javaweb分页显示_java分页查询原理思路

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效果图如下：

实现步骤：

1.创建实体User.class,参考代码如下：

public class User {
	private String name;
	private int age;
	private String gender;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getGender() {
		return gender;
	}

	public void setGender(String gender) {
		this.gender = gender;
	}

	public User(String name, int age, String gender) {
		super();
		this.name = name;
		this.age = age;
		this.gender = gender;
	}

	public User() {
	}

}

2.创建分页模型PageBean.class,参考代码如下：

public class PageBean<T> {
	
	private int pageNum; 
	private int pageSize; 
	private int totalRecord;  
	private int totalPage;  
	private List<T> list;
	private int start;
	private int end;
	private int fromIndex;
	private int toIndex;

	public PageBean(int pageNum, int pageSize, int totalRecord) {
		this.pageNum = pageNum;
		this.pageSize = pageSize;
		this.totalRecord = totalRecord;
		fromIndex=(pageNum-1)*pageSize;
		toIndex=pageNum*pageSize>totalRecord?totalRecord:pageNum*pageSize;

		if (totalRecord % pageSize == 0) {
			this.totalPage = totalRecord / pageSize;
		} else {
			this.totalPage = totalRecord / pageSize + 1;
		}
		start = 1;
		end = 5;
		if (totalPage <= 5) {
			end = this.totalPage;
		} else {
			start = pageNum - 2;
			end = pageNum + 2;

			if (start < 1) {
				start = 1;
				end = 5;
			}
			if (end > this.totalPage) {
				end = totalPage;
				start = end - 5;
			}
		}
	}

	public int getPageNum() {
		return pageNum;
	}

	public void setPageNum(int pageNum) {
		this.pageNum = pageNum;
	}

	public int getPageSize() {
		return pageSize;
	}

	public void setPageSize(int pageSize) {
		this.pageSize = pageSize;
	}

	public int getTotalRecord() {
		return totalRecord;
	}

	public int getFromIndex() {
		return fromIndex;
	}

	public void setFromIndex(int fromIndex) {
		this.fromIndex = fromIndex;
	}

	public int getToIndex() {
		return toIndex;
	}

	public void setToIndex(int toIndex) {
		this.toIndex = toIndex;
	}

	public void setTotalRecord(int totalRecord) {
		this.totalRecord = totalRecord;
	}

	public int getTotalPage() {
		return totalPage;
	}

	public void setTotalPage(int totalPage) {
		this.totalPage = totalPage;
	}

	public List<T> getList() {
		return list;
	}

	public void setList(List<T> list) {
		this.list = list.subList(fromIndex, toIndex);
	}

	public int getStart() {
		return start;
	}

	public void setStart(int start) {
		this.start = start;
	}

	public int getEnd() {
		return end;
	}

	public void setEnd(int end) {
		this.end = end;
	}

}

3.创建jsp页面，参考代码如下：

/**
 *index.jsp
 */
<%@ 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>Insert title here</title>
    </head>
    <body>
        <a href="${pageContext.request.contextPath }/main">分页显示</a>
    </body>
</html>

/**
 *main.jsp
 */
<%@ 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">
        <script type="text/javascript"
	    src="${pageContext.request.contextPath}/jquery/jquery.min.js"></script>
        <script type="text/javascript">
	    function gos() {
		var pageNum = $.trim($("#pageNum").val());
		if(isNaN(pageNum)){
			alert("输入的不是数字 ，请输入数字！");
			return ;
		}
		if(pageNum==""){
			alert("输入为空，请重新输入！");
			return ;
		}
		if(pageNum<1||pageNum>${requestScope.pageBean.totalPage}){
			alert("超出范围，请重新输入！");
			return ;
		}
            location.href="${pageContext.request.contextPath}/main?pageNum="+pageNum;
	}
        </script>
        <title>分页显示</title>
    </head>
    <body>
	<center>
		<table width="40%" style="text-align:center">
			<tr>
				<th>姓名</th>
				<th>性别</th>
				<th>年龄</th>
			</tr>
			<c:forEach items="${requestScope.pageBean.list }" var="i">
				<tr>
					<td>${i.name }</td>
					<td>${i.gender }</td>
					<td>${i.age }</td>
				</tr>
			</c:forEach>
		</table>
	</center>
	<br />
	<center>
	<a href="${pageContext.request.contextPath}/main?pageNum=1">首页</a>
	<c:if test="${requestScope.pageBean.pageNum ==1}">
		<c:forEach begin="${requestScope.pageBean.start}"
			end="${requestScope.pageBean.end}" var="i">
			<c:if test="${requestScope.pageBean.pageNum == i}">
                        ${i}
                    </c:if>
			<c:if test="${requestScope.pageBean.pageNum != i}">
				<a href="${pageContext.request.contextPath}/main?pageNum=${i}">${i}</a>
			</c:if>
		</c:forEach>
		<a
			href="${pageContext.request.contextPath}/main?pageNum=${requestScope.pageBean.pageNum+1}">下一页</a>
	</c:if>

