自定義標籤的方法實現分頁
首先需要一個分頁對象,在某個pojo裏面加上這三條屬性並生成get set方法
//當前頁
private Integer page;
//每頁數
private Integer size = 10;
//開始行
private Integer startRow = 0;
再加入自定義標籤的兩個類
package cn.wave.commons.util;
import java.io.IOException;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
/**
* 顯示格式 上一頁 1 2 3 4 5 下一頁
*/
public class NavigationTag extends TagSupport {
static final long serialVersionUID = 2372405317744358833L;
/**
* request 中用於保存Page<E> 對象的變量名,默認爲“page”
*/
private String bean = "page";
/**
* 分頁跳轉的url地址,此屬性必須
*/
private String url = null;
/**
* 顯示頁碼數量
*/
private int number = 5;
@Override
public int doStartTag() throws JspException {
JspWriter writer = pageContext.getOut();
HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
Page page = (Page)request.getAttribute(bean);
if (page == null)
return SKIP_BODY;
url = resolveUrl(url, pageContext);
try {
//計算總頁數
int pageCount = page.getTotal() / page.getSize();
if (page.getTotal() % page.getSize() > 0) {
pageCount++;
}
writer.print("<nav><ul class=\"pagination\">");
//顯示“上一頁”按鈕
if (page.getPage() > 1) {
String preUrl = append(url, "page", page.getPage() - 1);
preUrl = append(preUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + preUrl + "\">上一頁</a></li>");
} else {
writer.print("<li class=\"disabled\"><a href=\"#\">上一頁</a></li>");
}
//顯示當前頁碼的前2頁碼和後兩頁碼
//若1 則 1 2 3 4 5, 若2 則 1 2 3 4 5, 若3 則1 2 3 4 5,
//若4 則 2 3 4 5 6 ,若10 則 8 9 10 11 12
int indexPage = (page.getPage() - 2 > 0)? page.getPage() - 2 : 1;
for(int i=1; i <= number && indexPage <= pageCount; indexPage++, i++) {
if(indexPage == page.getPage()) {
writer.print( "<li class=\"active\"><a href=\"#\">"+indexPage+"<span class=\"sr-only\">(current)</span></a></li>");
continue;
}
String pageUrl = append(url, "page", indexPage);
pageUrl = append(pageUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + pageUrl + "\">"+ indexPage +"</a></li>");
}
//顯示“下一頁”按鈕
if (page.getPage() < pageCount) {
String nextUrl = append(url, "page", page.getPage() + 1);
nextUrl = append(nextUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + nextUrl + "\">下一頁</a></li>");
} else {
writer.print("<li class=\"disabled\"><a href=\"#\">下一頁</a></li>");
}
writer.print("</nav>");
} catch (IOException e) {
e.printStackTrace();
}
return SKIP_BODY;
}
private String append(String url, String key, int value) {
return append(url, key, String.valueOf(value));
}
/**
* 爲url 參加參數對兒
*
* @param url
* @param key
* @param value
* @return
*/
private String append(String url, String key, String value) {
if (url == null || url.trim().length() == 0) {
return "";
}
if (url.indexOf("?") == -1) {
url = url + "?" + key + "=" + value;
} else {
if(url.endsWith("?")) {
url = url + key + "=" + value;
} else {
url = url + "&" + key + "=" + value;
}
}
return url;
}
/**
* 爲url 添加翻頁請求參數
*
* @param url
* @param pageContext
* @return
* @throws javax.servlet.jsp.JspException
*/
private String resolveUrl(String url, javax.servlet.jsp.PageContext pageContext) throws JspException{
//UrlSupport.resolveUrl(url, context, pageContext)
Map params = pageContext.getRequest().getParameterMap();
for (Object key:params.keySet()) {
if ("page".equals(key) || "rows".equals(key)) continue;
Object value = params.get(key);
if (value == null) continue;
if (value.getClass().isArray()) {
url = append(url, key.toString(), ((String[])value)[0]);
} else if (value instanceof String) {
url = append(url, key.toString(), value.toString());
}
}
return url;
}
/**
* @return the bean
*/
public String getBean() {
return bean;
}
/**
* @param bean the bean to set
*/
public void setBean(String bean) {
this.bean = bean;
}
/**
* @return the url
*/
public String getUrl() {
return url;
}
/**
* @param url the url to set
*/
public void setUrl(String url) {
this.url = url;
}
public void setNumber(int number) {
