[DP-554] 검색어 자동완성 API (ES → MySQL 마이그레이션)

src/main/java/com/dreamypatisiel/devdevdev/domain/entity/TechKeyword.java

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+package com.dreamypatisiel.devdevdev.domain.entity;
+
+import jakarta.persistence.*;
+import lombok.AccessLevel;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@Table(indexes = {
+                @Index(name = "idx_tech_keyword_01", columnList = "chosung_key"),
+                @Index(name = "idx_tech_keyword_02", columnList = "jamo_key")
+})
+public class TechKeyword extends BasicTime {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, length = 100, columnDefinition = "varchar(100) COLLATE utf8mb4_bin")
+    private String keyword;
+
+    @Column(nullable = false, length = 300, columnDefinition = "varchar(300) COLLATE utf8mb4_bin")
+    private String jamoKey;
+
+    @Column(nullable = false, length = 150, columnDefinition = "varchar(150) COLLATE utf8mb4_bin")
+    private String chosungKey;
+
+    @Builder
+    private TechKeyword(String keyword, String jamoKey, String chosungKey) {
+        this.keyword = keyword;
+        this.jamoKey = jamoKey;
+        this.chosungKey = chosungKey;
+    }
+}

src/main/java/com/dreamypatisiel/devdevdev/domain/repository/techArticle/TechKeywordRepository.java

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+package com.dreamypatisiel.devdevdev.domain.repository.techArticle;
+
+import com.dreamypatisiel.devdevdev.domain.entity.TechKeyword;
+import com.dreamypatisiel.devdevdev.domain.repository.techArticle.custom.TechKeywordRepositoryCustom;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface TechKeywordRepository extends JpaRepository<TechKeyword, Long>, TechKeywordRepositoryCustom {
+}

src/main/java/com/dreamypatisiel/devdevdev/domain/repository/techArticle/custom/TechKeywordRepositoryCustom.java

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+package com.dreamypatisiel.devdevdev.domain.repository.techArticle.custom;
+
+import com.dreamypatisiel.devdevdev.domain.entity.TechKeyword;
+import org.springframework.data.domain.Pageable;
+
+import java.util.List;
+
+public interface TechKeywordRepositoryCustom {
+    List<TechKeyword> searchKeyword(String inputJamo, String inputChosung, Pageable pageable);
+}

src/main/java/com/dreamypatisiel/devdevdev/domain/repository/techArticle/custom/TechKeywordRepositoryImpl.java

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+package com.dreamypatisiel.devdevdev.domain.repository.techArticle.custom;
+
+import com.dreamypatisiel.devdevdev.domain.entity.TechKeyword;
+import com.querydsl.core.types.dsl.BooleanExpression;
+import com.querydsl.core.types.dsl.Expressions;
+import com.querydsl.core.types.dsl.NumberTemplate;
+import com.querydsl.jpa.JPQLQueryFactory;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Pageable;
+
+import java.util.List;
+
+import static com.dreamypatisiel.devdevdev.domain.entity.QTechKeyword.techKeyword;
+
+@RequiredArgsConstructor
+public class TechKeywordRepositoryImpl implements TechKeywordRepositoryCustom {
+
+    public static final String MATCH_AGAINST_FUNCTION = "match_against";
+    private final JPQLQueryFactory query;
+
+    @Override
+    public List<TechKeyword> searchKeyword(String inputJamo, String inputChosung, Pageable pageable) {
+        BooleanExpression jamoMatch = Expressions.booleanTemplate(
+                "function('" + MATCH_AGAINST_FUNCTION + "', {0}, {1}) > 0.0",
+                techKeyword.jamoKey, inputJamo
+        );
+
+        BooleanExpression chosungMatch = Expressions.booleanTemplate(
+                "function('" + MATCH_AGAINST_FUNCTION + "', {0}, {1}) > 0.0",
+                techKeyword.chosungKey, inputChosung
+        );
+
+        // 스코어 계산을 위한 expression
+        NumberTemplate<Double> jamoScore = Expressions.numberTemplate(Double.class,
+                "function('" + MATCH_AGAINST_FUNCTION + "', {0}, {1})",
+                techKeyword.jamoKey, inputJamo
+        );
+        NumberTemplate<Double> chosungScore = Expressions.numberTemplate(Double.class,
+                "function('" + MATCH_AGAINST_FUNCTION + "', {0}, {1})",
+                techKeyword.chosungKey, inputChosung
+        );
+
+        return query
+                .selectFrom(techKeyword)
+                .where(jamoMatch.or(chosungMatch))
+                .orderBy(
+                    // 더 높은 스코어를 우선으로 정렬
+                    Expressions.numberTemplate(Double.class, 
+                        "GREATEST({0}, {1})", jamoScore, chosungScore).desc(),
+                    // 동일한 스코어라면 키워드 길이가 짧은 것을 우선으로 정렬
+                    techKeyword.keyword.length().asc()
+                )
+                .limit(pageable.getPageSize())
+                .fetch();
+    }
+}

src/main/java/com/dreamypatisiel/devdevdev/domain/service/techArticle/keyword/TechKeywordService.java

