Added support for non null checks

Author: CollinAlpert

README.MD

@@ -45,7 +45,7 @@ Features
 ---------
 
 Current version works with predicates, functions and supports the following operators: >, >=, <, <=, =, !=, &&, ||, !
-
+ 
 Feel free to open an issue with any requests you might have.
 
 Install
@@ -56,7 +56,7 @@ You can include the Maven dependency:
 <dependency>
     <groupId>com.github.collinalpert</groupId>
     <artifactId>lambda2sql</artifactId>
-    <version>1.8.4</version>
+    <version>1.8.5</version>
 </dependency>
 ```
 

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.github.collinalpert</groupId>
     <artifactId>lambda2sql</artifactId>
-    <version>1.8.4</version>
+    <version>1.8.5</version>
     <packaging>jar</packaging>
 
     <name>lambda2sql</name>
@@ -60,7 +60,7 @@
         <dependency>
             <groupId>com.trigersoft</groupId>
             <artifactId>jaque</artifactId>
-            <version>2.3.0</version>
+            <version>2.4.0</version>
         </dependency>
 
         <dependency>

src/main/java/com/github/collinalpert/lambda2sql/LinkedListStack.java

@@ -17,13 +17,6 @@ public class LinkedListStack<T> {
 	private Node head;
 	private int elementCount;
 
-	/**
-	 * Constructor for creating an empty stack.
-	 */
-	public LinkedListStack() {
-		elementCount = 0;
-	}
-
 	/**
 	 * Pushes (adds) an element to the top of the stack.
 	 *

src/main/java/com/github/collinalpert/lambda2sql/ToSqlVisitor.java

@@ -28,7 +28,7 @@ public class ToSqlVisitor implements ExpressionVisitor<StringBuilder> {
 	ToSqlVisitor(String prefix) {
 		this.prefix = prefix;
 		this.sb = new StringBuilder();
-		arguments = new LinkedListStack<>();
+		this.arguments = new LinkedListStack<>();
 	}
 
 	/**
@@ -45,6 +45,10 @@ private static String toSqlOp(int expressionType) {
 				return "AND";
 			case ExpressionType.LogicalOr:
 				return "OR";
+			case ExpressionType.IsNull:
+				return " IS NULL";
+			case ExpressionType.IsNonNull:
+				return " IS NOT NULL";
 			case ExpressionType.Convert:
 				return "";
 		}
@@ -63,12 +67,12 @@ private static String toSqlOp(int expressionType) {
 	@Override
 	public StringBuilder visit(BinaryExpression e) {
 		//Handling for null parameters
-		if (e.getSecond() instanceof ParameterExpression && arguments.top().get(((ParameterExpression) e.getSecond()).getIndex()).getValue() == null) {
+		if (e.getSecond() instanceof ParameterExpression && !arguments.top().isEmpty() && arguments.top().get(((ParameterExpression) e.getSecond()).getIndex()).getValue() == null) {
 			if (e.getExpressionType() == ExpressionType.Equal) {
 				return Expression.isNull(e.getFirst()).accept(this);
 			}
 			if (e.getExpressionType() == ExpressionType.NotEqual) {
-				return Expression.unary(ExpressionType.LogicalNot, boolean.class, Expression.unary(ExpressionType.IsNull, boolean.class, e.getFirst())).accept(this);
+				return Expression.isNonNull(e.getFirst()).accept(this);
 			}
 		}
 
@@ -94,13 +98,13 @@ public StringBuilder visit(BinaryExpression e) {
 	 */
 	@Override
 	public StringBuilder visit(ConstantExpression e) {
+		if (e.getValue() == null) {
+			return sb.append("NULL");
+		}
 		if (e.getValue() instanceof LambdaExpression) {
 			((LambdaExpression) e.getValue()).getBody().accept(this);
 			return sb;
 		}
-		if (e.getValue() == null) {
-			return sb.append("NULL");
-		}
 		if (e.getValue() instanceof String) {
 			return sb.append("'").append(e.getValue().toString()).append("'");
 		}
@@ -193,16 +197,12 @@ public StringBuilder visit(ParameterExpression e) {
 	 */
 	@Override
 	public StringBuilder visit(UnaryExpression e) {
