diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/CaseExpression.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/CaseExpression.java
new file mode 100644
index 00000000..81c42322
--- /dev/null
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/CaseExpression.java
@@ -0,0 +1,94 @@
+package org.springframework.data.relational.core.sql;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static java.util.stream.Collectors.joining;
+
+/**
+ * Case with one or more conditions expression.
+ *
+ * Results in a rendered condition:
+ *
+ * CASE
+ * WHEN condition1 THEN result1
+ * WHEN condition2 THEN result2
+ * ELSE result
+ * END
+ *
+ *
+ *
+ * @author Sven Rienstra
+ * @since 3.4
+ */
+public class CaseExpression extends AbstractSegment implements Expression {
+ private final List whenList;
+ private final Expression elseExpression;
+
+ private CaseExpression(List 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 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 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 whenList, Expression elseExpression) {
+
+ List segments = new ArrayList<>();
+ segments.addAll(whenList);
+
+ if (elseExpression != null) {
+ segments.add(elseExpression);
+ }
+
+ return segments.toArray(new Segment[segments.size()]);
+ }
+}
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/When.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/When.java
new file mode 100644
index 00000000..e90338a9
--- /dev/null
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/When.java
@@ -0,0 +1,53 @@
+package org.springframework.data.relational.core.sql;
+
+/**
+ * When segment for Case statement.
+ *
+ * Results in a rendered condition: {@code WHEN THEN }.
+ *
+ *
+ * @author Sven Rienstra
+ * @since 3.4
+ */
+public class When extends AbstractSegment {
+ private final Condition condition;
+ private final Expression value;
+
+ private When(Condition condition, Expression value) {
+
+ super(condition, value);
+
+ this.condition = condition;
+ this.value = value;
+ }
+
+ /**
+ * Creates a new {@link When} given two {@link Expression} condition and {@link Literal} value.
+ *
+ * @param condition the condition {@link Expression}.
+ * @param value the {@link Literal} value.
+ * @return the {@link When}.
+ */
+ public static When when(Condition condition, Expression value) {
+ return new When(condition, value);
+ }
+
+ /**
+ * @return the condition
+ */
+ public Condition getCondition() {
+ return condition;
+ }
+
+ /**
+ * @return the value
+ */
+ public Expression getValue() {
+ return value;
+ }
+
+ @Override
+ public String toString() {
+ return "WHEN " + condition + " THEN " + value;
+ }
+}
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/CaseExpressionVisitor.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/CaseExpressionVisitor.java
new file mode 100644
index 00000000..8e66ccb7
--- /dev/null
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/CaseExpressionVisitor.java
@@ -0,0 +1,59 @@
+package org.springframework.data.relational.core.sql.render;
+
+import org.springframework.data.relational.core.sql.CaseExpression;
+import org.springframework.data.relational.core.sql.Literal;
+import org.springframework.data.relational.core.sql.Visitable;
+import org.springframework.data.relational.core.sql.When;
+
+/**
+ * Renderer for {@link CaseExpression}.
+ *
+ * @author Sven Rienstra
+ * @since 3.4
+ */
+public class CaseExpressionVisitor extends TypedSingleConditionRenderSupport implements PartRenderer {
+ private final StringBuilder part = new StringBuilder();
+
+ CaseExpressionVisitor(RenderContext context) {
+ super(context);
+ }
+
+ @Override
+ Delegation leaveNested(Visitable segment) {
+
+ if (hasDelegatedRendering()) {
+ CharSequence renderedPart = consumeRenderedPart();
+
+ if (segment instanceof When) {
+ part.append(" ");
+ part.append(renderedPart);
+ } else if (segment instanceof Literal) {
+ part.append(" ELSE ");
+ part.append(renderedPart);
+ }
+ }
+
+ return super.leaveNested(segment);
+ }
+
+ @Override
+ Delegation enterMatched(CaseExpression segment) {
+
+ part.append("CASE");
+
+ return super.enterMatched(segment);
+ }
+
+ @Override
+ Delegation leaveMatched(CaseExpression segment) {
+
+ part.append(" END");
+
+ return super.leaveMatched(segment);
+ }
+
+ @Override
+ public CharSequence getRenderedPart() {
+ return part;
+ }
+}
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ExpressionVisitor.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ExpressionVisitor.java
index 67e648fb..c3bdcebc 100644
--- a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ExpressionVisitor.java
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ExpressionVisitor.java
@@ -108,6 +108,10 @@ class ExpressionVisitor extends TypedSubtreeVisitor implements PartR
CastVisitor visitor = new CastVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
+ } else if (segment instanceof CaseExpression) {
+ CaseExpressionVisitor visitor = new CaseExpressionVisitor(context);
+ partRenderer = visitor;
+ return Delegation.delegateTo(visitor);
} else {
// works for literals and just and possibly more
value = segment.toString();
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitor.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitor.java
index 81a850bb..b536b899 100644
--- a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitor.java
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitor.java
@@ -15,7 +15,9 @@
*/
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.Expressions;
import org.springframework.data.relational.core.sql.OrderByField;
import org.springframework.data.relational.core.sql.SimpleFunction;
@@ -83,7 +85,7 @@ class OrderByClauseVisitor extends TypedSubtreeVisitor implements
return Delegation.delegateTo((SimpleFunctionVisitor)delegate);
}
- if (segment instanceof Expressions.SimpleExpression) {
+ if (segment instanceof Expressions.SimpleExpression || segment instanceof CaseExpression) {
delegate = new ExpressionVisitor(context);
return Delegation.delegateTo((ExpressionVisitor)delegate);
}
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/TypedSingleConditionRenderSupport.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/TypedSingleConditionRenderSupport.java
index 932ecef1..04b87f08 100644
--- a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/TypedSingleConditionRenderSupport.java
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/TypedSingleConditionRenderSupport.java
@@ -18,6 +18,7 @@ package org.springframework.data.relational.core.sql.render;
import org.springframework.data.relational.core.sql.Condition;
import org.springframework.data.relational.core.sql.Expression;
import org.springframework.data.relational.core.sql.Visitable;
+import org.springframework.data.relational.core.sql.When;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
@@ -26,6 +27,7 @@ import org.springframework.util.Assert;
* delegate nested {@link Expression} and {@link Condition} rendering.
