feat: add where relation attributes criteria expressions (#96)

* fix: add missing data.sql in example

* feat: add where relation attribute filter criteria expressions

* fix: polish merge example query name and description

* fix: Hibernate error using query specified join fetching

* fix: enable variable parameter bindings

* fix: polish relation criteria expression type name

* fix: reuse joins for relation criteria expression argument predicates

* fix: support AND/OR in relation attribute filters

* fix: use hint hibernate.query.passDistinctThrough=false

* chore: remove .project from git

* chore: polish and refactor internal DataFetcher code

* fix: clear entityManager session cache for every request

* chore: add Hibernate properties to examples

* chore: polish GraphQLJpaQueryDataFetcher internals

* Update README.md

* fix: reuse join for singular many-to-one attributes

* fix: use fetch=LAZY for all relations in example entity models

Author: igdianov

.project

@@ -150,7 +150,7 @@ Will return:
 
 Query Wrapper with Where Criteria Expressions
 -------------------------------------
-This library supports flexible type safe criteria expressions with user-friendly SQL query syntax semantics using `where` arguments and `select` field to specify the entity graph query with entiy attribute names as a combination of logical expressions like OR, AND, EQ, NE, GT, GE, LT, LR, IN, NIN, IS_NULL, NOT_NULL, BETWEEN, NOT_BETWEEN.
+This library supports flexible type safe criteria expressions with user-friendly SQL query syntax semantics using `where` arguments and `select` field to specify the entity graph query with entiy attribute names as a combination of logical expressions like EQ, NE, GT, GE, LT, LR, IN, NIN, IS_NULL, NOT_NULL, BETWEEN, NOT_BETWEEN. You can use logical AND/OR combinations in SQL criteria expressions to specify complex criterias to fetch your data from SQL database. If you omit, where argument, all entities will be returned.
 
 For Example: 
 
@@ -173,7 +173,200 @@ Will return:
         }
     }
 
-You can use familiar SQL criteria expressions to specify complex criterias to fetch your data from SQL database. If you omit, where argument, all entities will be returned.
+Relation Attributes in Where Criteria Expressions:
+----------------------------
+It is also possible to specify complex filters using many-to-one and one-to-many entity attributes in where criteria expressions with variable parameter bindings, i.e.
+
+Given the following query with many-to-one relation with variables `{"authorId": 1 }` :
+
+```
+query($authorId: Long) {  
+  Books(where: {
+    author: {id: {EQ: $authorId}}
+  }) {
+    select {
+      id
+      title
+      genre
+      author {
+        id
+        name
+      }
+    }
+  }
+}
+```
+
+will result in
+
+```
+{
+  "data": {
+    "Books": {
+      "select": [
+        {
+          "id": 2,
+          "title": "War and Peace",
+          "genre": "NOVEL",
+          "author": {
+            "id": 1,
+            "name": "Leo Tolstoy"
+          }
+        },
+        {
+          "id": 3,
+          "title": "Anna Karenina",
+          "genre": "NOVEL",
+          "author": {
+            "id": 1,
+            "name": "Leo Tolstoy"
+          }
+        }
+      ]
+    }
+  }
+}
+```
+
+And given the following query with one-to-many relation:
+
+```
+query {
+  Authors(where: {
+    books: {genre: {IN: NOVEL}}
+  }) {
+    select {
+      id
+      name
+      books {
+        id
+        title
+        genre
+      }
+    }
+  }
+}
+```
+
+will result in 
+
+```
+{
+  "data": {
+    "Authors": {
+      "select": [
+        {
+          "id": 1,
+          "name": "Leo Tolstoy",
+          "books": [
+            {
+              "id": 2,
+              "title": "War and Peace",
+              "genre": "NOVEL"
+            },
+            {
+              "id": 3,
+              "title": "Anna Karenina",
+              "genre": "NOVEL"
+            }
+          ]
+        }
+      ]
+    }
+  }
+}
+```
+
+It is possible to use compound criterias in where search expressions given:
+
+```
+query {
+  Authors(where: {
+    books: {
+      genre: {IN: NOVEL}
+      title: {LIKE: "War"}
+    }
+  }) {
+    select {
+      id
+      name
+      books {
+        id
+        title
+        genre
+      }
+    }
+  }
+}
+```
+
+Will return filtered inner collection result: 
+
+```
+{
+  "data": {
+    "Authors": {
+      "select": [
+        {
+          "id": 1,
+          "name": "Leo Tolstoy",
+          "books": [
+            {
+              "id": 2,
+              "title": "War and Peace",
+              "genre": "NOVEL"
+            }
+          ]
+        }
+      ]
+    }
+  }
+}
+```
+
+It is also possible to filter inner collections as follows:
+
+```
+query {
+  Authors(where: {
+    books: {genre: {IN: NOVEL}}
+  }) {
+    select {
+      id
+      name
+      books(where: {title: {LIKE: "War"}}) {
+        id
+        title
+        genre
+      }
+    }
+  }
+}
+```
+
+will result in 
+
+```
+{
+  "data": {
+    "Authors": {
+      "select": [
+        {
+          "id": 1,
+          "name": "Leo Tolstoy",
+          "books": [
+            {
+              "id": 2,
+              "title": "War and Peace",
+              "genre": "NOVEL"
+            }
+          ]
+        }
+      ]
+    }
+  }
+}
+```    
 
