Fix existed tag insert failed for articles

src/main/java/io/spring/infrastructure/mybatis/mapper/ArticleMapper.java

@@ -11,7 +11,7 @@ public interface ArticleMapper {
 
     Article findById(@Param("id") String id);
 
-    boolean findTag(@Param("tagName") String tagName);
+    Tag findTag(@Param("tagName") String tagName);
 
     void insertTag(@Param("tag") Tag tag);
 

src/main/java/io/spring/infrastructure/repository/MyBatisArticleRepository.java

@@ -29,10 +29,11 @@ public class MyBatisArticleRepository implements ArticleRepository {
 
     private void createNew(Article article) {
         for (Tag tag : article.getTags()) {
-            if (!articleMapper.findTag(tag.getName())) {
+            Tag targetTag = Optional.ofNullable(articleMapper.findTag(tag.getName())).orElseGet(() -> {
                 articleMapper.insertTag(tag);
-            }
-            articleMapper.insertArticleTagRelation(article.getId(), tag.getId());
+                return tag;
+            });
+            articleMapper.insertArticleTagRelation(article.getId(), targetTag.getId());
         }
         articleMapper.insert(article);
     }

src/main/resources/mapper/ArticleMapper.xml

@@ -54,9 +54,10 @@
         where A.id = #{id}
     </select>
 
-    <select id="findTag" resultType="java.lang.Boolean">
-        select count(*) from tags where name = #{tagName}
+    <select id="findTag" resultType="io.spring.core.article.Tag">
+        select id, name from tags where name = #{tagName}
     </select>
+
     <select id="findBySlug" resultMap="article">
         <include refid="selectArticle"/>
         where A.slug = #{slug}

src/test/java/io/spring/infrastructure/article/ArticleRepositoryTransactionTest.java

@@ -13,6 +13,7 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.junit4.SpringRunner;
 
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
 
 @RunWith(SpringRunner.class)
 @SpringBootTest
@@ -38,7 +39,7 @@ public class ArticleRepositoryTransactionTest {
         try {
             articleRepository.save(anotherArticle);
         } catch (Exception e) {
-            assertFalse(articleMapper.findTag("other"));
+            assertNull(articleMapper.findTag("other"));
         }
     }