allow doing left and right joins

Author: mhewedy

README.md

@@ -63,7 +63,7 @@ For spring-boot 3.x:
 <dependency>
   <groupId>com.github.mhewedy</groupId>
   <artifactId>spring-data-jpa-mongodb-expressions</artifactId>
-  <version>0.1.4</version>
+  <version>0.1.5</version>
 </dependency>
 
 ```

docs/include.adoc

@@ -1,5 +1,5 @@
 :author: Mohammad Hewedy, The Spring Data JPA MongoDB Expressions Team
-:revnumber: 0.1.4
+:revnumber: 0.1.5
 :jsondir: ../src/test/resources
 :sectlinks: true
 :source-highlighter: highlight.js

docs/query_specs.adoc

@@ -8,7 +8,7 @@ https://docs.mongodb.com/manual/tutorial/query-documents/[MongoDB Query Language
 and uses a subset of the language and converts it to Spring Data JPA Specifications under the hood.
 
 In this section we will see by example all the supported features started by basic querying to
-comparision operators to joins and other features.
+comparison operators to joins and other features.
 ****
 
 == Overview
@@ -313,6 +313,20 @@ in such case you can create a database _view_ and map it to an JPA Entity and th
 
 TIP: The returned properties are the properties of the primary Entity, which means the `projection` is not supported due to limitation in spring-data-jpa addressed in this https://github.com/mhewedy/spring-data-jpa-mongodb-expressions/issues/4[bug,role=external,window=_blank], until it is fixed and if you need to return properties from other entities involved in the join, you need to follow the database _view_ workaround mentioned in the previous tip.
 
+==== Left and right joins
+1. Left join uses notation `.<` and right join uses `.>`, exmaple on left join:
++
+[source,json]
+----
+include::{jsondir}/testLeftJoin.json[]
+----
+Generated SQL:
++
+[source,sql]
+----
+...  from employee join department on department.id=employee.department_id left join city on city.id=department.city_id where employee.first_name=? or city.name=?
+----
+
 === Embedded
 1. Using embedded fields:
 +

pom.xml

@@ -12,7 +12,7 @@
 
     <groupId>com.github.mhewedy</groupId>
     <artifactId>spring-data-jpa-mongodb-expressions</artifactId>
-    <version>0.1.4</version>
+    <version>0.1.5</version>
     <name>spring-data-jpa-mongodb-expressions</name>
     <description>Spring Data JPA Mongodb Expressions</description>
 

src/main/java/com/github/mhewedy/expressions/ExpressionsPredicateBuilder.java

@@ -1,12 +1,12 @@
 package com.github.mhewedy.expressions;
 
-import org.springframework.util.Assert;
-
 import jakarta.persistence.criteria.*;
 import jakarta.persistence.metamodel.Attribute;
 import jakarta.persistence.metamodel.ManagedType;
 import jakarta.persistence.metamodel.PluralAttribute;
 import jakarta.persistence.metamodel.SingularAttribute;
+import org.springframework.util.Assert;
+
 import java.time.*;
 import java.time.chrono.HijrahDate;
 import java.util.ArrayList;
@@ -16,9 +16,9 @@
 import java.util.stream.Collectors;
 
 import static com.github.mhewedy.expressions.Expression.*;
+import static jakarta.persistence.metamodel.Attribute.PersistentAttributeType;
 import static java.util.Collections.singletonList;
 import static java.util.stream.Collectors.toList;
-import static jakarta.persistence.metamodel.Attribute.PersistentAttributeType;
 
 class ExpressionsPredicateBuilder {
 
@@ -65,13 +65,13 @@ private static List<Predicate> getPredicates(CriteriaQuery<?> query, CriteriaBui
                         query.distinct(true);
                     }
 
-                    final String subField = extractSubField(singularExpression.field);
-                    if (!subField.isEmpty()) {
+                    final SubField subField = extractSubField(singularExpression.field);
+                    if (!subField.name.isEmpty()) {
                         final SingularExpression subExpression =
-                                new SingularExpression(subField, singularExpression.operator, singularExpression.value);
+                                new SingularExpression(subField.name, singularExpression.operator, singularExpression.value);
                         predicates.addAll(
                                 getPredicates(query, cb,
-                                        reuseOrCreateJoin((From<?, ?>) from, attribute, field),
+                                        reuseOrCreateJoin((From<?, ?>) from, attribute, field, subField.joinType),
                                         extractSubFieldType(attribute),
                                         singletonList(subExpression)
                                 )
@@ -83,8 +83,8 @@ private static List<Predicate> getPredicates(CriteriaQuery<?> query, CriteriaBui
                 Path exprPath = from.get((SingularAttribute) attribute);
 
                 if (PersistentAttributeType.EMBEDDED == attribute.getPersistentAttributeType()) {
-                    final String subField = extractSubField(singularExpression.field);
-                    attribute = extractSubFieldType(attribute).getAttribute(subField);
+                    final SubField subField = extractSubField(singularExpression.field);
+                    attribute = extractSubFieldType(attribute).getAttribute(subField.name);
                     exprPath = exprPath.get((SingularAttribute) attribute);
                 }
 
