[BAEL-1542] - Simple Tagging with JPA (#3626)

* Code samples for Simple Tagging with JPA

* Fix pom relative path for spring-jpa

persistence-modules/spring-jpa/pom.xml

@@ -13,7 +13,7 @@
 		<groupId>com.baeldung</groupId>
 		<artifactId>parent-modules</artifactId>
 		<version>1.0.0-SNAPSHOT</version>
-                        <relativePath>../</relativePath>
+		<relativePath>../../</relativePath>
 	</parent>
 
 	<dependencies>

persistence-modules/spring-jpa/src/main/java/org/baeldung/inmemory/persistence/dao/StudentRepository.java

@@ -2,6 +2,17 @@ package org.baeldung.inmemory.persistence.dao;
 
 import org.baeldung.inmemory.persistence.model.Student;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.util.List;
 
 public interface StudentRepository extends JpaRepository<Student, Long> {
+
+    @Query("SELECT s FROM Student s JOIN s.tags t WHERE t = LOWER(:tag)")
+    List<Student> retrieveByTag(@Param("tag") String tag);
+
+    @Query("SELECT s FROM Student s JOIN s.tags t WHERE s.name = LOWER(:name) AND t = LOWER(:tag)")
+    List<Student> retrieveByNameFilterByTag(@Param("name") String name, @Param("tag") String tag);
+
 }

persistence-modules/spring-jpa/src/main/java/org/baeldung/inmemory/persistence/model/Student.java

@@ -1,7 +1,10 @@
 package org.baeldung.inmemory.persistence.model;
 
+import javax.persistence.ElementCollection;
 import javax.persistence.Entity;
 import javax.persistence.Id;
+import java.util.ArrayList;
+import java.util.List;
 
 @Entity
 public class Student {
@@ -10,6 +13,9 @@ public class Student {
     private long id;
     private String name;
 
+    @ElementCollection
+    private List<String> tags = new ArrayList<>();
+
     public Student() {
     }
 
@@ -35,4 +41,11 @@ public class Student {
         this.name = name;
     }
 
+    public List<String> getTags() {
+        return tags;
+    }
+
+    public void setTags(List<String> tags) {
+        this.tags.addAll(tags);
+    }
 }

persistence-modules/spring-jpa/src/test/java/org/baeldung/persistence/repository/InMemoryDBIntegrationTest.java

@@ -12,6 +12,9 @@ import org.springframework.transaction.annotation.Transactional;
 
 import javax.annotation.Resource;
 
+import java.util.Arrays;
+import java.util.List;
+
 import static org.junit.Assert.assertEquals;
 
 @RunWith(SpringJUnit4ClassRunner.class)
@@ -34,4 +37,46 @@ public class InMemoryDBIntegrationTest {
         assertEquals("name incorrect", NAME, student2.getName());        
     }
 
+    @Test
+    public void givenStudentWithTags_whenSave_thenGetByTagOk(){
+        Student student = new Student(ID, NAME);
+        student.setTags(Arrays.asList("full time", "computer science"));
+        studentRepository.save(student);
+
+        Student student2 = studentRepository.retrieveByTag("full time").get(0);
+        assertEquals("name incorrect", NAME, student2.getName());
+    }
+
+    @Test
+    public void givenMultipleStudentsWithTags_whenSave_thenGetByTagReturnsCorrectCount(){
+        Student student = new Student(0, "Larry");
+        student.setTags(Arrays.asList("full time", "computer science"));
+        studentRepository.save(student);
+
+        Student student2 = new Student(1, "Curly");
+        student2.setTags(Arrays.asList("part time", "rocket science"));
+        studentRepository.save(student2);
+
+        Student student3 = new Student(2, "Moe");
+        student3.setTags(Arrays.asList("full time", "philosophy"));
+        studentRepository.save(student3);
+
+        Student student4 = new Student(3, "Shemp");
+        student4.setTags(Arrays.asList("part time", "mathematics"));
+        studentRepository.save(student4);
+
+        List<Student> students = studentRepository.retrieveByTag("full time");
+        assertEquals("size incorrect", 2, students.size());
+    }
+
+    @Test
+    public void givenStudentWithTags_whenSave_thenGetByNameAndTagOk(){
+        Student student = new Student(ID, NAME);
+        student.setTags(Arrays.asList("full time", "computer science"));
+        studentRepository.save(student);
+
+        Student student2 = studentRepository.retrieveByNameFilterByTag("John", "full time").get(0);
+        assertEquals("name incorrect", NAME, student2.getName());
+    }
+
 }