Specialized visitors should be abstract classes

Author: jeffgbutler

src/main/java/org/mybatis/dynamic/sql/insert/render/GeneralInsertValuePhraseVisitor.java

@@ -26,7 +26,7 @@
 import org.mybatis.dynamic.sql.util.StringConstantMapping;
 import org.mybatis.dynamic.sql.util.ValueMapping;
 
-public class GeneralInsertValuePhraseVisitor implements GeneralInsertMappingVisitor<FieldAndValueAndParameters> {
+public class GeneralInsertValuePhraseVisitor extends GeneralInsertMappingVisitor<FieldAndValueAndParameters> {
 
     protected RenderingStrategy renderingStrategy;
     private AtomicInteger sequence = new AtomicInteger(1);

src/main/java/org/mybatis/dynamic/sql/insert/render/ValuePhraseVisitor.java

@@ -25,7 +25,7 @@
 import org.mybatis.dynamic.sql.util.PropertyMapping;
 import org.mybatis.dynamic.sql.util.StringConstantMapping;
 
-public class ValuePhraseVisitor implements InsertMappingVisitor<FieldAndValue> {
+public class ValuePhraseVisitor extends InsertMappingVisitor<FieldAndValue> {
 
     protected RenderingStrategy renderingStrategy;
 

src/main/java/org/mybatis/dynamic/sql/update/render/SetPhraseVisitor.java

@@ -33,7 +33,7 @@
 import org.mybatis.dynamic.sql.util.UpdateMappingVisitor;
 import org.mybatis.dynamic.sql.util.ValueMapping;
 
-public class SetPhraseVisitor implements UpdateMappingVisitor<FragmentAndParameters> {
+public class SetPhraseVisitor extends UpdateMappingVisitor<FragmentAndParameters> {
 
     private AtomicInteger sequence;
     private RenderingStrategy renderingStrategy;

src/main/java/org/mybatis/dynamic/sql/util/GeneralInsertMappingVisitor.java

@@ -15,19 +15,19 @@
  */
 package org.mybatis.dynamic.sql.util;
 
-public interface GeneralInsertMappingVisitor<T> extends ColumnMappingVisitor<T> {
+public abstract class GeneralInsertMappingVisitor<T> implements ColumnMappingVisitor<T> {
     @Override
-    default T visit(SelectMapping mapping) {
+    public final T visit(SelectMapping mapping) {
         throw new UnsupportedOperationException();
     }
 
     @Override
-    default T visit(PropertyMapping mapping) {
+    public final T visit(PropertyMapping mapping) {
         throw new UnsupportedOperationException();
     }
 
     @Override
-    default T visit(ColumnToColumnMapping columnMapping) {
+    public final T visit(ColumnToColumnMapping columnMapping) {
         throw new UnsupportedOperationException();
     }
 }

src/main/java/org/mybatis/dynamic/sql/util/InsertMappingVisitor.java

@@ -15,19 +15,19 @@
  */
 package org.mybatis.dynamic.sql.util;
 
-public interface InsertMappingVisitor<T> extends ColumnMappingVisitor<T> {
+public abstract class InsertMappingVisitor<T> implements ColumnMappingVisitor<T> {
     @Override
-    default <R> T visit(ValueMapping<R> mapping) {
+    public final <R> T visit(ValueMapping<R> mapping) {
         throw new UnsupportedOperationException();
     }
 
     @Override
-    default T visit(SelectMapping mapping) {
+    public final T visit(SelectMapping mapping) {
         throw new UnsupportedOperationException();
     }
 
     @Override
-    default T visit(ColumnToColumnMapping columnMapping) {
+    public final T visit(ColumnToColumnMapping columnMapping) {
         throw new UnsupportedOperationException();
     }
 }

src/main/java/org/mybatis/dynamic/sql/util/UpdateMappingVisitor.java

@@ -15,9 +15,9 @@
  */
 package org.mybatis.dynamic.sql.util;
 
-public interface UpdateMappingVisitor<T> extends ColumnMappingVisitor<T> {
+public abstract class UpdateMappingVisitor<T> implements ColumnMappingVisitor<T> {
     @Override
-    default T visit(PropertyMapping mapping) {
+    public final T visit(PropertyMapping mapping) {
         throw new UnsupportedOperationException();
     }
 }

src/test/java/org/mybatis/dynamic/sql/util/ColumnMappingVisitorTest.java

@@ -99,7 +99,7 @@ public TestTable() {
         }
     }
 
-    private static class GeneralInsertVisitor implements GeneralInsertMappingVisitor<String> {
+    private static class GeneralInsertVisitor extends GeneralInsertMappingVisitor<String> {
         @Override
         public String visit(NullMapping mapping) {
             return "Null Mapping";
@@ -121,7 +121,7 @@ public <R> String visit(ValueMapping<R> mapping) {
         }
     }
 
-    private static class InsertVisitor implements InsertMappingVisitor<String> {
+    private static class InsertVisitor extends InsertMappingVisitor<String> {
         @Override
         public String visit(NullMapping mapping) {
             return "Null Mapping";
@@ -143,7 +143,7 @@ public String visit(PropertyMapping mapping) {
         }
     }
 
-    private static class UpdateVisitor implements UpdateMappingVisitor<String> {
+    private static class UpdateVisitor extends UpdateMappingVisitor<String> {
         @Override
         public String visit(NullMapping mapping) {
             return "Null Mapping";