Paging is a commonly used function in Java Web projects. Yesterday, a simple paging operation and search paging were implemented in Spring MVC, which is recorded here. The framework used is (MyBatis+SpringMVC+Spring).
First we need a pagination tool class:
1. Paging
import java.io.Serializable;
/**
* 分页
*/
public class Page implements Serializable {
private static final long serialVersionUID = -3198048449643774660L;
private int pageNow = 1; // 当前页数
private int pageSize = 4; // 每页显示记录的条数
private int totalCount; // 总的记录条数
private int totalPageCount; // 总的页数
@SuppressWarnings("unused")
private int startPos; // 开始位置，从0开始
@SuppressWarnings("unused")
private boolean hasFirst;// 是否有首页
@SuppressWarnings("unused")
private boolean hasPre;// 是否有前一页
@SuppressWarnings("unused")
private boolean hasNext;// 是否有下一页
@SuppressWarnings("unused")
private boolean hasLast;// 是否有最后一页
/**
* 通过构造函数 传入 总记录数 和 当前页
* @param totalCount
* @param pageNow
*/
public Page(int totalCount, int pageNow) {
this.totalCount = totalCount;
this.pageNow = pageNow;
}
/**
* 取得总页数，总页数=总记录数/总页数
* @return
*/
public int getTotalPageCount() {
totalPageCount = getTotalCount() / getPageSize();
return (totalCount % pageSize == 0) ? totalPageCount
: totalPageCount + 1;
}
public void setTotalPageCount(int totalPageCount) {
this.totalPageCount = totalPageCount;
}
public int getPageNow() {
return pageNow;
}
public void setPageNow(int pageNow) {
this.pageNow = pageNow;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getTotalCount() {
return totalCount;
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
}
/**
* 取得选择记录的初始位置
* @return
*/
public int getStartPos() {
return (pageNow - 1) * pageSize;
}
public void setStartPos(int startPos) {
this.startPos = startPos;
}
/**
* 是否是第一页
* @return
*/
public boolean isHasFirst() {
return (pageNow == 1) ? false : true;
}
public void setHasFirst(boolean hasFirst) {
this.hasFirst = hasFirst;
}
/**
* 是否有首页
* @return
*/
public boolean isHasPre() {
// 如果有首页就有前一页，因为有首页就不是第一页
return isHasFirst() ? true : false;
}
public void setHasPre(boolean hasPre) {
this.hasPre = hasPre;
}
/**
* 是否有下一页
* @return
*/
public boolean isHasNext() {
// 如果有尾页就有下一页，因为有尾页表明不是最后一页
return isHasLast() ? true : false;
}
public void setHasNext(boolean hasNext) {
this.hasNext = hasNext;
}
/**
* 是否有尾页
* @return
*/
public boolean isHasLast() {
// 如果不是最后一页就有尾页
return (pageNow == getTotalCount()) ? false : true;
}
public void setHasLast(boolean hasLast) {
this.hasLast = hasLast;
}
}With this tool class, first write the SQL statement in the XxxxMapper.xml configuration file of MyBatis, as follows:
<!-- 分页SQL语句 -->
<select id="selectProductsByPage" resultMap="返回值类型">
select
*
from 表名 WHERE user_id = #{userId,jdbcType=INTEGER} limit #{startPos},#{pageSize}
</select>
<!-- 取得记录的总数 -->
<select id="getProductsCount" resultType="long">
SELECT COUNT(*) FROM 表名 WHERE user_id = #{userId,jdbcType=INTEGER}
</select>Here we can see that 2 <select> need to pass in 3 and 1 parameters respectively. At this time, write the interface in the corresponding DAO file IXxxxDao to write the corresponding method, the method name and the id attribute value in mapper.xml Consistent:
/**
* 使用注解方式传入多个参数，用户产品分页，通过登录用户ID查询
* @param page
* @param userId
* @return startPos},#{pageSize}
*/
public List<Products> selectProductsByPage(@Param(value="startPos") Integer startPos,@Param(value="pageSize") Integer pageSize,@Param(value="userId") Integer userId);
/**
* 取得产品数量信息，通过登录用户ID查询
* @param userId
* @return
*/
public long getProductsCount(@Param(value="userId") Integer userId);After the interface definition is completed, you need to write the corresponding business interface and implementation method, define such a method in the interface, and then overwrite it in the implementation class:
/**
* 分页显示商品
* @param request
* @param model
* @param loginUserId
*/
void showProductsByPage(HttpServletRequest request,Model model,int loginUserId);The next method in the implementation class is to call the DAO layer and accept the parameters passed in by the Controller to process the business logic. The request is used to obtain the parameters passed in from the front end, and the model is used to return the processing result to the JSP page.
@Override
public void showProductsByPage(HttpServletRequest request, Model model,int loginUserId) {
String pageNow = request.getParameter("pageNow");
Page page = null;
List<ProductWithBLOBs> products = new ArrayList<ProductWithBLOBs>();
int totalCount = (int) productDao.getProductsCount(loginUserId);
if (pageNow != null) {
page = new Page(totalCount, Integer.parseInt(pageNow));
allProducts = this.productDao.selectProductsByPage(page.getStartPos(), page.getPageSize(), loginUserId);
} else {
page = new Page(totalCount, 1);
allProducts = this.productDao.selectProductsByPage(page.getStartPos(), page.getPageSize(), loginUserId);
}
model.addAttribute("products", products);
model.addAttribute("page", page);
}The next step is to write the controller. When the user needs to jump to the page of the real product, it needs to be processed by the corresponding method in the controller. This processing process is to call the method of the business layer to complete, and then return the result to the JSP Dynamic display, the server side generates a page and then transmits it to the client (browser) reality, which is an MVC process.
/**
* 初始化 “我的产品”列表 JSP页面,具有分页功能
*
* @param request
* @param model
* @return
*/
@RequestMapping(value = "映射路径", method = RequestMethod.GET)
public String showMyProduct(HttpServletRequest request, Model model) {
// 取得SESSION中的loginUser
User loginUser = (User) request.getSession().getAttribute("loginUser");
// 判断SESSION是否失效
if (loginUser == null || "".equals(loginUser)) {
return "redirect:/";
}
int loginUserId = loginUser.getUserId();
//此处的productService是注入的IProductService接口的对象
this.productService.showProductsByPage(request, model, loginUserId);
return "跳转到的JSP路径";
}I will not write the acceptance part of the JSP page. Everyone is the same, that is, it is written in combination with JSTL and EL. (I also make a judgment when the loop output is made. If the accepted parameter is empty, then there is no product in the output, only the acceptance When the parameter is not empty, the output is looped, using <<c:when test="${}"> combined with <c:otherwise>), here is only the relevant code for paging:
<!-- 分页功能 start -->
<div align="center">
<font size="2">共 ${page.totalPageCount} 页</font> <font size="2">第
${page.pageNow} 页</font> <a href="myProductPage?pageNow=1">首页</a>
<c:choose>
<c:when test="${page.pageNow - 1 > 0}">
<a href="myProductPage?pageNow=${page.pageNow - 1}">上一页</a>
</c:when>
<c:when test="${page.pageNow - 1 <= 0}">
<a href="myProductPage?pageNow=1">上一页</a>
</c:when>
</c:choose>
<c:choose>
<c:when test="${page.totalPageCount==0}">
<a href="myProductPage?pageNow=${page.pageNow}">下一页</a>
</c:when>
<c:when test="${page.pageNow + 1 < page.totalPageCount}">
<a href="myProductPage?pageNow=${page.pageNow + 1}">下一页</a>
</c:when>
<c:when test="${page.pageNow + 1 >= page.totalPageCount}">
<a href="myProductPage?pageNow=${page.totalPageCount}">下一页</a>
</c:when>
</c:choose>
<c:choose>
<c:when test="${page.totalPageCount==0}">
<a href="myProductPage?pageNow=${page.pageNow}">尾页</a>
</c:when>
<c:otherwise>
<a href="myProductPage?pageNow=${page.totalPageCount}">尾页</a>
</c:otherwise>
</c:choose>
</div>
<!-- 分页功能 End -->2. Query paging
Regarding query paging, the general process is exactly the same, except that the third parameter (loginUserId above) needs to accept the parameter input by the user. In this case, we need to accept the parameter input by the user in the controller (the <input> in the page uses the GET method) pass parameters), and then add it to SESSION to complete query paging (here, due to the hyperlink in the "next page", different JSP pages are used to process paging and search paging, and I have not found a single JSP page for the time being. In the method completed in the page, there is repeated code. The repeated code here is the code that outputs the content. It can be taken out separately, and then loaded into the required JSP page with an <include> tag, which can avoid the code repeat):
Here is the code of the controller for reference:
/**
* 通过 产品名称 查询产品
* @param request
* @param model
* @return
*/
@RequestMapping(value = "映射地址", method = RequestMethod.GET)
public String searchForProducts(HttpServletRequest request, Model model) {
HttpSession session = request.getSession();
String param = request.getParameter("param");
String condition = (String) session.getAttribute("condition");
//先判断SESSION中的condition是否为空
if (condition == null) {
condition = new String();
session.setAttribute("condition", condition);
//如果Session中的condition为空，再判断传入的参数是否为空，如果为空就跳转到搜索结果页面
if (param == null || "".equals(param)) {
return "private/space/ProductSearchResult";
}
}
//如果SESSION不为空，且传入的搜索条件param不为空，那么将param赋值给condition
if (param != null && !("".equals(param))) {
condition = param;
session.setAttribute("condition", condition);
}
//使用session中的condition属性值来作为查询条件
this.productService.showSearchedProductsByPage(request, model, condition);
return "跳转的页面";
}I have a WeChat public account, and I often share some dry goods related to Java technology; if you like my sharing, you can use WeChat to search for "Java Head" or "javatuanzhang" to follow.