waysun一路陽光

收藏自：http://www.tkk7.com/zhutianxiang/archive/2009/04/18/263837.html

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&nbsp;&nbsp;");

            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;
    }

}