SPR-7840: comparator dealing with nulls

org.springframework.expression/src/main/java/org/springframework/expression/spel/support/StandardTypeComparator.java

@@ -33,9 +33,9 @@ public class StandardTypeComparator implements TypeComparator {
 	public int compare(Object left, Object right) throws SpelEvaluationException {
 		// If one is null, check if the other is
 		if (left == null) {
-			return right == null ? 0 : 1;
+			return right == null ? 0 : -1;
 		} else if (right == null) {
-			return -1; // left cannot be null
+			return 1; // left cannot be null
 		}
 
 		// Basic number comparisons

org.springframework.expression/src/test/java/org/springframework/expression/spel/DefaultComparatorUnitTests.java

@@ -61,9 +61,9 @@ public class DefaultComparatorUnitTests {
 	@Test
 	public void testNulls() throws EvaluationException {
 		TypeComparator comparator = new StandardTypeComparator();
-		Assert.assertTrue(comparator.compare(null,"abc")>0);
+		Assert.assertTrue(comparator.compare(null,"abc")<0);
 		Assert.assertTrue(comparator.compare(null,null)==0);
-		Assert.assertTrue(comparator.compare("abc",null)<0);
+		Assert.assertTrue(comparator.compare("abc",null)>0);
 	}
 
 	@Test

org.springframework.expression/src/test/java/org/springframework/expression/spel/SpringEL300Tests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.expression.spel;
 
+import static org.junit.Assert.assertEquals;
+
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
@@ -767,5 +769,47 @@ public class SpringEL300Tests extends ExpressionTestCase {
 		}
 	}
 	
+	static class D {
+		public String a;
+		
+		private D(String s) {
+			a=s;
+		}
+		
+		public String toString() {
+			return "D("+a+")";
+		}
+	}
+	
+	@Test
+	public void testGreaterThanWithNulls_SPR7840() throws Exception {
+		List<D> list = new ArrayList<D>();
+		list.add(new D("aaa"));
+		list.add(new D("bbb"));
+		list.add(new D(null));
+		list.add(new D("ccc"));
+		list.add(new D(null));
+		list.add(new D("zzz"));
+		
+        StandardEvaluationContext ctx = new StandardEvaluationContext(list);
+        SpelExpressionParser parser = new SpelExpressionParser();        
+
+        String el1 = "#root.?[a < 'hhh']";
+        SpelExpression exp = parser.parseRaw(el1);
+        Object value = exp.getValue(ctx);
+        assertEquals("[D(aaa), D(bbb), D(null), D(ccc), D(null)]",value.toString());        
+
+        String el2 = "#root.?[a > 'hhh']";
+        SpelExpression exp2 = parser.parseRaw(el2);
+        Object value2 = exp2.getValue(ctx);
+        assertEquals("[D(zzz)]",value2.toString());
+        
+        // trim out the nulls first
+        String el3 = "#root.?[a!=null].?[a < 'hhh']";
+        SpelExpression exp3 = parser.parseRaw(el3);
+        Object value3 = exp3.getValue(ctx);
+        assertEquals("[D(aaa), D(bbb), D(ccc)]",value3.toString());
+	}
+
 	
 }