Java标签分页实现
Java实现标签分页
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????? 最近为了开发一个网站，里面要用分页功能，但是之前很少自己写分页标签，又不想用现成框架。所以自己参考了些资料，写了个分页例子测试了一下。
????? 代码主要分为三个类：
- PageTag 分页标签类Page 分页beanConstant 设置常量
???? Page代码：
/** * * @author byyang * */public class Page{private int current = 0; //当前页，默认为第一页private int size; //记录总数private int length; //每页的长度private String url; //访问路径public Page(int offset, int size, int length) {super();this.current = offset;this.size = size;this.length = length;}/** * 获取总页数 * @return */public int pageCount(){int pagecount = 0;if(this.size % this.length == 0){pagecount = this.size / this.length;}else{pagecount = this.size / this.length + 1;}return pagecount;}//最后一页开始条数public int lastPageOffset(){return this.size - lastPageSize();}//最后一页页大小public int lastPageSize(){int lastpagesize = 0;if(this.size % this.length == 0){lastpagesize = this.length;}else{lastpagesize = this.size % this.length;}return lastpagesize;}//获取起始页public int getOffset() {return current;}//总记录数public int getSize() {return size;}//每页大小public int getLength() {return length;}//获取访问路径public String getUrl() {return url;}//上一页public int getLastOffset(){int offset = this.getOffset() - this.getLength();if(offset > 0){return offset;}else{return 0;}}//下一页public int getNextOffset(){int offset = this.getOffset() + this.getLength();if(offset > this.getSize()){return getLastOffset();}else{return offset;}}public String getPageNavigation(){String pageNavigation = "";return pageNavigation;}public void setOffset(int offset) {this.current = offset;}public void setSize(int size) {this.size = size;}public void setLength(int length) {this.length = length;}public void setUrl(String url) {this.url = url;}}?
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?? 现在我们要实现PageTag标签类，自定义标签有两种实现TagSupport和SimpleTagSupport，两个都能实现这个功能，这个看个人选择了。
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import java.io.IOException;import javax.servlet.http.HttpServletRequest;import javax.servlet.jsp.JspException;import javax.servlet.jsp.JspWriter;import javax.servlet.jsp.tagext.TagSupport;import com.byyang.util.Constants;/** * doStartTag()和doEndTag()返回值处理: * SKIP_BODY (0) ：跳过了开始和结束标签之间的代码。 * EVAL_BODY_INCLUDE(1)：将body的内容输出到存在的输出流中 * SKIP_PAGE(5)： 忽略剩下的页面。 * EVAL_PAGE隐含(6)：继续执行下面的页 * @author yangby * */public class PageTag extends TagSupport{ private String url; public String getUrl(){ return this.url; } public void setUrl(String url) { this.url = url; } public int doEndTag()throws JspException{ return EVAL_PAGE; } public int doStartTag() throws JspException{ HttpServletRequest request = (HttpServletRequest)this.pageContext.getRequest(); //获取分页bean Page page = (Page)request.getAttribute("pager"); JspWriter out = this.pageContext.getOut(); //拼接分页信息 StringBuilder s = new StringBuilder(); s.append("共 " + ((page.getSize() - 1) / page.getLength() + 1) + " 页 "); //设置当前页第一条记录索引 String current = request.getParameter("current"); if(current != null && !"".equals(current)){ page.setOffset(Integer.parseInt(current)); } if (page.getSize() > page.getLength()){ //获取连接符pref String pref; if (this.url.indexOf("?") > -1){ pref = "&"; }else { pref = "?"; } this.doStart(s, page, pref); this.doBody(s, page, pref); this.doEnd(s,page,pref); }else{ s.append(" "); } s.append(" 共 " + page.getSize() + " 条记录"); try{ out.println(s.toString()); }catch (IOException e){ e.printStackTrace(); } return SKIP_BODY; } /** * //拼接"首页"和"<" * @param s * @param page * @param pref */ public void doStart(StringBuilder s,Page page,String pref){ if (page.getOffset() > 0){ s.append("<a href='" + this.url + pref + "current=0'>[首页]</a>\n" + "<a href='" + this.url + pref + "current=" + page.getLastOffset() + "'>[<]</a>\n"); }else{ s.append("<a href='" + this.url + pref + "current=0'>[首页]</a>\n" ); } } /** * 拼接"尾页"和">" * @param s * @param page * @param pref */ public void doEnd(StringBuilder s,Page page,String pref){ if (page.getOffset() < page.getSize() - page.getLength()) { s.append("<a href='" + this.url + pref + "current=" + page.getNextOffset() + "'>[>]</a>\n" + "<a href='" + this.url + pref + "current=" + page.lastPageOffset() + "'>[尾页]</a>\n"); }else{ s.append("\n"+ "<a href='" + this.url + pref + "current=" + page.lastPageOffset() + "'>[尾页]</a>\n"); } } /** * 数字连接 * @param s * @param page * @param pref */ public void doBody(StringBuilder s,Page page,String pref){ //显示半径 int radius = Constants.MAX_PAGE_INDEX / 2 * page.getLength(); //显示数字的连接从第几条开始 int startOffset; if ((page.getOffset() < radius) || (page.pageCount() <= Constants.MAX_PAGE_INDEX)){ startOffset = 0; }else{ if (page.getOffset() < page.getSize() - radius){ startOffset = page.getOffset() - radius; }else{ startOffset = (page.getSize() / page.getLength() - Constants.MAX_PAGE_INDEX) * page.getLength(); } } for (int i = startOffset; (i < page.getSize()) && (i < startOffset + Constants.MAX_PAGE_INDEX * page.getLength()); ){ if (i == page.getOffset()){ s.append("<b>" + (i / page.getLength() + 1) + "</b>\n"); }else{ s.append("<a href='" + this.url + pref + "current=" + i + "'>" + (i / page.getLength() + 1) + "</a>\n"); } i += page.getLength(); } }}?
编写tld文件mypage.tld：?
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<?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>2.5</tlib-version><jsp-version>1.2</jsp-version><short-name>mypage</short-name><uri>\tag-page</uri><tag><name>page</name><tag-class>com.byyang.tag.PageTag</tag-class><body-content>pg</body-content><attribute><name>url</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib>
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?? 配置web.xml
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<!-- 自定义标签 --> <jsp-config> <taglib> <taglib-uri>/tag-page</taglib-uri> <taglib-location>/WEB-INF/mypage.tld</taglib-location> </taglib></jsp-config>
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在jsp页面中添加如下代码：
<%@ taglib uri="/tag-page" prefix="pg"%>
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你可以放到一个公共jsp里面一块引。
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现在咱们可以测试一下了：
在jsp页面代码：
<div align="center"> <h2>图书列表</h2> <table border=1> <s:iterator var="book" status="index" value="books"> <s:if test="#index.odd == true"> <tr style="background-color: yellow"> </s:if> <s:else> <tr> </s:else> <td align="right">图书名称：</td> <td align="left"><s:property value="book"/></td> </tr> </s:iterator> </table> <pg:page url="getBookList.action"></pg:page> </div>
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Action中咱们设一个测试数据：
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public class BookAction extends BaseAction { private String[] books; private BookService bookService = new BookService(); public String execute() throws Exception { setBooks(bookService.getBookList()); Page page = new Page(1,65,5); request.setAttribute("pager", page); return SUCCESS; } public String[] getBooks() { return books; } public void setBooks(String[] books) { this.books = books; }}?好的，接下来启动tomcat，查看页面效果：