jdbc连接数据库

jdbc封装（其中一种）：
·创建数据库连接工具类JdbcUtil.java,将数据库参数写在配置文件jdbc.properties中
·dao（数据访问）层创建BaseDao.java类，该类是所有数据访问层进行增删改查操作类的父类

·配置文件jdbc.properties

driverClass=com.mysql.jdbc.Driverurl=jdbc:mysql://127.0.0.1:3306/数据库名?useUnicode=true&characterEncoding=utf-8username=rootpassword=admin

·解析配置文件工具类ConfigManager.java

/** * @author 落俗 *解析配置文件 */public class ConfigManager {    private static Properties props = null;    static{        InputStream is = null;        is = ConfigManager.class.getClassLoader().getResourceAsStream("jdbc.properties");        if(is == null){            throw new RuntimeException("文件读取失败");        }        props = new Properties();        try{            props.load(is);        }catch (IOException e){            e.printStackTrace();        }finally{            try{                is.close();            }catch(IOException e){                e.printStackTrace();            }        }    }    public static String getProperty(String key){        return props.getProperty(key);    }}

·数据库连接工具类JdbcUtil.java

/** * @author 落俗 * */public class JdbcUtils {    //读取配置文件    private static String driver = ConfigManager.getProperty("driverClass");    private static String url = ConfigManager.getProperty("url");    private static String username = ConfigManager.getProperty("username");    private static String password = ConfigManager.getProperty("password");    private static Connection con = null;    //静态代码块加载数据库驱动    static{        try{            Class.forName(driver);        }catch(ClassNotFoundException e){            e.printStackTrace();        }    }    //打开数据库连接    public static Connection getConnection(){        //Connection con = null;        try {            if(con == null || con.isClosed()){                con = DriverManager.getConnection(url,username,password);            }else{                return con;            }        } catch (SQLException e) {            e.printStackTrace();        }        return con;    }    /**     * 关闭连接     * @param con     * @param pstmt     * @param rs     */    public static void closeAll(Connection con, PreparedStatement pstmt,ResultSet  rs){        try {            if(rs != null && !rs.isClosed()){                rs.close();            }            if(pstmt != null && !pstmt.isClosed()){                pstmt.close();            }            if(con != null && !con.isClosed()){                con.close();            }        } catch (SQLException e) {            e.printStackTrace();        }    }}

·数据访问层的父类BaseDao.java

public class BaseDao {    private Connection conn = null;    public BaseDao(Connection conn){        this.conn = conn;    }    /**     * 增删改操作     * @param sql     * @param params     * @return  （1）数据操作语句DML的行数（2）对于无返回内容的sql语句返回0     */    public int executeUpdate(String sql, Object...params){  //Object...params 可变长的Object类型的数组        int result = 0;        PreparedStatement pstmt = null;//执行sql        try{            pstmt = conn.prepareStatement(sql);            if(params != null){                for(int i = 0; i < params.length; i++){                    pstmt.setObject(i+1, params[i]);                    //等价于pstmt.set类型(i+1, xxx);                }            }            result = pstmt.executeUpdate();//执行操作        }catch(SQLException e){            e.printStackTrace();        }finally{            JdbcUtils.closeAll(null, pstmt, null);        }        return result;    }    /**     * 查询操作，最后不关闭rs和pstmt     * @param sql     * @param params     * @return     */    public ResultSet executeQuery(String sql, Object...params){        PreparedStatement pstmt = null;        ResultSet rs = null;        try {            pstmt = conn.prepareStatement(sql);            if(params != null){                for(int i = 0; i < params.length; i++){                    pstmt.setObject(i+1, params[i]);                }            }            rs = pstmt.executeQuery();        } catch (SQLException e) {            e.printStackTrace();        }        return rs;    }}