feat: IssueFilterRepository (#9)

- 필터 기능 추가를 위한 Repository

BE/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'org.springframework.boot' version '2.5.0'
     id 'io.spring.dependency-management' version '1.0.11.RELEASE'
+    id "com.ewerk.gradle.plugins.querydsl" version "1.0.10"
     id 'java'
 }
 
@@ -22,6 +23,7 @@ dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
     implementation 'org.springframework.boot:spring-boot-starter-web'
     implementation 'com.auth0:java-jwt:3.16.0'
+    implementation 'com.querydsl:querydsl-jpa'
     runtimeOnly 'mysql:mysql-connector-java'
     compileOnly 'org.projectlombok:lombok'
     developmentOnly 'org.springframework.boot:spring-boot-devtools'
@@ -36,3 +38,20 @@ dependencies {
 test {
     useJUnitPlatform()
 }
+
+//querydsl 추가 시작
+def querydslDir = "$buildDir/generated/querydsl"
+querydsl {
+    jpa = true
+    querydslSourcesDir = querydslDir
+}
+sourceSets {
+    main.java.srcDir querydslDir
+}
+configurations {
+    querydsl.extendsFrom compileClasspath
+}
+compileQuerydsl {
+    options.annotationProcessorPath = configurations.querydsl
+}
+//querydsl 추가 끝

BE/src/main/java/com/codesquad/issuetracker/issue/domain/JpaIssueFilterRepository.java

@@ -0,0 +1,62 @@
+package com.codesquad.issuetracker.issue.domain;
+
+import com.codesquad.issuetracker.issue.dto.IssueFilter;
+import com.codesquad.issuetracker.issue.infra.IssueFilterRepository;
+import com.querydsl.core.types.dsl.BooleanExpression;
+import com.querydsl.jpa.impl.JPAQuery;
+import com.querydsl.jpa.impl.JPAQueryFactory;
+import org.springframework.stereotype.Repository;
+
+import javax.persistence.EntityManager;
+import java.util.List;
+
+import static com.codesquad.issuetracker.issue.domain.QIssue.issue;
+import static com.codesquad.issuetracker.label.domain.QLabel.label;
+import static com.codesquad.issuetracker.milestone.domain.QMilestone.milestone;
+import static com.codesquad.issuetracker.user.domain.QUser.user;
+
+@Repository
+public class JpaIssueFilterRepository implements IssueFilterRepository {
+
+    private final JPAQueryFactory jpaQueryFactory;
+
+    public JpaIssueFilterRepository(EntityManager em) {
+        this.jpaQueryFactory = new JPAQueryFactory(em);
+    }
+
+    @Override
+    public List<Issue> findByIssueFilter(IssueFilter issueFilter) {
+        JPAQuery<Issue> query = jpaQueryFactory
+                .select(issue)
+                .distinct()
+                .from(issue);
+
+        if (issueFilter.getLabel() != null && issueFilter.getLabel().length() > 0) {
+            query = query.innerJoin(issue.labels, label).on(label.name.contains(issueFilter.getLabel()));
+        }
+
+        if (issueFilter.getMilestone() != null && issueFilter.getMilestone().length() > 0) {
+            query = query.innerJoin(issue.milestone, milestone).on(milestone.title.contains(issueFilter.getMilestone()));
+        }
+
+        if (issueFilter.getAuthor() != null) {
+            query = query.innerJoin(issue.author, user).on(user.id.eq(issueFilter.getAssignee()));
+        }
+
+        if (issueFilter.getAssignee() != null) {
+            query = query.innerJoin(issue.assignees, user).on(user.id.eq(issueFilter.getAssignee()));
+        }
+
+        return query.where(
+                open(issueFilter.getOpen())
+        ).fetch();
+    }
+
+    private BooleanExpression open(Boolean open) {
+        if (open == null) {
+            return null;
+        }
+        return issue.open.eq(open);
+    }
+
+}

BE/src/main/java/com/codesquad/issuetracker/issue/dto/IssueFilter.java

@@ -0,0 +1,16 @@
+package com.codesquad.issuetracker.issue.dto;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.UUID;
+
+@Getter
+@Setter
+public class IssueFilter {
+    private UUID author;
+    private UUID assignee;
+    private String label;
+    private String milestone;
+    private Boolean open;
+}

BE/src/main/java/com/codesquad/issuetracker/issue/infra/IssueFilterRepository.java

@@ -0,0 +1,10 @@
+package com.codesquad.issuetracker.issue.infra;
+
+import com.codesquad.issuetracker.issue.domain.Issue;
+import com.codesquad.issuetracker.issue.dto.IssueFilter;
+
+import java.util.List;
+
+public interface IssueFilterRepository {
+    List<Issue> findByIssueFilter(IssueFilter issueFilter);
+}