实现百度分页效果的工具类

import java.io.IOException;
import java.io.UnsupportedEncodingException;
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;

import org.apache.commons.lang3.StringUtils;

/**
* 显示格式 上一页 1 2 3 4 5 下一页
*/
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\">");
// 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=\"" + preUrl + "\">上一页</a></li>");
} else {
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 = (page.getPage() - 2 > 0) ? page.getPage() - 2 : 1;
for (int i = 1; i <= number && indexPage <= pageCount; indexPage++, i++) {
if (indexPage == page.getPage()) {
writer.print("<li class=\"active\"><a href=\"#\">" + indexPage
+ "<span class=\"sr-only\">(current)</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>");
} else {
writer.print("<li class=\"disabled\"><a href=\"#\">下一页</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
*
* @param url
* @param key
* @param value
* @return
* @throws UnsupportedEncodingException
*/
private String append(String url, String key, String value) {
if (url == null || url.trim().length() == 0) {
return "";
}

if(StringUtils.isNotBlank(value)){
try {
value = new String(value.getBytes("ISO-8859-1"), "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}

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
*
* @param url
* @param pageContext
* @return
* @throws javax.servlet.jsp.JspException
*/
private String resolveUrl(String url, javax.servlet.jsp.PageContext pageContext) throws JspException {
// UrlSupport.resolveUrl(url, context, pageContext)
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;
}

/**
* @return the bean
*/
public String getBean() {
return bean;
}

/**
* @param bean
*            the bean to set
*/
public void setBean(String bean) {
this.bean = bean;
}

/**
* @return the url
*/
public String getUrl() {
return url;
}

/**
* @param url
*            the url to set
*/
public void setUrl(String url) {
this.url = url;
}

public void setNumber(int number) {
this.number = number;
}

}