java中自定义分页标签

/** 有关该方法的简介     * PageModel 类,分页的一个实体类     *  StudentInfo 类,该方法中已studentinfo表作为操作表，该类为表的字段属性     * UtilDB 类,数据库的连接与关闭     * StudentDao 类,表的查询类（分页查询）     * tag类,要继承TagSupport，继承后该类下有三个常用的方法（doStartTag，doAfterBody，doEndTag）     * tld类,相当于一个配置文件     *     *///PageModel 类import java.util.List;public class PageModel<T> {    // 定义当前页    private int pageNo;    // 每页显示的记录数    private int pageSize;    // 总记录数    private int count;    // 数据集合    private List<T> all;    public List<T> getAll() {        return all;    }    public void setAll(List<T> all) {        this.all = all;    }    /**     * 首页     *     * @return     */    public int getIndex() {        return 1;    }    /**     * 尾页     *     * @return     */    public int getLastPage() {        if (this.getCount() % this.getPageSize() == 0) {            return this.getCount() / this.getPageSize();        } else {            return this.getCount() / this.getPageSize() + 1;        }    }    /**     * 上一页     *     * @return     */    public int getPagePerv() {        if (this.getPageNo() - 1 < 1) {            return 1;        } else {            return this.getPageNo() - 1;        }    }    /**     * 下一页     *     * @return     */    public int getPageNext() {        if (this.getPageNo() + 1 > this.getLastPage()) {            return this.getLastPage();        } else {            return this.getPageNo() + 1;        }    }    /**     * 各属性的 get/set 方法     *     * @return     */    public int getPageNo() {        return pageNo;    }    public void setPageNo(int pageNo) {        this.pageNo = pageNo;    }    public int getPageSize() {        return pageSize;    }    public void setPageSize(int pageSize) {        this.pageSize = pageSize;    }    public int getCount() {        return count;    }    public void setCount(int count) {        this.count = count;    }}//StudentInfo 类public class StudentInfo {    private int stuNo;    private String name;    private String sex;    private int age;    public int getStuNo() {        return stuNo;    }    public void setStuNo(int stuNo) {        this.stuNo = stuNo;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public StudentInfo(int stuNo, String name, String sex, int age) {        super();        this.stuNo = stuNo;        this.name = name;        this.sex = sex;        this.age = age;    }}//UtilDB 类import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class UtilDB {    /**     * 得到数据库操作对象     */    private static Connection con=null;       /**     * 链接数据库     * @return     */    public static Connection getCon(){        try {            //加载驱动            Class.forName("oracle.jdbc.driver.OracleDriver");            //该连接方式为oracle的连接方式            con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "scott", "tiger");        } catch (Exception e) {            e.printStackTrace();        }        return con;    }       /**     * 关闭数据库     * @param pst     * @param rs     * @param con     * @throws SQLException     */    public static void closeDB(PreparedStatement pst,ResultSet rs,Connection con) throws SQLException{        if(pst!=null){            pst.close();        }        if(rs!=null){            rs.close();        }        if(con!=null){            con.close();        }    }}//StudentDao 类import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;import util.UtilDB;import entity.PageModel;import entity.StudentInfo;public class StudentDao {    /**     * 得到数据库操作对象     */       private static PreparedStatement pst=null;    private static ResultSet rs=null;    private static Connection con=null;       public PageModel<StudentInfo> selectAll(int pageNo,int pageSize){        //创建 pagemodel 对象        PageModel<StudentInfo> pm=new PageModel<StudentInfo>();        //创建集合，用于封装  student 信息        List<StudentInfo> slist=new ArrayList<StudentInfo>();               try {            //链接数据库            con=UtilDB.getCon();            pst=con.prepareStatement("select * from (select rownum r ,s.* from studentinfo s) where r between ("+pageNo+"-1)*10+1 and "+pageNo+"*"+pageSize+"");            //执行 sql 语句            rs=pst.executeQuery();            while(rs.next()){                //下标从 2 开始，因为 下标为 1 的是 rownum,如果从1开始会报错                StudentInfo s=new StudentInfo(rs.getInt(2), rs.getString(3), rs.getString(4), rs.getInt(5));                slist.add(s);            }            //为  pagemodel 类设置值            pm.setAll(slist);            pm.setPageNo(pageNo);            pm.setPageSize(pageSize);            pm.setCount(this.count());        } catch (Exception e) {            e.printStackTrace();        }finally{            try {                //关闭数据库                UtilDB.closeDB(pst, rs, con);            } catch (Exception e) {                e.printStackTrace();            }        }        return pm;    }       /**     * 得到总共有多少条数据     * @return     */    public int count(){        int count=0;        try {            //链接数据库            con=UtilDB.getCon();            pst=con.prepareStatement("select count(*) from  studentinfo");            //执行sql            rs=pst.executeQuery();            if(rs.next()){                count=rs.getInt(1);            }                   } catch (Exception e) {            e.printStackTrace();        }finally{            try {                //关闭数据库                UtilDB.closeDB(pst, rs, con);            } catch (SQLException e) {                e.printStackTrace();            }        }        return count;    }}//创建一个tag类(PageModelTag )import java.io.IOException;import java.util.Iterator;import java.util.List;import javax.servlet.jsp.JspException;import javax.servlet.jsp.JspWriter;import javax.servlet.jsp.tagext.TagSupport;import entity.PageModel;public class PageModelTag extends TagSupport {    //标签各属性    private String scope;    private String name;    private String var;    private String url;    private String colspan;       //定义分页对象    PageModel<?