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+package com.dreamypatisiel.devdevdev.domain.service.techArticle.keyword;
+
+import com.dreamypatisiel.devdevdev.domain.entity.TechKeyword;
+import com.dreamypatisiel.devdevdev.domain.repository.techArticle.TechKeywordRepository;
+import com.dreamypatisiel.devdevdev.global.utils.HangulUtils;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Service
+@Transactional(readOnly = true)
+@RequiredArgsConstructor
+public class TechKeywordService {
+    private final TechKeywordRepository techKeywordRepository;
+
+    /**
+     * @Note:
+     * @Author: 유소영
+     * @Since: 2025.08.13
+     * @param prefix
+     * @return 검색어(최대 20개)
+     */
+    public List<String> autocompleteKeyword(String prefix) {
+        String processedInput = prefix;
+
+        // 한글이 포함되어 있다면 자/모음 분리
+        if (HangulUtils.hasHangul(prefix)) {
+            processedInput = HangulUtils.convertToJamo(prefix);
+        }
+
+        // 불리언 검색을 위해 토큰 사이에 '+' 연산자 추가
+        String booleanPrefix = convertToBooleanSearch(processedInput);
+        Pageable pageable = PageRequest.of(0, 20);
+        List<TechKeyword> techKeywords = techKeywordRepository.searchKeyword(booleanPrefix, booleanPrefix, pageable);
+
+        // 응답 데이터 가공
+        return techKeywords.stream()
+                .map(TechKeyword::getKeyword)
+                .toList();
+    }
+
+    /**
+     * 불리언 검색을 위해 각 토큰 사이에 '+' 연산자를 추가하는 메서드
+     */
+    private String convertToBooleanSearch(String searchTerm) {
+        if (searchTerm == null || searchTerm.trim().isEmpty()) {
+            return searchTerm;
+        }
+
+        // 공백을 기준으로 토큰을 분리하고 각 토큰 앞에 '+' 추가
+        String[] tokens = searchTerm.trim().split("\\s+");
+        for (int i = 0; i < tokens.length; i++) {
+            tokens[i] = "+" + tokens[i];
+        }
+        return String.join(" ", tokens);
+    }
+}

src/main/java/com/dreamypatisiel/devdevdev/global/config/CustomMySQLFunctionContributor.java

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+package com.dreamypatisiel.devdevdev.global.config;
+
+import org.hibernate.boot.model.FunctionContributions;
+import org.hibernate.boot.model.FunctionContributor;
+
+import static org.hibernate.type.StandardBasicTypes.DOUBLE;
+
+public class CustomMySQLFunctionContributor implements FunctionContributor {
+    private static final String MATCH_AGAINST_FUNCTION = "match_against";
+    private static final String MATCH_AGAINST_PATTERN = "match (?1) against (?2 in boolean mode)";
+
+    @Override
+    public void contributeFunctions(FunctionContributions functionContributions) {
+        functionContributions.getFunctionRegistry()
+                .registerPattern(MATCH_AGAINST_FUNCTION, MATCH_AGAINST_PATTERN,
+                        functionContributions.getTypeConfiguration().getBasicTypeRegistry().resolve(DOUBLE));
+    }
+}