-		if (e.getFirst() instanceof UnaryExpression && e.getExpressionType() == ExpressionType.LogicalNot) {
-			if (e.getFirst().getExpressionType() == ExpressionType.IsNull) {
-				return ((UnaryExpression) e.getFirst()).getFirst().accept(this).append(" IS NOT NULL");
-			}
+		if (e.getExpressionType() == ExpressionType.LogicalNot) {
+			sb.append("!");
+			return e.getFirst().accept(this);
 		}
-		if (e.getExpressionType() == ExpressionType.IsNull) {
-			return e.getFirst().accept(this).append(" IS NULL");
-		}
-		sb.append(toSqlOp(e.getExpressionType()));
-		return e.getFirst().accept(this);
+		e.getFirst().accept(this);
+		return sb.append(toSqlOp(e.getExpressionType()));
 	}
 
 }

src/main/java/com/github/collinalpert/lambda2sql/functions/SerializedFunctionalInterface.java

@@ -4,6 +4,7 @@
 
 /**
  * An interface functional interfaces can extend to become serialized.
+ * Functional interfaces which extend this interface can be converted to SQL statements.
  *
  * @author Collin Alpert
  * @see Serializable

src/test/java/com/github/collinalpert/lambda2sql/test/Lambda2SqlTest.java

@@ -116,6 +116,33 @@ void testParentheses() {
 		assertPredicateEqual("person.age = 18 AND (person.isAdult OR person.name = 'Steve')", p2);
 	}
 
+	//@Test
+	//This section does not work yet!
+	void testJavaFunctions() {
+		var name = "Steve";
+		var age = 18;
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE 'Steve%'", person -> person.getAge() >= age || person.getName().startsWith("Steve"));
+		assertPredicateEqual("person.name LIKE 'Steve%'", person -> person.getName().startsWith("Steve"));
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE 'Steve%'", person -> person.getAge() >= age || person.getName().startsWith(name));
+		assertPredicateEqual("person.name LIKE 'Steve%'", person -> person.getName().startsWith(name));
+		assertPredicateEqual("person.age >= 18 OR person.name NOT LIKE 'Steve%'", person -> person.getAge() >= age || !person.getName().startsWith(name));
+		assertPredicateEqual("person.name NOT LIKE 'Steve%'", person -> !person.getName().startsWith(name));
+
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE '%Steve'", person -> person.getAge() >= age || person.getName().endsWith("Steve"));
+		assertPredicateEqual("person.name LIKE '%Steve'", person -> person.getName().endsWith("Steve"));
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE '%Steve'", person -> person.getAge() >= age || person.getName().endsWith(name));
+		assertPredicateEqual("person.name LIKE '%Steve'", person -> person.getName().endsWith(name));
+		assertPredicateEqual("person.age >= 18 OR person.name NOT LIKE '%Steve'", person -> person.getAge() >= age || !person.getName().endsWith(name));
+		assertPredicateEqual("person.name NOT LIKE '%Steve'", person -> !person.getName().endsWith(name));
+
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE '%Steve%'", person -> person.getAge() >= age || person.getName().contains("Steve"));
+		assertPredicateEqual("person.name LIKE '%Steve%'", person -> person.getName().contains("Steve"));
+		assertPredicateEqual("person.age >= 18 OR person.name LIKE '%Steve%'", person -> person.getAge() >= age || person.getName().contains(name));
+		assertPredicateEqual("person.name LIKE '%Steve%'", person -> person.getName().contains(name));
+		assertPredicateEqual("person.age >= 18 OR person.name NOT LIKE '%Steve%'", person -> person.getAge() >= age || !person.getName().contains(name));
+		assertPredicateEqual("person.name NOT LIKE '%Steve%'", person -> !person.getName().contains(name));
+	}
+
 	private void assertPredicateEqual(String expectedSql, SqlPredicate<IPerson> p) {
 		var sql = Lambda2Sql.toSql(p, "person");
 		Assertions.assertEquals(expectedSql, sql);