JAVA:自定义标签-分页-List数据显示

显示List的类

import java.io.IOException;
import java.util.List;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.IterationTag;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * 分页显示List对象数据
 *
 */
public class PageList extends TagSupport {
    /**
     * 表格样式
     */
    String tableStyle = " border='1px solid gray'";
    
    /**
     * 第一行格式
     * @see 标题列，左对齐好看点
     */
    String firstLineStyle = " style='vertical-align:middle; text-align:left;'";
    
    /**
     * 鼠标悬停事件:查看一行时,添加背景色
     */
    String onMounse = "onmousemove='javascript:function addBack(x)" + 
            "{x.style.background=\"orange\" };addBack(this)' onmouseout='javascription:function noBack(x)" +"{x.style.background=\"\" };noBack(this)'";
    
    private int currentNum = -1;
    private int endNum = -1;
    
    public int getCurrentNum() {
        return currentNum;
    }
    
    /**
     * 保存在request对象中的数据集合的关键字
     */
    private String dataKey;
    
    public void setDataKey(String dataKey) {
        this.dataKey = dataKey;
    }

    @SuppressWarnings({ "static-access", "rawtypes" })
    @Override
    public int doStartTag() throws JspException {
        Object obj = pageContext.getAttribute(dataKey);
        if (null == obj)
        {
            return super.SKIP_BODY;
        }
        List pageList = (List) obj;
        if (pageList.isEmpty())
        {
            return super.SKIP_BODY;
        }
        currentNum = -1;
        endNum = pageList.size();
        JspWriter out = pageContext.getOut();
        StringBuffer sb = new StringBuffer();
        sb.append("<table width='400px' cellspacing='0' cellpadding='4' " + tableStyle + ">");
        sb.append("<tr " + firstLineStyle + ">");
        try {
            out.write(sb.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 执行当前标签里的内容
        return EVAL_BODY_INCLUDE;
    }
    
    /**
     * Tag.SKIP_PAGE：表示立刻停止执行网页
     * Tag.EVAL_PAGE：表示按正常的流程继续执行JSP网页
     */
    public int doEndTag() throws JspException {
        JspWriter out = pageContext.getOut();
        try {
            out.print("</table> ");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return EVAL_PAGE;
    }
    
    @SuppressWarnings("unchecked")
    public int doAfterBody() throws JspException {
        currentNum++; // 自增,0表示已经运行了一次
        JspWriter out = pageContext.getOut();
        if (currentNum < endNum) {
            List<Object> objs = (List<Object>) pageContext.findAttribute(dataKey);
            Object obj = objs.get(getCurrentNum());
            pageContext.setAttribute("dateKey", obj);
            try {
                out.print("</tr><tr " + onMounse + ">");
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return IterationTag.EVAL_BODY_AGAIN;
        } else {
            try {
                out.print("</tr>");
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return IterationTag.SKIP_BODY;
        }
    }

    /**
     * 第一行数据前添加title(表头)
     * @return
     */
    public boolean isTitle() {
        if (currentNum == -1) {
            return true;
        }
        return false;
    }
}

显示List里对象数据的类

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

import org.apache.commons.lang3.StringUtils;


/**
 * 分页显示List对象数据:显示每个对象具体内容
 *
 */
public class ListColumn extends TagSupport {
    /**
     * 显示的列头(表头)
     */
    private String header;
    
    /**
     * 鼠标悬停时显示的内容
     */
    private String title;

    private String name;
    // 是一个class结构，通过反射技术得到对象的数据类型，不提供setter访问器
    private Class entity = null;
    
    /**
     * 当前标签为显示对象的具体字段，不单独使用
     */
    @Override
    public int doStartTag() throws JspException {
        Tag tag = this.getParent();
        if (!(tag instanceof PageList))
        {
            throw new JspException("Tag can't be used alone.To use it with tagList");
        }
        PageList pTag = (PageList) this.getParent();
        JspWriter out = pageContext.getOut();
        StringBuffer buffer = new StringBuffer();
        try {
            String currTitle = "";
            if (StringUtils.isNotEmpty(title)) {
                currTitle = "\" title=" + title + "\"";//getTexts(
            }
            if (pTag.isTitle()) { // 输出标题
                buffer.append("<th>" + header + "</th>");
            } else { // 输出身体
                buffer.append("<td "  + currTitle + ">"); // body交给页面添加内容
                // 设置 数据到身体
                Object object = pageContext.getAttribute("dateKey");
                // 通过反射得到obj对象的数据类型
                entity = object.getClass();
                String value = "";
                // 得到getter访问器的名称
                String getMethodName = "get" + name.substring(0, 1).toUpperCase() + name.substring(1);
                // 使用反射技术得到该类型（entity）中定义的方法对象
                Method method = entity.getDeclaredMethod(getMethodName, null);
                if (method != null) {
                    // 调用method对象的invoke方法，从而得到该方法的返回值
                    value = method.invoke(object, null).toString();
                }
                buffer.append(value);
            }
            out.print(buffer.toString());            
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return EVAL_BODY_INCLUDE;
    }
    
    public void setHeader(String header) {
        this.header = header;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int doEndTag() throws JspException {
        PageList pTag = (PageList) this.getParent();
        JspWriter out = pageContext.getOut();
        try {
            if (pTag.isTitle()) { // 是否是标题
                // out.print( "<td>"+title+"</td>");
            } else { // 输出身体
                out.print("</td>");
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return EVAL_PAGE;
    }
}

tld.xml自定义标签描述文件

修改tag-class为真实包路径

<?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>2.0</jsp-version>
    <short-name>page</short-name>
    <uri>tags/page</uri>
    <!-- 父标签 -->
    <tag>
        <name>list</name>
        <!-- 修改为真实包路径 -->
        <tag-class>xxx.PageList</tag-class>
        <!-- scriptless 主体可以有内容, 而jsp容器会去处理里面的jsp元素, 换句话就是可以是文本, EL表达式, 标准动作甚至另一个自定义标记. -->
        <body-content>scriptless</body-content>

        <attribute>
            <name>dataKey</name>
            <required>true</required>
            <!-- rtexprvalue 是否允许表达式 不允许时${1+1}出错 -->
            <rtexprvalue>false</rtexprvalue>
        </attribute>
    </tag>
    <!-- 子标签 -->
    <tag>
        <name>column</name>
        <!-- 修改为真实包路径 -->
        <tag-class>xxx.ListColumn</tag-class>
        <body-content>scriptless</body-content>
        <attribute>
            <name>header</name>
            <required>true</required>
            <!-- rtexprvalue 是否允许表达式 不允许时${1+1}出错 -->
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>title</name>
            <required>false</required>
            <!-- rtexprvalue 是否允许表达式 不允许时${1+1}出错 -->
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>name</name>
            <required>true</required>
            <!-- rtexprvalue 是否允许表达式 不允许时${1+1}出错 -->
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

使用

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="xxx.user.*"%>
<%@ taglib prefix="page" uri="/tags/page"%>

<html>

<body>
    <%
        User user = new User();
        user.setName("name");
        List<User> users = new ArrayList<User>();
        users.add(user);
        pageContext.setAttribute("users", users);
    %>
    <page:list dataKey="users">
        <page:column name="name" header="用户名"></page:column>
        <%--<page:column name="xxx" header="xxx"></page:column>--%>
    </page:list>
</body>
</html>