add setParent

src/main/java/com/alibaba/druid/sql/ast/expr/SQLBinaryOpExpr.java

@@ -41,8 +41,8 @@ public class SQLBinaryOpExpr extends SQLExprImpl implements Serializable {
 
     public SQLBinaryOpExpr(SQLExpr left, SQLExpr right, SQLBinaryOperator operator){
 
-        this.left = left;
-        this.right = right;
+        setLeft(left);
+        setRight(right);
         this.operator = operator;
     }
 

src/main/java/com/alibaba/druid/sql/ast/expr/SQLCaseExpr.java

@@ -63,6 +63,9 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
     }
 
     public void setValueExpr(SQLExpr valueExpr) {
+        if (valueExpr != null) {
+            valueExpr.setParent(this);
+        }
         this.valueExpr = valueExpr;
     }
 
@@ -71,6 +74,9 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
     }
 
     public void setElseExpr(SQLExpr elseExpr) {
+        if (elseExpr != null) {
+            elseExpr.setParent(this);
+        }
         this.elseExpr = elseExpr;
     }
 
@@ -78,6 +84,13 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
         return this.items;
     }
 
+    public void addItem(Item item) {
+        if (item != null) {
+            item.setParent(this);
+            this.items.add(item);
+        }
+    }
+
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
             acceptChild(visitor, this.valueExpr);
@@ -99,8 +112,8 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
 
         public Item(SQLExpr conditionExpr, SQLExpr valueExpr){
 
-            this.conditionExpr = conditionExpr;
-            this.valueExpr = valueExpr;
+            setConditionExpr(conditionExpr);
+            setValueExpr(valueExpr);
         }
 
         public SQLExpr getConditionExpr() {
@@ -108,6 +121,9 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
         }
 
         public void setConditionExpr(SQLExpr conditionExpr) {
+            if (conditionExpr != null) {
+                conditionExpr.setParent(this);
+            }
             this.conditionExpr = conditionExpr;
         }
 
@@ -116,6 +132,9 @@ public class SQLCaseExpr extends SQLExprImpl implements Serializable {
         }
 
         public void setValueExpr(SQLExpr valueExpr) {
+            if (valueExpr != null) {
+                valueExpr.setParent(this);
+            }
             this.valueExpr = valueExpr;
         }
 

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -241,7 +241,7 @@ public class SQLExprParser extends SQLParser {
                 accept(Token.THEN);
                 SQLExpr valueExpr = expr();
                 SQLCaseExpr.Item caseItem = new SQLCaseExpr.Item(testExpr, valueExpr);
-                caseExpr.getItems().add(caseItem);
+                caseExpr.addItem(caseItem);
 
                 while (lexer.token() == Token.WHEN) {
                     lexer.nextToken();

src/main/java/com/alibaba/druid/sql/visitor/functions/Isnull.java

@@ -38,7 +38,7 @@ public class Isnull implements Function {
         SQLExpr condition = parameters.get(0);
         condition.accept(visitor);
         Object itemValue = condition.getAttributes().get(EVAL_VALUE);
-        if (itemValue == null || itemValue == EVAL_VALUE_NULL) {
+        if (itemValue == EVAL_VALUE_NULL) {
             return Boolean.TRUE;
         } else {
             return Boolean.FALSE;