#220 - Refactor StatementMapper.

Use limit/offset instead of Page and accept Expression objects to declare a select list.

Author: mp911de

Diff for: src/main/java/org/springframework/data/r2dbc/core/DefaultStatementMapper.java

@@ -19,7 +19,6 @@
 import java.util.Collection;
 import java.util.List;
 
-import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.r2dbc.dialect.BindMarkers;
@@ -84,9 +83,9 @@ public PreparedOperation<?> getMappedObject(SelectSpec selectSpec) {
 	private PreparedOperation<Select> getMappedObject(SelectSpec selectSpec,
 			@Nullable RelationalPersistentEntity<?> entity) {
 
-		Table table = Table.create(toSql(selectSpec.getTable()));
-		List<Column> columns = table.columns(toSql(selectSpec.getProjectedFields()));
-		SelectBuilder.SelectFromAndJoin selectBuilder = StatementBuilder.select(columns).from(table);
+		Table table = selectSpec.getTable();
+		SelectBuilder.SelectFromAndJoin selectBuilder = StatementBuilder.select(getSelectList(selectSpec, entity))
+				.from(table);
 
 		BindMarkers bindMarkers = this.dialect.getBindMarkersFactory().create();
 		Bindings bindings = Bindings.empty();
@@ -106,17 +105,34 @@ private PreparedOperation<Select> getMappedObject(SelectSpec selectSpec,
 			selectBuilder.orderBy(createOrderByFields(table, mappedSort));
 		}
 
-		if (selectSpec.getPage().isPaged()) {
-
-			Pageable page = selectSpec.getPage();
+		if (selectSpec.getLimit() > 0) {
+			selectBuilder.limit(selectSpec.getLimit());
+		}
 
-			selectBuilder.limitOffset(page.getPageSize(), page.getOffset());
+		if (selectSpec.getOffset() > 0) {
+			selectBuilder.offset(selectSpec.getOffset());
 		}
 
 		Select select = selectBuilder.build();
 		return new DefaultPreparedOperation<>(select, this.renderContext, bindings);
 	}
 
+	protected List<Expression> getSelectList(SelectSpec selectSpec, @Nullable RelationalPersistentEntity<?> entity) {
+
+		if (entity == null) {
+			return selectSpec.getSelectList();
+		}
+
+		List<Expression> selectList = selectSpec.getSelectList();
+		List<Expression> mapped = new ArrayList<>(selectList.size());
+
+		for (Expression expression : selectList) {
+			mapped.add(updateMapper.getMappedObject(expression, entity));
+		}
+
+		return mapped;
+	}
+
 	private Collection<? extends OrderByField> createOrderByFields(Table table, Sort sortToUse) {
 
 		List<OrderByField> fields = new ArrayList<>();

Diff for: src/main/java/org/springframework/data/r2dbc/core/StatementMapper.java

@@ -22,6 +22,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.BiFunction;
 import java.util.stream.Collectors;
 
 import org.springframework.data.domain.Pageable;
@@ -30,6 +31,9 @@
 import org.springframework.data.r2dbc.mapping.SettableValue;
 import org.springframework.data.r2dbc.query.Criteria;
 import org.springframework.data.r2dbc.query.Update;
+import org.springframework.data.relational.core.sql.Column;
+import org.springframework.data.relational.core.sql.Expression;
+import org.springframework.data.relational.core.sql.Table;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.lang.Nullable;
 
@@ -179,19 +183,23 @@ default DeleteSpec createDelete(SqlIdentifier table) {
 	 */
 	class SelectSpec {
 
-		private final SqlIdentifier table;
-		private final List<SqlIdentifier> projectedFields;
+		private final Table table;
+		private final List<String> projectedFields;
+		private final List<Expression> selectList;
 		private final @Nullable Criteria criteria;
 		private final Sort sort;
-		private final Pageable page;
+		private final long offset;
+		private final int limit;
 
-		protected SelectSpec(SqlIdentifier table, List<SqlIdentifier> projectedFields, @Nullable Criteria criteria,
-				Sort sort, Pageable page) {
+		protected SelectSpec(Table table, List<String> projectedFields, List<Expression> selectList,
+				@Nullable Criteria criteria, Sort sort, int limit, long offset) {
 			this.table = table;
 			this.projectedFields = projectedFields;
+			this.selectList = selectList;
 			this.criteria = criteria;
 			this.sort = sort;
-			this.page = page;
+			this.offset = offset;
+			this.limit = limit;
 		}
 