src/main/java/com/dreamypatisiel/devdevdev/global/utils/HangulUtils.java

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+package com.dreamypatisiel.devdevdev.global.utils;
+
+/**
+ * 한글 처리를 위한 유틸리티 클래스
+ */
+public abstract class HangulUtils {
+
+    // 한글 유니코드 범위
+    private static final int HANGUL_START = 0xAC00; // '가'
+    private static final int HANGUL_END = 0xD7A3;   // '힣'
+
+    // 자모 유니코드 범위
+    private static final int JAMO_START = 0x1100;   // 'ㄱ'
+    private static final int JAMO_END = 0x11FF;     // 'ㅿ'
+
+    // 호환 자모 유니코드 범위
+    private static final int COMPAT_JAMO_START = 0x3130; // 'ㄱ'
+    private static final int COMPAT_JAMO_END = 0x318F;   // 'ㆎ'
+
+    // 한글 분해를 위한 상수
+    private static final int CHOSUNG_COUNT = 19;
+    private static final int JUNGSUNG_COUNT = 21;
+    private static final int JONGSUNG_COUNT = 28;
+
+    // 초성 배열
+    private static final char[] CHOSUNG = {
+            'ㄱ', 'ㄲ', 'ㄴ', 'ㄷ', 'ㄸ', 'ㄹ', 'ㅁ', 'ㅂ', 'ㅃ', 'ㅅ',
+            'ㅆ', 'ㅇ', 'ㅈ', 'ㅉ', 'ㅊ', 'ㅋ', 'ㅌ', 'ㅍ', 'ㅎ'
+    };
+
+    // 중성 배열
+    private static final char[] JUNGSUNG = {
+            'ㅏ', 'ㅐ', 'ㅑ', 'ㅒ', 'ㅓ', 'ㅔ', 'ㅕ', 'ㅖ', 'ㅗ', 'ㅘ',
+            'ㅙ', 'ㅚ', 'ㅛ', 'ㅜ', 'ㅝ', 'ㅞ', 'ㅟ', 'ㅠ', 'ㅡ', 'ㅢ', 'ㅣ'
+    };
+
+    // 종성 배열 (첫 번째는 받침 없음)
+    private static final char[] JONGSUNG = {
+            '\0', 'ㄱ', 'ㄲ', 'ㄳ', 'ㄴ', 'ㄵ', 'ㄶ', 'ㄷ', 'ㄹ', 'ㄺ',
+            'ㄻ', 'ㄼ', 'ㄽ', 'ㄾ', 'ㄿ', 'ㅀ', 'ㅁ', 'ㅂ', 'ㅄ', 'ㅅ',
+            'ㅆ', 'ㅇ', 'ㅈ', 'ㅊ', 'ㅋ', 'ㅌ', 'ㅍ', 'ㅎ'
+    };
+
+    /**
+     * 문자열에 한글이 포함되어 있는지 확인
+     */
+    public static boolean hasHangul(String text) {
+        if (text == null || text.isEmpty()) {
+            return false;
+        }
+
+        for (char ch : text.toCharArray()) {
+            if (isHangul(ch)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * 한글 문자열을 자모로 분해
+     */
+    public static String convertToJamo(String text) {
+        if (text == null || text.isEmpty()) {
+            return text;
+        }
+
+        StringBuilder result = new StringBuilder();
+
+        for (char ch : text.toCharArray()) {
+            if (isCompleteHangul(ch)) {
+                // 완성된 한글 문자를 자모로 분해
+                int unicode = ch - HANGUL_START;
+
+                int chosungIndex = unicode / (JUNGSUNG_COUNT * JONGSUNG_COUNT);
+                int jungsungIndex = (unicode % (JUNGSUNG_COUNT * JONGSUNG_COUNT)) / JONGSUNG_COUNT;
+                int jongsungIndex = unicode % JONGSUNG_COUNT;
+
+                result.append(CHOSUNG[chosungIndex]);
+                result.append(JUNGSUNG[jungsungIndex]);
+
+                if (jongsungIndex > 0) {
+                    result.append(JONGSUNG[jongsungIndex]);
+                }
+            } else {
+                // 한글이 아니거나 이미 자모인 경우 그대로 추가
+                result.append(ch);
+            }
+        }
+
+        return result.toString();
+    }
+
+    /**
+     * 한글 문자열에서 초성만 추출
+     */
+    public static String extractChosung(String text) {
+        if (text == null || text.isEmpty()) {
+            return text;
+        }
+
+        StringBuilder result = new StringBuilder();
+
+        for (char ch : text.toCharArray()) {
+            if (isCompleteHangul(ch)) {
+                // 완성된 한글 문자에서 초성 추출
+                int unicode = ch - HANGUL_START;
+                int chosungIndex = unicode / (JUNGSUNG_COUNT * JONGSUNG_COUNT);
+                result.append(CHOSUNG[chosungIndex]);
+            } else if (isChosung(ch)) {
+                // 이미 초성인 경우 그대로 추가
+                result.append(ch);
+            } else if (!isHangul(ch)) {
+                // 한글이 아닌 문자는 그대로 추가
+                result.append(ch);
+            }
+            // 중성, 종성은 무시
+        }
+
+        return result.toString();
+    }
+
+    /**
+     * 문자가 한글인지 확인 (완성형 한글 + 자모)
+     */
+    private static boolean isHangul(char ch) {
+        return isCompleteHangul(ch) || isJamo(ch) || isCompatJamo(ch);
+    }
+
+    /**
+     * 문자가 완성된 한글인지 확인
+     */
+    private static boolean isCompleteHangul(char ch) {
+        return ch >= HANGUL_START && ch <= HANGUL_END;
+    }
+
+    /**
+     * 문자가 자모인지 확인
+     */
+    private static boolean isJamo(char ch) {
+        return ch >= JAMO_START && ch <= JAMO_END;
+    }
+
+    /**
+     * 문자가 호환 자모인지 확인
+     */
+    private static boolean isCompatJamo(char ch) {
+        return ch >= COMPAT_JAMO_START && ch <= COMPAT_JAMO_END;
+    }
+
+    /**
+     * 문자가 초성인지 확인
+     */
+    private static boolean isChosung(char ch) {
+        for (char chosung : CHOSUNG) {
+            if (ch == chosung) {
+                return true;
+            }
+        }
+        return false;
+    }
+}