Polishing.

Remove unecessary toString calls. Make Cast.create public to align with other factory methods. Fix AbstractSegment.toString

See #1066
Original pull request: #1071.

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.relational.core.sql;
 
-import java.util.Arrays;
-
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -70,7 +68,6 @@ abstract class AbstractSegment implements Segment {
 
 	@Override
 	public String toString() {
-		return StringUtils.collectionToDelimitedString(Arrays.asList(children), ", ", getClass().getSimpleName() + "(",
-				")");
+		return getClass().getSimpleName() + "(" + StringUtils.arrayToDelimitedString(children, ", ") + ")";
 	}
 }

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

@@ -57,6 +57,6 @@ class AliasedExpression extends AbstractSegment implements Aliased, Expression {
 	 */
 	@Override
 	public String toString() {
-		return expression.toString() + " AS " + alias;
+		return expression + " AS " + alias;
 	}
 }

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

@@ -18,7 +18,7 @@ package org.springframework.data.relational.core.sql;
 import org.springframework.util.Assert;
 
 /**
- * Represents a CAST expression like {@code CAST(something AS JSON}.
+ * Represents a {@code CAST} expression like {@code CAST(something AS JSON}.
  *
  * @author Jens Schauder
  * @since 2.3
@@ -39,13 +39,13 @@ public class Cast extends AbstractSegment implements Expression {
 	}
 
 	/**
-	 * Creates a new CAST expression.
+	 * Creates a new {@code CAST} expression.
 	 *
 	 * @param expression the expression to cast. Must not be {@literal null}.
 	 * @param targetType the type to cast to. Must not be {@literal null}.
-	 * @return guaranteed to be not {@literal null}.
+	 * @return the {@code CAST} for {@code expression} into {@code targetType}.
 	 */
-	static Expression create(Expression expression, String targetType) {
+	public static Expression create(Expression expression, String targetType) {
 		return new Cast(expression, targetType);
 	}
 

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

@@ -116,6 +116,6 @@ public class Comparison extends AbstractSegment implements Condition {
 
 	@Override
 	public String toString() {
-		return left.toString() + " " + comparator + " " + right.toString();
+		return left + " " + comparator + " " + right;
 	}
 }

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

@@ -55,6 +55,7 @@ public abstract class Expressions {
 
 	/**
 	 * @return a new {@link Cast} expression.
+	 * @since 2.3
 	 */
 	public static Expression cast(Expression expression, String targetType) {
 		return Cast.create(expression, targetType);

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/Not.java

@@ -45,6 +45,6 @@ public class Not extends AbstractSegment implements Condition {
 	 */
 	@Override
 	public String toString() {
-		return "NOT " + condition.toString();
+		return "NOT " + condition;
 	}
 }

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

@@ -38,6 +38,6 @@ public class SubselectExpression extends AbstractSegment implements Expression {
 	 */
 	@Override
 	public String toString() {
-		return "(" + subselect.toString() + ")";
+		return "(" + subselect + ")";
 	}
 }

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 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;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@link AbstractSegment}.
+ *
+ * @author Mark Paluch
+ */
+class AbstractSegmentTests {
+
+	@Test // GH-1066
+	void shouldReportToStringCorrectly() {
+
+		Table table = Table.create("foo");
+		AbstractSegment segment = new AbstractTestSegment(table.column("col1"), table.column("col2"));
+
+		assertThat(segment).hasToString("AbstractTestSegment(foo.col1, foo.col2)");
+	}
+}

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

@@ -20,7 +20,7 @@ package org.springframework.data.relational.core.sql;
  *
  * @author Jens Schauder
  */
-public class AbstractTestSegment extends AbstractSegment{
+public class AbstractTestSegment extends AbstractSegment {
 	protected AbstractTestSegment(Segment... children) {
 		super(children);
 	}