通用分页（二）

通用分页（二）

注：通用分页核心思路
将上一次查询请求再发一次，只不过页码变了

1.如何将斗破查询关键字传到下一次请求？
将查询参数保存到pagebean中
Map paramMap 存储参数键值对

2.如何将上一次查询请求再发一次？
在pagebean定义一个属性存放上一次的请求

分页图解：

BookServlet业务逻辑处理：（控制层）

    package com.qiuwenfan.web;
    
    import java.io.IOException;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.qiuwenfan.dao.BookDao;
    import com.qiuwenfan.entity.Book;
    import com.qiuwenfan.util.PageBean;
    
    public class BookServlet extends HttpServlet {
    
    	private static final long serialVersionUID = 5155489692716490057L;
    	private BookDao bookDao = new BookDao();
    	
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doPost(req, resp);
    	}
    	
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		String bname = req.getParameter("bname");
    		Book book = new Book();
    		book.setBname(bname);
    		PageBean pageBean = new PageBean();
    		pageBean.setRequest(req);
    		try {
    			List<Book> list = bookDao.list(book, pageBean);
    			req.setAttribute("bookList", list);
    			req.setAttribute("pageBean", pageBean);
    			req.getRequestDispatcher("/bookList.jsp").forward(req, resp);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    
    }

PageTag代码：（视图层）

如何将上一次查询请求再发一次
String contextPath = req.getContextPath();//根目录
String url = req.getServletPath();//请求的地址
req.getRequestURL() //获取请求全路径
Map<String, String[]> parameterMap = req.getParameterMap();//获得请求中的所有参数

注1：不能将分页表单嵌套到其它表单中，否则不能提交表单！！！

    package com.qiuwenfan.tag;
    
    import java.io.IOException;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.Set;
    
    import javax.servlet.jsp.JspException;
    import javax.servlet.jsp.JspWriter;
    import javax.servlet.jsp.tagext.BodyTagSupport;
    
    import com.qiuwenfan.util.PageBean;
    
    public class PageTag extends BodyTagSupport {
    
    	private static final long serialVersionUID = 1L;
    
    	private PageBean pageBean;
    
    	@Override
    	public int doStartTag() throws JspException {
    		JspWriter out = pageContext.getOut();
    		try {
    			out.print(toHTML());
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    		return SKIP_BODY;
    	}
    
    	public String toHTML() {
    		StringBuilder sb = new StringBuilder();
    		// 下一次请求提交到后台的表单html代码拼接
    		sb.append("<form id='pageBeanForm' action='" + pageBean.getUrl() + "' method='post'>");
    		sb.append("<input type='hidden' name='page'>");
    		Map<String, String[]> paMap = pageBean.getPaMap();
    		if (paMap != null && paMap.size() > 0) {
    			Set<Entry<String, String[]>> entrySet = paMap.entrySet();
    			for (Entry<String, String[]> entry : entrySet) {
    				for (String val : entry.getValue()) {
    					if (!"page".equals(entry.getKey()))
    						sb.append("<input type='hidden' name='" + entry.getKey() + "' value='" + val + "'>");
    				}
    			}
    		}
    		sb.append("</form>");
    
    		// 拼接分页条
    		sb.append("<div style='text-align: right; font-size: 12px;'>");
    		sb.append(" 每页" + pageBean.getRows() + "条，共" + pageBean.getTotal() + "条，第" + pageBean.getPage() + "页，共"
    				+ pageBean.getMaxPage() + "页&nbsp;&nbsp;<a ");
    		sb.append(" href='javascript:gotoPage(1)'>首页</a>&nbsp;&nbsp;<a");
    		sb.append(" href='javascript:gotoPage(" + pageBean.getPrevionPage() + ")'>上一页</a>&nbsp;&nbsp;<a");
    		sb.append(" href='javascript:gotoPage(" + pageBean.getNextPage() + ")'>下一页</a>&nbsp;&nbsp;<a");
    		sb.append(" href='javascript:gotoPage(" + pageBean.getMaxPage() + ")'>尾页</a>&nbsp;&nbsp;<input type='text'");
    		sb.append(" id='skipPage'");
    		sb.append(" style='text-align: center; font-size: 12px; width: 50px;'>&nbsp;&nbsp;<a");
    		sb.append(" href='javascript:skipPage()'>Go</a>");
    		sb.append("</div>");
    
