JSP自定义标签

在jsp中使用自定义标签完成分页操作

在WEB-INF下创建commons.tld

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
  "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
	<tlib-version>2.0</tlib-version>
	<jsp-version>1.2</jsp-version>
	<short-name>common</short-name><!-- 简称 -->
	<uri>test-uri</uri>
	<display-name>Common Tag</display-name><!-- 显示名称 -->
	<description>Common Tag library</description><!-- 描述 -->

	<tag>
		<name>page</name><!-- 标签名 -->
		<!-- 自定义标签库对应类 -->
		<tag-class>com.java.common.utils.NavigationTag</tag-class>
		<body-content>JSP</body-content>
		<description>create navigation for paging</description><!-- 描述 -->
		<attribute><!-- 屬性 -->
			<name>bean</name>
			<rtexprvalue>true</rtexprvalue><!-- 是否可修改 -->
		</attribute>
		<attribute>
			<name>number</name>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>url</name>
			<required>true</required><!-- 是否必须 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>
</taglib>

创建自定义标签库类并继承TagSupport

package com.java.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;

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 = 2372405317744358833L;

    /**
     * request中用于保存Page<E> 对象的变量名 默认为"page" 对应自定义标签库标签的属性
     */
    private String bean = "page";

    /**
     * 分页跳转的url地址 此属性不可或缺 对应自定义标签库标签的属性
     */
    private String url = null;

    /**
     * 显示页码数量 对应自定义标签库标签的属性
     */
    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 url
     */
    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 + "&amp;" + key + "=" + value;
            }
        }
        return url;
    }

    /**
     * 为url 添加翻页请求参数
     * @param url
     * @param pageContext
     * @return url
     * @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;
    }

    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;
    }
}

分页所需参数实体类

package com.java.common.utils;

import java.util.List;

public class Page<T> {

	private int total;
	private int page;
	private int size;
    private List<T> rows;
	public int getTotal() {
		return total;
	}
	public void setTotal(int total) {
		this.total = total;
	}
	public int getPage() {
		return page;
	}
	public void setPage(int page) {
		this.page = page;
	}
	public int getSize() {
		return size;
	}
	public void setSize(int size) {
		this.size = size;
	}
	public List<T> getRows() {
		return rows;
	}
	public void setRows(List<T> rows) {
		this.rows = rows;
	}
}

测试

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@ page trimDirectiveWhitespaces="true"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="test" uri="http://test-uri/common/"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
%>
<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>Test</title>
</head>
<body>
<test:page url="${pageContext.request.contextPath }/customer/list.action" />
</body>
</html>

转载于:https://www.cnblogs.com/setlilei/p/10629429.html