Better Type Constraints for Map/Filter

Author: jeffgbutler

src/main/java/org/mybatis/dynamic/sql/AbstractListValueCondition.java

@@ -24,8 +24,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-public abstract class AbstractListValueCondition<T>
-        implements VisitableCondition<T> {
+public abstract class AbstractListValueCondition<T> implements VisitableCondition<T> {
     protected final Collection<T> values;
     protected final Callback emptyCallback;
 
@@ -67,22 +66,22 @@ private Collection<T> applyFilter(Predicate<? super T> predicate) {
         return values.stream().filter(predicate).collect(Collectors.toList());
     }
 
-    protected <S> S filterSupport(Predicate<? super T> predicate,
-            BiFunction<Collection<T>, Callback, S> constructor, S self, Supplier<S> empty) {
+    protected <S extends AbstractListValueCondition<T>> S filterSupport(Predicate<? super T> predicate,
+            BiFunction<Collection<T>, Callback, S> constructor, S self, Supplier<S> emptySupplier) {
         if (shouldRender()) {
             Collection<T> filtered = applyFilter(predicate);
-            return filtered.isEmpty() ? empty.get() : constructor.apply(filtered, emptyCallback);
+            return filtered.isEmpty() ? emptySupplier.get() : constructor.apply(filtered, emptyCallback);
         } else {
             return self;
         }
     }
 
-    protected <R, S> S mapSupport(Function<? super T, ? extends R> mapper,
-            BiFunction<Collection<R>, Callback, S> constructor, Supplier<S> empty) {
+    protected <R, S extends AbstractListValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper,
+            BiFunction<Collection<R>, Callback, S> constructor, Supplier<S> emptySupplier) {
         if (shouldRender()) {
             return constructor.apply(applyMapper(mapper), emptyCallback);
         } else {
-            return empty.get();
+            return emptySupplier.get();
         }
     }
 

src/main/java/org/mybatis/dynamic/sql/AbstractNoValueCondition.java

@@ -25,9 +25,10 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
         return visitor.visit(this);
     }
 
-    protected <S> S filterSupport(BooleanSupplier booleanSupplier, Supplier<S> empty, S self) {
+    protected <S extends  AbstractNoValueCondition<?>> S filterSupport(BooleanSupplier booleanSupplier,
+            Supplier<S> emptySupplier, S self) {
         if (shouldRender()) {
-            return booleanSupplier.getAsBoolean() ? self : empty.get();
+            return booleanSupplier.getAsBoolean() ? self : emptySupplier.get();
         } else {
             return self;
         }

src/main/java/org/mybatis/dynamic/sql/AbstractSingleValueCondition.java

@@ -35,20 +35,21 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
         return visitor.visit(this);
     }
 
-    protected <S> S filterSupport(Predicate<? super T> predicate, Supplier<S> empty, S self) {
+    protected <S extends AbstractSingleValueCondition<T>> S filterSupport(Predicate<? super T> predicate,
+            Supplier<S> emptySupplier, S self) {
         if (shouldRender()) {
-            return predicate.test(value) ? self : empty.get();
+            return predicate.test(value) ? self : emptySupplier.get();
         } else {
             return self;
         }
     }
 
-    protected <R, S> S mapSupport(Function<? super T, ? extends R> mapper, Function<R, S> constructor,
-            Supplier<S> empty) {
+    protected <R, S extends AbstractSingleValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper,
+            Function<R, S> constructor, Supplier<S> emptySupplier) {
         if (shouldRender()) {
             return constructor.apply(mapper.apply(value));
         } else {
-            return empty.get();
+            return emptySupplier.get();
         }
     }
 

src/main/java/org/mybatis/dynamic/sql/AbstractTwoValueCondition.java

@@ -43,22 +43,21 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
         return visitor.visit(this);
     }
 
-    protected <S> S filterSupport(BiPredicate<? super T, ? super T> predicate, Supplier<S> empty, S self) {
+    protected <S extends AbstractTwoValueCondition<T>> S filterSupport(BiPredicate<? super T, ? super T> predicate,
+            Supplier<S> emptySupplier, S self) {
         if (shouldRender()) {
-            return predicate.test(value1, value2) ? self : empty.get();
+            return predicate.test(value1, value2) ? self : emptySupplier.get();
         } else {
             return self;
         }
     }
 
-    protected <R, S> S mapSupport(Function<? super T, ? extends R> mapper1,
-                                 Function<? super T, ? extends R> mapper2,
-                                 BiFunction<R, R, S> constructor,
-                                 Supplier<S> empty) {
+    protected <R, S extends AbstractTwoValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper1,
+            Function<? super T, ? extends R> mapper2, BiFunction<R, R, S> constructor, Supplier<S> emptySupplier) {
         if (shouldRender()) {
             return constructor.apply(mapper1.apply(value1), mapper2.apply(value2));
         } else {
-            return empty.get();
+            return emptySupplier.get();
         }
     }