Java簡單部落格系統(二)靜態頁面動態化顯示資料表內容
(一)準備工作
建立java Web專案基礎的四個package
將JSP相關庫和MySQL資料驅動包放到相應的目錄
下面列出com.java.util中的三個類的程式碼,在專案中經常用到,基本是參照java1234.com小鋒老師的專案程式碼稍作寫出來的。
public class DbUtil { //定義獲取資料庫連線的方法 private String dburl="jdbc:mysql://127.0.0.1:3306/db_blog?useSSL=false&serverTimezone=GMT"; private String username="root";private String password="root"; private String driver="com.mysql.cj.jdbc.Driver"; //mysql-connector-java-8.0.12.jar包需要放在WEB/INF/lib下 public Connection getConnection() throws Exception{ Class.forName(driver); Connection conn=DriverManager.getConnection(dburl,username,password);return conn; } //定義斷開連線的方法 public void closeConnection(Connection conn) throws SQLException{ if(conn!=null){ conn.close(); } }
}
public class StringUtil { public static boolean isEmpty(String str){ if(str==null||str.equals("")){return true; }else{ return false; } } public static boolean isNotEmpty(String str){ if(str!=null&&!str.equals("")){ return true; }else{ return false; } } }
public class DateUtil { public static String Date2String(Date date,String format){ String result=""; SimpleDateFormat sdf=new SimpleDateFormat(format); if(date!=null){ result=sdf.format(date); } return result; }//日期轉換成字串 public static Date String2Date(String str,String format) throws Exception{ if(StringUtil.isEmpty(str)){ return null; } SimpleDateFormat sdf=new SimpleDateFormat(format); return sdf.parse(str); }//字串轉換成日期 }
(二)實現思路——玩的是SQL遊戲,以blog部落格資訊的展示為例;
1.Blog.java類
私有域基本和資料表字段對應,在加上get和set方法。資料設計參看之前的部落格:
https://www.cnblogs.com/sanyun/p/9944249.html
public class Blog { private int blogId; private int userId; private String userName; private String title; private String content; private String blogType; private Date createTime; private int views=0; private int likes=0; private int comments=0; /** * @return the userName */ public String getUserName() { return userName; } /** * @param userName the userName to set */ public void setUserName(String userName) { this.userName = userName; } /* *下面省略了很多get,set方法,以上的私有域都應該有get,set方法*/ }
2.BlogDao類
因為首頁以各種現實現實部落格內容,以時間排序的,4小時內的,10天內的,所以DAO方法最好以SQL語句作為入參之一。
在這個類中,按照傳進來的SQL查詢資料庫,遍歷返回的結果集,結果集中每條記錄資訊儲存在一個Blog物件中(這就是前面Blog.java私有域和資料表字段一致的原因),將所有查詢出的結果初始化出一堆Blog物件,放入List中返回。
public class BlogDao { public List<Blog> queryBlog(Connection conn,String sql) throws Exception{ ArrayList<Blog> blogList=new ArrayList<>(); PreparedStatement stat=conn.prepareStatement(sql); ResultSet rs=stat.executeQuery(); while(rs.next()){ Blog blog=new Blog(); blog.setBlogId(rs.getInt("blogId")); //根據列名獲取列資料 blog.setBlogType(rs.getString("blogType")); blog.setContent(rs.getString("content")); blog.setLikes(rs.getInt("likes")); blog.setTitle(rs.getString("title")); blog.setUserId(rs.getInt("userId")); blog.setUserName(rs.getString("userName")); blog.setViews(rs.getInt("views")); blog.setCreateTime(DateUtil.String2Date(rs.getString("createTime"),"yyyy-MM-dd HH:mm:ss")); //將資料庫日期型別轉換成java日期型別 blogList.add(blog); } return blogList; } }
3.HomeServlet類
從前面靜態頁面的設計可以知道:
(1)連結面板:
查詢48小時內閱讀量最多的前10條部落格標題:
SELECT * FROM blog WHERE createTime BETWEEN SUBDATE(LOCALTIME(),2) AND LOCALTIME() ORDER BY views DESC LIMIT 0,10;
查詢2天內評論數最多的前10條部落格標題:
SELECT * FROM blog WHERE createTime BETWEEN SUBDATE(LOCALTIME(),10) AND LOCALTIME() ORDER BY likes DESC LIMIT 0,10;
查詢積分數最多的前20名部落格姓名:
SELECT * FROM USER ORDER BY points DESC LIMIT 0,20;
(2)頁面主體
按時間順序逆序查詢出部落格:
SELECT * FROM blog ORDER BY createTime DESC;
