more bulletproof reply sequence generator.

1 files changed, 12 insertions, 10 deletions

diff --git a/juick-core/src/main/java/com/juick/server/MessagesQueries.java b/juick-core/src/main/java/com/juick/server/MessagesQueries.java
index b39de0ed..e6188a86 100644
--- a/juick-core/src/main/java/com/juick/server/MessagesQueries.java
+++ b/juick-core/src/main/java/com/juick/server/MessagesQueries.java
@@ -158,24 +158,26 @@ public class MessagesQueries {
     public static int getReplyIDIncrement(JdbcTemplate sql, int mid) {
         return sql.execute((ConnectionCallback<Integer>) conn -> {
             conn.setAutoCommit(false);
-            try (PreparedStatement ps = conn.prepareStatement("UPDATE messages SET maxreplyid=maxreplyid+1 WHERE message_id=?")) {
-                ps.setInt(1, mid);
-                if (ps.executeUpdate() != 1) {
-                    throw new IncorrectResultSizeDataAccessException("Cannot find a message to update: " + mid, 1, 0);
-                }
-            }
-            try (PreparedStatement ps = conn.prepareStatement("SELECT maxreplyid FROM messages WHERE message_id=?")) {
+            final int replyNo;
+            try (PreparedStatement ps = conn.prepareStatement("SELECT maxreplyid+1 FROM messages WHERE message_id=? FOR UPDATE")) {
                 ps.setInt(1, mid);
                 try (ResultSet resultSet = ps.executeQuery()) {
                     if (resultSet.next()) {
-                        int rv = resultSet.getInt(1);
-                        conn.commit();
-                        return rv;
+                        replyNo = resultSet.getInt(1);
                     } else {
                         throw new IncorrectResultSizeDataAccessException("while getting getReplyIDIncrement, mid=" + mid, 1, 0);
                     }
                 }
             }
+            try (PreparedStatement ps = conn.prepareStatement("UPDATE messages SET maxreplyid=? WHERE message_id=?")) {
+                ps.setInt(1, mid);
+                ps.setInt(2, replyNo);
+                if (ps.executeUpdate() != 1) {
+                    throw new IncorrectResultSizeDataAccessException("Cannot find a message to update: " + mid, 1, 0);
+                }
+            }
+            conn.commit();
+            return replyNo;
         });
 
     }