jdbc 多个不确定参数的查询

public List<User> getList(User user)
		throws Exception
	{
		Connection conn = null;
		PreparedStatement pstm = null;
		ResultSet rs = null;
		List<User> result = new ArrayList<User>();
		StringBuffer sql = new StringBuffer().append("select * from table where sex = ? ");
		
		List<Object> list = new ArrayList<Object>();
		// 如果不确定部分的查询条件不为空值时，Sql增加查询条件
		//user 传递的Bean
		this.addStatement(user, list, sql);
		
		//ConnectionManager 定义的连接类
		conn = ConnectionManager.connectionDb();
		pstm = conn.prepareStatement(sql.toString());
		//参数和？绑定
		this.pstSetObject(pstm, list);
		
		System.out.println(sql.toString());
		//具体操作数据库套路就不罗嗦了 
		
		return result;
	}
	
	//判断查询条件是否为空，不为空时增加查询条件
	//user查询条件封装成的对象，sql 查询语句，list 存放查询条件对象
	private void addStatement(User user,List<Object> list,StringBuffer sql)
	{
		if(!"".equals(user.getUsername()))
		{
			sql.append("AND name = ? ");
			list.add(user.getUsername());
		}
		if(!"".equals(user.getPassword()))
		{
			sql.append("AND password = ? ");
			list.add(user.getPassword());
		}
		if(user.getAge() > 0 && user.getAge() < 120)
		{
			sql.append("AND age = ? ");
			list.add(user.getAge());
		}
	}
	
	//把条件作为参数传给PreparedStatement
	private void pstSetObject(PreparedStatement pstm,List<Object> list) throws SQLException
	{
		if(list != null)
		{
			for(int i = 0; i < list.size(); i++)
			{
				//+1 是因为有一个确定的参数，如果都为动态不确定的参数，可以多判断一下
				pstm.setObject(i + 1, list.get(i));
			}
		}
	}