近期在做的S2SH項目，因為多處用到分頁，BOSS要求小弟將其抽象出來。小弟不才，實際參與開發的經驗也就1年。
于是花了點時間將其做成自定義標簽供所有需要分頁的業務調用。小結一下，供新手參考
自定義標簽使用如下：
JSP頁面引入：
<%@ taglib uri="/htdz-tag" prefix="htdz-tag"%>
在需要擺放翻頁的相關按鈕處使用：
<htdz-tag:PagerTag pagesize="${pagesize}" rowcount="${rowcount}" currpagenum="${currpagenum}" action="${action}"/>
以下介紹如何自定義標簽：
1.首先是針對自定義標簽的描述：
創建WEB-INF/tags/htdz-tag.tld標簽描述文件：
<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>htdz tag</description>
<display-name>htdz tag</display-name>
<tlib-version>1.0</tlib-version>
<short-name>htdz-tag</short-name>
<uri>/htdz-tag</uri>
<tag>
<!--分頁控件使用說明：
1.最全參數用法：<htdz-tag:PagerTag pagesize="${pagesize}" rowcount="${rowcount}" currpagenum="${currpagenum}" action="${action}" className="button_small"/>
1.最簡參數用法：<htdz-tag:PagerTag pagesize="${pagesize}" rowcount="${rowcount}" currpagenum="${currpagenum}" action="${action}"/>
參數說明：
1. pagesize為每頁記錄數(必寫)
2. rowcount為總記錄數(必寫)
3. currpagenum為當前頁數(必寫)
4. className為分頁按鈕樣式，如果不寫，則為默認樣式
5. action為URL請求路徑(必寫)
-->
<description>分頁控件</description>
<!--JSP里使用時的標簽名-->
<name>PagerTag</name>
<!--用以將自定義標簽解析成控件的Java類-->
<tag-class>com.htdz.util.tag.PagerTag</tag-class>
<body-content>JSP</body-content>
<!--每個attribute代表標簽的一個屬性-->
<attribute>
<description>pagesize:每頁條數</description>
<!--屬性名-->
<name>pagesize</name>
<!--是否必填屬性-->
<required>true</required>
<!--此屬性值是否接受EL,<%= 之類的形式-->
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<description>rowcount:總記錄數</description>
<name>rowcount</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<description>currpagenum:當前頁數</description>
<name>currpagenum</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<description>action:URL請求路徑</description>
<name>action</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<description>className:用于客戶端確定分頁按鈕的樣式</description>
<name>className</name>
<required>false</required>
</attribute>
</tag>
</taglib>
2.創建用于將標簽解析為頁面翻頁控件的類
PagerTag.java
public class PagerTag extends TagSupport {
public static final int USER_PAGESIZE = 5;// 禮品搜索--每頁記錄數
private static final String DEFAULT_BUTTON_CLASS= "button_small"; //翻頁按鈕默認樣式
private static final String DISABLE_BUTTON_CLASS= "button_small_disable"; //失效按鈕默認樣式
private int pagesize;
private int rowcount;
private int currpagenum;
private String action;
private String className;
public PagerTag() {
}
public void setPagesize(int pagesize) {
this.pagesize = pagesize;
}
public void setRowcount(int rowcount) {
this.rowcount = rowcount;
}
public void setCurrpagenum(int currpagenum) {
this.currpagenum = currpagenum;
}
public void setClassName(String className) {
this.className = className;
}
public void setAction(String action) {
this.action = action;
}
public int doStartTag() throws JspException {
if (new Integer(pagesize) == null) {
throw new JspException("PagerTag標簽中缺乏pagesize屬性！");
}else if(pagesize==0){
throw new JspException("PagerTag標簽中的pagesize屬性無值！");
}
if (new Integer(rowcount) == null) {
throw new JspException("PagerTag標簽中缺乏rowcount屬性！");
}
if (new Integer(currpagenum) == null) {
throw new JspException("PagerTag標簽中缺乏currpagenum屬性！");
}
if (action == null) {
throw new JspException("PagerTag標簽中缺乏action屬性！");
}else if(action.length()==0){
throw new JspException("PagerTag標簽中的action屬性無值！");
}
//如果頁面標簽中沒寫className屬性，則讓翻頁按鈕應用默認的按鈕樣式
if(className==null||className.length()==0){
className = DEFAULT_BUTTON_CLASS;
}
//獲取總頁數
int totalpagesize = getTotalpagesize(rowcount);
//用以標志是否能上翻
boolean noUp = false;
//用以標志是否能下翻
boolean noDown = false;
//聲明應用于'首頁'，'上一頁'按鈕的樣式(因為此倆按鈕要么同時失效，要么同時可用)
String buttonClass1 = className;
//聲明應用于'下一頁'，'尾頁'按鈕的樣式(同上)
String buttonClass2 = className;
//如果無記錄，則設置總頁數與當前頁數都為1
if(rowcount==0){
currpagenum = 1;
totalpagesize = 1;
}
//如果當前頁是第一頁
if(currpagenum==1){
noUp = true;
//設置'首頁'，'上一頁'按鈕失效樣式
buttonClass1 = DISABLE_BUTTON_CLASS;
}
//如果當前頁是最大頁
if(currpagenum==totalpagesize){
noDown = true;
//設置'下一頁'，'尾頁'按鈕失效樣式
buttonClass2 = DISABLE_BUTTON_CLASS;
}
try {
StringBuffer html = new StringBuffer();
html.append(currpagenum+"/"+totalpagesize+"頁");
html.append("<input class="+buttonClass1+" type=\"button\" value=\"首頁\" onclick=\"turnPage('first','"+currpagenum+"','"+totalpagesize+"','"+action+"')\" ");
