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1.c3p0的使用	public static void main(String[] args) throws SQLException {		QueryRunner qr = JDBCUtil.getQueryRunner();		String sql = "select * from t_emp where id=?";//一个对象		String sql2 = "select * from t_emp where id in(?,?,?)";		Emp emp = qr.query(sql, new BeanHandler
   
    (Emp.class),2);		List
    
      list = qr.query(sql2, new BeanListHandler
     
      (Emp.class),2,3,5);		System.out.println(emp);		System.out.println("-----------------");		for (Emp emp2 : list) {			System.out.println(emp2);		}	}//1.根据用户名查询用户是否存在	@Override	public User findUserByName(String name) throws SQLException {		QueryRunner qr = JDBCUtil.getQueryRunner();		String sql = "select * from t_user where uname=?";		return qr.query(sql, new BeanHandler
      
       (User.class),name);	}	//2.添加用户	@Override	public int addUser(User user) throws SQLException {		QueryRunner qr = JDBCUtil.getQueryRunner();		String sql = "insert into t_user(uname,pwd,mobile,utype) values(?,?,?,?)";		Object [] params = {user.getUname(),user.getPwd(),user.getMobile(),user.getUtype()};		return qr.update(sql,params);	}	//3.登录验证用户名	@Override	public User findUserForLogin(User user) throws SQLException {		QueryRunner qr = JDBCUtil.getQueryRunner();		String sql = "select * from t_user where uname=? and pwd=? and utype=?";		Object [] params = {user.getUname(),user.getPwd(),user.getUtype()};		return qr.query(sql, new BeanHandler
       
        (User.class),params);	}2.	//1.查询所有	@Test  //单元测试	public void demo1() throws SQLException {		QueryRunner qr = JDBCUtil.getQueryRunner();		String sql = "select * from t_emp";		List
        
          list = qr.query(sql, new BeanListHandler
         
          (Emp.class)); for (Emp emp : list) { System.out.println(emp); } //BeanListHandler对象的集合 } //2.查询指定的条件（一个或多个条件） @Test public void demo2() throws SQLException { QueryRunner qr = JDBCUtil.getQueryRunner(); /*String sql = "select * from t_emp where id=?"; Emp emp = qr.query(sql, new BeanHandler
          
           (Emp.class),3L); System.out.println(emp);*/ String sql2 = "select * from t_emp where deptid=? and gender=?"; List
           
             list = qr.query(sql2, new BeanListHandler
            
             (Emp.class),1L,"男"); for (Emp emp2 : list) { System.out.println(emp2); } } //3.查询指定的列 @Test public void demo3() throws SQLException { QueryRunner qr = JDBCUtil.getQueryRunner(); String sql = "select ename from t_emp"; List
             
               enames = qr.query(sql, new ColumnListHandler
              
               ()); for (String ename : enames) { System.out.println(ename); } String sql2 = "select ename,salary from t_emp"; List
               
                 list = qr.query(sql2, new BeanListHandler
                
                 (Emp.class)); for (Emp emp : list) { System.out.println(emp); } System.out.println("----------------------------"); List
                 
                   enames = qr.query(sql2, new ColumnListHandler
                  
                   ("ename")); for (String ename : enames) { System.out.print(ename+"\t"); } System.out.println("-----------------------------"); List
                   
                     salarys = qr.query(sql2, new ColumnListHandler
                    
                     ("salary")); for (Double salary : salarys) { System.out.print(salary+"\t"); } } //4.组函数查询 @Test public void demo4() throws SQLException { QueryRunner qr = JDBCUtil.getQueryRunner(); String sql = "select count(*) from t_emp"; Long count = qr.query(sql, new ScalarHandler
                     
                      ()); System.out.println(count); String sql2 = "select max(salary),min(salary),avg(salary) as avg from t_emp"; Double max = qr.query(sql2, new ScalarHandler
                      
                       (1)); Double min = qr.query(sql2, new ScalarHandler
                       
                        (2)); Double avg = qr.query(sql2, new ScalarHandler
                        
                         ("avg")); 或 Double avg = qr.query(sql2, new ScalarHandler
                         
                          (3)); System.out.println(max); System.out.println(min); System.out.println(avg); } // 4.1查询商品总记录数 @Override public Long findCount(String keyword) throws SQLException { QueryRunner qr = JDBCUtil.getQueryRunner(); String sql = "select count(*) from t_product where info like ?"; return qr.query(sql, new ScalarHandler
                          
                           (), "%" + keyword + "%"); } //5.多表查询 @Test public void demo5() throws SQLException { QueryRunner qr = JDBCUtil.getQueryRunner(); String sql = "select e.*,d.dname from t_emp e,dept d where e.deptid=d.id"; List
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    
   

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