FINERACT-1724: Final touches for Client V2 search API

fineract-core/src/main/java/org/apache/fineract/infrastructure/core/jpa/CriteriaQueryFactory.java

@@ -19,23 +19,35 @@
 package org.apache.fineract.infrastructure.core.jpa;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Supplier;
+import javax.persistence.EntityManager;
+import javax.persistence.TypedQuery;
 import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.Order;
+import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.jpa.domain.Specification;
+import org.springframework.data.support.PageableExecutionUtils;
 import org.springframework.stereotype.Component;
 
 @Component
+@RequiredArgsConstructor
 public class CriteriaQueryFactory {
 
-    public List<Order> fromPageable(Pageable pageable, CriteriaBuilder cb, Root<?> root) {
-        return fromPageable(pageable, cb, root, () -> null);
+    private final EntityManager entityManager;
+
+    public List<Order> ordersFromPageable(Pageable pageable, CriteriaBuilder cb, Root<?> root) {
+        return ordersFromPageable(pageable, cb, root, () -> null);
     }
 
-    public List<Order> fromPageable(Pageable pageable, CriteriaBuilder cb, Root<?> root, Supplier<Order> defaultOrderSupplier) {
+    public List<Order> ordersFromPageable(Pageable pageable, CriteriaBuilder cb, Root<?> root, Supplier<Order> defaultOrderSupplier) {
         List<Order> orders = new ArrayList<>();
         Sort sort = pageable.getSort();
         if (sort.isSorted()) {
@@ -54,4 +66,56 @@ public class CriteriaQueryFactory {
         }
         return orders;
     }
+
+    public <S, U> Page<S> readPage(TypedQuery<S> query, Class<U> domainClass, Pageable pageable, Specification<U> spec) {
+
+        if (pageable.isPaged()) {
+            query.setFirstResult((int) pageable.getOffset());
+            query.setMaxResults(pageable.getPageSize());
+        }
+
+        return PageableExecutionUtils.getPage(query.getResultList(), pageable, () -> executeCountQuery(getCountQuery(spec, domainClass)));
+    }
+
+    private static long executeCountQuery(TypedQuery<Long> query) {
+        List<Long> totals = query.getResultList();
+        long total = 0L;
+
+        for (Long element : totals) {
+            total += element == null ? 0 : element;
+        }
+        return total;
+    }
+
+    private <S> TypedQuery<Long> getCountQuery(Specification<S> spec, Class<S> domainClass) {
+        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
+        CriteriaQuery<Long> query = builder.createQuery(Long.class);
+
+        Root<S> root = query.from(domainClass);
+
+        applySpecificationToCriteria(root, spec, query);
+
+        if (query.isDistinct()) {
+            query.select(builder.countDistinct(root));
+        } else {
+            query.select(builder.count(root));
+        }
+
+        // Remove all Orders the Specifications might have applied
+        query.orderBy(Collections.emptyList());
+
+        return entityManager.createQuery(query);
+    }
+
+    public <S, U> Root<U> applySpecificationToCriteria(Root<U> root, Specification<U> spec, CriteriaQuery<S> query) {
+
+        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
+        Predicate predicate = spec.toPredicate(root, query, builder);
+
+        if (predicate != null) {
+            query.where(predicate);
+        }
+
+        return root;
+    }
 }