*
* @author Mark Paluch
+ * @author Sven Rienstra
* @since 1.1
*/
abstract class TypedSingleConditionRenderSupport extends TypedSubtreeVisitor {
@@ -40,8 +42,8 @@ abstract class TypedSingleConditionRenderSupport extends Ty
@Override
Delegation enterNested(Visitable segment) {
- if (segment instanceof Expression) {
- ExpressionVisitor visitor = new ExpressionVisitor(context);
+ if (segment instanceof When) {
+ WhenVisitor visitor = new WhenVisitor(context);
current = visitor;
return Delegation.delegateTo(visitor);
}
@@ -52,6 +54,12 @@ abstract class TypedSingleConditionRenderSupport extends Ty
return Delegation.delegateTo(visitor);
}
+ if (segment instanceof Expression) {
+ ExpressionVisitor visitor = new ExpressionVisitor(context);
+ current = visitor;
+ return Delegation.delegateTo(visitor);
+ }
+
throw new IllegalStateException("Cannot provide visitor for " + segment);
}
diff --git a/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/WhenVisitor.java b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/WhenVisitor.java
new file mode 100644
index 00000000..70e8c1da
--- /dev/null
+++ b/spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/WhenVisitor.java
@@ -0,0 +1,48 @@
+package org.springframework.data.relational.core.sql.render;
+
+import org.springframework.data.relational.core.sql.Visitable;
+import org.springframework.data.relational.core.sql.When;
+
+/**
+ * Renderer for {@link When} segments.
+ *
+ * @author Sven Rienstra
+ * @since 3.4
+ */
+public class WhenVisitor extends TypedSingleConditionRenderSupport implements PartRenderer {
+ private final StringBuilder part = new StringBuilder();
+ private boolean conditionRendered;
+
+ WhenVisitor(RenderContext context) {
+ super(context);
+ }
+
+ @Override
+ Delegation leaveNested(Visitable segment) {
+
+ if (hasDelegatedRendering()) {
+
+ if (conditionRendered) {
+ part.append(" THEN ");
+ }
+
+ part.append(consumeRenderedPart());
+ conditionRendered = true;
+ }
+
+ return super.leaveNested(segment);
+ }
+
+ @Override
+ Delegation enterMatched(When segment) {
+
+ part.append("WHEN ");
+
+ return super.enterMatched(segment);
+ }
+
+ @Override
+ public CharSequence getRenderedPart() {
+ return part;
+ }
+}
diff --git a/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitorUnitTests.java b/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitorUnitTests.java
index e04fea49..baadc8b0 100644
--- a/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitorUnitTests.java
+++ b/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/OrderByClauseVisitorUnitTests.java
@@ -18,14 +18,7 @@ package org.springframework.data.relational.core.sql.render;
import static org.assertj.core.api.Assertions.*;
import org.junit.jupiter.api.Test;
-import org.springframework.data.relational.core.sql.Column;
-import org.springframework.data.relational.core.sql.Expression;
-import org.springframework.data.relational.core.sql.Expressions;
-import org.springframework.data.relational.core.sql.OrderByField;
-import org.springframework.data.relational.core.sql.SQL;
-import org.springframework.data.relational.core.sql.Select;
-import org.springframework.data.relational.core.sql.SimpleFunction;
-import org.springframework.data.relational.core.sql.Table;
+import org.springframework.data.relational.core.sql.*;
import java.util.Arrays;
import java.util.List;
@@ -129,4 +122,18 @@ class OrderByClauseVisitorUnitTests {
assertThat(visitor.getRenderedPart().toString()).isEqualTo("1 ASC");
}
+
+ @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));
+ 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");
+ }
}
diff --git a/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/SelectRendererUnitTests.java b/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/SelectRendererUnitTests.java
index 68842f50..1251aefd 100644
--- a/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/SelectRendererUnitTests.java
+++ b/spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/SelectRendererUnitTests.java
@@ -688,6 +688,23 @@ class SelectRendererUnitTests {
assertThat(rendered).isEqualTo("SELECT e.*, e.id FROM employee e");
}
+ @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))) //
+ .elseExpression(SQL.literalOf(3));
+
+ Select select = StatementBuilder.select(caseExpression) //
+ .from(table) //
+ .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");
+ }
+
/**
* Tests the rendering of analytic functions.
*/