Properly render NOT.

Closes #1653

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

@@ -15,16 +15,7 @@
  */
 package org.springframework.data.relational.core.sql.render;
 
-import org.springframework.data.relational.core.sql.AndCondition;
-import org.springframework.data.relational.core.sql.Between;
-import org.springframework.data.relational.core.sql.Comparison;
-import org.springframework.data.relational.core.sql.Condition;
-import org.springframework.data.relational.core.sql.ConstantCondition;
-import org.springframework.data.relational.core.sql.In;
-import org.springframework.data.relational.core.sql.IsNull;
-import org.springframework.data.relational.core.sql.Like;
-import org.springframework.data.relational.core.sql.NestedCondition;
-import org.springframework.data.relational.core.sql.OrCondition;
+import org.springframework.data.relational.core.sql.*;
 import org.springframework.lang.Nullable;
 
 /**
@@ -103,6 +94,10 @@ private DelegatingVisitor getDelegation(Condition segment) {
 			return new ConstantConditionVisitor(context, builder::append);
 		}
 
+		if (segment instanceof Not) {
+			return new NotConditionVisitor(context, builder::append);
+		}
+
 		return null;
 	}
 

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

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2019-2023 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.NestedCondition;
+import org.springframework.data.relational.core.sql.Visitable;
+import org.springframework.lang.Nullable;
+
+/**
+ * Renderer for {@link NestedCondition}. Uses a {@link RenderTarget} to call back for render results.
+ *
+ * @author Jens Schauder
+ * @since 3.2
+ */
+class NotConditionVisitor extends TypedSubtreeVisitor<NestedCondition> {
+
+	private final RenderContext context;
+	private final RenderTarget target;
+
+	private @Nullable ConditionVisitor conditionVisitor;
+
+	NotConditionVisitor(RenderContext context, RenderTarget target) {
+
+		this.context = context;
+		this.target = target;
+	}
+
+	@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;
+	}
+
+	@Override
+	Delegation leaveNested(Visitable segment) {
+
+		if (conditionVisitor != null) {
+
+			target.onRendered("NOT (" + conditionVisitor.getRenderedPart() + ")");
+			conditionVisitor = null;
+		}
+
+		return super.leaveNested(segment);
+	}
+}