Struts2中实现自定义分页标签

Struts2中实现自定义标签很简单，主要分为3步：

    1.创建taglib文件(.tld)，编写标签声明。

    2.编写自定义标签类。

    3.在页面中使用标签。

    下面以一个自定义的分页标签为例，进行说明。

    其实，开发自定义标签并不需要Struts2的支持，一般情况下，只需要继承javax.servlet.jsp.tagext.BodyTagSupport类，重写doStartTag，doEndTag等方法即可。这里在实现自定义标签时，继承的2个类分别是org.apache.struts2.views.jsp.ComponentTagSupport和org.apache.struts2.components.Component，ComponentTagSupport实际上是对BodyTagSupport的一次封装，看一下ComponentTagSupport类的继承关系就明了了：

Java代码 
java.lang.Object   
  extended by javax.servlet.jsp.tagext.TagSupport   
      extended by javax.servlet.jsp.tagext.BodyTagSupport   
          extended by org.apache.struts2.views.jsp.StrutsBodyTagSupport   
              extended by org.apache.struts2.views.jsp.ComponentTagSupport 
java.lang.Object
  extended by javax.servlet.jsp.tagext.TagSupport
      extended by javax.servlet.jsp.tagext.BodyTagSupport
          extended by org.apache.struts2.views.jsp.StrutsBodyTagSupport
              extended by org.apache.struts2.views.jsp.ComponentTagSupport

继承ComponentTagSupport类是为了获得标签中的属性值，并包装成Component对象。继承Component类是为了从Struts2中的ValueStack中获得相对应的值。

1.声明自定义标签。

首先，需要创建一个tld文件，这是一个标准的XML文件，这个文件中就包含有对自定义标签的声明，声明指出了标签的名字，实现标签的类，标签的属性等信息。当在页面中使用该标签时，web服务器就会从这个文件中找出相对应的标签类，并实例化后执行。这个文件其实与struts.xml文件的作用相类似。

tangs.tld

Xml代码 
<?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>2.2.3</tlib-version>  
    <jsp-version>1.2</jsp-version>  
    <short-name>tangs</short-name>  
    <uri>/tangs</uri>  
    <display-name>"Tangs Tags"</display-name>  
       
        <tag>  
            <name>pages</name>  
            <tag-class>com.tangs.tag.PageTag</tag-class>   //标签类   
            <body-content>empty</body-content>  
            <attribute>   //标签中的属性   
                <name>cpage</name>  //属性名   
                <required>true</required>  //是否必须   
                <rtexprvalue>true</rtexprvalue>  //表示该自定义标签的某属性的值可以直接指定或者通过动态计算指定   
            </attribute>  
            <attribute>  
                <name>total</name>  
                <required>true</required>  
                <rtexprvalue>true</rtexprvalue>  
            </attribute>  
            <attribute>  
                <name>url</name>  
                <required>true</required>  
                <rtexprvalue>true</rtexprvalue>  
            </attribute>  
        </tag>  
</taglib> 
2.编写标签类

PageTag.java

Java代码 
package com.tangs.tag;   
  
import com.opensymphony.xwork2.util.ValueStack;   
import javax.servlet.http.HttpServletRequest;   
import javax.servlet.http.HttpServletResponse;   
import org.apache.struts2.components.Component;   
import org.apache.struts2.views.jsp.ComponentTagSupport;   
  
/**  
* 分页标签  
* @author tangs  
*/  
public class PageTag extends ComponentTagSupport {   
    private String cpage;  //当前页   
    private String total;  //总页数   
    private String url;  //请求地址   
  
    public void setCpage(String cpage) {   
        this.cpage = cpage;   
    }   
  
    public void setTotal(String total) {   
        this.total = total;   
    }   
  
    public void setUrl(String url) {   
        this.url = url;   
    }   
  
    @Override  
    public Component getBean(ValueStack arg0, HttpServletRequest arg1, HttpServletResponse arg2) {   
        return new Pages(arg0); //返回Pages Component，分页的逻辑处理都在这个Component中   
    }   
  
    //获得参数   
    protected void populateParams() {   
        super.populateParams();   
           
