Java-页面分页效果

水深无声 2022-01-21 02:15 327阅读 0赞

# 分页模板 #

### 1、首先建立一个工具包msq.utils ###

新建两个类

NavigationTag.java

package msq.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;
    	private String bean = "page";//request 中用于保存Page<E> 对象的变量名,默认为“page”
    	private String url = null;//分页跳转的url地址,此属性必须
    	private int number = 5;//显示页码数量	
    	
    	private int goPage = 1;//显示要跳转到的页码
    	@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.getTotalRecordCount() / page.getPageSize();
    			if (page.getTotalRecordCount() % page.getPageSize() > 0) {
    				pageCount++;
    			}
    			writer.print("<nav><ul class=\"pagination\">");
    			
    			//首页链接路径
    			String homeUrl = append(url, "currentPage", 1);
    			homeUrl = append(homeUrl, "pageSize", page.getPageSize());
    			//末页链接路径
    			String backUrl = append(url, "currentPage", pageCount);	
    			backUrl = append(backUrl, "pageSize", page.getPageSize());
    			// 显示“首页  上一页”按钮
    			if (page.getCurrentPage() > 1) {
    				String preUrl = append(url, "currentPage", page.getCurrentPage() - 1);
    				preUrl = append(preUrl, "pageSize", page.getPageSize());
    				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 number2=number/2;  //总共显示number页，分为前后各一半
    			int indexPage =1;
    			if(page.getCurrentPage() - number2 <=0){  //处理前几页
    				indexPage=1; //起始页码位置
    			}else if(pageCount-page.getCurrentPage() <=number2){  //处理尾几页
    				indexPage=pageCount-number+1;//从最后向前number-1页
    				if(indexPage<=0)indexPage=1;  //防止出现负数页码
    			}else{
    				indexPage= page.getCurrentPage() - number2; //中间页码
    			}
    			for (int i= 1;i <= number && indexPage <= pageCount;indexPage++,i++){
    				if (indexPage == page.getCurrentPage()) {
    					writer.print("<li class=\"active\"><a href=\"#\">" + indexPage+"<span class=\"sr-only\"></span></a></li>");
    					continue;
    				}
    				String pageUrl = append(url, "currentPage", indexPage);
    				pageUrl = append(pageUrl, "pageSize", page.getPageSize());
    				writer.print("<li><a href=\"" + pageUrl + "\">" + indexPage + "</a></li>");
    			}
    			// 显示“下一页”按钮
    			if (page.getCurrentPage() < pageCount) {
    				String nextUrl = append(url, "currentPage", page.getCurrentPage() + 1);
    				nextUrl = append(nextUrl, "pageSize", page.getPageSize());
    				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("<li class=\"disabled\"><a  href='javascript:void(0)'>共" + pageCount + "页" + page.getTotalRecordCount() + "条记录</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 添加参数对儿
    	 */
    	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 ("currentPage".equals(key) || "pageSize".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 void setUrl(String url) {
    		this.url = url;
    	}
    	public void setNumber(int number) {
    		this.number = number;
    	}
    }

Page.java

package msq.utils;
    
    import java.util.List;
    
    public class Page<T> {		
    	private Integer totalRecordCount;//总记录数
    	private Integer pageSize;//一页几条记录
    	private Integer currentPage;	//当前页号
    	private List<T> list;//当前页的记录list，传递给页面
    	
    	public Integer getTotalRecordCount() {
    		return totalRecordCount;
    	}
    	public void setTotalRecordCount(Integer total) {
    		this.totalRecordCount = total;
    	}
    	public Integer getPageSize() {
    		return pageSize;
    	}
    	public void setPageSize(Integer size) {
    		this.pageSize = size;
    	}
    	public Integer getCurrentPage() {
    		return currentPage;
    	}
    	public void setCurrentPage(Integer page) {
    		this.currentPage = page;
    	}
    	public List<T> getList() {
    		return list;
    	}
    	public void setList(List<T> rows) {
    		this.list = rows;
    	}
    	
    	
    
    }

### 2、在工程的WebRoot/WEB-INF下新建标签文件tle ###

新建标签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>1.0</tlib-version>
     
     <jsp-version>1.2</jsp-version>
     
     <short-name>common</short-name>
     
     <uri>http://www.nynu.edu.cn/page</uri>
     
     <display-name>Common Tag</display-name>
     
     <description>Common Tag library</description>
     
     <tag>
      
      <name>page</name>
      
      <tag-class>msq.utils.NavigationTag</tag-class>
      
      <body-content>JSP</body-content>
      
      <description>create navigation for paging</description>
      
      <attribute>
       
       <name>url</name>
       
       <required>true</required>
       
       <rtexprvalue>true</rtexprvalue>
      </attribute>
      <attribute>
       <name>number</name>
       <rtexprvalue>true</rtexprvalue>
      </attribute>
     </tag>
    </taglib>

### 3、在需要加分页效果的页面前加标签注解 ###

<%@ taglib prefix="mypage" uri="http://www.nynu.edu.cn/page" %>

### 4、在合适的位置放上分页效果图 ###

url="与后台连接到页面地址"

<mypage:page url="#"  ></mypage:page>

### 5、新建一个类CustomPo，当前类继承CustomPo类 ###

package msq.po;
    
    public class CustomPo {
       Integer start;
       Integer pageSize;
    public Integer getStart() {
    	return start;
    }
    public void setStart(Integer start) {
    	this.start = start;
    }
    public Integer getPageSize() {
    	return pageSize;
    }
    public void setPageSize(Integer pageSize) {
    	this.pageSize = pageSize;
    }
       
       
    }

### 6、在后台的查找类中依次加上两个参数 ###

controller包

@RequestParam(name="currentPage",defaultValue="1")Integer currentPage,//起始页
    @RequestParam(name="PageSize",defaultValue="10")Integer PageSize,//页大小

将原先用来储存数据的List<T> 改成 Page<T>

在查询的基础上分页只需要再加一个参数即可

### 7、更改对应的sql语句 ，加上限制条件 ###

<sql id="sqlLimit">
          <if test="start!=null and pageSize!=null">
             limit #{start},#{pageSize}
          </if>
        </sql>

### 最后效果 ###

![2019060716563043.png][]

[2019060716563043.png]: /images/20220121/94c37a263ae243a19d7d9650967a5d30.png