通用分页的前台数据展示
本章思路
- 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）
- 自定义page分页标签（助手类、tld、jsp引用标签库）
- 将按钮条写入标签助手类
- 将隐藏的form表单写入标签助手类
- 将对应的js代码写入标签助手类
- 测试通用分页是否完善
1：上一次写的PageBean只有四个属性（page 页码 、rows 页大小 、total 总记录数 、pagination 是否分页 ），而这一次我添加了两个属性（url 点击下一页或者上一页所需要的地址、paramMap 存储参数键值对），将分页更加完善，具体实体类（PageBean）如下：
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"));
this.setRows(req.getParameter("rows"));
this.setPagination(req.getParameter("pagination"));
// 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请求所携带的所有参数
this.setParamMap(req.getParameterMap());
}
public void setPagination(String pagination) {
if (StringUtils.isNotBlank(pagination)) {
this.setPagination(!"false".equals(pagination));
}
}
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 PageBean() {
super();
}
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 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 + "]";
}
/**
* 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;
}
}2：新建一个标签助手类PageTag.java(对标签进行拼接)：定义一个pageBean属性，在此之前，我们先看看前台标签bookList.jsp页
bookList.jsp:
PageTag.java:(对前台标签进行拼接)
public class PageTag extends BodyTagSupport {
private static final long serialVersionUID = 2411829139570358249L;
private PageBean pageBean;//私有，不被外界访问
@Override
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
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 <a ");
sb.append(" href='javascript:gotoPage(1)'>首页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getPreviousPage()+")'>上一页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getNextPage()+")'>下一页</a> <a");
sb.append(" href='javascript:gotoPage("+pageBean.getMaxPage()+")'>尾页</a> <input type='text'");
sb.append(" id='skipPage'");
sb.append(" style='text-align: center; font-size: 12px; width: 50px;'> <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;
}
}3：BookServlet.java：前台与后台的桥梁
public class BookServlet extends HttpServlet {
private BookDao bookDao = new BookDao();
private static final long serialVersionUID = -7654671804738498584L;
@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");
// String page = req.getParameter("page");
Book book = new Book();
book.setBname(bname);
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);
req.setAttribute("pagebean", pageBean);
req.getRequestDispatcher("bookList.jsp").forward(req, resp);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}配置bookSevlet同时我们还要配置解决中文乱码的问题，新建EncodingFiter.java来处理，并且在web.xml中配置，这样能解决本项目中的所有中文乱码的问题
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();
}
}
}在web.xml中的配置如下(/*：应用所有界面)：
4：首先自定义Z标签，然后用Z标签测试
z.tid:
<?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>zking 1.1 core library</description>
<display-name>zking core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>c</short-name>
<uri>/zking</uri>
<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.zking.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>
<!-- 是否支持表达式 -->
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>完善bookList.jsp 进行测试，只要在初始bookList.jsp中加一行代码即可
效果图：（本页功能都可使用）
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