        Pages pages = (Pages)component;   
        pages.setCpage(cpage);   
        pages.setTotal(total);   
        pages.setUrl(url);   
    }   
} 
package com.tangs.tag;

import com.opensymphony.xwork2.util.ValueStack;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts2.components.Component;
import org.apache.struts2.views.jsp.ComponentTagSupport;

/**
* 分页标签
* @author tangs
*/
public class PageTag extends ComponentTagSupport {
    private String cpage;  //当前页
    private String total;  //总页数
    private String url;  //请求地址

    public void setCpage(String cpage) {
        this.cpage = cpage;
    }

    public void setTotal(String total) {
        this.total = total;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    @Override
    public Component getBean(ValueStack arg0, HttpServletRequest arg1, HttpServletResponse arg2) {
        return new Pages(arg0); //返回Pages Component，分页的逻辑处理都在这个Component中
    }

    //获得参数
    protected void populateParams() {
        super.populateParams();
       
        Pages pages = (Pages)component;
        pages.setCpage(cpage);
        pages.setTotal(total);
        pages.setUrl(url);
    }
}
    Pages.java

Java代码 
package com.tangs.tag;   
  
import com.opensymphony.xwork2.util.ValueStack;   
import java.io.IOException;   
import java.io.Writer;   
import java.util.logging.Level;   
import java.util.logging.Logger;   
import org.apache.struts2.components.Component;   
  
/**  
* 分页逻辑Bean  
* @author tangs  
*/  
public class Pages extends Component {   
    private String cpage;   
    private String total;   
    private String url;   
  
    public String getCpage() {   
        return cpage;   
    }   
  
    public void setCpage(String cpage) {   
        this.cpage = cpage;   
    }   
  
    public String getTotal() {   
        return total;   
    }   
  
    public void setTotal(String total) {   
        this.total = total;   
    }   
  
    public String getUrl() {   
        return url;   
    }   
  
    public void setUrl(String url) {   
        this.url = url;   
    }   
       
       
    public Pages(ValueStack arg0) {   
        super(arg0);   
    }   
  
    @Override  
    public boolean start(Writer writer) {   
        boolean result = super.start(writer);   
        try {   
            StringBuilder str = new StringBuilder();   
            boolean isValid = true;   
               
            //从ValueStack中取出数值   
            if (isValid) {   
                if (total.startsWith("%{") && total.endsWith("}")) {   
                    total = total.substring(2, total.length() -1);   
                    total = (String)this.getStack().findValue(total);   
                    isValid = total == null ? false : true;   
                } else {   
                    isValid = false;   
                }   
            }   
            if (isValid) {   
                if (cpage.startsWith("%{") && cpage.endsWith("}")) {   
                    cpage = cpage.substring(2, cpage.length() - 1);   
                    cpage = (String)this.getStack().findValue(cpage);   
                    isValid = cpage == null ? false : true;   
                } else {   
                    isValid = false;   
                }   
            }   
            if (isValid) {   
                if (url.startsWith("%{") && url.endsWith("}")) {   
                    url = url.substring(2, url.length() - 1);   
                    url = (String)this.getStack().findValue(url);   
                    isValid = url == null ? false : true;   
                } else {   
                    isValid = false;   
                }   
            }   
  
