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通用分页功能

2022-07-25 23:02:00 【一只奈良森屿】

目录

总体思路：

优化之前代码：

1.首先编写一个实体类：

2.DButil类，用于连接数据库

3.PageBean类

4.BaseDao类

5.StudentDdao类，继承BaseDao\

运行结果：

优化之后代码（封装成一个标签库）：

1.编写tag类：

2.编写tld文件：

3.在jsp页面，调用运行

总体思路：

1） 为了提高查询性能及节约网络流量，每次只查询指定的记录数，而不是全部，
在数量比较大时很有用
2）当点击下一页或指定页面的数据时，将带着所有的查询条件，再次执行查询

优化之前代码：

1.首先编写一个实体类：

package com.zking.reflect;

public class Student {
	private int sid;

	private String sname;

	public Integer age;
	
	private double score;
	
	private String clazz;
	
	public double getScore() {
		return score;
	}

	public void setScore(double score) {
		this.score = score;
	}

	public String getClazz() {
		return clazz;
	}

	public void setClazz(String clazz) {
		this.clazz = clazz;
	}

	
	public Student(int sid, String sname, Integer age, double score, String clazz) {
		super();
		this.sid = sid;
		this.sname = sname;
		this.age = age;
		this.score = score;
		this.clazz = clazz;
	}


	static{
		System.out.println("加载进jvm中！");
	}

	public Student() {
		super();
		System.out.println("调用无参构造方法创建了一个学生对象");
	}

	public Student(int sid) {
		super();
		this.sid = sid;
		System.out.println("调用带一个参数的构造方法创建了一个学生对象");
	}

	@Override
	public String toString() {
		return "Student [sid=" + sid + ", sname=" + sname + ", age=" + age + "]";
	}

	public Student(int sid, String sname) {
		super();
		this.sid = sid;
		this.sname = sname;
		System.out.println("调用带二个参数的构造方法创建了一个学生对象");
	}

	@SuppressWarnings("unused")
	private Student(Integer age) {
		System.out.println("调用Student类私有的构造方法创建一个学生对象");
		this.age = age;
	}

	public int getSid() {
		return sid;
	}

	public void setSid(int i) {
		this.sid = i;
	}

	public String getSname() {
		return sname;
	}

	public void setSname(String sname) {
		this.sname = sname;
	}

	public void hello() {
		System.out.println("你好！我是" + this.sname);
	}

	public void hello(String name) {
		System.out.println(name + "你好！我是" + this.sname);
	}

	@SuppressWarnings("unused")
	private Integer add(Integer a, Integer b) {
		return new Integer(a.intValue() + b.intValue());
	}
}

2.DButil类，用于连接数据库

package com.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public final class DBUtil {

	private static String DRIVER_NAME = "com.mysql.jdbc.Driver";

	private static String DB_URL = "jdbc:mysql://localhost:3306/t234?useUnicode=true&characterEncoding=utf-8&useSSL=false";

	private static String DB_USER = "root";

	private static String DB_PASSWORD = "123456";

	private DBUtil() {
	}

	static {
		try {
			Class.forName(DRIVER_NAME);

		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}

	public static Connection getConection() throws SQLException {
		Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
		return connection;
	}

	public static void closeDB(ResultSet rs, Statement ps, Connection con) {

		try {
			if (rs != null && !rs.isClosed()) {
				rs.close();
			}

			if (ps != null && !ps.isClosed()) {
				ps.close();
			}

			if (con != null && !con.isClosed()) {
				con.close();
			}

		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	public static void closeDB(ResultSet rs, Statement ps) {

		try {
			if (rs != null && !rs.isClosed()) {
				rs.close();
			}

			if (ps != null && !ps.isClosed()) {
				ps.close();
			}

		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

}

3.PageBean类

package com.util;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import com.mysql.jdbc.StringUtils;

public class PageBean {

	/**
	 * 页码
	 */
	private int page = 1;

	/**
	 * 每页显示的记录数
	 */
	private int rows = 10;

	/**
	 * 总记录数
	 */
	private int total = 0;

	/**
	 * 是否分页
	 */
	private boolean pagination = true;

