通用分页

最新推荐文章于 2024-08-06 16:33:54 发布

原创最新推荐文章于 2024-08-06 16:33:54 发布 · 175 阅读

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CC 4.0 BY-SA版权

本文详细介绍了使用Java实现通用分页查询的过程，包括实体类、分页工具类、Servlet处理及自定义分页标签的创建，展示了如何通过PageBean类进行分页逻辑处理，以及在JSP页面中展示分页结果。

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通用分页02

1.首先写一个实体类(这是不可少的)

public class Book {
	private int bid;
	private String bname;
	private float price;

    public Book() {}

	public int getBid() {
		return bid;
	}

	public void setBid(int bid) {
		this.bid = bid;
	}

	public String getBname() {
		return bname;
	}

	public void setBname(String bname) {
		this.bname = bname;
	}

	public float getPrice() {
		return price;
	}

	public void setPrice(float price) {
		this.price = price;
	}

	@Override
	public String toString() {
		return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
	}

	public Book(int bid, String bname, float price) {
		this.bid = bid;
		this.bname = bname;
		this.price = price;
	}
}

分页工具类：PageTag(同时增加属性和封装与一些方法：)

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;
	
	private Map<String, String[]> paramMap =new HashMap<>();
	
	public void setRequest (HttpServletRequest req) {
		this.setPage(req.getParameter("page")); //传它的页码
		this.setRows(req.getParameter("rows"));//页码大小
		this.setPagination(req.getParameter("pagination"));//是否分页
//		getRequestURL获取到浏览器请求的全路径 
		this.setUrl(req.getRequestURL().toString());
//		getParameterMap可以获取到一次url请求所携带的所以参数
		this.setParamMap(req.getParameterMap());
	}
	
	
	private void setPagination(String pageination) {
		if(StringUtils.isNotBlank(pageination))
		this.setPagination(!"false".equals(pageination));
	}

	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 PageBean() {
		super();
	}

	public int getPage() {
		return page;
	}
	
	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 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 + "]";
	}
	
	/**
	 * 获取到总页数
	 * @return
	 */
	public int getMaxPage() {
		return this.total%this.rows ==0 ?
				this.total/this.rows :
				(this.total/this.rows)+1;
	}
	
	/**
	 * 获取到下一页页码
	 * @return
	 */
	public int getNextPage() {
		return this.page <this.getMaxPage() ? this.page+1 :this.page;
	}

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

接下来肯定是助手类pagetag:

public class PageTag extends BodyTagSupport {
	private static final long serialVersionUID = 249991175546207586L;
	private PageBean pageBean;

	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.write(toHTML());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return super.doStartTag();
	}

	public String toHTML() {
		StringBuffer sb = new StringBuffer();
		// 下一次请求提交到后台的表单html代码拼接
		pageBean = new PageBean();
		sb.append("<form id='pageBeanForm' action='" + pageBean.getUrl() + "' method='post'>");
		Map<String, String[]> paramMap = pageBean.getParamMap();
		if (paramMap != null && paramMap.size() > 0) {
			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 ");
		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>");
		
		// 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;
	}
}

接下来把bname值传到Bookservlet类中去:

public class BookServlet extends HttpServlet {

	private static final long serialVersionUID = 2027863948806664653L;
	private BookDao bookDao =new BookDao();
	
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String bname =req.getParameter("bname");
//		String page =req.getParameter("page");
		Book book =new Book();
		book.setBname(bname);//设置bname的值
		PageBean pageBean =new PageBean();  
		pageBean.setRequest(req);
		try {
			//查询出符合条件的某一页的记录数
			List<Book> list = bookDao.list(book, pageBean); 
			
			req.setAttribute("bookList", list); //调用bookDao传过来的值
			
			req.setAttribute("pagebean", pageBean);
			
			req.getRequestDispatcher("bookList.jsp").forward(req, resp);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}	
}

配置tld标签：

<tag>
    <!-- 标签库中的标签名 -->
    <name>page</name>
    <!-- 标签对应的助手类的全路径名 -->
    <tag-class>com.ylt.tags.PageTag</tag-class>
    <!-- jsp -->
    <body-content>JSP</body-content>
    <attribute>
        <!-- 属性名 -->
        <name>pageBean</name>
        <!-- 属性值是否必填 -->
        <required>true</required>
        <!-- 是否支持表达试 -->
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

最后到jsp页面运气结果：

<body>
<h2>小说目录</h2>
	<br>
	<form action="${pageContext.request.contextPath}/bookServlet"
		method="post">
   <!-- <input type="hidden" name="rows" value="20"> -->
		<input type="hidden" name="pagination" value="false">
		书名：<input type="text" name="bname"> <input type="submit" value="确定">
	</form>
	<table border="1" width="100%">
		<tr>
			<td>编号</td>
			<td>名称</td>
			<td>价格</td>
		</tr>
		<c:forEach items="${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>

在这里插入图片描述
由此可得思路：
1、对pagebean增强（添加url、paramMap属性，添加初始化pagebean的方法、最大页、上一页、下一页方法）
2、自定义page分页标签（助手类、tld、jsp引用标签库）
3、将按钮条写入标签助手类
4、将隐藏的form表单写入标签助手类
5、将对应的js代码写入标签助手类
6、测试通用分页是否完善