            if (isValid) {   
                Integer cpageInt = Integer.valueOf(cpage);   
                //当前页与总页数相等   
                if (cpage.equals(total)) {   
                    //如果total = 1，则无需分页，显示“[第1页] [共1页]”   
                    if ("1".equals(total)) {   
                        str.append("[第 " + cpage + " 页]");   
                        str.append(" [共 " + total + " 页]");   
                    } else {   
                        //到达最后一页,显示“[首页] [上一页] [末页]”   
                        str.append("<a href='");   
                        str.append(url);   
                        str.append("?cpage=1&total="+total+"&url="+url);   
                        str.append("'>[首页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + (cpageInt - 1) + "&total=" + total+"&url="+url);   
                        str.append("'>[上一页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);   
                        str.append("'>[末页]</a>");   
                    }   
                } else {   
                    //当前页与总页数不相同   
                    if ("1".equals(cpage)) {   
                        //第一页，显示“[首页] [下一页] [末页]”   
                        str.append("<a href='");   
                        str.append(url);   
                        str.append("?cpage=1&total="+total+"&url="+url);   
                        str.append("'>[首页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + (cpageInt + 1) + "&total=" + total+"&url="+url);   
                        str.append("'>[下一页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);   
                        str.append("'>[末页]</a>");   
                    } else {   
                        //不是第一页，显示“[首页] [上一页] [下一页] [末页]”   
                        str.append("<a href='");   
                        str.append(url);   
                        str.append("?cpage=1&total="+total+"&url="+url);   
                        str.append("'>[首页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + (cpageInt - 1) + "&total=" + total+"&url="+url);   
                        str.append("'>[上一页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + (cpageInt + 1) + "&total=" + total+"&url="+url);   
                        str.append("'>[下一页]</a> <a href='");   
                        str.append(url);   
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);   
                        str.append("'>[末页]</a>");   
                    }   
                }   
            }   
              
            writer.write(str.toString());   
               
        } catch (IOException ex) {   
            Logger.getLogger(Pages.class.getName()).log(Level.SEVERE, null, ex);   
        }   
        return result;   
    }   
} 
package com.tangs.tag;

import com.opensymphony.xwork2.util.ValueStack;
import java.io.IOException;
import java.io.Writer;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.struts2.components.Component;

/**
* 分页逻辑Bean
* @author tangs
*/
public class Pages extends Component {
    private String cpage;
    private String total;
    private String url;

    public String getCpage() {
        return cpage;
    }

    public void setCpage(String cpage) {
        this.cpage = cpage;
    }

    public String getTotal() {
        return total;
    }

    public void setTotal(String total) {
        this.total = total;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
   
   
    public Pages(ValueStack arg0) {
        super(arg0);
    }

    @Override
    public boolean start(Writer writer) {
        boolean result = super.start(writer);
        try {
            StringBuilder str = new StringBuilder();
            boolean isValid = true;
           
            //从ValueStack中取出数值
            if (isValid) {
                if (total.startsWith("%{") && total.endsWith("}")) {
                    total = total.substring(2, total.length() -1);
                    total = (String)this.getStack().findValue(total);
                    isValid = total == null ? false : true;
                } else {
                    isValid = false;
                }
            }
            if (isValid) {
                if (cpage.startsWith("%{") && cpage.endsWith("}")) {
                    cpage = cpage.substring(2, cpage.length() - 1);
                    cpage = (String)this.getStack().findValue(cpage);
                    isValid = cpage == null ? false : true;
                } else {
                    isValid = false;
                }
            }
            if (isValid) {
                if (url.startsWith("%{") && url.endsWith("}")) {
                    url = url.substring(2, url.length() - 1);
                    url = (String)this.getStack().findValue(url);
                    isValid = url == null ? false : true;
                } else {
                    isValid = false;
                }
            }

            if (isValid) {
                Integer cpageInt = Integer.valueOf(cpage);
                //当前页与总页数相等
                if (cpage.equals(total)) {
                    //如果total = 1，则无需分页，显示“[第1页] [共1页]”
                    if ("1".equals(total)) {
                        str.append("[第 " + cpage + " 页]");
                        str.append(" [共 " + total + " 页]");
                    } else {
                        //到达最后一页,显示“[首页] [上一页] [末页]”
                        str.append("<a href='");
                        str.append(url);
                        str.append("?cpage=1&total="+total+"&url="+url);
                        str.append("'>[首页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + (cpageInt - 1) + "&total=" + total+"&url="+url);
                        str.append("'>[上一页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);
                        str.append("'>[末页]</a>");
                    }
                } else {
                    //当前页与总页数不相同
                    if ("1".equals(cpage)) {
                        //第一页，显示“[首页] [下一页] [末页]”
                        str.append("<a href='");
                        str.append(url);
                        str.append("?cpage=1&total="+total+"&url="+url);
                        str.append("'>[首页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + (cpageInt + 1) + "&total=" + total+"&url="+url);
                        str.append("'>[下一页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);
                        str.append("'>[末页]</a>");
                    } else {
                        //不是第一页，显示“[首页] [上一页] [下一页] [末页]”
                        str.append("<a href='");
                        str.append(url);
                        str.append("?cpage=1&total="+total+"&url="+url);
                        str.append("'>[首页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + (cpageInt - 1) + "&total=" + total+"&url="+url);
                        str.append("'>[上一页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + (cpageInt + 1) + "&total=" + total+"&url="+url);
                        str.append("'>[下一页]</a> <a href='");
                        str.append(url);
                        str.append("?cpage=" + total + "&total=" + total+"&url="+url);
                        str.append("'>[末页]</a>");
                    }
                }
            }
          
