Handle ConstantCondition in ConditionVisitor.

Original pull request #978
Closes #907

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

@@ -27,6 +27,7 @@ import org.springframework.util.Assert;
  * @author Mark Paluch
  * @author Jens Schauder
  * @author Meng Zuozhu
+ * @author Daniele Canteri
  * @since 1.1
  * @see SQL
  * @see Expressions
@@ -303,20 +304,6 @@ public abstract class Conditions {
 		return notIn(column, new SubselectExpression(subselect));
 	}
 
-	static class ConstantCondition extends AbstractSegment implements Condition {
-
-		private final String condition;
-
-		ConstantCondition(String condition) {
-			this.condition = condition;
-		}
-
-		@Override
-		public String toString() {
-			return condition;
-		}
-	}
-
 	// Utility constructor.
 	private Conditions() {}
 }

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

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2019-2021 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;
+
+/**
+ * {@link Condition} representing fixed sql statement
+ *
+ * @author Daniele Canteri
+ * @since 2.3
+ */
+public class ConstantCondition extends AbstractSegment implements Condition {
+
+    private final String condition;
+
+    ConstantCondition(String condition) {
+        this.condition = condition;
+    }
+
+    @Override
+    public String toString() {
+        return condition;
+    }
+}

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

@@ -19,6 +19,7 @@ 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;
@@ -32,6 +33,7 @@ import org.springframework.lang.Nullable;
  *
  * @author Mark Paluch
  * @author Jens Schauder
+ * @author Daniele Canteri
  * @since 1.1
  * @see AndCondition
  * @see OrCondition
@@ -101,6 +103,10 @@ class ConditionVisitor extends TypedSubtreeVisitor<Condition> implements PartRen
 			return new NestedConditionVisitor(context, builder::append);
 		}
 
+		if (segment instanceof ConstantCondition) {
+			return new ConstantConditionVisitor(context, builder::append);
+		}
+
 		return null;
 	}
 

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

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2019-2021 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.ConstantCondition;
+
+/**
+ * Renderer for {@link ConstantCondition}. Uses a {@link RenderTarget} to call back for render results.
+ *
+ * @author Daniele Canteri
+ * @since 2.3
+ */
+class ConstantConditionVisitor extends TypedSingleConditionRenderSupport<ConstantCondition> {
+
+	private final RenderTarget target;
+
+	ConstantConditionVisitor(RenderContext context, RenderTarget target) {
+		super(context);
+		this.target = target;
+	}
+
+	/**
+	 *
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#leaveMatched(org.springframework.data.relational.core.sql.Visitable)
+	 */
+	@Override
+	Delegation leaveMatched(ConstantCondition segment) {
+
+		target.onRendered(segment.toString());
+
+		return super.leaveMatched(segment);
+	}
+
+}

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

@@ -29,6 +29,7 @@ import org.springframework.data.relational.core.sql.Table;
  * Unit tests for rendered {@link org.springframework.data.relational.core.sql.Conditions}.
  *
  * @author Mark Paluch
+ * @author Daniele Canteri
  */
 public class ConditionRendererUnitTests {
 
@@ -230,4 +231,14 @@ public class ConditionRendererUnitTests {
 
 		assertThat(sql).endsWith("WHERE my_table.left NOT IN (my_table.right)");
 	}
+
+	@Test // DATAJDBC-907
+	public void shouldRenderJust() {
+
+		String sql = SqlRenderer.toString(StatementBuilder.select(left).from(table)
+				.where(Conditions.just("sql"))
+				.build());
+
+		assertThat(sql).endsWith("WHERE sql");
+	}
 }