通用分页 之 分页标签（二）

通用分页 之 分页标签

1.导入资源

DBAccess.java config.properties资源文件 连接数据库
EncodingFiter.java 乱码处理
StringUtils.java 判断是否存在
Book .java 实体类
PageTag.java 自定义标签的助手类
BookDao.java dao方法
PageBean.java 分页的工具类

2.分析 分页的需求

页码，每页所要展示的数据，总记录数，是否分页，点击下一页或者上一页所需要的地址，存取分页时所需要的参数

分页的工具类

package com.zking.util;

import java.util.HashMap;
import java.util.Map;

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
	private boolean pagination = true;// 是否分页
	private String url;// 点击下一页或者上一页所需要的地址
	private Map<String, String[]> paramMap = new HashMap<>();// 存取分页时所需要的参数

	public void setRequest(HttpServletRequest req) {
		this.setPage(req.getParameter("page"));// 从servlet中接收page，再重载setPage
		this.setRows(req.getParameter("rows"));
		this.setPagination(req.getParameter("pagination"));
		// getRequestURIL 获取到游览器的全路径
		this.setUrl(req.getRequestURL().toString());
		// getParameterMap 可以获取到一次URL请求所携带的所有参数
		this.setParamMap(req.getParameterMap());
	}

	private void setPagination(String pagination) {
		if (StringUtils.isNotBlank(pagination)) {
			this.setPagination(!"false".equals(pagination));// 是否分页
		}
	}

	private void setRows(String rows) {
		if (StringUtils.isNotBlank(rows)) {
			this.setRows(Integer.valueOf(rows));// 设置rows的值，每页展示多少数据
		}
	}

	private void setPage(String page) {
		if (StringUtils.isNotBlank(page)) {
			this.setPage(Integer.valueOf(page));// 设置page的值，展示的页数
		}
	}

	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public Map<String, String[]> getParamMap() {
		return paramMap;
	}
	public void setParamMap(Map<String, String[]> paramMap) {
		this.paramMap = paramMap;
	}
	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;
	}

	/**
	 * 获取总页数
	 * 
	 * @return
	 */
	public int getMaxPage() {
		return this.total % this.rows == 0 ? this.total % this.rows : this.total / this.rows + 1;
	}

	/**
	 * 获取下一页页码
	 * 
	 * @return
	 */
	public int getNextPage() {
		return this.page < this.getMaxPage() ? this.page + 1 : this.page;
	}

	/**
	 * 获取上一页页码
	 * 
	 * @return
	 */
	public int getPreviousPage() {
		return this.page > 1 ? this.page - 1 : this.page;
	}

	@Override
	public String toString() {
		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
	}

}

3.前台的标签

我们不能直接运行这个界面，这个界面需要点击查询之后才能有数据。因为我们没有传值

下面是我们的select界面的代码也是我们分页的桥梁

package com.zking.web;

import java.io.IOException;
import java.sql.SQLException;
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.zking.dao.BookDao;
import com.zking.entity.Book;
import com.zking.util.PageBean;

public class Bookservlet extends HttpServlet {
	private BookDao bookdao = new BookDao();//私有化dao方法，外部不能被访问
	private static final long serialVersionUID = 4806795866251349977L;
	@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");//接收bname，查询的关键字
		Book book = new Book();
		book.setBname(bname);
		PageBean pageBean = new PageBean();
		pageBean.setRequest(req);//将一些数据存到pageBean里
		try {
			List<Book> list = bookdao.list(book, pageBean);//查询出符合条件的某一页的记录数
			req.setAttribute("bookList", list);//存值
			req.setAttribute("pagebean", pageBean);
			req.getRequestDispatcher("bookList.jsp").forward(req, resp);//转发
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}

z标签，也就是我们的分页标签还有一个主要的类-----助手类，整个分页的灵魂所在。

package com.zking.tag;

import java.io.IOException;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;

import com.zking.util.PageBean;

/**
 * 自定义标签  分页
 * @author huguiyun
 *
 */
public class PageTag extends BodyTagSupport {

	private static final long serialVersionUID = -3609493782238830873L;
	private PageBean pageBean;

	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.write(toHTML());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	private String toHTML() {
		StringBuffer sb = new StringBuffer();
		//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'>");
		Map<String, String[]> paramMap = pageBean.getParamMap();
		if(paramMap!=null && paramMap.size()>0) {//查询后的分页，传参
			for (Entry<String,String[]> entry : paramMap.entrySet()) {
				if(!"page".equals(entry.getKey())) {
					for(String val : entry.getValue()) {						
						sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+val+"'>");
					}
				}
			}
		}
		sb.append("<input type='hidden' name='page'>");
		sb.append("</form>");
		
		//分页条html代码拼接
		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 href='javascript:gotoPage(1)'>首页</a>&nbsp;&nbsp;<a");
		sb.append(" href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>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>");
		
		
		//分页所需调用的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;
	}
}

没有模糊查的分页结果
有模糊查的分页结果