java - 使用 JDBC 语句执行查询时出现 NullPointerException

Question

我正在尝试通过 MySQL 连接到存储在本地主机上的数据库，并且我正在尝试插入一个新语句，但我收到了一个我以前从未见过的奇怪错误。我不确定我的插入语句是否不正确，或者代码本身是否不正确。

我收到的错误是

Exception in thread "main" java.lang.NullPointerException
    at DatabaseConnect.main(DatabaseConnect.java:24)
Java Result: 1

//

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class DatabaseConnect {

    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;

            //start JDBC
            try {
            //Register JDBC driver
            System.out.println("Connecting to Database...");
            Class.forName("com.mysql.jdbc.Driver"); //connect using JDBC driver 
            System.out.println("Connection to driver Successful");
            System.out.println("Connecting to Database");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/courseproject", "root", "root"); //connection to database
            System.out.println("Connection to Database successful");
            System.out.println("execute insert statement");
            statement.execute("INSERT INTO courseproject.agent (AGT_ID, AGT_LNAME, AGT_FNAME, AGT_STREET, ADD_ZIP, AGT_PHONE, AGT_EMAIL, OFF_CODE) VALUES ('6', 'firstname', 'lastname', 'street address', '34398', '348374', 'sfhf@aol.com', '35464') ");
        } catch(ClassNotFoundException error){
            System.out.println("Error: " + error.getMessage());

        }catch(SQLException error){
            System.out.println("Error: " + error.getMessage());
        }




    }

}

Answer 1

语句未初始化。您应该创建一个声明:

statement = connection.createStatement()

还要记住，完成后必须关闭语句和与数据库的连接。