            writer.write(str.toString());
           
        } catch (IOException ex) {
            Logger.getLogger(Pages.class.getName()).log(Level.SEVERE, null, ex);
        }
        return result;
    }
}
3.服务端

服务端主要是获得请求然后转向显示的页面

DisplayAction.java

Java代码 
/*  
* To change this template, choose Tools | Templates  
* and open the template in the editor.  
*/  
  
package com.tangs.action;   
  
import com.opensymphony.xwork2.ActionSupport;   
  
/**  
*  
* @author tangs  
*/  
public class DisplayAction extends ActionSupport {   
    private String cpage;   
    private String total;   
    private String url;   
  
    public String list() {   
           
        //Get data from server   
        //...   
        //这里没有做任何逻辑，直接跳转到了页面   
        return SUCCESS;   
    }   
    public String getCpage() {   
        return cpage;   
    }   
  
    public void setCpage(String cpage) {   
        this.cpage = cpage;   
    }   
  
    public String getTotal() {   
        return total;   
    }   
  
    public void setTotal(String total) {   
        this.total = total;   
    }   
  
    public String getUrl() {   
        return url;   
    }   
  
    public void setUrl(String url) {   
        this.url = url;   
    }   
       
       
} 
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

package com.tangs.action;

import com.opensymphony.xwork2.ActionSupport;

/**
*
* @author tangs
*/
public class DisplayAction extends ActionSupport {
    private String cpage;
    private String total;
    private String url;

    public String list() {
       
        //Get data from server
        //...
        //这里没有做任何逻辑，直接跳转到了页面
        return SUCCESS;
    }
    public String getCpage() {
        return cpage;
    }

    public void setCpage(String cpage) {
        this.cpage = cpage;
    }

    public String getTotal() {
        return total;
    }

    public void setTotal(String total) {
        this.total = total;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
   
   
}
  struts.xml

Xml代码 
<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd" >  
<struts>  
    <package name="tagTest" extends="struts-default">  
                <action name="list" class="com.tangs.action.DisplayAction">  
                    <result name="success">/list.jsp</result>  
                </action>  
    </package>  
</struts> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd" >
<struts>
<package name="tagTest" extends="struts-default">
                <action name="list" class="com.tangs.action.DisplayAction">
                    <result name="success">/list.jsp</result>
                </action>
</package>
</struts>
 

4.在页面中使用标签

list.jsp

Html代码 
<%@page contentType="text/html" pageEncoding="UTF-8"%>  
<%@ taglib prefix="tangs" uri="/WEB-INF/tangs.tld"%>  
<%@ taglib prefix="s" uri="/WEB-INF/struts-tags.tld"%>  
  
<html>  
    <head>  
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
        <title>List</title>  
    </head>  
    <body>  
        共 <s:property value="total"/> 页 第 <s:property value="cpage"/> 页<br>  
        <tangs:pages cpage="%{cpage}" total="%{total}" url="%{url}"/>  
    </body>  
</html>  

http://localhost:8888/TagTest/list.action?cpage=2&total=5&url=list.action

评论

1 楼 maosenmin 2009-04-18  

如果有多个查询条件任意组合查询，那当在点下一页时url=list.action ,可这个时候并不像第一次由查询页面进入直接把查询参数带进来，而这个时候怎样把查询页面的查询条件带过来呢？