09 dbutil 使用

JdbcUtil的改进(c3p0的使用)

public class JdbcUtil {
    //一个数据库只需要一个连接池对象,所以使用static 
    private static DataSource ds  = new ComboPooledDataSource(); 
    
    /**
     * 获取连接池对象方法
     */
    public static DataSource getDataSource(){
        return ds;
    }
    
    /**
     * 获取连接对象
     */
    public static Connection getConnection(){
        try {
            return ds.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
    
    //关闭顺序为ResultSet Statement Connection
    public static void close(Connection conn,Statement st){
        try {
            if (st!=null)
                st.close();
            if (conn!=null)
                conn.close();//如今的close是把连接对象放回连接池中
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    
    public static void close(Connection conn,Statement st,ResultSet rs){
        
        try {
            if (rs!=null)
                rs.close();
            close(conn,st);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
}

1. 导包

Paste_Image.png

2. update()的使用

public static void main(String[] args) {
        QueryRunner qr = new QueryRunner(JdbcUtil.getDataSource());
        
        try {
            qr.update("insert into employee values(?,?,?,?,?,?)", new Object[]{null,"dd",22,"贵州","13123225786","男"});
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

3. query()的使用

public class Demo2 {

    public static void main(String[] args) {
        QueryRunner qr = new QueryRunner(JdbcUtil.getDataSource());
        
        /**
         * ResultSetHandler接口: 用于把结果集封装成不同类型的对象
         *  ArrayHandler类: 把结果集的第一行结果封装成对象数组 
         *  ArrayListHandler类： 把结果集的每一行结果封装成对象数组，把每个对象数组放入List集合中
         *  BeanHandler类： 把结果集的第一行，封装成javabean对象(常用)
         *  BeanListHandler类： 把结果集的每行封装成javabean，把每个javabean放入List集合中（常用）
         *  ScalarHandler类：查询聚合函数(例如:count(*))  (常用)
         */
        //t1(qr);
        
        
        //t2(qr);
        
        //t3(qr);

        //t4(qr);
        
        try {
            long count = (Long)qr.query("select count(*) from student", new ScalarHandler(), new Object[]{});
            System.out.println(count);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void t4(QueryRunner qr) {
        try {
            List<Student> stu= (List<Student>)qr.query("select * from student", new BeanListHandler(Student.class), new Object[]{});
            for (Student student : stu) {
                System.out.println(student);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void t3(QueryRunner qr) {
        try {
            Student stu= (Student)qr.query("select * from student where id=?", new BeanHandler(Student.class), new Object[]{1});//获取第一个bean对象
            System.out.println(stu);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void t2(QueryRunner qr) {
        try {
            List<Object[]> values = (List<Object[]>)qr.query("select * from student", new ArrayListHandler(), new Object[]{});
            for (Object[] arr : values) {//行
                for (Object object : arr) {
                    System.out.print(object+"\t");
                }
                System.out.println();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void t1(QueryRunner qr) {
        try {
            Object[] values = (Object[])qr.query("select * from student", new ArrayHandler(), new Object[]{});
            for (Object object : values) {
                System.out.println(object);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    
}