1.编写数据库连接属性jdbc-mysql.properties


username=root
password=123
url=jdbc:mysql://localhost:3306/makefriends
driverClassName=com.mysql.jdbc.Driver




2.编写DBConnection数据库公共操作类


package com.yun.utility;

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

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;

public class DBConnection {
  private static String user;
  private static String password;
  private static String url;
  static {
    try {
      ClassLoader classLoader = DBConnection.class.getClassLoader();
      // 数据库的配置文件路径
      InputStream is = classLoader.getResourceAsStream("config/prop/jdbc-mysql.properties");
      Properties props = new Properties();
      props.load(is);
      url = props.getProperty("url");
      user = props.getProperty("username");
      password = props.getProperty("password");
      Class.forName(props.getProperty("driverClassName"));
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("ClassNotFound");
    } catch (IOException e) {
      throw new RuntimeException("IO");
    }
  }

  public static Connection getConnection() throws Exception {
    return (Connection) DriverManager.getConnection(url, user, password);
  }

  
  public static Statement getStatement() throws SQLException{
    return (Statement) DriverManager.getConnection(url, user, password).createStatement();
  }
  
  
  
  public static void close(ResultSet rs, Statement stat, Connection conn) throws Exception {
    if (rs != null) {
      rs.close();
    }
    if (stat != null) {
      stat.close();
    }
    if (conn != null) {
      conn.close();
    }
  }

  public static void close(Statement stat, Connection conn) throws Exception {
    if (stat != null) {
      stat.close();
    }
    if (conn != null) {
      conn.close();
    }
  }

}




3.编写测试类


package com.yun.test;

import java.sql.ResultSet;
import java.sql.SQLException;

import com.mysql.jdbc.Statement;
import com.yun.utility.DBConnection;

public class testDBConnection {
  public static void main(String[] args) throws SQLException  {
    Statement statement= DBConnection.getStatement();
    String sql="select * from yunuser";
    ResultSet rs=statement.executeQuery(sql);
    while(rs.next())
        {
            System.out.println(rs.getString(2));
        }
  }

}