterReg = servletContext.addFilter("CharacterEncodingFilter", utf8Filter);
        utf8FilterReg.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), false, "/*");

        // windows-31j を適用するフィルター
        CharacterEncodingFilter sjisFilter = new CharacterEncodingFilter();
        sjisFilter.setEncoding("windows-31j");
        sjisFilter.setForceEncoding(true);

        FilterRegistration.Dynamic sjisFilterReg = servletContext.addFilter("sjisEncodingFilter", sjisFilter);
        sjisFilterReg.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), false, "/custom-header2*", "/custom-header3/*");
    }
}

コントローラ

package com.example.helloworld4.app.welcome;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;


/**
 * Handles requests for the application home page.
 */
@Controller
public class HelloController {

    @SuppressWarnings("deprecation")
    @RequestMapping("/custom-header")
    public ResponseEntity<String> getCustomHeaderResponse() {
        HttpHeaders headers = new HttpHeaders();
        headers.add("Custom-Header", "CustomValue");
        headers.add(HttpHeaders.CONTENT_TYPE, "application/json; UTF-8");
        //headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
        
        return new ResponseEntity<>("ああああ", headers, HttpStatus.OK);
    }
    
    @SuppressWarnings("deprecation")
    @RequestMapping("/custom-header2")
    public ResponseEntity<String> getCustomHeaderResponse2() {
        HttpHeaders headers = new HttpHeaders();
        headers.add("Custom-Header", "CustomValue");
        headers.add(HttpHeaders.CONTENT_TYPE, "application/json; charset=windows-31j");
        //headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
        
        return new ResponseEntity<>("いいい", headers, HttpStatus.OK);
    }
    
    @SuppressWarnings("deprecation")
    @RequestMapping("/custom-header3")
    public ResponseEntity<String> getCustomHeaderResponse3() {
        HttpHeaders headers = new HttpHeaders();
        headers.add("Custom-Header", "CustomValue");
        headers.add(HttpHeaders.CONTENT_TYPE, "application/json; charset=windows-31j");
        //headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
        
        return new ResponseEntity<>("ううう", headers, HttpStatus.OK);
    }
}

curl実行

C:\Users\rurur>curl -I POST http://localhost:8080/helloworld4/custom-header
curl: (6) Could not resolve host: POST
HTTP/1.1 200
X-Track: 7436fb82cf6242c6a8f10e6e30c65ee4
Custom-Header: CustomValue
Content-Type: application/json; UTF-8;charset=UTF-8
Content-Length: 18
Date: Sun, 06 Apr 2025 13:59:41 GMT

C:\Users\rurur>curl -I POST http://localhost:8080/helloworld4/custom-header2
curl: (6) Could not resolve host: POST
HTTP/1.1 200
X-Track: 2e39b3ac6f9540b1b75b79f76f50c542
Custom-Header: CustomValue
Content-Type: application/json;charset=windows-31j
Content-Length: 9
Date: Sun, 06 Apr 2025 13:59:33 GMT


C:\Users\rurur>curl -I POST http://localhost:8080/helloworld4/custom-header3
curl: (6) Could not resolve host: POST
HTTP/1.1 200
X-Track: 933bf2e270a24f7d94e8d21a07ecad1c
Custom-Header: CustomValue
Content-Type: application/json;charset=windows-31j
Content-Length: 9
Date: Sun, 06 Apr 2025 13:59:48 GMT