一、实现图书的分页
1、前端Thymeleaf分页模板
html
<!--
number 页码从1开始,如:1,2,3,...
offset 页码偏移量。如果页码是从0开始,则偏移量为-1;如果页码从1开始,偏移量为0
totalPages 总页数
url 地址 如:/my , /my?id=1, /my/book?id=1&limit=10
1、会自动向url中添加页码,如:/your?id=1&page=1, /your/book?id=1&limit=10&page=1
2、当超过totalPages>maxButtons时,会显示...代替多余的按钮
3、maxButtons>=floatButtons*2
-->
<ul class="pagination" th:fragment="page_pager(number, offset, totalPages, url)" th:with="maxButtons=10,floatButtons=5" xmlns:th="http://www.thymeleaf.org">
<style>
.pagination {
display: inline-block;
padding-left: 300px;
margin: 20px 0;
border-radius: 4px
}
.pagination > li {
display: inline
}
.pagination > li > a, .pagination > li > span {
position: relative;
float: left;
padding: 6px 12px;
margin-left: -1px;
line-height: 1.42857143;
color: #337ab7;
text-decoration: none;
background-color: #fff;
border: 1px solid #ddd
}
.pagination > li:first-child > a, .pagination > li:first-child > span {
margin-left: 0;
border-top-left-radius: 4px;
border-bottom-left-radius: 4px
}
.pagination > li:last-child > a, .pagination > li:last-child > span {
border-top-right-radius: 4px;
border-bottom-right-radius: 4px
}
.pagination > li > a:focus, .pagination > li > a:hover, .pagination > li > span:focus, .pagination > li > span:hover {
z-index: 2;
color: #23527c;
background-color: #eee;
border-color: #ddd
}
.pagination > .active > a, .pagination > .active > a:focus, .pagination > .active > a:hover, .pagination > .active > span, .pagination > .active > span:focus, .pagination > .active > span:hover {
z-index: 3;
color: #fff;
cursor: default;
background-color: #337ab7;
border-color: #337ab7
}
.pagination > .disabled > a, .pagination > .disabled > a:focus, .pagination > .disabled > a:hover, .pagination > .disabled > span, .pagination > .disabled > span:focus, .pagination > .disabled > span:hover {
color: #777;
cursor: not-allowed;
background-color: #fff;
border-color: #ddd
}
.pagination-lg > li > a, .pagination-lg > li > span {
padding: 10px 16px;
font-size: 18px;
line-height: 1.3333333
}
.pagination-lg > li:first-child > a, .pagination-lg > li:first-child > span {
border-top-left-radius: 6px;
border-bottom-left-radius: 6px
}
.pagination-lg > li:last-child > a, .pagination-lg > li:last-child > span {
border-top-right-radius: 6px;
border-bottom-right-radius: 6px
}
.pagination-sm > li > a, .pagination-sm > li > span {
padding: 5px 10px;
font-size: 12px;
line-height: 1.5
}
.pagination-sm > li:first-child > a, .pagination-sm > li:first-child > span {
border-top-left-radius: 3px;
border-bottom-left-radius: 3px
}
.pagination-sm > li:last-child > a, .pagination-sm > li:last-child > span {
border-top-right-radius: 3px;
border-bottom-right-radius: 3px
}
</style>
<!-- 上一页 -->
<li th:if="${number == 1}"><span>上一页</span></li>
<li th:if="${number > 1}"><a th:href="@{${url}(pageNum=${number+offset-1})}">上一页</a></li>
<!-- 首页 -->
<li th:if="${number == 1}" class="active"><span>1</span></li>
<li th:if="${number > 1}"><a th:href="@{${url}(pageNum=${1+offset})}">1</a></li>
<th:block th:if="${totalPages>2 && totalPages<=maxButtons}" th:each="i : ${#numbers.sequence(2,totalPages-1)}">
<li th:if="${number == i}" class="active"><span th:text="${i}">页码</span></li>
<li th:if="${number != i}"><a th:href="@{${url}(pageNum=${i+offset})}" th:text="${i}">页码</a></li>
</th:block>
<th:block th:if="${totalPages > maxButtons}">
<th:block th:if="${(number-(floatButtons/2)) <= 2}" th:each="i : ${#numbers.sequence(2,2+floatButtons-1)}">
<li th:if="${number == i}" class="active"><span th:text="${i}">页码</span></li>
<li th:if="${number != i}"><a th:href="@{${url}(pageNum=${i+offset})}" th:text="${i}">页码</a></li>
</th:block>
<!-- ... -->
<li th:if="${(number-(floatButtons/2))>2}"><span>...</span></li>
