通用分页（2）

做分页的具体思路
1、补全servlet
2、页面展示
3、分页重要参数（page、rows、是否分页、上一次请求、上一次的表单参数）
4、自定义分页标签

创建工具类

/**
 * 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;
//	保留上一次请求携带的参数
	private Map<String, Object>paMap=new HashMap<>();
/**
 * pageBean初始化方法
 * @param req
 */
	public void setRequest(HttpServletRequest req) {
		this.setPage(req.getParameter("page"));
		this.setRows(req.getParameter("rows"));
		this.setPagination(req.getParameter("pagination"));
	}

public void setPagination(String pagination) {
	if ("false".equals(pagination)) {
		this.setPagination(false);
	}
}

public void setRows(String rows) {
	if (StringUtils.isNotBlank(rows)) {
		this.setRows(Integer.valueOf(rows));
	}
}

public 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;
}


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() {
	// 1 limit 0,10
	// 2 limit 10,10
	// 3 limit 20,10
	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 getPreviousPage() {
	return this.page > 1 ? this.page - 1 : this.page;
}

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BookServlet类

public class BookServlet extends HttpServlet{

	private static final long serialVersionUID = 6759869517309547417L;
    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) {
			// TODO: handle exception
			e.printStackTrace();
		}
    }
} 

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防止传值时出现中文乱码-过滤器

/**
 * 中文乱码处理
 * 
 */
public class EncodingFiter implements Filter {

	private String encoding = "UTF-8";// 默认字符集

	public EncodingFiter() {
		super();
	}

	public void destroy() {
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;

		// 中文处理必须放到 chain.doFilter(request, response)方法前面
		res.setContentType("text/html;charset=" + this.encoding);
		if (req.getMethod().equalsIgnoreCase("post")) {
			req.setCharacterEncoding(this.encoding);
		} else {
			Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
			Set set = map.keySet();// 取出所有参数名
			Iterator it = set.iterator();
			while (it.hasNext()) {
				String name = (String) it.next();
				String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
				for (int i = 0; i < values.length; i++) {
					values[i] = new String(values[i].getBytes("ISO-8859-1"),
							this.encoding);
				}
			}
		}

		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		String s = filterConfig.getInitParameter("encoding");// 读取web.xml文件中配置的字符集
		if (null != s && !s.trim().equals("")) {
			this.encoding = s.trim();
		}
	}

}

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设置标签PageTag助手类

public class PageTag extends BodyTagSupport{

	private static final long serialVersionUID = 2325051425456014648L;
    private PageBean pageBean;
	public PageBean getPageBean() {
		return pageBean;
	}
	public void setPageBean(PageBean pageBean) {
		this.pageBean = pageBean;
	}
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.print(toHTML());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return SKIP_BODY;
	}

	private String toHTML() {
		StringBuilder sb = new StringBuilder();
		
//		拼接下一次分页请求所提交的分页表单
		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 value : entry.getValue()) {
					if(!"page".equals(entry.getKey()))
						sb.append("<input type='hidden' name='"+entry.getKey()+"' value='"+value+"' >");
				}
			}
		}
		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.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>");
		
//		拼接分页的javascript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();
	}

}

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配置tld

<?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>yq 1.1 core library</description>
	<display-name>yq core</display-name>
	<tlib-version>1.1</tlib-version>
	<short-name>c</short-name>
	<uri>/yq</uri>

	<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.yq.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>
	
	

</taglib>

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BookList

<%@ 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="/yq" 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">
		<!-- 查询时点击下一页时展示20条数据 -->
		<!-- <input type="hidden" name="rows" value="20"> -->
		<!-- 不想分页 -->
		<!-- <input type="hidden" name="paginaation" value="false"> -->
		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>
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