Question

尝试将记录插入数据库时，我一直收到空指针异常。我正在进入网络应用程序类，所以我这是我第一次在eclipse中处理数据库。我相信这一行初始化了我的连接变量：

this.connection = DriverManager.getConnection(url, uname, pwd);

...但它仍然说连接为空。它所指的行是：

PreparedStatement ps = connection.prepareStatement(query);

package dbHelpers;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import package1.Customer;


public class AddCustomerQuery {
public Connection connection;

public AddCustomerQuery(String dbName, String uname, String pwd){
    String url = "jdbc:mysql://localhost:3306/" + dbName;

    try {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        this.connection = DriverManager.getConnection(url, uname, pwd); 
    } catch (InstantiationException | IllegalAccessException
            | ClassNotFoundException | SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public void addCustomer(Customer customer){

    String query = "insert into customer (firstName, lastName, emailAddress, password, gender, phoneNumber, street, city, state, zip) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
    try {   
    PreparedStatement ps = connection.prepareStatement(query);
        ps.setString(1, customer.getFirstName());
        ps.setString(2, customer.getLastName());
        ps.setString(3, customer.getEmailAddress());
        ps.setString(4, customer.getPassword());
        ps.setString(5, customer.getGender());
        ps.setString(6, customer.getPhoneNumber());
        ps.setString(7, customer.getStreet());
        ps.setString(8, customer.getCity());
        ps.setString(9, customer.getState());
        ps.setString(10, customer.getZip());

        ps.executeUpdate();

    } catch (SQLException e) {
        // TODO Auto-generated catch block
                e.printStackTrace();
    }

}

}

Answer 1

首先检查你的mysql daatbase服务器用户名，密码，数据库名称等。，。因为默认情况下mysql服务器端口号是3306，可能是在安装时你更改了服务器的端口号。

PreparedStatement抛出java.lang.NullPointerException

1 个答案: