DATAJDBC-490 - Support condition grouping.

We now support condition groups (WHERE (a = b OR b = c) AND (e = f)) with the SQL AST via Condition.group().

Original pull request: #193.

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/Condition.java

@@ -48,9 +48,19 @@ public interface Condition extends Segment {
 	/**
 	 * Creates a {@link Condition} that negates this {@link Condition}.
 	 *
-	 * @return the negated  {@link Condition}.
+	 * @return the negated {@link Condition}.
 	 */
 	default Condition not() {
 		return new Not(this);
 	}
+
+	/**
+	 * Wraps a {@link Condition} into a condition group that groups the nested {@link Condition} using parentheses.
+	 *
+	 * @return the grouped {@link Condition}.
+	 * @since 2.0
+	 */
+	default Condition group() {
+		return new ConditionGroup(this);
+	}
 }

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/ConditionGroup.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.sql;
+
+/**
+ * Condition group wrapping a nested {@link Condition} with parentheses.
+ *
+ * @author Mark Paluch
+ * @since 2.0
+ */
+public class ConditionGroup extends MultipleCondition implements Condition {
+
+	ConditionGroup(Condition condition) {
+		super("", condition);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
+	@Override
+	public String toString() {
+		return "(" + super.toString() + ")";
+	}
+}

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ConditionGroupVisitor.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2019-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.sql.render;
+
+import org.springframework.data.relational.core.sql.Condition;
+import org.springframework.data.relational.core.sql.ConditionGroup;
+import org.springframework.data.relational.core.sql.Visitable;
+import org.springframework.lang.Nullable;
+
+/**
+ * Renderer for {@link ConditionGroup}. Uses a {@link RenderTarget} to call back for render results.
+ *
+ * @author Mark Paluch
+ * @since 2.0
+ */
+class ConditionGroupVisitor extends TypedSubtreeVisitor<ConditionGroup> {
+
+	private final RenderContext context;
+	private final RenderTarget target;
+
+	private @Nullable ConditionVisitor conditionVisitor;
+
+	ConditionGroupVisitor(RenderContext context, RenderTarget target) {
+		this.context = context;
+		this.target = target;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#enterNested(org.springframework.data.relational.core.sql.Visitable)
+	 */
+	@Override
+	Delegation enterNested(Visitable segment) {
+
+		DelegatingVisitor visitor = getDelegation(segment);
+
+		return visitor != null ? Delegation.delegateTo(visitor) : Delegation.retain();
+	}
+
+	@Nullable
+	private DelegatingVisitor getDelegation(Visitable segment) {
+
+		if (segment instanceof Condition) {
+			return conditionVisitor = new ConditionVisitor(context);
+		}
+
+		return null;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#leaveNested(org.springframework.data.relational.core.sql.Visitable)
+	 */
+	@Override
+	Delegation leaveNested(Visitable segment) {
+
+		if (conditionVisitor != null) {
+			target.onRendered("(" + conditionVisitor.getRenderedPart() + ")");
+			conditionVisitor = null;
+		}
+
+		return super.leaveNested(segment);
+	}
+}

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ConditionVisitor.java

@@ -18,6 +18,7 @@ package org.springframework.data.relational.core.sql.render;
 import org.springframework.data.relational.core.sql.AndCondition;
 import org.springframework.data.relational.core.sql.Comparison;
 import org.springframework.data.relational.core.sql.Condition;
+import org.springframework.data.relational.core.sql.ConditionGroup;
 import org.springframework.data.relational.core.sql.In;
 import org.springframework.data.relational.core.sql.IsNull;
 import org.springframework.data.relational.core.sql.Like;
@@ -41,7 +42,7 @@ import org.springframework.lang.Nullable;
 class ConditionVisitor extends TypedSubtreeVisitor<Condition> implements PartRenderer {
 
 	private final RenderContext context;
-	private StringBuilder builder = new StringBuilder();
+	private final StringBuilder builder = new StringBuilder();
 
 	ConditionVisitor(RenderContext context) {
 		this.context = context;
@@ -86,6 +87,10 @@ class ConditionVisitor extends TypedSubtreeVisitor<Condition> implements PartRen
 			return new InVisitor(context, builder::append);
 		}
 
+		if (segment instanceof ConditionGroup) {
+			return new ConditionGroupVisitor(context, builder::append);
+		}
+
 		return null;
 	}
 

spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/ConditionRendererUnitTests.java

@@ -37,12 +37,39 @@ public class ConditionRendererUnitTests {
 	@Test // DATAJDBC-309
 	public void shouldRenderEquals() {
 
-		String sql = SqlRenderer
-				.toString(StatementBuilder.select(left).from(table).where(left.isEqualTo(right)).build());
+		String sql = SqlRenderer.toString(StatementBuilder.select(left).from(table).where(left.isEqualTo(right)).build());
 
 		assertThat(sql).endsWith("WHERE my_table.left = my_table.right");
 	}
 
+	@Test // DATAJDBC-490
+	public void shouldRenderEqualsGroup() {
+
+		String sql = SqlRenderer
+				.toString(StatementBuilder.select(left).from(table).where(left.isEqualTo(right).group()).build());
+
+		assertThat(sql).endsWith("WHERE (my_table.left = my_table.right)");
+	}
+
+	@Test // DATAJDBC-490
+	public void shouldRenderAndGroup() {
+
+		String sql = SqlRenderer.toString(StatementBuilder.select(left).from(table)
+				.where(left.isEqualTo(right).and(left.isGreater(right)).group()).build());
+
+		assertThat(sql).endsWith("WHERE (my_table.left = my_table.right AND my_table.left > my_table.right)");
+	}
+
+	@Test // DATAJDBC-490
+	public void shouldRenderAndGroupOr() {
+
+		String sql = SqlRenderer.toString(StatementBuilder.select(left).from(table)
+				.where(left.isEqualTo(right).and(left.isGreater(right)).group().or(left.like(right))).build());
+
+		assertThat(sql).endsWith(
+				"WHERE (my_table.left = my_table.right AND my_table.left > my_table.right) OR my_table.left LIKE my_table.right");
+	}
+
 	@Test // DATAJDBC-309
 	public void shouldRenderNotEquals() {
 
@@ -76,8 +103,7 @@ public class ConditionRendererUnitTests {
 	@Test // DATAJDBC-309
 	public void shouldRenderIsGreater() {
 
-		String sql = SqlRenderer
-				.toString(StatementBuilder.select(left).from(table).where(left.isGreater(right)).build());
+		String sql = SqlRenderer.toString(StatementBuilder.select(left).from(table).where(left.isGreater(right)).build());
 
 		assertThat(sql).endsWith("WHERE my_table.left > my_table.right");
 	}