	/**
	 * 记录查询的url，以便于点击分页时再次使用
	 */
	private String url;

	/**
	 * 存放请求参数，用于生成隐藏域中的元素
	 */
	private Map<String, String[]> parameterMap;

	/**
	 * 根据传入的Request初始化分页对象
	 * 
	 * @param request
	 */
	public void setRequest(HttpServletRequest request) {
		//每一次查询获取页码
		if (!StringUtils.isNullOrEmpty(request.getParameter("page"))) {
			this.page = Integer.valueOf(request.getParameter("page"));
		}
		//每一页的显示条数
		if (!StringUtils.isNullOrEmpty(request.getParameter("rows"))) {
			this.rows = Integer.valueOf(request.getParameter("rows"));
		}
		//是否分页
		if (!StringUtils.isNullOrEmpty(request.getParameter("pagination"))) {
			this.pagination = Boolean.valueOf(request.getParameter("pagination"));
		}

		this.url = request.getRequestURI();
		this.parameterMap = request.getParameterMap();

		request.setAttribute("pageBean", this);
	}

	public int getPage() {
		return page;
	}

	public void setPage(int page) {
		this.page = page;
	}

	public int getRows() {
		return rows;
	}

	public void setRows(int rows) {
		this.rows = rows;
	}

	public int getTotal() {
		return total;
	}

	public void setTotal(int total) {
		this.total = total;
	}

	public boolean isPagination() {
		return pagination;
	}

	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public Map<String, String[]> getParameterMap() {
		return parameterMap;
	}

	public void setParameterMap(Map<String, String[]> parameterMap) {
		this.parameterMap = parameterMap;
	}
	
	// 计算起始页码，从0开始，每一页显示10条数据
	//0--9  (1-1)*10
	//10--19	(2-1)*10
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

	// 获取总页数,如果判断！=0（存在余数），那么就会加一行显示多余的条数
	public int getTotalPage() { 
		if (this.getTotal() % this.rows == 0) {
			return this.getTotal() / this.rows;
		} else {
			return this.getTotal() / this.rows + 1;
		}
	}

	// 上一页，如果判断-1后>0，那么就可以进行上一页
	public int getPreviousPage() {
		return this.page - 1 > 0 ? this.page - 1 : 1;
	}

	// 下一页，如果判断+1后>总页数，那么就不可以进行下一页
	public int getNextPage() {
		return this.page + 1 > getTotalPage() ? getTotalPage() : this.page + 1;
	}

}

4.BaseDao类

package com.util;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import com.mysql.jdbc.StringUtils;

public class PageBean {

	/**
	 * 页码
	 */
	private int page = 1;

	/**
	 * 每页显示的记录数
	 */
	private int rows = 10;

	/**
	 * 总记录数
	 */
	private int total = 0;

	/**
	 * 是否分页
	 */
	private boolean pagination = true;

	/**
	 * 记录查询的url，以便于点击分页时再次使用
	 */
	private String url;

	/**
	 * 存放请求参数，用于生成隐藏域中的元素
	 */
	private Map<String, String[]> parameterMap;

	/**
	 * 根据传入的Request初始化分页对象
	 * 
	 * @param request
	 */
	public void setRequest(HttpServletRequest request) {
		//每一次查询获取页码
		if (!StringUtils.isNullOrEmpty(request.getParameter("page"))) {
			this.page = Integer.valueOf(request.getParameter("page"));
		}
		//每一页的显示条数
		if (!StringUtils.isNullOrEmpty(request.getParameter("rows"))) {
			this.rows = Integer.valueOf(request.getParameter("rows"));
		}
		//是否分页
		if (!StringUtils.isNullOrEmpty(request.getParameter("pagination"))) {
			this.pagination = Boolean.valueOf(request.getParameter("pagination"));
		}

		this.url = request.getRequestURI();
		this.parameterMap = request.getParameterMap();

		request.setAttribute("pageBean", this);
	}

	public int getPage() {
		return page;
	}

	public void setPage(int page) {
		this.page = page;
	}

	public int getRows() {
		return rows;
	}

	public void setRows(int rows) {
		this.rows = rows;
	}

	public int getTotal() {
		return total;
	}

	public void setTotal(int total) {
		this.total = total;
	}

	public boolean isPagination() {
		return pagination;
	}

	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public Map<String, String[]> getParameterMap() {
		return parameterMap;
	}

	public void setParameterMap(Map<String, String[]> parameterMap) {
		this.parameterMap = parameterMap;
	}
	