    		// 拼接分页所需要调用的js代码
    		sb.append("<script type='text/javascript'>");
    		sb.append(" function gotoPage(page) {");
    		sb.append("  document.getElementById('pageBeanForm').page.value = page;");
    		sb.append("  document.getElementById('pageBeanForm').submit();");
    		sb.append(" }");
    		sb.append(" function skipPage() {");
    		sb.append("  var page = document.getElementById('skipPage').value;");
    		sb.append("  if(!page || isNaN(page) || parseInt(page)<1 || parseInt(page)>" + pageBean.getMaxPage() + "){");
    		sb.append("   alert('请输入1~N的数字');");
    		sb.append("   return;");
    		sb.append("  }");
    		sb.append("  gotoPage(page);");
    		sb.append(" }");
    		sb.append("</script>");
    
    		return sb.toString();
    	}
    
    	public PageBean getPageBean() {
    		return pageBean;
    	}
    
    	public void setPageBean(PageBean pageBean) {
    		this.pageBean = pageBean;
    	}
    }

z.tld代码：

<tag>
  <!-- 填写的是标签库中的标签名 -->
    <name>page</name>
    <!-- 标签对应后台助手类 -->
    <tag-class>com.qiuwenfan.tag.PageTag</tag-class>
    <!-- 标签类别 -->
    <body-content>JSP</body-content>
    <attribute>
    <!-- 自定义标签中属性 -->
        <name>pageBean</name>
        <!-- 属性值是否必填 -->
        <required>true</required>
        <!-- 是否支持表达式EL表达式/ognl表达式 -->
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

bookList.jsp显示页面：

    <%@ page language="java" contentType="text/html; charset=utf-8"
        pageEncoding="utf-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>  
    <%@ taglib uri="/QWF" prefix="z" %>  
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Insert title here</title>
    </head>
    <body>
    <h2>小说目录</h2>
    	<br>
    
    	<form action="${pageContext.request.contextPath}/bookServlet"
    		method="post">
    		书名：<input type="text" name="bname"> <input type="submit"
    			value="确定">
    	</form>
    	<table border="1" width="100%">
    		<tr>
    			<td>编号</td>
    			<td>名称</td>
    			<td>价格</td>
    		</tr>
    		<c:forEach items="${bookList }" var="b">
    			<tr>
    				<td>${b.bid }</td>
    				<td>${b.bname }</td>
    				<td>${b.price }</td>
    			</tr>
    		</c:forEach>
    	</table>
    <z:page pageBean="${pageBean}"></z:page>
    	
    </body>
    </html>

配置PageBean：

    package com.qiuwenfan.util;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    
    /**
     * 分页工具类
     *
     */
    public class PageBean {
    
    	private int page = 1;// 页码
    
    	private int rows = 10;// 页大小
    
    	private int total = 0;// 总记录数
    	
    //	保留上一次的请求地址
    	private String url;
    //	保留上一次请求所携带的参数
    	private Map<String, String[]> paMap = new HashMap<>();
    	
    	/**
    	 * pageBean初始化方法
    	 * @param httpServlet
    	 */
    	public void setRequest(HttpServletRequest req) {
    		this.setPage(req.getParameter("page"));
    		this.setRows(req.getParameter("rows"));
    		this.setPagination(req.getParameter("pagination"));
    		
    		this.setUrl(req.getRequestURL().toString());
    		this.setPaMap(req.getParameterMap());
    	}
    	
    	private void setPagination(String pagination) {
    		if("false".equals(pagination)) {
    			this.setPagination(false);
    		}
    	}
    
    	private void setRows(String rows) {
    		if(StringUtils.isNotBlank(rows)) {
    			this.setRows(Integer.valueOf(rows));
    		}
    	}
    
    	private void setPage(String page) {
    		if(StringUtils.isNotBlank(page)) {
    			this.setPage(Integer.valueOf(page));
    		}
    	}
    
    	public String getUrl() {
    		return url;
    	}
    
    	public void setUrl(String url) {
    		this.url = url;
    	}
    
    	public Map<String, String[]> getPaMap() {
    		return paMap;
    	}
    
    	public void setPaMap(Map<String, String[]> paMap) {
    		this.paMap = paMap;
    	}
    
    
    	private boolean pagination = true;// 是否分页
    
    	public PageBean() {
    		super();
    	}
    
    	public int getPage() {
    		return page;
    	}
    
    	public void setPage(int page) {
    		this.page = page;
    	}
    
    	public int getRows() {
    		return rows;
    	}
    
    	public void setRows(int rows) {
    		this.rows = rows;
    	}
    
    	public int getTotal() {
    		return total;
    	}
    
    	public void setTotal(int total) {
    		this.total = total;
    	}
    
    	public void setTotal(String total) {
    		this.total = Integer.parseInt(total);
    	}
    
    	public boolean isPagination() {
    		return pagination;
    	}
    
    	public void setPagination(boolean pagination) {
    		this.pagination = pagination;
    	}
    
    	/**
    	 * 获得起始记录的下标
    	 * 
    	 * @return
    	 */
    	public int getStartIndex() {
    		return (this.page - 1) * this.rows;
    	}
    
    	@Override
    	public String toString() {
    		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
    	}
    
    	/**
    	 * 最大页码
    	 * @return
    	 */
    	public int getMaxPage() {
    		return this.total % this.rows == 0 ? this.total/this.rows : this.total/this.rows+1;
    	}
    	
    	/**
    	 * 获取下一页
    	 * @return
    	 */
    	public int getNextPage() {
    		return this.page < this.getMaxPage() ? this.page+1 : this.page;
    	}
    	
    	/**
    	 * 获取上一页
    	 * @return
    	 */
    	public int getPrevionPage() {
    		return this.page > 1 ? this.page-1 : this.page;
    	}
    }

图片结果：