package com.itheima.common.utils;
import java.io.IOException;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
/**
* 显示格式:首页 上一页 1 2 3 4 5下一页 尾页
*/
public class NavigationTag extends TagSupport {
static final long serialVersionUID = 2372405317744358833L;
/**
* request 中用于保存Page<E> 对象的变量名,默认为“page”
*/
private String bean = "page";
/**
* 分页跳转的url地址,此属性必须
*/
private String url = null;
/**
* 显示页码数量
*/
private int number = 5;
@Override
public int doStartTag() throws JspException {
JspWriter writer = pageContext.getOut();
HttpServletRequest request =
(HttpServletRequest) pageContext.getRequest();
Page page = (Page) request.getAttribute(bean);
if (page == null)
return SKIP_BODY;
url = resolveUrl(url, pageContext);
try {
// 计算总页数
int pageCount = page.getTotal() / page.getSize();
if (page.getTotal() % page.getSize() > 0) {
pageCount++;
}
writer.print("<nav><ul class=\"pagination\">");
//首页链接路径
String homeUrl = append(url, "page", 1);
//末页链接路径
String backUrl = append(url, "page", pageCount);
// 显示“上一页”按钮
if (page.getPage() > 1) {
String preUrl = append(url, "page", page.getPage() - 1);
preUrl = append(preUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + homeUrl + "\">" + "首页</a></li>");
writer.print("<li><a href=\"" + preUrl + "\">" + "上一页</a></li>");
} else {
writer.print("<li class=\"disabled\"><a href=\"#\">" + "首页 </a></li>");
writer.print("<li class=\"disabled\"><a href=\"#\">" + "上一页 </a></li>");
}
// 显示当前页码的前2页码和后两页码
// 若1 则 1 2 3 4 5, 若2 则 1 2 3 4 5, 若3 则1 2 3 4 5,
// 若4 则 2 3 4 5 6 ,若10 则 8 9 10 11 12
int indexPage =1;
if(page.getPage() - 2 <=0){
indexPage=1;
}else if(pageCount-page.getPage() <=2){
indexPage=pageCount-4;
}else{
indexPage= page.getPage() - 2;
}
for (int i= 1;i <= number && indexPage <= pageCount;indexPage++,i++){
if (indexPage == page.getPage()) {
writer.print("<li class=\"active\"><a href=\"#\">" + indexPage
+"<spanclass=\"sr-only\"></span></a></li>");
continue;
}
String pageUrl = append(url, "page", indexPage);
pageUrl = append(pageUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + pageUrl + "\">" + indexPage + "</a></li>");
}
// 显示“下一页”按钮
if (page.getPage() < pageCount) {
String nextUrl = append(url, "page", page.getPage() + 1);
nextUrl = append(nextUrl, "rows", page.getSize());
writer.print("<li><a href=\"" + nextUrl + "\">" + "下一页</a></li>");
writer.print("<li><a href=\"" + backUrl + "\">" + "尾页</a></li>");
} else {
writer.print("<li class=\"disabled\"><a href=\"#\">" + "下一页</a></li>");
writer.print("<li class=\"disabled\"><a href=\"#\">" + "尾页</a></li>");
}
writer.print("</nav>");
} catch (IOException e) {
e.printStackTrace();
}
return SKIP_BODY;
}
private String append(String url, String key, int value) {
return append(url, key, String.valueOf(value));
}
/**
* 为url 参加参数对儿
*/
private String append(String url, String key, String value) {
if (url == null || url.trim().length() == 0) {
return "";
}
if (url.indexOf("?") == -1) {
url = url + "?" + key + "=" + value;
} else {
if (url.endsWith("?")) {
url = url + key + "=" + value;
} else {
url = url + "&" + key + "=" + value;
}
}
return url;
}
/**
* 为url 添加翻页请求参数
*/
private String resolveUrl(String url,
javax.servlet.jsp.PageContext pageContext) throws JspException {
Map params = pageContext.getRequest().getParameterMap();
for (Object key : params.keySet()) {
if ("page".equals(key) || "rows".equals(key)){
continue;
}
Object value = params.get(key);
if (value == null){
continue;
}
if (value.getClass().isArray()) {
url = append(url, key.toString(), ((String[]) value)[0]);
} else if (value instanceof String) {
url = append(url, key.toString(), value.toString());
}
}
return url;
}
public String getBean() {
return bean;
}
public void setBean(String bean) {
this.bean = bean;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public void setNumber(int number) {
this.number = number;
}
}