 Collection Filtering
 --------------------

README.md

@@ -19,6 +19,7 @@
 import java.util.Collection;
 
 import javax.persistence.Entity;
+import javax.persistence.FetchType;
 import javax.persistence.Id;
 import javax.persistence.OneToMany;
 
@@ -32,6 +33,6 @@ public class Author {
 
 	String name;
 
-	@OneToMany(mappedBy="author")
+	@OneToMany(mappedBy="author", fetch=FetchType.LAZY)
 	Collection<Book> books;
 }

graphql-jpa-query-boot-starter/.project

@@ -19,6 +19,7 @@
 import javax.persistence.Entity;
 import javax.persistence.EnumType;
 import javax.persistence.Enumerated;
+import javax.persistence.FetchType;
 import javax.persistence.Id;
 import javax.persistence.ManyToOne;
 
@@ -32,7 +33,7 @@ public class Book {
 
 	String title;
 
-	@ManyToOne
+	@ManyToOne(fetch=FetchType.LAZY)
 	Author author;
 
 	@Enumerated(EnumType.STRING)

graphql-jpa-query-example-merge/src/main/java/com/introproventures/graphql/jpa/query/example/books/Author.java

@@ -22,13 +22,15 @@
 import javax.persistence.Entity;
 import javax.persistence.EnumType;
 import javax.persistence.Enumerated;
+import javax.persistence.FetchType;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.JoinTable;
 import javax.persistence.ManyToMany;
 import javax.persistence.OrderBy;
 
 import com.introproventures.graphql.jpa.query.annotation.GraphQLDescription;
+
 import lombok.EqualsAndHashCode;
 import lombok.Getter;
 import lombok.Setter;
@@ -50,14 +52,14 @@ public abstract class Character {
     String name;
 
     @GraphQLDescription("Who are the known friends to this character")
-    @ManyToMany
-    @JoinTable(name="character_friends",
+    @ManyToMany(fetch = FetchType.LAZY)
+    @JoinTable(name="character_friends", 
             joinColumns=@JoinColumn(name="source_id", referencedColumnName="id"),
             inverseJoinColumns=@JoinColumn(name="friend_id", referencedColumnName="id"))
     Set<Character> friends; 
 
     @GraphQLDescription("What Star Wars episodes does this character appear in")
-    @ElementCollection(targetClass = Episode.class)
+    @ElementCollection(targetClass = Episode.class, fetch = FetchType.LAZY)
     @Enumerated(EnumType.ORDINAL)
     @OrderBy
     Set<Episode> appearsIn;

graphql-jpa-query-example-merge/src/main/java/com/introproventures/graphql/jpa/query/example/books/Book.java

@@ -17,11 +17,13 @@
 package com.introproventures.graphql.jpa.query.example.starwars;
 
 import javax.persistence.Entity;
+import javax.persistence.FetchType;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.ManyToOne;
 
 import com.introproventures.graphql.jpa.query.annotation.GraphQLDescription;
+
 import lombok.Data;
 
 @Entity
@@ -39,7 +41,7 @@ public class CodeList {
     boolean active;
     String description;
 
-    @ManyToOne
+    @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "parent_id")
     CodeList parent;
 

graphql-jpa-query-example-merge/src/main/java/com/introproventures/graphql/jpa/query/example/starwars/Character.java

@@ -35,7 +35,7 @@ public class Human extends Character {
     @JoinColumn(name = "favorite_droid_id")
     Droid favoriteDroid;
 
-    @ManyToOne
+    @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "gender_code_id")
     CodeList gender;