statement.setString(1、"ffname");声明。llname"setString (2); 所以，代码看起来像这样:
更新
我尝试连接netbeans与SQL，但我仍然有一个问题。我想，还是少了点什么。
在这里，我创建了这个类:(这里现在出现错误-另一方面，我不知道，如果它是完全正确的)public class connection {
public Connection con;
public void dbConnect(){
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String connectionUrl = "jdbc:sqlserver://FIO\SQLEXPRESS;" +
"databaseName=Feedback;integratedSecurity=true";
con = DriverManager.getConnection(connectionUrl);
} catch (SQLException e) {
System.out.println("SQL Exception: "+ e.toString());
} catch (ClassNotFoundException cE) {
System.out.println("Class Not Found Exception: "+ cE.toString());
}
}
public Connection getConnection() {
return con;
}
static PreparedStatement prepareStatement(String sql) {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}
}
然后，在另一个名为Questions的类中，我尝试准备语句并从数据库加载信息:
public class Questions {
public void doQuestion()
{...
...
...
...
connection con = new connection();
con.dbConnect();
PreparedStatement preparedStatement;
try{
**preparedStatement = con.getConnection().createStatement();**
String sql = "SELECT Answer FROM Feedback.dbo.Question1 WHERE TrainerFirstName=? AND TrainerLastName=?"
preparedStatement.setString(1,"ffname");
preparedStatement.setString(2, "llname");
ResultSet result = preparedStatement.executeQuery(sql);
while(result.next())
{
System.out.println(result.getString(1) + result.getString(2));
}
}catch (SQLException ex) {
Logger.getLogger(Questions.class.getName()).log(Level.SEVERE, null, ex);
}
...
...
...
...
...
}
}
Netbeans下划线:"preparedStatement = con.getConnection().createStatement(); ", due to "incompatible types: Statement cannot be converted to PreparedStatement."
我克服不了。
然后我试着做这样的事情来解决问题，但问题仍然存在，即使以不同的方式。:
public class Questions {
public void doQuestion()
{...
...
...
...
connection con = new connection();
con.dbConnect();
Statement statement;
try {
statement = con.getConnection().createStatement();
String sql = "SELECT Answer FROM Feedback.dbo.Question1 WHERE TrainerFirstName=? AND TrainerLastName=?"
**statement.setString(1,"ffname");
statement.setString(2, "llname");**
ResultSet rs = statement.executeQuery(sql);
while (rs.next()) {
System.out.println(rs.getString(1) + rs.getString(2));
}
} catch (SQLException ex) {
Logger.getLogger(Questions.class.getName()).log(Level.SEVERE, null, ex);
}
这里，Netbeans下划线"statement.setString(1,"ffname");声明。llname"setString (2);"
由于标签:"无法找到符号象征:方法setString (int,字符串)
语句类型然后，我尝试以不同的形式发送字符串sql:
String sql = "SELECT Answer FROM Feedback.dbo.Question1 WHERE TrainerFirstName="+ffname+"AND TrainerLastName="+llname
statement.setString(1、"ffname");声明。llname"setString (2); 所以，代码看起来像这样:
public class Questions {
public void doQuestion()
{...
...
...
...
connection con = new connection();
con.dbConnect();
Statement statement;
try {
statement = con.getConnection().createStatement();
String sql = "SELECT Answer FROM Feedback.dbo.Question1 WHERE TrainerFirstName="+ffname+"AND TrainerLastName="+llname
ResultSet rs = statement.executeQuery(sql);
while (rs.next()) {
System.out.println(rs.getString(1) + rs.getString(2));
}
} catch (SQLException ex) {
Logger.getLogger(Questions.class.getName()).log(Level.SEVERE, null, ex);
}
这样，一切似乎都很好，但是当我运行一个项目时，出现错误并指向:" statement = cont . getconnection (). createstatement ();当然，程序也会崩溃。
我真不知道该怎么办。
如果有人有想法，请写下来。
非常感谢。
在这个简单的例子中，我连接到一个数据库并创建一个语句，但我不使用cont . getconnection()。createStatement，但只是cont。createStatement()尝试这样做可能是问题所在。我在这里留下了我已经学过的使用I数据库的整个sql演示，如果你将来有其他问题，它可以帮助你。如果您的问题仍然存在，请告诉我。
public static void main(String[] args) {
String url = "jdbc:mysql://localhost:3306/";
String dbName = "pc_control";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "";
try {
Class.forName(driver).newInstance();
Connection conn = DriverManager.getConnection(url + dbName, userName, password);
Statement st = conn.createStatement();
ResultSet res = st.executeQuery("SELECT * FROM computers");
while (res.next()) {
int comp_id = res.getInt("computer_id");
int emp_id = res.getInt("employee_id");
String image = res.getString("image");
String brand = res.getString("brand");
String model = res.getString("model");
String m_board = res.getString("m_board");
String processor = res.getString("processor");
int ram = res.getInt("ram");
String hdd = res.getString("hdd");
String os = res.getString("os");
String ip_add = res.getString("ip_add");
System.out.println(comp_id + "t" + emp_id + "t" + image + "t" + brand + "t" +
model + "t" + m_board + "t" + processor + "t" + ram + "t" + hdd + "t"
+ os + "t" + ip_add + "t");
}//
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
更新
我们将尝试以这种方式或类似的方式重新定义您的连接类。
我希望这对你有帮助。我很抱歉我不能指出你的错误，但是你对连接的实现对我来说有点奇怪。
public class MySqlConnection {
static String url = "jdbc:mysql://localhost:3306/";
static String dbName = "pc_control";
static String driver = "com.mysql.jdbc.Driver";
static String userName = "root";
static String password = "";
static Statement st;
static Connection conn;
public MySqlConnection() {
}
public static boolean connect() {
try {
Class.forName(driver).newInstance();
conn = DriverManager.getConnection(url + dbName, userName, password);
} catch (Exception e) {
e.printStackTrace();
}
return true;
}
public static ResultSet read(String query)
{
ResultSet res = null;
try {
st = conn.createStatement();
res = st.executeQuery(query);
} catch (SQLException ex) {
Logger.getLogger(MySqlConnection.class.getName()).log(Level.SEVERE, null, ex);
}
return res;
}
}
要执行查询，只需从任何其他类调用该方法:
String query = "SELECT * FROM computers WHERE computer_id= " + id; //or whatever
ResultSet res = MySqlConnection.read(query);
这是一个netbeans上的准备语句示例
Connection con = null;
PreparedStatement ptmt = null;
public void add(Archivos archivos) {
try {
String query = "INSERT INTO archivosemisor "
+ "(rfcEmisor, cer, llave, password, idError, resultado)"
+ " VALUES (?,?,?,?,?,?)";
con = getConnection();
ptmt = con.prepareStatement(query);
ptmt.setString(1, archivos.getRfcEmisor());
ptmt.setString(2, archivos.getCer());
ptmt.setString(3, archivos.getLlave());
ptmt.setString(4, archivos.getPassword());
ptmt.setString(5, archivos.getIdError());
ptmt.setString(6, archivos.getResultado());
ptmt.executeUpdate();
} catch (SQLException e) {
.......
} finally {
.....
}
}
希望对你有所帮助