准备语句时PreparedStatement资源泄漏

Question

我怀疑这可能是假阳性，但我不能确定，所以我有点困惑。我正在使用Eclipse Neon，问题出现在我准备声明的第三次。我在下面做了一些几乎相同的事情，没有错误。

try{
        Connection con = MySQL.connection;
        PreparedStatement ps = con.prepareStatement("SELECT * from UsernameData "
                + "WHERE UUID = '" + player.getUniqueId() + "'");
        ResultSet rs = ps.executeQuery();
        if(rs.next() == true){
            ps = con.prepareStatement("update UsernameData set UUID = ?, Username = ? where UUID = ?");
            ps.setString(1, uuid);
            ps.setString(2, username);
            ps.setString(3, uuid);
            ps.execute();
            ps.close();
            rs.close();
            return;
        }
        ps = con.prepareStatement("insert into UsernameData(UUID, Username)"
                + " values (?, ?)");
        ps.setString(1, uuid);
        ps.setString(2, username);
        ps.execute();
        ps.close();
        rs.close();
        return;
    }catch(SQLException e){
        Bukkit.getServer().getLogger().warning("SQL Error: " + e);
    }

Answer 1

当您在插入时踩踏ps时，您不会关闭第一组资源。

你还应该考虑使用try-with-resources:

    try (Connection con = MySQL.connection;
            PreparedStatement ps = con.prepareStatement("SELECT * from UsernameData "
                    + "WHERE UUID = '" + player.getUniqueId() + "'");
            PreparedStatement ps2 = con.prepareStatement("update UsernameData set UUID = ?, Username = ? where UUID = ?");
            PreparedStatement ps3 = con.prepareStatement("insert into UsernameData(UUID, Username)"
                    + " values (?, ?)");
            ResultSet rs = ps.executeQuery()) {
        if (rs.next() == true) {
            ps2.setString(1, uuid);
            ps2.setString(2, username);
            ps2.setString(3, uuid);
            ps2.execute();
            return;
        }
        ps3.setString(1, uuid);
        ps3.setString(2, username);
        ps3.execute();
        return;
    } catch (SQLException e) {
        Bukkit.getServer().getLogger().warning("SQL Error: " + e);
    }

是的，第二个和第三个PreparedStatement可能被浪费了。如果你愿意，你可以把它们包装在自己的try-with-resources中。

但是问题的关键是你践踏了ps变量