在**Result.next()**循环中被覆盖的数据

Question

我有一个搜索按钮，它会进入我的数据库并搜索一个名称，但当同一名称有两个条目时，它只会让我返回一个，我不知道为什么。下面是我现在使用的代码。

 public boolean search(String str1, String username){//search function for the access history search with two parameters
    boolean condition = true;
    String dataSourceName = "securitySystem";//setting string datasource to the securitySystem datasource
    String dbUrl = "jdbc:odbc:" + dataSourceName;//creating the database path for the connection
    try{
        //Type of connection driver used    
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        //Connection variable or object param: dbPath, userName, password
        Connection con = DriverManager.getConnection(dbUrl, "", "");
        Statement statement = con.createStatement();//creating the statement which is equal to the connection statement
        if (!(username.equals(""))){
            PreparedStatement ps = con.prepareStatement("select * from securitysystem.accessHistory where name = ?");//query to be executed
            ps.setString(1, username);//insert the strings into the statement
            ResultSet rs=ps.executeQuery();//execute the query
            if(rs.next()){//while the rs (ResultSet) has returned data to cycle through
                JTable table = new JTable(buildTableModel(rs));//build a JTable which is reflective of the ResultSet (rs)
            JOptionPane.showMessageDialog(null, new JScrollPane(table));//put scrollpane on the table
        }
        else{
                JOptionPane.showMessageDialog(null,"There has been no system logins at this time");// else- show a dialog box with a message for the user
            }
}
statement.close();//close the connection
    } catch (Exception e) {//catch error
        System.out.println(e);
    }
    return condition;   
}

Answer 1

以下是如何使用TableModel向表中添加数据的示例。

假设你有这些初始模型条件

String[] columnNames = {"Column1", "Column2", "Column3"};
DefaultTableModel model = new DefaultTablModel(columnNames, 0);
JTable table = new JTable(model);
...

你应该做类似的事情

while (rs.next()){
    String s1 = rs.getString(1);
    String s2 = rs.getString(2);
    String s3 = rs.getString(3);
    Object[] row = {s1, s2, s3};
    model.addRow(row);
}

---

编辑：要直接从数据库中获取列名，您需要使用ResultSetMetaData。

试试这个方法。

public DefaultTableModel buildTableModel(ResultSet rs){
    ResultSetMetaData rsMeta = rs.getMetaData();
    int cloumns = rsMeta.getColumnCount();
    String columnNames = new String[columns];
    for (int i = 1; i <= columns; i++){
        columnNames[i - 1] = rsMeta.getColumnName(i);
    }
    DefaultTableModel model = new DefaultTableModel(columnNames, 0);
    while (rs.next()){
        // Just an example retrieving data. Fill in what you need
        String s1 = rs.getString(1);
        String s2 = rs.getString(2);
        String s3 = rs.getString(3);
        Object[] row = {s1, s2, s3};
        model.addRow(row);
        // End example
    }
    return model;
}

然后，

if (rs != null){
    JTable table = new JTable(buildTableModel(rs));
}

Answer 2

您的代码多次调用rs.next()。在上面的搜索方法中，在调用buildTableModel(...)方法之前先调用它，这实际上浪费了一行从未使用过的数据。

相反，只需将ResultSet传递到方法中，而不调用next，然后在buildTableModel(...)内部使用while循环来填充数据向量。如果向量为空，则引发异常，或返回一个包含0行的TableModel。