JPA Entity Graph.

2018-11-23 17:00:08 +01:00
parent 9127733ad1
commit 64bc8a412d
8 changed files with 428 additions and 19 deletions
@@ -0,0 +1,26 @@
+package com.baeldung.jpa.entitygraph;
+
+import com.baeldung.jpa.entitygraph.model.Post;
+import com.baeldung.jpa.entitygraph.repo.PostRepository;
+
+public class MainApp {
+
+    public static void main(String... args) {
+        Long postId = 1L;
+        Post post = null;
+        PostRepository postRepository = new PostRepository();
+
+        //Using EntityManager.find().
+        post = postRepository.find(postId);
+        post = postRepository.findWithEntityGraph(postId);
+        post = postRepository.findWithEntityGraph2(postId);
+
+        //Using JPQL: Query and TypedQuery
+        post = postRepository.findUsingJpql(postId);
+
+        //Using Criteria API
+        post = postRepository.findUsingCriteria(postId);
+
+        postRepository.clean();
+    }
+}
@@ -0,0 +1,63 @@
+package com.baeldung.jpa.entitygraph.model;
+
+import javax.persistence.*;
+
+@Entity
+public class Comment {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    private String reply;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn
+    private Post post;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn
+    private User user;
+    //...
+
+    public Comment() {
+    }
+
+    public Comment(String reply, Post post, User user) {
+        this.reply = reply;
+        this.post = post;
+        this.user = user;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getReply() {
+        return reply;
+    }
+
+    public void setReply(String reply) {
+        this.reply = reply;
+    }
+
+    public Post getPost() {
+        return post;
+    }
+
+    public void setPost(Post post) {
+        this.post = post;
+    }
+
+    public User getUser() {
+        return user;
+    }
+
+    public void setUser(User user) {
+        this.user = user;
+    }
+}
@@ -0,0 +1,86 @@
+package com.baeldung.jpa.entitygraph.model;
+
+import javax.persistence.*;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
+
+@NamedEntityGraph(
+        name = "post-entity-graph",
+        attributeNodes = {
+                @NamedAttributeNode("subject"),
+                @NamedAttributeNode("user"),
+                @NamedAttributeNode("comments"),
+        }
+)
+@NamedEntityGraph(
+        name = "post-entity-graph-with-comment-users",
+        attributeNodes = {
+                @NamedAttributeNode("subject"),
+                @NamedAttributeNode("user"),
+                @NamedAttributeNode(value = "comments", subgraph = "comments-subgraph"),
+        },
+        subgraphs = {
+                @NamedSubgraph(
+                        name = "comments-subgraph",
+                        attributeNodes = {
+                                @NamedAttributeNode("user")
+                        }
+                )
+        }
+)
+@Entity
+public class Post {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+    private String subject;
+    @OneToMany(mappedBy = "post")
+    private List<Comment> comments = new ArrayList<>();
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn
+    private User user;
+    //...
+
+    public Post() {
+    }
+
+    public Post(String subject, User user) {
+        this.subject = subject;
+        this.user = user;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getSubject() {
+        return subject;
+    }
+
+    public void setSubject(String subject) {
+        this.subject = subject;
+    }
+
+    public List<Comment> getComments() {
+        return comments;
+    }
+
+    public void setComments(List<Comment> comments) {
+        this.comments = comments;
+    }
+
+    public User getUser() {
+        return user;
+    }
+
+    public void setUser(User user) {
+        this.user = user;
+    }
+}
@@ -0,0 +1,48 @@
+package com.baeldung.jpa.entitygraph.model;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+    private String name;
+    private String email;
+
+    //...
+
+    public User() {
+    }
+
+    public User(String email) {
+        this.email = email;
+    }
+
+    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 String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+}
@@ -0,0 +1,93 @@
+package com.baeldung.jpa.entitygraph.repo;
+
+import com.baeldung.jpa.entitygraph.model.Post;
+
+import javax.persistence.*;
+import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaQuery;
+import javax.persistence.criteria.Root;
+import java.util.HashMap;
+import java.util.Map;
+
+public class PostRepository {
+    private EntityManagerFactory emf = null;
+
+
+    public PostRepository() {
+        Map properties = new HashMap();
+        properties.put("hibernate.show_sql", "true");
+        properties.put("hibernate.format_sql", "true");
+        emf = Persistence.createEntityManagerFactory("entity-graph-pu", properties);
+    }
+
+    public Post find(Long id) {
+        EntityManager entityManager = emf.createEntityManager();
+
+        Post post = entityManager.find(Post.class, id);
+
+        entityManager.close();
+        return post;
+    }
+
+    public Post findWithEntityGraph(Long id) {
+        EntityManager entityManager = emf.createEntityManager();
+
+        EntityGraph entityGraph = entityManager.getEntityGraph("post-entity-graph");
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("javax.persistence.fetchgraph", entityGraph);
+        Post post = entityManager.find(Post.class, id, properties);
+
+        entityManager.close();
+        return post;
+    }
+
+    public Post findWithEntityGraph2(Long id) {
+        EntityManager entityManager = emf.createEntityManager();
+
+        EntityGraph<Post> entityGraph = entityManager.createEntityGraph(Post.class);
+        entityGraph.addAttributeNodes("subject");
+        entityGraph.addAttributeNodes("user");
+        entityGraph.addSubgraph("comments")
+                .addAttributeNodes("user");
+
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("javax.persistence.fetchgraph", entityGraph);
+        Post post = entityManager.find(Post.class, id, properties);
+
+        entityManager.close();
+        return post;
+    }
+
+    public Post findUsingJpql(Long id) {
+        EntityManager entityManager = emf.createEntityManager();
+
+        EntityGraph entityGraph = entityManager.getEntityGraph("post-entity-graph-with-comment-users");
+        Post post = entityManager.createQuery("Select p from Post p where p.id=:id", Post.class)
+                .setParameter("id", id)
+                .setHint("javax.persistence.fetchgraph", entityGraph)
+                .getSingleResult();
+
+        entityManager.close();
+        return post;
+    }
+
+    public Post findUsingCriteria(Long id) {
+        EntityManager entityManager = emf.createEntityManager();
+
+        EntityGraph entityGraph = entityManager.getEntityGraph("post-entity-graph-with-comment-users");
+        CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
+        CriteriaQuery<Post> criteriaQuery = criteriaBuilder.createQuery(Post.class);
+        Root<Post> root = criteriaQuery.from(Post.class);
+        criteriaQuery.where(criteriaBuilder.equal(root.<Long>get("id"), id));
+        TypedQuery<Post> typedQuery = entityManager.createQuery(criteriaQuery);
+        typedQuery.setHint("javax.persistence.loadgraph", entityGraph);
+        Post post = typedQuery.getSingleResult();
+
+        entityManager.close();
+        return post;
+    }
+
+    public void clean() {
+        emf.close();
+    }
+}