无法在以下函数中发现SQL语法错误:导致异常

Question

我一直收到以下错误.

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: 
You have an error in your SQL syntax; check
the manual that corresponds to your MySQL server version for 
the right syntax to use near '= 3' at line 1

我浏览了整个代码,此时只有2个SQL函数被调用,能够导致此错误:

1. 读

   public void Read (String userName) /*have checked validity*/
   try {
       con = getConnection();
   
       PreparedStatement pstmt = con.prepareStatement("SELECT * FROM " + 
                                 tableName + 
                                " WHERE userName=?");
   
           pstmt.setString(1,userName);
   
       ResultSet rs = pstmt.executeQuery();
   
       User user;
       PrintQuery(rs);
       rs.close();
       pstmt.close();
       releaseConnection(con);
       return user;
   
   }
   

2. 的GetItem

    public void getItem(int userid) /*have checked validity*/
    try {
       con = getConnection();
   
       Statement stmt = con.createStatement();
   
       PreparedStatement pstmt = con.prepareStatement("SELECT * FROM " 
                                 + tableName +"WHERE UserId=?");
       pstmt.setInt(1,userid);
       rs = pstmt.executeQuery();
       PrintQuery(rs);
       stmt.close();
       releaseConnection(con);
   
   }
   

我现在坚持了几个小时,我无法解决它.我已仔细检查以查看这些参数是否为空等等.它们不是.事实上,它们都很好地存在于数据库中.我无法弄清楚我哪里出错了.任何帮助都感激不尽.

Answer 1

错误已启用,GetName因为在tableName和WHERE子句之间的连接期间缺少额外的空间

+ tableName +" WHERE UserId=?");
           // ^ add extra space here