	// 计算起始页码，从0开始，每一页显示10条数据
	//0--9  (1-1)*10
	//10--19	(2-1)*10
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

	// 获取总页数,如果判断！=0（存在余数），那么就会加一行显示多余的条数
	public int getTotalPage() { 
		if (this.getTotal() % this.rows == 0) {
			return this.getTotal() / this.rows;
		} else {
			return this.getTotal() / this.rows + 1;
		}
	}

	// 上一页，如果判断-1后>0，那么就可以进行上一页
	public int getPreviousPage() {
		return this.page - 1 > 0 ? this.page - 1 : 1;
	}

	// 下一页，如果判断+1后>总页数，那么就不可以进行下一页
	public int getNextPage() {
		return this.page + 1 > getTotalPage() ? getTotalPage() : this.page + 1;
	}

}

5.StudentDdao类，继承BaseDao\

package com.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

import com.mysql.jdbc.StringUtils;
import com.zking.reflect.Student;

public class StudentDao extends BaseDao {

	public List<Student> getStudents02(String sname, PageBean pageBean) {
		String sql = "select * from t_student t ";
		List<Object> param = new ArrayList<>();
		if (!StringUtils.isNullOrEmpty(sname)) {
			sql += "where sname like ?";
			param.add(sname + "%");
		}
		List<Student> list = this.query(sql, param.toArray(), pageBean, new IConvert<Student>() {

			@Override
			public List<Student> convert(ResultSet rs) throws SQLException {
				List<Student> list = new ArrayList<>();
				while (rs.next()) {
					Student stu = new Student();
					stu.setSid(rs.getInt("sid"));
					stu.setSname(rs.getString("sname"));
					stu.setScore(rs.getDouble("score"));
					stu.setClazz(rs.getString("class"));
				}
				return list;
			}
		});
		return list;
	}

	public static void main(String[] args) {
		StudentDao dao = new StudentDao();
		PageBean pageBean = new PageBean();
		pageBean.setRows(5);
		List<Student> students = dao.getStudents02("张", new PageBean());
		students.forEach(s -> System.out.println(s));
	}

}

运行结果：

 

优化之后代码（封装成一个标签库）：

1.编写tag类：

package com.zking.tag;

import java.io.IOException;
import java.util.Map;

import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;

import com.util.PageBean;

public class PagingTag extends BodyTagSupport {

	private PageBean pageBean;

	public void setPageBean(PageBean pageBean) {
		this.pageBean = pageBean;
	}

	@Override
	public int doStartTag() {
		JspWriter out = this.pageContext.getOut();
		try {
			out.print(buildHtml());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		return SKIP_BODY;

	}

	// 动态生成分页html元素
	private String buildHtml() {

		String pagingToll = "<div style=\"text-align: right; width: 98%;\">\r\n" + "		第" + pageBean.getPage()
				+ "页&nbsp;&nbsp;&nbsp; 共" + pageBean.getTotalPage() + "条记录&nbsp;&nbsp;&nbsp;\r\n"
				+ "		<a href=\"javascript:goPage(1)\">首页</a>&nbsp;&nbsp;&nbsp; <a\r\n"
				+ "			href=\"javascript:goPage(" + pageBean.getPreviousPage() + ")\">上页</a>&nbsp;&nbsp;&nbsp;\r\n"
				+ "		<a href=\"javascript:goPage(" + pageBean.getNextPage() + ")\">下页</a>&nbsp;&nbsp;&nbsp;\r\n"
				+ "		<a href=\"javascript:goPage(" + pageBean.getTotalPage() + ")\">尾页</a>&nbsp;&nbsp;&nbsp;\r\n"
				+ "		第<input type=\"text\" size=\"2\" id=\"pageNumber\"\r\n"
				+ "			onkeyup=\"toPage(event,this.value)\" /> <a href=\"javascript:goPage(docment.getElementById('pageNumber').value)\">GO</a>" + "	</div>";
		// 用于隐藏表单，用于分页查询
		String hiddenForm = "<form action=\"" + pageBean.getUrl()
				+ " id=\"pagingForm\" method=\"post\"><form action=\"${pageBean.url}\" id=\"pagingForm\" method=\"post\">";
		hiddenForm += "<input type=\" hidden\" name=\"page\" value=\"" + pageBean.getPage() + "\" />";
		// 获取到所有的查询参数
		Map<String, String[]> parameterMap = pageBean.getParameterMap();
		// 数组就相当于你的爱好，那么爱好就包括，唱跳，rap，篮球。。。
		for (Map.Entry<String, String[]> param : parameterMap.entrySet()) {
			// 获取所有的键、值
			String paramName = param.getKey();
			if ("page".equals(paramName))
				continue;
			String[] values = param.getValue();
			for (String val : values) {
				hiddenForm += "<input type=\" hidden\" name=\"" + paramName + "\" value=\"" + val + "\" />";
			}
			hiddenForm += "</form>";
		}

