Polishing.

Minor formatting.
Adding author tag in Javadoc.
Fixing warnings.

Original pull request #1844

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

@@ -1,9 +1,11 @@
 package org.springframework.data.relational.core.sql;
 
+import org.springframework.lang.Nullable;
+
 import java.util.ArrayList;
 import java.util.List;
 
-import static java.util.stream.Collectors.joining;
+import static java.util.stream.Collectors.*;
 
 /**
  * Case with one or more conditions expression.
@@ -22,73 +24,64 @@ import static java.util.stream.Collectors.joining;
  * @since 3.4
  */
 public class CaseExpression extends AbstractSegment implements Expression {
-    private final List<When> whenList;
-    private final Expression elseExpression;
-
-    private CaseExpression(List<When> whenList, Expression elseExpression) {
-
-        super(children(whenList, elseExpression));
-        this.whenList = whenList;
-        this.elseExpression = elseExpression;
-    }
-
-    /**
-     * Create CASE {@link Expression} with initial {@link When} condition.
-     * @param condition initial {@link When} condition
-     * @return the {@link CaseExpression}
-     */
-    public static CaseExpression create(When condition) {
-        return new CaseExpression(List.of(condition), null);
-    }
-
-    /**
-     * Add additional {@link When} condition
-     * @param condition the {@link When} condition
-     * @return the {@link CaseExpression}
-     */
-    public CaseExpression when(When condition) {
-        List<When> conditions = new ArrayList<>(this.whenList);
-        conditions.add(condition);
-        return new CaseExpression(conditions, elseExpression);
-    }
-
-    /**
-     * Add ELSE clause
-     * @param elseExpression the {@link Expression} else value
-     * @return the {@link CaseExpression}
-     */
-    public CaseExpression elseExpression(Literal elseExpression) {
-        return new CaseExpression(whenList, elseExpression);
-    }
-
-    /**
-     * @return the {@link When} conditions
-     */
-    public List<When> getWhenList() {
-        return whenList;
-    }
-
-    /**
-     * @return the ELSE {@link Literal} value
-     */
-    public Expression getElseExpression() {
-        return elseExpression;
-    }
-
-    @Override
-    public String toString() {
-        return "CASE " + whenList.stream().map(When::toString).collect(joining(" ")) + (elseExpression != null ? " ELSE " + elseExpression : "") + " END";
-    }
-
-    private static Segment[] children(List<When> whenList, Expression elseExpression) {
-
-        List<Segment> segments = new ArrayList<>();
-        segments.addAll(whenList);
-
-        if (elseExpression != null) {
-            segments.add(elseExpression);
-        }
-
-        return segments.toArray(new Segment[segments.size()]);
-    }
+
+	private final List<When> whenList;
+	@Nullable
+	private final Expression elseExpression;
+
+	private static Segment[] children(List<When> whenList, @Nullable Expression elseExpression) {
+
+		List<Segment> segments = new ArrayList<>(whenList);
+
+		if (elseExpression != null) {
+			segments.add(elseExpression);
+		}
+
+		return segments.toArray(new Segment[0]);
+	}
+
+	private CaseExpression(List<When> whenList, @Nullable Expression elseExpression) {
+
+		super(children(whenList, elseExpression));
+
+		this.whenList = whenList;
+		this.elseExpression = elseExpression;
+	}
+
+	/**
+	 * Create CASE {@link Expression} with initial {@link When} condition.
+	 *
+	 * @param condition initial {@link When} condition
+	 * @return the {@link CaseExpression}
+	 */
+	public static CaseExpression create(When condition) {
+		return new CaseExpression(List.of(condition), null);
+	}
+
+	/**
+	 * Add additional {@link When} condition
+	 *
+	 * @param condition the {@link When} condition
+	 * @return the {@link CaseExpression}
+	 */
+	public CaseExpression when(When condition) {
+		List<When> conditions = new ArrayList<>(this.whenList);
+		conditions.add(condition);
+		return new CaseExpression(conditions, elseExpression);
+	}
+
+	/**
+	 * Add ELSE clause
+	 *
+	 * @param elseExpression the {@link Expression} else value
+	 * @return the {@link CaseExpression}
+	 */
+	public CaseExpression elseExpression(Expression elseExpression) {
+		return new CaseExpression(whenList, elseExpression);
+	}
+
+	@Override
+	public String toString() {
+		return "CASE " + whenList.stream().map(When::toString).collect(joining(" ")) + (elseExpression != null ? " ELSE " + elseExpression : "") + " END";
+	}
 }

