BAEL-6348 persist List<String> in JPA (#13897)

* BAEL-6348 persist List<String> in JPA

* Update naming

persistence-modules/spring-data-jpa-repo-3/src/main/java/com/baeldung/spring/data/jpa/listrepositories/entity/Library.java

@@ -0,0 +1,66 @@
+package com.baeldung.spring.data.jpa.listrepositories.entity;
+
+import jakarta.persistence.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Entity(name = "library")
+public class Library {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    private String name;
+
+    @Convert(converter = StringListConverter.class)
+    @Column(name = "addresses", nullable = false)
+    private List<String> addresses = new ArrayList<>();
+
+    @ElementCollection(targetClass = String.class, fetch = FetchType.EAGER)
+    @CollectionTable(name = "book", joinColumns = @JoinColumn(name = "library_id"))
+    @Column(name = "book", nullable = false)
+    private List<String> books = new ArrayList<>();
+
+    public Library() {
+    }
+
+    public Library(String name, List<String> addresses, List<String> books) {
+        this.name = name;
+        this.addresses = addresses;
+        this.books = books;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getAddresses() {
+        return addresses;
+    }
+
+    public void setAddresses(List<String> addresses) {
+        this.addresses = addresses;
+    }
+
+    public List<String> getBooks() {
+        return books;
+    }
+
+    public void setBooks(List<String> books) {
+        this.books = books;
+    }
+}

persistence-modules/spring-data-jpa-repo-3/src/main/java/com/baeldung/spring/data/jpa/listrepositories/entity/StringListConverter.java

@@ -0,0 +1,25 @@
+package com.baeldung.spring.data.jpa.listrepositories.entity;
+
+import jakarta.persistence.AttributeConverter;
+import jakarta.persistence.Converter;
+
+import java.util.Arrays;
+import java.util.List;
+
+
+import static java.util.Collections.*;
+
+@Converter
+public class StringListConverter implements AttributeConverter<List<String>, String> {
+    private static final String SPLIT_CHAR = ";";
+
+    @Override
+    public String convertToDatabaseColumn(List<String> stringList) {
+        return stringList != null ? String.join(SPLIT_CHAR, stringList) : "";
+    }
+
+    @Override
+    public List<String> convertToEntityAttribute(String string) {
+        return string != null ? Arrays.asList(string.split(SPLIT_CHAR)) : emptyList();
+    }
+}

persistence-modules/spring-data-jpa-repo-3/src/main/java/com/baeldung/spring/data/jpa/listrepositories/repository/LibraryRepository.java

@@ -0,0 +1,13 @@
+package com.baeldung.spring.data.jpa.listrepositories.repository;
+
+import com.baeldung.spring.data.jpa.listrepositories.entity.Library;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.data.repository.query.Param;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface LibraryRepository extends CrudRepository<Library, Long> {
+    @Query("SELECT l FROM library l JOIN FETCH l.books WHERE l.id = (:id)")
+    Library findById(@Param("id") long id);
+}

persistence-modules/spring-data-jpa-repo-3/src/test/java/com/baeldung/spring/data/jpa/listrepositories/repository/LibraryIntegrationTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.spring.data.jpa.listrepositories.repository;
+
+import com.baeldung.spring.data.jpa.listrepositories.entity.Library;
+import jakarta.transaction.Transactional;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import java.util.Arrays;
+
+@SpringBootTest
+public class LibraryIntegrationTest {
+
+    @Autowired
+    private LibraryRepository libraryRepository;
+
+    @Test
+    @Transactional
+    public void givenLibrary_whenGetAddressesAndGetBooks_thenGetListOfItems(){
+        Library library = new Library();
+        library.setAddresses(Arrays.asList("Address 1", "Address 2"));
+        library.setBooks(Arrays.asList("Book 1", "Book 2"));
+
+        libraryRepository.save(library);
+        Library lib = libraryRepository.findById(library.getId().longValue());
+
+        Assertions.assertEquals(2, lib.getAddresses().size());
+        Assertions.assertEquals(2, lib.getBooks().size());
+    }
+
+}