SSM框架利用自定义标签分页

2018-10-19 06:30:00来源:博客园 阅读 ()

新老客户大回馈,云服务器低至5折

分页通常是令人头疼的一件事,然而,这里将介绍一种新方法

这是一种巧妙地方法:

后端自定义JSP标签,这样在前端方面做分页会变得很简单

这里需要一种新技术:自定义标签

 

举例:在JSP动态页面技术中:我们都知道有c标签:

只需要在头导入:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

使用示例:

<c:forEach items="${industry}" var="item">
    <option value="${item.id}"
            <c:if test="${item.id == xxx}"> 
              xxx
            </c:if>>${item.item_name }
        </option>
</c:forEach>

 

这些都是基本知识:

那么是否可以自定义标签呢?

可以:我随便写一堆:yiqing标签库,URI随意写为:yiqing is handsome

<%@ taglib prefix="yiqing" uri="YiqingIsHandsome"%>

然而,如果你在JSP页面搞这么一个东西,会红线报错

 

如何让他不报错呢?

可以:写一个TLD文件:

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>
    <uri>YiqingIsHandsome</uri>
    <display-name>Common Tag</display-name>
    <description>Common Tag library</description>

    <tag>
        <name>page</name>
        <tag-class>org.dreamtech.common.utils.NavigationTag</tag-class>
        <body-content>JSP</body-content>
        <description>create navigation for paging</description>
        <attribute>
            <name>bean</name>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>number</name>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>url</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

 

这里要保证两处的URI一致,name属性是标签库内的page标签

下边的attribute配置是为了后面使用该标签库来实现分页的

这里有三个属性:先解释一下:

bean和number是可以选择的参数,具体意义下面介绍

url是必须的参数:分页跳转的URL(交给哪个Controller来处理)

 

这里还看到一个class属性:这个就是核心的类,处理标签分页功能的类:

注意:

1.这里的这个分页核心类是根据Bootstrap前端框架编写的,其他前端框架可能不适用

   不过,只需要略修改下代码就可以通用

2.需要有Tomcat的支持包(相当于废话)

package org.dreamtech.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 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
     */
    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
     * @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;
    }
    
}

 

 

当然,也需要有个分页Page实体类:

package org.dreamtech.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;
    }
    
    
    
}

 

 

OK,这时候我在前端JSP页面只需要写这一行即可完成分页:

                            <yiqing:page url="${pageContext.request.contextPath }/xxxx" />

 

 

接下来做一个实际使用的示例:

前端发送查询条件进行客户查询:

 

前端JSP页面的查询表单:(JSP代码就不给了,没什么意义)

 

传递过来了一个查询对象:

分别是客户名称模糊输入,选择的来源行业以及级别

 

public class QueryVo {

    // 客户信息
    private String custName;
    private String custSource;
    private String custIndustry;
    private String custLevel;

    // 当前页信息
    private Integer page;

    // 每页数
    private Integer size = 10;

    private Integer startRow = 0;

    public Integer getStartRow() {
        return startRow;
    }

    public void setStartRow(Integer startRow) {
        this.startRow = startRow;
    }

    public String getCustName() {
        return custName;
    }

    public void setCustName(String custName) {
        this.custName = custName;
    }

    public String getCustSource() {
        return custSource;
    }

    public void setCustSource(String custSource) {
        this.custSource = custSource;
    }

    public String getCustIndustry() {
        return custIndustry;
    }

    public void setCustIndustry(String custIndustry) {
        this.custIndustry = custIndustry;
    }

    public String getCustLevel() {
        return custLevel;
    }

    public void setCustLevel(String custLevel) {
        this.custLevel = custLevel;
    }

    public Integer getPage() {
        return page;
    }

    public void setPage(Integer page) {
        this.page = page;
    }

    public Integer getSize() {
        return size;
    }

    public void setSize(Integer size) {
        this.size = size;
    }

}
View Code

 

Controller层:

        Page<Customer> page = customerService.selectPageByQueryVo(vo);
        model.addAttribute("page", page);

 

Service层:这里的startRow和下面的

    public Page<Customer> selectPageByQueryVo(QueryVo vo) {
        Page<Customer> page = new Page<Customer>();
        vo.setSize(5);
        page.setSize(5);
        if (vo != null) {
            if (vo.getPage() != null) {
                vo.setStartRow((vo.getPage() - 1) * vo.getSize());
                page.setPage(vo.getPage());
            }
            page.setTotal(customerDao.customerCountByQueryVo(vo));
            page.setRows(customerDao.selectCustomerListByQueryVo(vo));
        }
        // 每页
        page.setSize(5);

        return page;
    }

 

DAO层映射:

    <select id="selectCustomerListByQueryVo" parameterType="QueryVo"
        resultType="Customer">
        select * from customer
        <where>
            <if test="custName!=null and custName!=''">
                cust_name like "%"#{custName}"%"
            </if>
            <if test="custSource!=null and custSource!=''">
                and cust_source = #{custSource}
            </if>
            <if test="custIndustry!=null and custIndustry!=''">
                and cust_industry = #{custIndustry}
            </if>
            <if test="custLevel!=null and custLevel!=''">
                and cust_level = #{custLevel}
            </if>
        </where>
        limit #{startRow},#{size}
    </select>

 

 

这样就可以查到信息了:

并且右下角自动分页

分页很智能,当前页总是显示在中间一格,最后一页和第一页无法点击的细节也有

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