因此,在Servlet的doPost(HttpServletRequest request, HttpServletResponse response)方法中,主要做的工作是:
(1)查詢資料庫獲得部落格列表,不同的SQL語句部落格列表不一樣。
(2)重點是:將查詢出來的資訊列表作為請求的引數,以便被主頁(home.jsp)獲取。
(3)forward跳轉到主頁home.jsp:request.getRequestDispatcher("home.jsp").forward(request, response);
步驟(1),(2)程式碼如下
private void showNavContent(HttpServletRequest request, HttpServletResponse response) { // TODO Auto-generated method stub //左邊面板顯示的列表資訊 Connection conn=null; try { conn=dbutil.getConnection(); String sql="SELECT * FROM blog WHERE createTime BETWEEN SUBDATE(LOCALTIME(),2) AND LOCALTIME() ORDER BY views DESC LIMIT 0,10; "; List<Blog> viewsMoreblogList=blogDao.queryBlog(conn,sql); request.setAttribute("viewsMoreblogList", viewsMoreblogList); sql="SELECT * FROM blog WHERE createTime BETWEEN SUBDATE(LOCALTIME(),10) AND LOCALTIME() ORDER BY likes DESC LIMIT 0,10; "; List<Blog> likesMoreblogList=blogDao.queryBlog(conn,sql); request.setAttribute("likesMoreblogList", likesMoreblogList); sql="SELECT * FROM USER ORDER BY points DESC LIMIT 0,20;"; List<User> userList=userDao.queryUser(conn,sql); request.setAttribute("userList", userList); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } }
private void showBlogsByTime(HttpServletRequest request,HttpServletResponse response){ Connection conn=null; try { conn=dbutil.getConnection(); String sql="SELECT * FROM blog ORDER BY createTime DESC;"; //mySQL不支援top語法 List<Blog> latestBlogList=blogDao.queryBlog(conn, sql); for(Blog blog:latestBlogList){ int num=commentDao.getCommentNumByBlogId(conn,blog.getBlogId()); blog.setComments(num); //評論數 } request.setAttribute("blogList", latestBlogList); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } }
4.主頁home.jsp顯示資料表內容
(1)匯入JSP標籤庫
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%> <%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
(2)獲取請求屬性中的內容,主要使用JSP的c:forEach標籤將部落格列表資訊顯示出來
例如連結面板顯示的“48小時閱讀排行榜””
靜態
<div class="data_list"> <div class="list_header">48小時閱讀排行榜</div> <div class="list"> <ul> <li><a href="#">程式設計師,你焦慮嗎?</a></li> <li><a href="#">國內開源社群鉅作AspectCore-Framework入門</a></li> ... </ul> </div> </div
動態
<div class="data_list"> <div class="list_header"><a href="Home?action=showByViews">48小時閱讀排行榜</a></div> <div class="list"> <ul> <c:forEach var="vblog" items="${viewsMoreblogList}"> <li><a href="#">${fn:substring(vblog.title,0,20)}</a></li> </c:forEach> </ul> </div> </div>
又比如,部落格列表動態化之後如下所示:
<div class="blogContent"> <c:forEach var="blog" items="${blogList}"> <div class="blogItem"> <div class="digg"> <div class="diggit"> <span class="diggnum"> ${blog.likes}</span> <!-- 推薦數 --> </div> <div class="clear"></div> <!-- 中間隔開的空白 --> <div class="digg_tip"><span class="glyphicon glyphicon-thumbs-up" aria-hidden="true"></span> 推薦</div> <div class="digg_text" id="message"></div> </div> <div class="item_body"> <div class="title"><a href="#">${blog.title}</a></div> <div class="abstract"><p>${fn:substring(blog.content,0,200)}...<p></span></div> <div class="footer"><a>${blog.userName}</a> <fmt:formatDate value="${blog.createTime}" type="date" pattern="yyyy-MM-dd HH:mm:ss"/> <span class="glyphicon glyphicon-comment" aria-hidden="true"></span> 評論(${blog.comments}) <span class="glyphicon glyphicon-eye-open" aria-hidden="true"></span> 閱讀(${blog.views})</div> <!-- 注意格式化串一定要正確 --> </div> </div> </c:forEach> </div>
上面有很些細節的地方
截斷部落格內容顯示200字:${fn:substring(blog.content,0,200)}
日期格式化:<fmt:formatDate value="${blog.createTime}" type="date" pattern="yyyy-MM-dd HH:mm:ss"/>
到這裡,整個主頁功能就基本實現了。