@@ -188,13 +188,13 @@ private static List<Predicate> getPredicates(CriteriaQuery<?> query, CriteriaBui
                         query.distinct(true);
                     }
 
-                    final String subField = extractSubField(listExpression.field);
-                    if (!subField.isEmpty()) {
+                    final SubField subField = extractSubField(listExpression.field);
+                    if (!subField.name.isEmpty()) {
                         final ListExpression subExpression =
-                                new ListExpression(subField, listExpression.operator, listExpression.values);
+                                new ListExpression(subField.name, listExpression.operator, listExpression.values);
                         predicates.addAll(
                                 getPredicates(query, cb,
-                                        reuseOrCreateJoin((From<?, ?>) from, attribute, field),
+                                        reuseOrCreateJoin((From<?, ?>) from, attribute, field, subField.joinType),
                                         extractSubFieldType(attribute),
                                         singletonList(subExpression)
                                 )
@@ -206,8 +206,8 @@ private static List<Predicate> getPredicates(CriteriaQuery<?> query, CriteriaBui
                 Path exprPath = from.get((SingularAttribute) attribute);
 
                 if (PersistentAttributeType.EMBEDDED == attribute.getPersistentAttributeType()) {
-                    final String subField = extractSubField(listExpression.field);
-                    attribute = extractSubFieldType(attribute).getAttribute(subField);
+                    final SubField subField = extractSubField(listExpression.field);
+                    attribute = extractSubFieldType(attribute).getAttribute(subField.name);
                     exprPath = exprPath.get((SingularAttribute) attribute);
                 }
 
@@ -266,11 +266,11 @@ private static List<Predicate> getPredicates(CriteriaQuery<?> query, CriteriaBui
         }
     }
 
-    private static Path<?> reuseOrCreateJoin(From<?, ?> from, Attribute<?, ?> attribute, String field) {
+    private static Path<?> reuseOrCreateJoin(From<?, ?> from, Attribute<?, ?> attribute, String field, JoinType joinType) {
         return from.getJoins().stream()
                 .filter(it -> it.getAttribute() == attribute)
                 .findFirst()
-                .orElseGet(() -> from.join(field));
+                .orElseGet(() -> from.join(field, joinType));
     }
 
     @SuppressWarnings({"rawtypes"})
@@ -283,9 +283,23 @@ private static String extractField(String field) {
         return field.contains(".") ? field.split("\\.")[0] : field;
     }
 
-    private static String extractSubField(String field) {
+    private static SubField extractSubField(String field) {
         //if field is "abc.efg.xyz", then return "efg.xyz", so to support n-level association
-        return Arrays.stream(field.split("\\.")).skip(1).collect(Collectors.joining("."));
+        String subField = Arrays.stream(field.split("\\.")).skip(1).collect(Collectors.joining("."));
+        JoinType joinType;
+        if (subField.startsWith("<")) { /// .<
+            subField = subField.substring(1);
+            joinType = JoinType.LEFT;
+        } else if (subField.startsWith(">")) {  ///  .>
+            subField = subField.substring(1);
+            joinType = JoinType.RIGHT;
+        } else {
+            joinType = JoinType.INNER;
+        }
+        return new SubField(subField, joinType);
+    }
+
+    private record SubField(String name, JoinType joinType) {
     }
 
     @SuppressWarnings({"rawtypes", "unchecked"})

src/test/java/com/github/mhewedy/expressions/ExpressionsRepositoryImplTest.java

@@ -1,5 +1,6 @@
 package com.github.mhewedy.expressions;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.mhewedy.expressions.model.*;
 import jakarta.persistence.EntityManager;
@@ -89,7 +90,7 @@ public void setup() {
                         Instant.parse("2009-12-03T10:15:30.00Z"),
                         (short) 1,
                         true,
-                        new Department(null, "sw arch", new City(null, "giaz")),
+                        new Department(null, "sw arch", null),
                         Arrays.asList(new Task(null, "fix sw arch", ACTIVE), new Task(null, "fix sw arch", ACTIVE)),
                         UUID.randomUUID(),
                         Lang.AR,
@@ -733,6 +734,17 @@ public void testTheList() {
         // where last_name=? and (age in (? , ?) or birth_date<?)
     }
 
+    @Test
+    public void testLeftJoin() throws JsonProcessingException {
+        String json = loadResourceJsonFile("testLeftJoin");
+
+        Expressions expressions = new ObjectMapper().readValue(json, Expressions.class);
+
+        List<Employee> employeeList = employeeRepository.findAll(expressions);
+        assertThat(employeeList.size()).isEqualTo(3);
+
+    }
+
     @SneakyThrows
     private String loadResourceJsonFile(String name) {
         File file = ResourceUtils.getFile("classpath:" + name + ".json");

src/test/resources/testLeftJoin.json

@@ -0,0 +1,10 @@
+{
+  "$or": [
+    {
+      "firstName": "farida"
+    },
+    {
+      "department.<city.name": "cairo"
+    }
+  ]
+}