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

@@ -10,6 +10,7 @@ package org.springframework.data.relational.core.sql;
  * @since 3.4
  */
 public class When extends AbstractSegment {
+
     private final Condition condition;
     private final Expression value;
 

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

@@ -24,7 +24,7 @@ import org.springframework.util.Assert;
  *
  * @author Mark Paluch
  * @author Jens Schauder
- * @since 1.1
+ * @author Sven Rienstra
  * @see Column
  * @see SubselectExpression
  */
@@ -48,7 +48,7 @@ class ExpressionVisitor extends TypedSubtreeVisitor<Expression> implements PartR
 	/**
 	 * Creates an {@code ExpressionVisitor}.
 	 *
-	 * @param context must not be {@literal null}.
+	 * @param context       must not be {@literal null}.
 	 * @param aliasHandling controls if columns should be rendered as their alias or using their table names.
 	 * @since 2.3
 	 */
@@ -109,6 +109,7 @@ class ExpressionVisitor extends TypedSubtreeVisitor<Expression> implements PartR
 			partRenderer = visitor;
 			return Delegation.delegateTo(visitor);
 		} else if (segment instanceof CaseExpression) {
+
 			CaseExpressionVisitor visitor = new CaseExpressionVisitor(context);
 			partRenderer = visitor;
 			return Delegation.delegateTo(visitor);
@@ -132,7 +133,7 @@ class ExpressionVisitor extends TypedSubtreeVisitor<Expression> implements PartR
 
 		if (segment instanceof InlineQuery) {
 
-			NoopVisitor<InlineQuery> partRenderer = new NoopVisitor(InlineQuery.class);
+			NoopVisitor<InlineQuery> partRenderer = new NoopVisitor<>(InlineQuery.class);
 			return Delegation.delegateTo(partRenderer);
 		}
 		return super.enterNested(segment);

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

@@ -16,8 +16,8 @@
 package org.springframework.data.relational.core.sql.render;
 
 
-import org.springframework.data.relational.core.sql.Column;
 import org.springframework.data.relational.core.sql.CaseExpression;
+import org.springframework.data.relational.core.sql.Column;
 import org.springframework.data.relational.core.sql.Expressions;
 import org.springframework.data.relational.core.sql.OrderByField;
 import org.springframework.data.relational.core.sql.SimpleFunction;
@@ -31,6 +31,7 @@ import org.springframework.lang.Nullable;
  * @author Jens Schauder
  * @author Chirag Tailor
  * @author Koen Punt
+ * @author Sven Rienstra
  * @since 1.1
  */
 class OrderByClauseVisitor extends TypedSubtreeVisitor<OrderByField> implements PartRenderer {
@@ -39,7 +40,8 @@ class OrderByClauseVisitor extends TypedSubtreeVisitor<OrderByField> implements
 
 	private final StringBuilder builder = new StringBuilder();
 
-	@Nullable private PartRenderer delegate;
+	@Nullable
+	private PartRenderer delegate;
 
 	private boolean first = true;
 
@@ -69,7 +71,7 @@ class OrderByClauseVisitor extends TypedSubtreeVisitor<OrderByField> implements
 
