[TD-3796]<test>: test null value in JDBC-JNI

src/connector/jdbc/src/test/java/com/taosdata/jdbc/cases/NullValueInResultSetForJdbcJniTest.java

@@ -0,0 +1,64 @@
+package com.taosdata.jdbc.cases;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.sql.*;
+
+public class NullValueInResultSetForJdbcJniTest {
+
+    private static final String host = "127.0.0.1";
+    Connection conn;
+
+    @Test
+    public void test() {
+        try (Statement stmt = conn.createStatement()) {
+            ResultSet rs = stmt.executeQuery("select * from weather");
+            ResultSetMetaData meta = rs.getMetaData();
+            while (rs.next()) {
+                for (int i = 1; i <= meta.getColumnCount(); i++) {
+                    Object value = rs.getObject(i);
+                    System.out.print(meta.getColumnLabel(i) + ": " + value + "\t");
+                }
+                System.out.println();
+            }
+
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Before
+    public void before() throws SQLException {
+        final String url = "jdbc:TAOS://" + host + ":6030/?user=root&password=taosdata";
+        conn = DriverManager.getConnection(url);
+        try (Statement stmt = conn.createStatement()) {
+            stmt.execute("drop database if exists test_null");
+            stmt.execute("create database if not exists test_null");
+            stmt.execute("use test_null");
+            stmt.execute("create table weather(ts timestamp, f1 int, f2 bigint, f3 float, f4 double, f5 smallint, f6 tinyint, f7 bool, f8 binary(64), f9 nchar(64))");
+            stmt.executeUpdate("insert into weather(ts, f1) values(now+1s, 1)");
+            stmt.executeUpdate("insert into weather(ts, f2) values(now+2s, 2)");
+            stmt.executeUpdate("insert into weather(ts, f3) values(now+3s, 3.0)");
+            stmt.executeUpdate("insert into weather(ts, f4) values(now+4s, 4.0)");
+            stmt.executeUpdate("insert into weather(ts, f5) values(now+5s, 5)");
+            stmt.executeUpdate("insert into weather(ts, f6) values(now+6s, 6)");
+            stmt.executeUpdate("insert into weather(ts, f7) values(now+7s, true)");
+            stmt.executeUpdate("insert into weather(ts, f8) values(now+8s, 'hello')");
+            stmt.executeUpdate("insert into weather(ts, f9) values(now+9s, '涛思数据')");
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @After
+    public void after() {
+        try {
+            if (conn != null)
+                conn.close();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+    }
+}