this.number = number;
}
}
page類
package cn.wave.commons.util;
import java.util.List;
public class Page<T> {
private int total;
private int page;
private int size;
private List<T> rows;
public int getTotal() {
return total;
}
public void setTotal(int total) {
this.total = total;
}
public int getPage() {
return page;
}
public void setPage(int page) {
this.page = page;
}
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
public List<T> getRows() {
return rows;
}
public void setRows(List<T> rows) {
this.rows = rows;
}
}
標籤模板文件,在WEB-INF下建一個tld文件夾,在把這個文件放進去,命名commons.tld
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlib-version>2.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>common</short-name>
<uri>http://itcast.cn/common/</uri>
<display-name>Common Tag</display-name>
<description>Common Tag library</description>
<tag>
<name>page</name>
<tag-class>cn.wave.commons.util.NavigationTag</tag-class>
<body-content>JSP</body-content>
<description>create navigation for paging</description>
<attribute>
<name>bean</name>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>number</name>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>url</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
然後再jsp頁面導入標籤庫
<%@taglib prefix="itheima" uri="http://itcast.cn/common/"%>
jsp裏面的for循環後加入標籤
<div id="dataDiv">
<img src="images/result.gif" />
<table class="dt" border="1px">
<tr id="firstTr">
<th>部門ID</th>
<th>部門名稱</th>
<th>編輯</th>
</tr>
<c:forEach items="${page.rows}" var="item">
<tr class="tdbg1">
<td>${item.id}</td>
<td>${item.depName}</td>
<td>
<a href="updateDepartment.jsp?id=${item.id}&depName=${item.depName}">
<img src="img/modify.gif" />
</a>
<a href="<c:url value='/DepartmentServlet?method=delete&id=${item.id}'/> ">
<img src="img/delete.gif" />
</a>
</td>
</tr>
</c:forEach>
</table>
</div>
<!-- 把這個插入就行,這裏面的樣式是bootstrap裏面的-->
<div class="col-md-12 text-right">
<itheima:page url="${pageContext.request.contextPath }/DepartmentServlet?method=selectAll" />
</div>
servlet方法,就是一直獲取最開始定義的分頁對象,然後把這個對象放進page裏面
Map<String, String[]> map = request.getParameterMap();
Department department = CommonUtils.toBean(map, Department.class);
cn.wave.commons.util.Page<Department> page = departmentService.selectAll(department);
request.setAttribute("page", page);
service
public Page<Department> selectAll(Department department){
Page<Department> page = new Page<Department>();
page.setSize(5);
department.setSize(5);
if (null !=department.getPage()) {
page.setPage(department.getPage());
department.setStartRow((department.getPage() -1)*department.getSize());
}
page.setTotal(departmentDao.count());
page.setRows(departmentDao.selectAll(department));
return page;
}
dao裏面查詢的時候加上limit,再加一個count方法
public List<Department> selectAll(Department department){
Connection con = DBUtil.getConnection();
PreparedStatement ptmt = null;
ResultSet res = null;
String sql = "select * from crm_department limit ?,?";
List<Department> list = new ArrayList<>();
try {
ptmt = con.prepareStatement(sql);
ptmt.setInt(1, department.getStartRow());
ptmt.setInt(2, department.getSize());
res = ptmt.executeQuery();
while(res.next()){
Department department1 = new Department();
department1.setId(res.getInt("id"));
department1.setDepName(res.getString("depName"));
department1.setIsCancel(res.getInt("isCancel"));
list.add(department1);
}
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
public int count(){
Connection con = DBUtil.getConnection();
PreparedStatement ptmt = null;
ResultSet res = null;
String sql = "select count(*) from crm_department ";
int total = 0;
try {
ptmt = con.prepareStatement(sql);
res = ptmt.executeQuery();
if(res.next()){
total = res.getInt(1);
}
} catch (SQLException e) {
e.printStackTrace();
}
return total;
}
分頁完成