 		String nullPrecedence = context.getSelectRenderContext().evaluateOrderByNullHandling(segment.getNullHandling());
 		if (!nullPrecedence.isEmpty()) {
-			
+
 			builder.append(" ") //
 					.append(nullPrecedence);
 		}
@@ -82,12 +84,12 @@ class OrderByClauseVisitor extends TypedSubtreeVisitor<OrderByField> implements
 
 		if (segment instanceof SimpleFunction) {
 			delegate = new SimpleFunctionVisitor(context);
-			return Delegation.delegateTo((SimpleFunctionVisitor)delegate);
+			return Delegation.delegateTo((SimpleFunctionVisitor) delegate);
 		}
 
 		if (segment instanceof Expressions.SimpleExpression || segment instanceof CaseExpression) {
 			delegate = new ExpressionVisitor(context);
-			return Delegation.delegateTo((ExpressionVisitor)delegate);
+			return Delegation.delegateTo((ExpressionVisitor) delegate);
 		}
 
 		return super.enterNested(segment);

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

@@ -10,6 +10,7 @@ import org.springframework.data.relational.core.sql.When;
  * @since 3.4
  */
 public class WhenVisitor extends TypedSingleConditionRenderSupport<When> implements PartRenderer {
+
     private final StringBuilder part = new StringBuilder();
     private boolean conditionRendered;
 

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

@@ -29,6 +29,7 @@ import java.util.List;
  * @author Mark Paluch
  * @author Jens Schauder
  * @author Koen Punt
+ * @author Sven Rienstra
  */
 class OrderByClauseVisitorUnitTests {
 
@@ -125,15 +126,16 @@ class OrderByClauseVisitorUnitTests {
 
 	@Test
 	void shouldRenderOrderByCase() {
+
 		Table employee = SQL.table("employee").as("emp");
 		Column column = employee.column("name");
 
-		CaseExpression caseExpression = CaseExpression.create(When.when(column.isNull(), SQL.literalOf(1))).elseExpression(SQL.literalOf(2));
+		CaseExpression caseExpression = CaseExpression.create(When.when(column.isNull(), SQL.literalOf(1))).elseExpression(SQL.literalOf(column));
 		Select select = Select.builder().select(column).from(employee).orderBy(OrderByField.from(caseExpression).asc()).build();
 
 		OrderByClauseVisitor visitor = new OrderByClauseVisitor(new SimpleRenderContext(NamingStrategies.asIs()));
 		select.visit(visitor);
 
-		assertThat(visitor.getRenderedPart().toString()).isEqualTo("CASE WHEN emp.name IS NULL THEN 1 ELSE 2 END ASC");
+		assertThat(visitor.getRenderedPart().toString()).isEqualTo("CASE WHEN emp.name IS NULL THEN 1 ELSE emp.name END ASC");
 	}
 }

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

@@ -31,6 +31,7 @@ import java.util.List;
  *
  * @author Mark Paluch
  * @author Jens Schauder
+ * @author Sven Rienstra
  */
 class SelectRendererUnitTests {
 
@@ -690,11 +691,12 @@ class SelectRendererUnitTests {
 
 	@Test
 	void rendersCaseExpression() {
+
 		Table table = SQL.table("table");
 		Column column = table.column("name");
 
 		CaseExpression caseExpression = CaseExpression.create(When.when(column.isNull(), SQL.literalOf(1))) //
-				.when(When.when(column.isNotNull(), SQL.literalOf(2))) //
+				.when(When.when(column.isNotNull(), column)) //
 				.elseExpression(SQL.literalOf(3));
 
 		Select select = StatementBuilder.select(caseExpression) //
@@ -702,7 +704,7 @@ class SelectRendererUnitTests {
 				.build();
 
 		String rendered = SqlRenderer.toString(select);
-		assertThat(rendered).isEqualTo("SELECT CASE WHEN table.name IS NULL THEN 1 WHEN table.name IS NOT NULL THEN 2 ELSE 3 END FROM table");
+		assertThat(rendered).isEqualTo("SELECT CASE WHEN table.name IS NULL THEN 1 WHEN table.name IS NOT NULL THEN table.name ELSE 3 END FROM table");
 	}
 
 	/**