数据库连接

package com.yyh.test; import java.sql.*; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; public class DBTool { //默认参数 public String ip = "127.0.0.1"; public int port = 3306; public String user="root", password="admin", charset ="utf8", dbName="db1"; private static boolean DriverLoaded=false; //使用默认参数链接数据库 public DBTool() throws ClassNotFoundException { if(DriverLoaded)return; try { Class.forName("com.mysql.jdbc.Driver"); System.out.println("DBTools message:数据库驱动加载成功!"); } catch (ClassNotFoundException e) { System.out.println("DBTools Error:驱动程序加载失败!"); throw e; } DriverLoaded=true; } //自定义参数初始化 public DBTool(String ip, int port, String user, String password, String dbName) throws ClassNotFoundException { this(); this.ip = ip; this.port = port; this.user = user; this.password = password; this.dbName = dbName; } //自定义参数初始化 public DBTool(String user, String password, String dbName) throws ClassNotFoundException { this(); this.user = user; this.password = password; this.dbName = dbName; } //获取一个链接 public Connection getConnection() throws SQLException { String url = String.format("jdbc:mysql://%s:%s/%s?characterEncoding=%s&user=%s&password=%s&useSSL=false",ip,port,dbName,charset,user,password); try { return DriverManager.getConnection(url); } catch (SQLException e) { System.out.println("DBTools Error 数据库连接失败!"); throw e; } } //执行查询语句 public List<Map<String,Object>> executeQuery(String sql, Object...args) throws SQLException { ArrayList<Map<String, Object>> res = new ArrayList<>(); ResultSet resultSet = null; PreparedStatement preparedStatement = null; Connection connection = null; try { connection = getConnection(); preparedStatement = getPreparedStatement(connection, sql, args); resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { resultSet.getMetaData().getColumnCount(); HashMap<String, Object> map = new HashMap<>(); for (int i = 1; i <= resultSet.getMetaData().getColumnCount() ; i++) { map.put(resultSet.getMetaData().getColumnName(i),resultSet.getObject(i)); } res.add(map); } } catch (SQLException e) { e.printStackTrace(); throw e; } finally { if(resultSet != null) resultSet.close(); if(preparedStatement != null) preparedStatement.close(); if(connection != null) connection.close(); } return res; } //sql参数预处理 private PreparedStatement getPreparedStatement(Connection connection, String sql, Object[] args) throws SQLException { PreparedStatement preparedStatement = connection.prepareStatement(sql); int count = sql.length() - sql.replace("?", "").length(); if(count != args.length){ throw new SQLException("DBTool Error: 参数个数不匹配"); } for (int i = 0; i < args.length; i++) { preparedStatement.setObject(i+1,args[i]); } return preparedStatement; } //执行更新语句 public boolean executeUpdate(String sql,Object...args) throws SQLException { try { Connection connection = getConnection(); PreparedStatement preparedStatement = getPreparedStatement(connection, sql, args); int i = preparedStatement.executeUpdate(); if (i>0){return true;} } catch (SQLException e) { e.printStackTrace(); throw e; } return false; }}