Implement filter for no value conditions

Author: jeffgbutler

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

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2016-2020 the original author or authors.
+ *    Copyright 2016-2021 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.
@@ -15,26 +15,8 @@
  */
 package org.mybatis.dynamic.sql;
 
-import java.util.Objects;
-import java.util.function.BooleanSupplier;
-
 public abstract class AbstractNoValueCondition<T> implements VisitableCondition<T> {
 
-    private final BooleanSupplier booleanSupplier;
-
-    protected AbstractNoValueCondition() {
-        booleanSupplier = () -> true;
-    }
-
-    protected AbstractNoValueCondition(BooleanSupplier booleanSupplier) {
-        this.booleanSupplier = Objects.requireNonNull(booleanSupplier);
-    }
-
-    @Override
-    public boolean shouldRender() {
-        return booleanSupplier.getAsBoolean();
-    }
-
     @Override
     public <R> R accept(ConditionVisitor<T, R> visitor) {
         return visitor.visit(this);

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotNull.java

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2016-2020 the original author or authors.
+ *    Copyright 2016-2021 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.
@@ -25,16 +25,55 @@ public IsNotNull() {
         super();
     }
 
-    protected IsNotNull(BooleanSupplier booleanSupplier) {
-        super(booleanSupplier);
-    }
-
     @Override
     public String renderCondition(String columnName) {
         return columnName + " is not null"; //$NON-NLS-1$
     }
 
+    /**
+     * If the supplier returns true, returns this condition. Else returns a new condition that will not render.
+     *
+     * @deprecated replaced by {@link IsNotNull#filter(BooleanSupplier)}
+     * @param booleanSupplier function that specifies whether the condition should render
+     * @param <S> condition type - not used except for compilation compliance
+     * @return If the condition should render, returns this condition. Else a new condition that will not
+     *     render.
+     */
+    @Deprecated
     public <S> IsNotNull<S> when(BooleanSupplier booleanSupplier) {
-        return new IsNotNull<>(booleanSupplier);
+        return filter(booleanSupplier);
+    }
+
+    /**
+     * If the supplier returns true, returns this condition. Else returns a new condition that will not render.
+     *
+     * @param booleanSupplier function that specifies whether the condition should render
+     * @param <S> condition type - not used except for compilation compliance
+     * @return If the condition should render, returns this condition. Else a new condition that will not
+     *     render.
+     */
+    public <S> IsNotNull<S> filter(BooleanSupplier booleanSupplier) {
+        if (booleanSupplier.getAsBoolean()) {
+            @SuppressWarnings("unchecked")
+            IsNotNull<S> self = (IsNotNull<S>) this;
+            return self;
+        } else {
+            return EmptyIsNotNull.empty();
+        }
+    }
+
+    public static class EmptyIsNotNull<T> extends IsNotNull<T> {
+        private static final IsNotNull<?> EMPTY = new EmptyIsNotNull<>();
+
+        public static <T> EmptyIsNotNull<T> empty() {
+            @SuppressWarnings("unchecked")
+            EmptyIsNotNull<T> t = (EmptyIsNotNull<T>) EMPTY;
+            return t;
+        }
+
+        @Override
+        public boolean shouldRender() {
+            return false;
+        }
     }
 }

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNull.java

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2016-2020 the original author or authors.
+ *    Copyright 2016-2021 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.
@@ -25,16 +25,55 @@ public IsNull() {
         super();
     }
 
-    protected IsNull(BooleanSupplier booleanSupplier) {
-        super(booleanSupplier);
-    }
-
     @Override
     public String renderCondition(String columnName) {
         return columnName + " is null"; //$NON-NLS-1$
     }
 
+    /**
+     * If the supplier returns true, returns this condition. Else returns a new condition that will not render.
+     *
+     * @deprecated replaced by {@link IsNull#filter(BooleanSupplier)}
+     * @param booleanSupplier function that specifies whether the condition should render
+     * @param <S> condition type - not used except for compilation compliance
+     * @return If the condition should render, returns this condition. Else a new condition that will not
+     *     render.
+     */
+    @Deprecated
     public <S> IsNull<S> when(BooleanSupplier booleanSupplier) {
-        return new IsNull<>(booleanSupplier);
+        return filter(booleanSupplier);
+    }
+
+    /**
+     * If the supplier returns true, returns this condition. Else returns a new condition that will not render.
+     *
+     * @param booleanSupplier function that specifies whether the condition should render
+     * @param <S> condition type - not used except for compilation compliance
+     * @return If the condition should render, returns this condition. Else a new condition that will not
+     *     render.
+     */
+    public <S> IsNull<S> filter(BooleanSupplier booleanSupplier) {
+        if (booleanSupplier.getAsBoolean()) {
+            @SuppressWarnings("unchecked")
+            IsNull<S> self = (IsNull<S>) this;
+            return self;
+        } else {
+            return EmptyIsNull.empty();
+        }
+    }
+
+    public static class EmptyIsNull<T> extends IsNull<T> {
+        private static final EmptyIsNull<?> EMPTY = new EmptyIsNull<>();
+
+        public static <T> EmptyIsNull<T> empty() {
+            @SuppressWarnings("unchecked")
+            EmptyIsNull<T> t = (EmptyIsNull<T>) EMPTY;
+            return t;
+        }
+
+        @Override
+        public boolean shouldRender() {
+            return false;
+        }
     }
 }