递归构建tree

class ClientTreeReader {

	private StringBuffer sbTree = new StringBuffer();
	
	public String read() {
		Connection conn = null;
		try {
			conn = DBUtil.getConnection();
			read(conn, 0, 0);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBUtil.closeAll(null, null, conn);
		}
		return sbTree.toString();
	}
	
	private void read(Connection conn, int id, int level)
		throws SQLException {
		String sql = "select * from t_client where pid=?";
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			rs = pstmt.executeQuery();
			while (rs.next()) {
				
				//加入div标签
				sbTree.append("<div>");
				sbTree.append("\n");
				//加缩进
				for (int i = 0; i < level; i++) {
					sbTree.append("<img src=\"../images/white.gif\">");
					sbTree.append("\n");
				}
				
				//如果不是叶子节点，递归查询子节点
				if (Constant.NO.equals(rs.getString("is_leaf"))) {
					//加入加号图片
					sbTree.append("<img alt=\"展开\" style=\"cursor:hand;\" onClick=\"display('" + rs.getInt("id")
							+ "');\" id=\"img" + rs.getInt("id") + "\" src=\"../images/plus.gif\">");
					sbTree.append("\n");
					//加入关闭的文件夹图片
					sbTree.append("<img id=\"im" + rs.getInt("id") + "\" src=\"../images/closedfold.gif\">");
					sbTree.append("\n");
					//加入a标签
					sbTree.append("<a href=\"client_node_crud.jsp?id=" + rs.getInt("id") + "\" target=\"clientDispAreaFrame\">");
					//拼接字符串内容
					sbTree.append(rs.getString("name")).append("<br>");
					//a结束标签
					sbTree.append("</a>");
					sbTree.append("\n");
					//加入隐藏的div标签
					sbTree.append("<div id=div" + rs.getInt("id") + " style='display: none;'>");
					sbTree.append("\n");
					read(conn, rs.getInt("id"), level + 1);
				} else {
					//加入减号图片和打开的文件夹图片
					sbTree.append("<img src=\"../images/minus.gif\">")
						.append("<img src=\"../images/openfold.gif\">");
					sbTree.append("\n");
					//加入a标签
					if (Constant.NO.equals(rs.getString("is_client"))) {
						//如果不是分销商，链接地址为client_node_crud.html
						sbTree.append("<a href=\"client_node_crud.jsp?id=" + rs.getInt("id") + "\" target=\"clientDispAreaFrame\">");
					} else {
						//如果不是分销商，链接地址为client_crud.html
						sbTree.append("<a href=\"client_crud.jsp?id=" + rs.getInt("id") + "\" target=\"clientDispAreaFrame\">");
					}
					//拼接字符串内容
					sbTree.append(rs.getString("name")).append("<br>");
					//a结束标签
					sbTree.append("</a>");
					sbTree.append("\n");
					//加入隐藏div标签
					sbTree.append("<div id=div" + rs.getInt("id") + " style='display: none;'>");
					sbTree.append("\n");
				}
				
				//div结束标签
				sbTree.append("</div></div>\n");
				
			}
		} finally {
			DBUtil.closeAll(rs, pstmt, null);
		}
	}
	
	public static void main(String[] args) {
		ClientTreeReader ctr = new ClientTreeReader();
		System.out.println(ctr.read());
	}
}