NamedParameterUtils.parseSqlStatement should parse :{x} style parameter correctly

In my opinion, we should parse ":{x}" style parameter as "x" is parameter using "NamedParameterUtils.parseSqlStatement",
so the condition "j - i > 2" is the correct condition, not "j - i > 3", because if "i" is the index of
":" in ":{x}", and "j" is the index of "}" in ":{x}",  "j - i == 3" is true.
Also add a test case for SPR-16663.

Author: nkjackzhang

spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java

@@ -130,7 +130,7 @@ public static ParsedSql parseSqlStatement(final String sql) {
 						throw new InvalidDataAccessApiUsageException(
 								"Non-terminated named parameter declaration at position " + i + " in statement: " + sql);
 					}
-					if (j - i > 3) {
+					if (j - i > 2) {
 						parameter = sql.substring(i + 2, j);
 						namedParameterCount = addNewNamedParameter(namedParameters, namedParameterCount, parameter);
 						totalParameterCount = addNamedParameter(parameterList, totalParameterCount, escapes, i, j + 1, parameter);

spring-jdbc/src/test/java/org/springframework/jdbc/core/namedparam/NamedParameterUtilsTests.java

@@ -253,6 +253,18 @@ public void parseSqlStatementWithEmptyBracketsOrBracketsInQuotes() throws Except
 		assertEquals(expectedSql2, finalSql2);
 	}
 
+	@Test
+	public void parseSqlStatementWithSingleLetterInBrackets() {
+		String expectedSql = "select foo from bar where baz = b?z";
+		String sql = "select foo from bar where baz = b:{p}z";
+		
+		ParsedSql parsedSql = NamedParameterUtils.parseSqlStatement(sql);
+		assertEquals(1, parsedSql.getParameterNames().size());
+		assertEquals("p", parsedSql.getParameterNames().get(0));
+		String finalSql = NamedParameterUtils.substituteNamedParameters(parsedSql, null);
+		assertEquals(expectedSql, finalSql);
+	}
+
 	@Test  // SPR-2544
 	public void parseSqlStatementWithLogicalAnd() {
 		String expectedSql = "xxx & yyyy";