> pm=null;    //迭代器    Iterator iter=null;          public int doStartTag() throws JspException {        Object obj=null;        //判断是哪个作用域        if("page".equals(scope)){            obj=pageContext.getAttribute(name, pageContext.PAGE_SCOPE);        }        if("request".equals(scope)){            obj=pageContext.getAttribute(name, pageContext.REQUEST_SCOPE);        }        if("session".equals(scope)){            obj=pageContext.getAttribute(name, pageContext.SESSION_SCOPE);        }        if("application".equals(scope)){            obj=pageContext.getAttribute(name, pageContext.APPLICATION_SCOPE);        }        // 将 obj 转化成  pm        pm=(PageModel<?>) obj;        List all=pm.getAll();        iter=all.iterator();        if(iter.hasNext()){            pageContext.setAttribute(var, iter.next());            //执行doAfterBody()方法           return EVAL_BODY_INCLUDE;        }else{            return super.doStartTag();        }           }    public int doAfterBody() throws JspException {        if(iter.hasNext()){            pageContext.setAttribute(var, iter.next());           //再一次执行doStartTag()，doStartTag与doAfterBody这样就相当于一个循环            return EVAL_BODY_AGAIN;        }else{            return super.doAfterBody();        }           }    public int doEndTag() throws JspException {        //创建输出流对象        JspWriter out=pageContext.getOut();        String href=url+"?pageNo=";        try {            out.print("<tr align='center'>");                out.print("<td colspan="+colspan+">");                out.print("共"+pm.getCount()+"条记录，当前    "+pm.getPageNo()+" / "+pm.getLastPage()+"   ");                out.print("<a href="http://zxs71717.blog.163.com/blog/+href+1+">首页</a>");                out.print("<a href="http://zxs71717.blog.163.com/blog/+href+pm.getPagePerv()+">上一页</a>");                out.print("<a href="http://zxs71717.blog.163.com/blog/+href+pm.getPageNext()+">下一页</a>");                out.print("<a href="http://zxs71717.blog.163.com/blog/+href+pm.getLastPage()+">尾页</a>");                out.print("</td>");            out.print("</tr>");        } catch (IOException e) {            e.printStackTrace();        }        return super.doEndTag();    }          public String getScope() {        return scope;    }    public void setScope(String scope) {        this.scope = scope;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getVar() {        return var;    }    public void setVar(String var) {        this.var = var;    }    public String getUrl() {        return url;    }    public void setUrl(String url) {        this.url = url;    }    public String getColspan() {        return colspan;    }    public void setColspan(String colspan) {        this.colspan = colspan;    }       //创建一个tld<taglib> <tlib-version>1.0</tlib-version> <jsp-version>1.2</jsp-version> <short-name>fenye</short-name> <uri>www.fenyeo2</uri>  <tag>    //下面的红色代码很重要     <name>fenye</name>     <tag-class>tag.PageModelTag</tag-class>     //设置标签中的属性，各属性的name要与tag类中的属性对应，如果不对应，在映射的时候会出现问题    <attribute>        <name>scope</name>        //设置该属性是否是该标签的必须属性以及在该标签中是否可以使用EL表达式        <required>true</required>        <rtexprvalue>true</rtexprvalue>    </attribute>    <attribute>        <name>name</name>        <required>true</required>        <rtexprvalue>true</rtexprvalue>    </attribute>    <attribute>        <name>var</name>        <required>true</required>        <rtexprvalue>true</rtexprvalue>    </attribute>    <attribute>        <name>url</name>        <required>true</required>        <rtexprvalue>true</rtexprvalue>    </attribute>    <attribute>        <name>colspan</name>        <required>true</required>        <rtexprvalue>true</rtexprvalue>    </attribute> </tag>//创建一个index.jsp页面，通过超链接跳转的下面的servletpublic class StudentServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //此处最好用一下 doPost 方法,表单的默认提交方式为get        doPost(request, response);    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //创建StudentDao类的一个对象        StudentDao dao=new StudentDao();        //当前页        int pageNo=1;        //每页显示的条数        int pageSize=10;        //获取页面传过来的当前的页码        String pageNos=request.getParameter("pageNo");        //判断pageNos，并设置pageNo        if(pageNos!=null && !"".equals(pageNos)){            pageNo=Integer.parseInt(pageNos);        }        //调用分页查询的方法        PageModel<StudentInfo> pm=dao.selectAll(pageNo, pageSize);        //把分页查询出来的数据保存的request        request.setAttribute("pm", pm);        //跳转        request.getRequestDispatcher("../list.jsp").forward(request, response);    }}   //list.jsp页面的主要代码//要想使用自定义标签，必须有如下的一个步骤，uri为该标签的tld文件中的uri，prefix的值可以自定义<%@ taglib uri="www.fenyeo2" prefix="my" %><table border="1" cellpadding="0" cellspacing="0" align="center" width="60%" height="50%">                 <tr align="center">               <td>学号</td>               <td>姓名</td>               <td>性别</td>               <td>年龄</td>           </tr>          //my 是prefix的值，fenye是tld中的name           <my:fenye url="servlet/StudentServlet" var="s" name="pm" scope="request" colspan="4">               //使用的EL表达式（${ }）,也可以用java代码（< % =    % >）               <tr align="center">                   <td>${s.stuNo }</td>                   <td>${s.name }</td>                   <td>${s.sex }</td>                   <td>${s.age }</td>               </tr>                     </my:fenye>       </table>