数据库连接池，DBUtil的模板，dbcp，c3p0

数据库连接池，DBUtil的模板，Druid使用(重点)

一、DBUtil模板

public class DBUtilTest {

    public static Connection connection;
    public static final String URL = "jdbc:mysql:///demo";
    public static final String USERNAME = "";
    public static final String PASSWORD = "";

    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static void testQuery() throws SQLException {
        connection = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        String sql = "select * from emp where id = ?";
        QueryRunner runner = new QueryRunner();
        Emp query = runner.query(connection, sql, new BeanHandler<Emp>(Emp.class), 1);
        System.out.println(query);
    }

    public static void testQuery2() throws SQLException {
        connection = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        String sql = "select * from emp";
        QueryRunner runner = new QueryRunner();
        List<Emp> query = runner.query(connection, sql, new BeanListHandler<Emp>(Emp.class));
        query.forEach((x)->{
            System.out.println(x);
        });
    }

    public static void insert() throws SQLException {
        connection = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        String sql = "insert emp values(null,?,?)";
        QueryRunner runner = new QueryRunner();
        runner.update(connection,sql,1,2);
    }
    public static void main(String[] args) throws SQLException {
        testQuery2();
    }
}

二、数据库连接池

数据库连接池是为了减少频繁开关连接的时间，分析应该具备几个属性

1.初始大小

2.每次扩容大小

3.连接池最大个数

4.空闲连接死亡时间

各种数据库连接池

• DBCP
• C3P0
• Druid
• hikariCP

2.1.DBCP模板

public static void main(String[] args) throws SQLException {
        // 数据库连接池资源
        BasicDataSource basicDataSource = new BasicDataSource();
        basicDataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
        basicDataSource.setUrl("jdbc:mysql:///demo");
        basicDataSource.setUsername("");
        basicDataSource.setPassword("");

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet rs = null;

        connection = basicDataSource.getConnection();
        String sql = "select * from emp";
        preparedStatement = connection.prepareStatement(sql);
        rs = preparedStatement.executeQuery();
        while (rs.next()){
            System.out.println(rs.getInt(1)+
                    rs.getString(2)+
                    rs.getString(3));
        }
        connection.close();
    }

2.2.C3P0

public static void main(String[] args) throws PropertyVetoException, SQLException {
    ComboPooledDataSource cpds = new ComboPooledDataSource();
    cpds.setDriverClass( "com.mysql.cj.jdbc.Driver" ); //loads the jdbc driver
    cpds.setJdbcUrl( "jdbc:mysql://120.78.206.78:3306/demo" );
    cpds.setUser("root");
    cpds.setPassword("Root123..");
    cpds.setMaxStatements( 180 );
    Connection conn = cpds.getConnection();
    System.out.println(conn);
    conn.close();
}

第二种参照官网，进行xml配置

2.3.druid

druid是性能最好的数据库连接池

dbcp和c3p0区别，c3p0会自动回收不使用的连接