jsp自定自定义标签

2019独角兽企业重金招聘Python工程师标准>>>

1 先要导入一个jar包

导入的jar包

2 自定一个标签库 &＃xff0c;该库放在WEB-INF/tld下面输入图片说明

3 需要实现该类 extends TagSupport 实现里面的方法重载TagSupport类的方法

4 在jsp页面引入该标签库并使用

5 在web.xml文件中配置该标签 &＃xff08;不过这个不是必须的&＃xff09; 输入图片说明

6 现在给出一个显示页码的自定义处理类

package com.shi.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;import org.apache.taglibs.standard.tag.common.core.UrlSupport;/*** 显示格式上一页 1 2 3 4 5 下一页*/ public class NavigationTag extends TagSupport {static final long serialVersionUID &＃61; 2372405317744358833L;/*** request 中用于保存Page 对象的变量名,默认为“page”*/private String bean &＃61; "page";/*** 分页跳转的url地址,此属性必须*/private String url &＃61; null;/*** 显示页码数量*/private int number &＃61; 5;&＃64;Overridepublic int doStartTag() throws JspException {JspWriter writer &＃61; pageContext.getOut();HttpServletRequest request &＃61; (HttpServletRequest) pageContext.getRequest();Page page &＃61; (Page)request.getAttribute(bean); if (page &＃61;&＃61; null) return SKIP_BODY;url &＃61; resolveUrl(url, pageContext);try {//计算总页数int pageCount &＃61; page.getTotal() / page.getSize();if (page.getTotal() % page.getSize() > 0) {pageCount&＃43;&＃43;;}writer.print("

");//显示“上一页”按钮if (page.getPage() > 1) {String preUrl &＃61; append(url, "page", page.getPage() - 1);preUrl &＃61; append(preUrl, "rows", page.getSize());writer.print("上一页
");} else {writer.print("上一页
");}//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 12int indexPage &＃61; (page.getPage() - 2 > 0)? page.getPage() - 2 : 1;  for(int i&＃61;1; i <&＃61; number && indexPage <&＃61; pageCount; indexPage&＃43;&＃43;, i&＃43;&＃43;) {if(indexPage &＃61;&＃61; page.getPage()) {writer.print( ""&＃43;indexPage&＃43;"(current)
");continue;}String pageUrl  &＃61; append(url, "page", indexPage);pageUrl &＃61; append(pageUrl, "rows", page.getSize());writer.print(""&＃43; indexPage &＃43;"
");}//显示“下一页”按钮if (page.getPage() 下一页");} else {writer.print("下一页
");}writer.print("

");} 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* * &＃64;param url* &＃64;param key* &＃64;param value* &＃64;return*/private String append(String url, String key, String value) {if (url &＃61;&＃61; null || url.trim().length() &＃61;&＃61; 0) {return "";}if (url.indexOf("?") &＃61;&＃61; -1) {url &＃61; url &＃43; "?" &＃43; key &＃43; "&＃61;" &＃43; value;} else {if(url.endsWith("?")) {url &＃61; url &＃43; key &＃43; "&＃61;" &＃43; value;} else {url &＃61; url &＃43; "&" &＃43; key &＃43; "&＃61;" &＃43; value;}}return url;}/*** 为url 添加翻页请求参数* * &＃64;param url* &＃64;param pageContext* &＃64;return* &＃64;throws javax.servlet.jsp.JspException*/private String resolveUrl(String url, javax.servlet.jsp.PageContext pageContext) throws JspException{//UrlSupport.resolveUrl(url, context, pageContext)Map params &＃61; pageContext.getRequest().getParameterMap();for (Object key:params.keySet()) {if ("page".equals(key) || "rows".equals(key)) continue;Object value &＃61; params.get(key);if (value &＃61;&＃61; null) continue;if (value.getClass().isArray()) {url &＃61; append(url, key.toString(), ((String[])value)[0]);} else if (value instanceof String) {url &＃61; append(url, key.toString(), value.toString());}}return url;}/*** &＃64;return the bean*/public String getBean() {return bean;}/*** &＃64;param bean the bean to set*/public void setBean(String bean) {this.bean &＃61; bean;}/*** &＃64;return the url*/public String getUrl() {return url;}/*** &＃64;param url the url to set*/public void setUrl(String url) {this.url &＃61; url;}public void setNumber(int number) {this.number &＃61; number;}}