if(noUp){
html.append("disabled=\"true\"");
}
html.append("/>");
html.append("<input class="+buttonClass1+" type=\"button\" value=\"上一頁\" onclick=\"turnPage('up','"+currpagenum+"','"+totalpagesize+"','"+action+"')\" ");
if(noUp){
html.append("disabled=\"true\"");
}
html.append("/>");
html.append("<input class="+buttonClass2+" type=\"button\" value=\"下一頁\" onclick=\"turnPage('down','"+currpagenum+"','"+totalpagesize+"','"+action+"')\"");
if(noDown){
html.append("disabled=\"true\"");
}
html.append("/>");
html.append("<input class="+buttonClass2+" type=\"button\" value=\"尾頁\" onclick=\"turnPage('last','"+currpagenum+"','"+totalpagesize+"','"+action+"')\" ");
if(noDown){
html.append("disabled=\"true\"");
}
html.append("/>");
html.append(currpagenum+"/"+totalpagesize+"頁 ");
html.append("<input type=\"text\" maxlength=\"3\" id=\"text\" size=\"3\" onkeypress=\"return checkInput(event);\" />頁");
html.append("<input class="+className+" type=\"button\" value=\"GO\" onclick=\"turnPage('to','"+currpagenum+"','"+totalpagesize+"','"+action+"')\" />");
pageContext.getOut().println(html.toString());
} catch (Exception e) {
throw new JspException(e.getMessage());
}
return this.SKIP_BODY;
}
/**
* 根據總記錄數得到總頁數
*
* @param rowcount
* 總記錄數
* @return 總頁數
*/
public int getTotalpagesize(int rowcount) {
int totalpagesize = 0;
if (rowcount % pagesize == 0) {
totalpagesize = rowcount / pagesize;
} else {
totalpagesize = rowcount / pagesize + 1;
}
return totalpagesize;
}
}
到此為止，自定義標簽書已完成。
可應用于項目各處，
只要頁面上遵循標簽描述規則，后臺該給標簽屬性傳值的時候記得傳就行了。
以下用一個簡單的例子來說明一下，紅色字體顯示的部分別忘記寫就行了。
UserAction.java:
public class UserAction extends ActionSupport {
private UserService userService;
private List<User> users;
public String findUser(){
String str = null;
HttpServletRequest request = ServletActionContext.getRequest();
Map sessionMap = ActionContext.getContext().getSession();
String currpagenum= "1";
try {
String pagenum = request.getParameter("pagenum ");
if(pagenum != null && pagenum .length()!=0){
currpagenum= pagenum ;
}
} catch (Exception e) {
}
//查詢用戶記錄
users= userService.findUser(pageNum);
if(users.size!=0){
request.setAttribute("users", users);
int rowcount = userService.getCount();
request.setAttribute("rowcount ",rowcount );
request.setAttribute("currpagenum",currpagenum);
str = "success";//成功視圖
}else{
message = "無記錄!"
str = "failure";//失敗視圖
}
request.setAttribute("pagesize", PagerTag.USER_PAGESIZE);
request.setAttribute("action", "findUser.action);
//返回視圖
return str;
}
public UserService getUserService() {
return userService;
}
public void setUserService(UserService userService) {
this.userService = userService;
}
public List<User> getUsers(){
return users;
}
public void setUsers(List<User> users){
this.users = users;
}
}
UserService.java:
public class UserService {
private UserDao userDao;
public List<User> findUser(String pageNum){
List<User> userList = userDao.findUser(pageNum);
return userList;
}
public int getCount(){
int count = userDao.getCount();
return count;
}
public UserDao getUserDao() {
return userDao;
}
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
}
UserDao.java:
public class UserDao extends HibernateDaoSupport {
/**
* 查詢用戶
* @return User對象集合
*/
public List<User> findUser(String pagenum) {
List<User> users = null;
Session session = null;
try {
int myPagenum= Integer.parseInt(pagenum);
String hql = "from User";
session = this.getSession();
Query query = session.createQuery(hql);
query.setFirstResult(Pager.USER_PAGESIZE * (myPagenum - 1));
query.setMaxResults(Pager.USER_PAGESIZE);
users = query.list();
session.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (session != null) {
session.close();
}
}
return users;
}
/**
* 獲取用戶總記錄數
* @return 用戶總記錄數
*/
public int getCount(){
String hql ="select count(id) from User";
Session session = null;
int count =0;
try {
session = this.getSession();
Query query = session.createQuery(hql);
List list = query.list();
session.flush();
count = Integer.parseInt(list.get(0).toString());
} catch (Exception e) {
e.printStackTrace();
} finally{
session.close();
}
return count;
}
}