JDBC连接Mysql出现问题！

Question

Insert 类 调用 JdbcUtil类时出现异常，但代码没有红叉，请大神指教！

//第一个类

package com.jdbc.util;

import java.io.InputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Properties;

public class JdbcUtil {

    //数据库的连接的URL
    private static String url = null;
    //数据库用户名
    private static String user = null;
    //数据库密码
    private static String password = null;
    //驱动程序类
    private static String driverClass = null ;

public static void main(String[] args) {

//static {

    //注册驱动     
    try {       
            //创建Properties对象，接入jdbc.properties配置文件
              Properties prop = new Properties();
            //使用类路径方式读取配置文件
              InputStream in = JdbcUtil.class.getResourceAsStream("/jdbc.properties");
            //加载文件
              prop.load(in);
            //读取配置文件的内容
               url = prop.getProperty("url");
               user = prop.getProperty("user");
               password = prop.getProperty("password");
               driverClass = prop.getProperty("driverClass");
               Class.forName(driverClass);
                System.out.println(url);
                System.out.println(user);
                System.out.println(password);
                System.out.println(driverClass);

                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
               } catch (Exception e) {
                    e.printStackTrace();
              }       
  }

//获取连接方法

public static Connection getConn() {

try {
    Connection conn = DriverManager.getConnection(url, user, password);
    return conn;
} catch (SQLException e) {
    e.printStackTrace();
     throw new RuntimeException(e);
}

}

//释放资源方法

public static void close(ResultSet rs,Statement stmt,Connection conn) {

if(rs != null) {     
   try {
        rs.close();
       } catch (SQLException e) {
         e.printStackTrace();
         throw new RuntimeException(e);
      }
    } 

if(stmt != null) {
    try {
        stmt.close();
        } catch (SQLException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      }
   }

if(conn != null) {
    try {
          conn.close();
        } catch (SQLException e) {
          e.printStackTrace();
          throw new RuntimeException(e);
      }
  }

}

}

//jdbc.properties配置文件:

url=jdbc:mysql://localhost:3306/test

user=root

password=root

driverClass=com.mysql.jdbc.Driver

//第二个类
package com.crud.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import com.jdbc.util.JdbcUtil;

public class Insert {

public static void main(String[] args) {
     test();

}
public static void test() {
Connection conn = null;
PreparedStatement stmt =null;
ResultSet rs = null ;

try {
    //获取连接
    conn = JdbcUtil.getConn();
    String sql = "INSERT INTO student(id,name,age) VALUES(?,?,?)";

    //创建prepareStatement对象
    stmt = conn.prepareStatement(sql);
    //设置参数
    stmt.setInt(1, 7);
    stmt.setString(2, "奥巴马");
    stmt.setInt(3, 22);
    //发送参数到数据库
    rs = stmt.executeQuery();
} catch (Exception e) {
    e.printStackTrace();
}finally {
    //关闭资源
     JdbcUtil.close(rs, stmt, conn);
}

}

}

Answer 1

删 public static void main(String[] args) {
放开 static

over！

更新(insert、update、delete)用 executeUpdate

算了，给你代码吧，自己理解

 package com.jdbc.util;

//import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JdbcUtil
{
    // 数据库的连接的URL
    private static String url = null;

    // 数据库用户名
    private static String user = null;

    // 数据库密码
    private static String password = null;

    // 驱动程序类
    private static String driverClass = null;


    public static void main(String[] args)
    {
        System.out.println(getConn());
    }

    /**
     * 只注册一次，静态代码块
     */
    static
    {
        // 注册驱动
        try
        {
            // 创建Properties对象，接入jdbc.properties配置文件
            Properties prop = new Properties();
            // 使用类路径方式读取配置文件
            InputStream in = JdbcUtil.class.getResourceAsStream("/jdbc.properties");
            // 加载文件
            prop.load(in);
            // 读取配置文件的内容
            url = prop.getProperty("url");
            user = prop.getProperty("user");
            password = prop.getProperty("password");
            driverClass = prop.getProperty("driverClass");
            Class.forName(driverClass);
            System.out.println(url);
            System.out.println(user);
            System.out.println(password);
            System.out.println(driverClass);

        }
        catch (ClassNotFoundException e)
        {
            e.printStackTrace();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    /**
     * 获取连接方法
     */

    public static Connection getConn()
    {
        try
        {
            Connection conn = DriverManager.getConnection(url, user, password);
            return conn;
        }
        catch (SQLException e)
        {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    /**
     * 释放资源方法
     */
    public static void close(ResultSet rs, Statement stmt, Connection conn)
    {
        if (rs != null)
        {
            try
            {
                rs.close();
            }
            catch (SQLException e)
            {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }

        if (stmt != null)
        {
            try
            {
                stmt.close();
            }
            catch (SQLException e)
            {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }

        if (conn != null)
        {
            try
            {
                conn.close();
            }
            catch (SQLException e)
            {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }
    }

}

package com.crud.util;

import java.sql.Connection;
import java.sql.PreparedStatement;

import com.jdbc.util.JdbcUtil;

public class Insert
{

public static void main(String[] args)
{
    test();
}

public static void test()
{
    Connection conn = null;
    PreparedStatement stmt = null;

    try
    {
        // 获取连接
        conn = JdbcUtil.getConn();
        String sql = "INSERT INTO student(id,name,age) VALUES(?,?,?)";

        // 创建prepareStatement对象
        stmt = conn.prepareStatement(sql);
        // 设置参数
        stmt.setInt(1, 7);
        stmt.setString(2, "奥巴马");
        stmt.setInt(3, 22);
        // 发送参数到数据库
        stmt.executeUpdate();
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
    finally
    {
        // 关闭资源
        JdbcUtil.close(null, stmt, conn);
    }
}

}