错误：SQLException：参数索引超出范围（1>参数数量，为0）

Question

即使上面准备好的语句的语法是正确的，我仍然遇到以下错误：

  

java.sql.SQLException：参数索引超出范围（1>参数数量，为0）

预期结果是以下代码必须返回表的值

try{
        conn = DatabaseMain.getConnection();
        String instqury = "Select quality_name,quality_size,quality_weight,quality_spec from quality where quality_code = '?'";
        pst1 = conn.prepareStatement(instqury);
        pst1.setString(1, quality);

        rs1 = pst1.executeQuery();
        rs1.next();
        name.setText(String.valueOf(rs1.getString("quality_name")));

    }
    catch(Exception e){
        e.printStackTrace();
        System.out.println("Error in setting labels for Machine View");
    }

Answer 1

请勿将占位符放在单引号之间

String instqury = 
    "Select quality_name,quality_size,quality_weight,quality_spec " + 
    "from quality where quality_code = ?";
                                       ^-- here

Answer 2

尝试在占位符？中删除单引号吗？查询正在将其读取为提供的值。