java web--页面分页技术

你的名字 2023-02-15 00:23 2阅读 0赞

在设计信息浏览页面时，如果信息量很大，则经常需要分页显示信息。在这种情况下，分页技术就可以很好的帮助到我们。

**目录**

1.分页技术的设计思想

2.分页的具体实现

3.分页实例

--------------------

### 1.分页技术的设计思想 ###

按照“表示层--控制层--DAO层--数据层”的分层设计思想：首先DAO对象提供分页查询的方法；在控制层调用DAO中的方法完成指定页数据的查询；然后在表示层通过EL表达式和JSTL将该页数据显示出来。

### 2.分页的具体实现 ###

①在DAO对象中提供两个方法用来计算总页数和查询指定页数据。

②控制层提供一个servlet类，调用DAO对象查询数据并指派页面显示数据。

③输出页面使用EL和JSTL显示查询结果

### 3.分页实例 ###

User.java--暂时记录信息

package bean2;
    
    public class User {
    	private String id;
    	private String name;
    	private String sex;
    	public User() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	public User(String id, String name, String sex) {
    		super();
    		this.id = id;
    		this.name = name;
    		this.sex = sex;
    	}
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getSex() {
    		return sex;
    	}
    	public void setSex(String sex) {
    		this.sex = sex;
    	}
    	
    }

JdbcUtil.java--连接数据库

package bean2;
    
    import java.io.IOException;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.Properties;
    
    public class JdbcUtil {
    	private static String driver;
    	private static String url;
    	private static String user;
    	private static String password;
    	private static Properties pr=new Properties();
    	public JdbcUtil(){
    		super();
    	}
    	static 
    	{
    		try {
    			pr.load(JdbcUtil.class.getClassLoader().getResourceAsStream("db.properties"));
    		    driver=pr.getProperty("driver");
    		    url=pr.getProperty("url");
    		    user=pr.getProperty("user");
    		    password=pr.getProperty("password");
    		    try {
    				Class.forName(driver);
    			} catch (ClassNotFoundException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    	public static Connection getConnection() throws SQLException
    	{
    		return DriverManager.getConnection(url,user,password);
    	}
    	public static void free(Connection conn,Statement pstmt,ResultSet rs) throws Exception
    	{
    		if(conn!=null){conn.close();}
    		if(pstmt!=null){pstmt.close();}
    		if(rs!=null){rs.close();}
    	}
    }

db.properties--记录数据库信息

driver=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost:3306/ccc?useUnicode=true&characterEncoding=UTF-8
    user=root
    password=2411030483

UserDao.java--定义功能

package bean2;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    
    public class UserDao {
    public int getPageCount() throws Exception{
    	int recordCount=0,t1=0,t2=0;
    	Connection conn=JdbcUtil.getConnection();
    	String sql="select count(*) from student";
    	PreparedStatement pstmt=conn.prepareStatement(sql);
    	ResultSet rs=pstmt.executeQuery();
    	rs.next();
    	recordCount=rs.getInt(1);
    	t1=recordCount%5;
    	t2=recordCount/5;
    	JdbcUtil.free(conn, pstmt, rs);
    	return t1==0?t2:t2+1;
    }
    public List<User> listUser(int pageNo) throws Exception{
    	int pageSize=5;
    	int startRecno=(pageNo-1)*pageSize;
    	ArrayList<User> userList=new ArrayList<User>();
    	Connection conn=JdbcUtil.getConnection();
    	String sql="select * from student order by id limit ?,?";
    	PreparedStatement pstmt=conn.prepareStatement(sql);
    	pstmt.setInt(1,startRecno);
    	pstmt.setInt(2, pageSize);
    	ResultSet rs=pstmt.executeQuery();
    	while(rs.next()){
    		User user=new User();
    		user.setId(rs.getString(1));
    		user.setName(rs.getString(2));
    		user.setSex(rs.getString(3));
    		userList.add(user);
    	}
    	JdbcUtil.free(conn, pstmt, rs);
    	return userList;
    }
    }

page.java--servlet类，用以完成最终的功能调用

package bean2;
    
    import java.io.IOException;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /**
     * Servlet implementation class page
     */
    @WebServlet("/page")
    public class page extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        /**
         * @see HttpServlet#HttpServlet()
         */
        public page() {
            super();
            // TODO Auto-generated constructor stub
        }
    
    	/**
    	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		int pageNo=1;
    		int pagesize=1;
    		String strPageNo=request.getParameter("pageNo");
    		if(strPageNo!=null){
    			pageNo=Integer.parseInt(strPageNo);
    		}
    		UserDao userDao=new UserDao();
    		try {
    			List<User> userlist=userDao.listUser(pageNo);
    			request.setAttribute("userlist", userlist);
    			Integer pageCount=new Integer(userDao.getPageCount());
    			request.setAttribute("pageCount", pageCount);
    			request.setAttribute("pageNo", pageNo);
    			request.getRequestDispatcher("userlist.jsp").forward(request, response);
    		} catch (Exception e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		
    	}
    
    	/**
    	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doGet(request, response);
    	}
    
    }

tiaozhuan.jsp--跳转页面，可以不使用，如果不使用的话，需要直接运行servlet类，来获取页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>跳转页面</title>
    </head>
    <body>
    <p>跳转页面</p>
    <hr>
    <form action="page" method="post">
    <table><tr><td>
    <input type="submit" value="发送"></td><td>
    <input type="reset" value="取消">
    </td></tr>
    </table>
    </form>
    </body>
    </html>

userlist.jsp--显示页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
            <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>用户列表</title>
    <style>
    th,td{width:150px;border:2px solid gray;text-align:center;padding:2px 10px;}
    table{border-collapse:collapse;}
    body{text-align:center;}
    a{text-decoration:none;}
    </style>
    </head>
    <body>
    <c:if test="${pageCount>0}">
    <h2>所有用户信息</h2>
    共有${pageCount}页，这是第${pageNo}页
    <c:if test="${pageNo>1}">
    <a href="page?pageNo=1">第一页</a>
    <a href="page?pageNo=${pageNo-1}">上一页</a>
    </c:if>
    <c:if test="${pageNo!=pageCount}">
    <a href="page?pageNo=${pageNo+1}">下一页</a>
    <a href="page?pageNo=${pageCount}">最后一页</a>
    </c:if>
    <table align="center">
    <tr><th>用户编号</th><th>用户名</th><th>性别</th></tr>
    <c:forEach items="${userlist }" var="user">
    <tr><td>${user.id }</td><td>${user.name }</td><td>${user.sex }</td></tr>
    </c:forEach>
    </table>
    <br>
    </c:if>
    <c:if test="${pageCount==0}">
    <p>目前没有记录</p>
    </c:if>
    </body>
    </html>

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