		String js = "<script type=\"text/javascript\">\r\n" + "		function goPage(pageNum) {\r\n"
				+ "			let form = document.getElementById = (\"pagingForm\");\r\n"
				+ "			form.page.value = pageNum;\r\n" + "			form.submit();\r\n" + "		}\r\n"
				+ "		function toPage(e, pageNum) {\r\n" + "			if (e.keyCode == 13) {\r\n"
				+ "				goPage(pageNum);\r\n" + "			}\r\n" + "		}\r\n" + "	</script>";
		return pagingToll + hiddenForm + js;
	}
}

2.编写tld文件：

<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
   "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!-- 标签库描述符 -->
<taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor">
	<tlib-version>1.0</tlib-version>
	<jsp-version>1.2</jsp-version>
	<short-name>Simple Tags</short-name>
	<uri>/nlsy</uri>

	<tag>
		<name>out</name>
		<tag-class>com.zking.tag.OutTag</tag-class>
		<body-content>empty</body-content>
		<attribute>
			<name>val</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<description>out标签val属性，用于输出val的值</description>
		</attribute>
		<attribute>
			<name>defaultVal</name>
			<required>false</required>
			<rtexprvalue>false</rtexprvalue>
			<description>用于定义默认值</description>
		</attribute>
	</tag>

	<tag>
		<name>if</name>
		<tag-class>com.zking.tag.IfTag</tag-class>
		<body-content>jsp</body-content>
		<attribute>
			<name>test</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<description>if标签</description>
		</attribute> 
	</tag>
	<tag>
		<name>foreach</name>
		<tag-class>com.zking.tag.ForeachTag</tag-class>
		<body-content>jsp</body-content>
		<attribute>
			<name>items</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>var</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
	</tag>
	<tag>
	<name>paging</name>
	<tag-class>com.zking.tag.PagingTag</tag-class>
	<body-content>empty</body-content>
	<description>分页标签</description>
	<attribute>
		<name>pageBean</name>
		<required>true</required>
		<rtexprvalue>true</rtexprvalue>
	</attribute>
	</tag>
</taglib>

3.在jsp页面，调用运行

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@taglib prefix="n" uri="/nlsy"%>
<!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>Insert title here</title>
</head>
<body>
	<h1>学生信息</h1>

	<form action="<%=request.getContextPath()%>/students" method="post">
		<input type="text" name="sname"> <input type="submit"
			value="查询">
	</form>

	<table border="1" style="width: 98%;">

		<tr>
			<td>学号</td>
			<td>姓名</td>
			<td>年龄</td>
			<td>备注</td>
		</tr>

		<c:forEach items="${students}" var="student">
			<tr>
				<td>${student.sid}</td>
				<td>${student.sname}</td>
				<td>${student.age}</td>
				<td>${student.remark}</td>
			</tr>
		</c:forEach>

	</table>
<n:paging pageBean="${pageBean }"/>
</body>
</html>

运行结果：

 

 

原网站

版权声明
本文为[一只奈良森屿]所创，转载请带上原文链接，感谢
https://blog.csdn.net/qq_62881798/article/details/125864365

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