<th:block th:if="${((number-(floatButtons/2))>2) && ((number+(floatButtons/2)-(floatButtons%2==0?1:0)) < (totalPages-1))}"
th:each="i : ${#numbers.sequence(number-(floatButtons/2),number+(floatButtons/2)-(floatButtons%2==0?1:0))}">
<li th:if="${number == i}" class="active"><span th:text="${i}">页码</span></li>
<li th:if="${number != i}"><a th:href="@{${url}(pageNum=${i+offset})}" th:text="${i}">页码</a></li>
</th:block>
<!-- ... -->
<li th:if="${(number+(floatButtons/2)-(floatButtons%2==0?1:0)) < (totalPages-1)}"><span>...</span></li>
<th:block th:if="${(number+(floatButtons/2)-(floatButtons%2==0?1:0)) >= (totalPages-1)}" th:each="i : ${#numbers.sequence(totalPages-floatButtons,totalPages-1)}">
<li th:if="${number == i}" class="active"><span th:text="${i}">页码</span></li>
<li th:if="${number != i}"><a th:href="@{${url}(pageNum=${i+offset})}" th:text="${i}">页码</a></li>
</th:block>
</th:block>
<!-- 最后一页 -->
<li th:if="${totalPages>1 && number == totalPages}" class="active"><span th:text="${totalPages}">页码</span></li>
<li th:if="${totalPages>1 && number != totalPages}"><a th:href="@{${url}(pageNum=${totalPages+offset})}" th:text="${totalPages}">页码</a></li>
<!-- 下一页 -->
<li th:if="${number >= totalPages}"><span>下一页</span></li>
<li th:if="${number < totalPages}"><a th:href="@{${url}(pageNum=${number+offset+1})}">下一页</a></li>
</ul>
2、后端PageBean封装
java
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class PageBean <T>{
// 当前页码
private int currentPage=1;
// 每页显示条数
private int pageSize=4;
// 总页数
private int totalPage;
// 总记录数
private int totalCount;
// 当前页数据
private List<T> records;
public PageBean(int currentPage, int pageSize, int totalCount, List<T> records) {
this.currentPage = currentPage;
this.pageSize = pageSize;
this.totalCount = totalCount;
this.records = records;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
// 计算总页数
this.totalPage = totalCount % pageSize == 0 ? (totalCount / pageSize) : (totalCount / pageSize + 1);
}
}
3、后端底层Dao操作数据库
java
public List<Books> queryByPage(int pageNum, int pageSize, Books books) throws Exception {
String sql = "select id,title,author,isbn,stock,publish_date publishDate,category from books order by id limit ?,? ";
return executeQuery(Books.class,sql,(pageNum-1)*pageSize,pageSize);
}
分析:(当前页-1)*每页个数
java
-- one (1-1)*4
select * from books where title like '%%' or author like '%%' limit 0,4
-- two (2-1)*4
select * from books where title like '%%' or author like '%%' limit 4,4
-- three (3-1)*4
select * from books where title like '%%' or author like '%%' limit 8,4
-- four (4-1)*4
select * from books where title like '%%' or author like '%%' limit 12,4
-- five (5-1)*4
select * from books where title like '%%' or author like '%%' limit 16,4
4、业务层Service调Dao层
java
@Override
public List<Books> findByPage(int pageNum, int pageSize, Books books) throws Exception {
return booksDao.queryByPage(pageNum,pageSize,books);
}
5、控制层Servlet调用Service层
java
public void findPage(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
CustomTemplateEngine engine = CustomTemplateEngine.getInstance(req);
try {
// 获取当前页码
String strPageNum = req.getParameter("pageNum");
//判断当前页码是否小于1
int pageNum = (strPageNum == null || strPageNum.equals("")) ? 1 : Integer.parseInt(strPageNum);
// 每页显示条数
int pageSize = 4;
// 获取书籍总个数
int totalCount = booksService.findBook().size();
// 查询书籍信息
List<Books> books = booksService.findByPage(pageNum, pageSize, null);
// 封装分页信息
PageBean<Books> pageBean = new PageBean(pageNum, pageSize, totalCount, books);
// 计算总页数
pageBean.setTotalPage(totalCount);
// System.out.println("pageBean=>>>" + pageBean);
// 将书籍信息保存到request域中
req.setAttribute("books", pageBean);
} catch (Exception e) {
throw new RuntimeException(e);
}
// 转发到list.html页面
engine.processTemplate("book/list", req, resp);
}
6、运行效果