 		/**
@@ -212,7 +220,23 @@ public static SelectSpec create(String table) {
 		 * @since 1.1
 		 */
 		public static SelectSpec create(SqlIdentifier table) {
-			return new SelectSpec(table, Collections.emptyList(), null, Sort.unsorted(), Pageable.unpaged());
+			return new SelectSpec(Table.create(table), Collections.emptyList(), Collections.emptyList(), null,
+					Sort.unsorted(), -1, -1);
+		}
+
+		public SelectSpec doWithTable(BiFunction<Table, SelectSpec, SelectSpec> function) {
+			return function.apply(getTable(), this);
+		}
+
+		/**
+		 * Associate {@code projectedFields} with the select and create a new {@link SelectSpec}.
+		 *
+		 * @param projectedFields
+		 * @return the {@link SelectSpec}.
+		 * @since 1.1
+		 */
+		public SelectSpec withProjection(String... projectedFields) {
+			return withProjection(Arrays.asList(projectedFields));
 		}
 
 		/**
@@ -237,7 +261,25 @@ public SelectSpec withProjection(Collection<SqlIdentifier> projectedFields) {
 			List<SqlIdentifier> fields = new ArrayList<>(this.projectedFields);
 			fields.addAll(projectedFields);
 
-			return new SelectSpec(this.table, fields, this.criteria, this.sort, this.page);
+			List<Expression> selectList = new ArrayList<>(this.selectList);
+			projectedFields.stream().map(s -> Column.create(s, table)).forEach(selectList::add);
+
+			return new SelectSpec(this.table, fields, selectList, this.criteria, this.sort, this.limit, this.offset);
+		}
+
+		/**
+		 * Associate {@code expressions} with the select list and create a new {@link SelectSpec}.
+		 *
+		 * @param expressions
+		 * @return the {@link SelectSpec}.
+		 * @since 1.1
+		 */
+		public SelectSpec withProjection(Expression... expressions) {
+
+			List<Expression> selectList = new ArrayList<>(this.selectList);
+			selectList.addAll(Arrays.asList(expressions));
+
+			return new SelectSpec(this.table, projectedFields, selectList, this.criteria, this.sort, this.limit, this.offset);
 		}
 
 		/**
@@ -247,7 +289,8 @@ public SelectSpec withProjection(Collection<SqlIdentifier> projectedFields) {
 		 * @return the {@link SelectSpec}.
 		 */
 		public SelectSpec withCriteria(Criteria criteria) {
-			return new SelectSpec(this.table, this.projectedFields, criteria, this.sort, this.page);
+			return new SelectSpec(this.table, this.projectedFields, this.selectList, criteria, this.sort, this.limit,
+					this.offset);
 		}
 
 		/**
@@ -259,10 +302,12 @@ public SelectSpec withCriteria(Criteria criteria) {
 		public SelectSpec withSort(Sort sort) {
 
 			if (sort.isSorted()) {
-				return new SelectSpec(this.table, this.projectedFields, this.criteria, sort, this.page);
+				return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, sort, this.limit,
+						this.offset);
 			}
 
-			return new SelectSpec(this.table, this.projectedFields, this.criteria, this.sort, this.page);
+			return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, this.sort, this.limit,
+					this.offset);
 		}
 
 		/**
@@ -277,21 +322,48 @@ public SelectSpec withPage(Pageable page) {
 
 				Sort sort = page.getSort();
 
-				return new SelectSpec(this.table, this.projectedFields, this.criteria, sort.isSorted() ? sort : this.sort,
-						page);
+				return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria,
+						sort.isSorted() ? sort : this.sort, page.getPageSize(), page.getOffset());
 			}
 
-			return new SelectSpec(this.table, this.projectedFields, this.criteria, this.sort, page);
+			return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, this.sort, this.limit,
+					this.offset);
 		}
 
-		public SqlIdentifier getTable() {
+		/**
+		 * Associate a result offset with the select and create a new {@link SelectSpec}.
+		 *
+		 * @param page
+		 * @return the {@link SelectSpec}.
+		 */
+		public SelectSpec offset(long offset) {
+			return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, this.sort, this.limit,
+					offset);
+		}
+
+		/**
+		 * Associate a result limit with the select and create a new {@link SelectSpec}.
+		 *
+		 * @param page
+		 * @return the {@link SelectSpec}.
+		 */
+		public SelectSpec limit(int limit) {
+			return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, this.sort, limit,
+					this.offset);
+		}
+
+		public Table getTable() {
 			return this.table;
 		}
 
 		public List<SqlIdentifier> getProjectedFields() {
 			return Collections.unmodifiableList(this.projectedFields);
 		}
 
+		public List<Expression> getSelectList() {
+			return Collections.unmodifiableList(selectList);
+		}
+
 		@Nullable
 		public Criteria getCriteria() {
 			return this.criteria;
@@ -301,8 +373,12 @@ public Sort getSort() {
 			return this.sort;
 		}
 
-		public Pageable getPage() {
-			return this.page;
+		public long getOffset() {
+			return this.offset;
+		}
+
+		public int getLimit() {
+			return this.limit;
 		}
 	}