	<c:if
		test="${requestScope.pageBean.pageNum > 1 && requestScope.pageBean.pageNum < requestScope.pageBean.totalPage}">
		<a
			href="${pageContext.request.contextPath}/main?pageNum=${requestScope.pageBean.pageNum-1}">上一页</a>
		<c:forEach begin="${requestScope.pageBean.start}"
			end="${requestScope.pageBean.end}" var="i">
			<c:if test="${requestScope.pageBean.pageNum == i}">
                        ${i}
                    </c:if>
			<c:if test="${requestScope.pageBean.pageNum != i}">
				<a href="${pageContext.request.contextPath}/main?pageNum=${i}">${i}</a>
			</c:if>
		</c:forEach>
		<a
			href="${pageContext.request.contextPath}/main?pageNum=${requestScope.pageBean.pageNum+1}">下一页</a>
	</c:if>

	<c:if
		test="${requestScope.pageBean.pageNum == requestScope.pageBean.totalPage}">
		<a
			href="${pageContext.request.contextPath}/main?pageNum=${requestScope.pageBean.pageNum-1}">上一页</a>
		<c:forEach begin="${requestScope.pageBean.start}"
			end="${requestScope.pageBean.end}" var="i">
			<c:if test="${requestScope.pageBean.pageNum == i}">
                        ${i}
                    </c:if>
			<c:if test="${requestScope.pageBean.pageNum != i}">
				<a href="${pageContext.request.contextPath}/main?pageNum=${i}">${i}</a>
			</c:if>
		</c:forEach>
	    </c:if>
	    <a
		href="${pageContext.request.contextPath}/main?pageNum=${requestScope.pageBean.totalPage}">尾页</a><br><br>
	跳转到
	    <input type="text" id="pageNum" size="1px"></input>页
	    <a href="javascript:gos()">确定</a>, 共[${requestScope.pageBean.totalPage }]页,[${requestScope.pageBean.totalRecord}]条记录
	</center>
    </body>
</html>

4.创建Servlets.class，参考代码如下：

@WebServlet("/main")
public class Servlets extends HttpServlet {

	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String page = request.getParameter("pageNum");
		int pageNum = Integer.parseInt((page == null ? "1" : page));
		int pageSize = 5;
		Service s = new Service();
		PageBean<User> pb = s.findAll(pageNum, pageSize);
		request.setAttribute("pageBean", pb);
		request.getRequestDispatcher("/main.jsp").forward(request, response);
	}
}

5.创建Service.class，参考代码如下：

public class Service {
	public PageBean<User> findAll(int pageNum, int pageSize) {
		UserDao userDao = new UserDao();
		List<User> users = userDao.findAll();
		int totalRecord = users.size();
		PageBean<User> pb = new PageBean<>(pageNum, pageSize, totalRecord);
		pb.setList(users);
		return pb;
	}
}

6.创建UserDao.class，参考代码如下：

public class UserDao {
	List<User> users=new ArrayList<>();
	User user;
	public List<User> findAll(){
		for(int i=1;i<99;i++){
			user=new User("name-"+i, (int)(100*Math.random()), (int)(10*Math.random())%2==1?"男":"女");
			users.add(user);
		}
		return users;
	}
}

需注意的问题：

1.需在WebContent下创建文件夹jquery，在他里面放入jquery.min.js这个文件。否则跳转功能异常。

2.index.jsp与main.jsp都在WebContent文件夹下。