关于标签属性值的传递问题——以日历标签为例 - JavaEE网站开发课件 - 课外天地李树青

关于自定义标签的属性处理

1、利用请求中的变量
注意这些变量的初始值
标签类：
package taglib;

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

public class CalendarTag extends TagSupport {
String style = "";
String cssFilePath = "";

        public void setStyle(String style) {
                this.style = style;
                if (style.toLowerCase().equals("sky"))
                        cssFilePath = "css1.css";
                else
                        cssFilePath = "css2.css";
        }

        public int doEndTag() throws JspException {
                try {
                        String year = pageContext.getRequest().getParameter("year");
                        String month = pageContext.getRequest().getParameter("month");
                        pageContext.getOut().print(
                                        "<link rel=stylesheet href='" + cssFilePath
                                                        + "' type='text/css'>");
                        java.text.DecimalFormat myformat = new java.text.DecimalFormat("00");//
                        java.util.GregorianCalendar gregorianCalendar = new java.util.GregorianCalendar();
                        int j = 1;
                        if (year != null && month != null) {
                                gregorianCalendar.set(gregorianCalendar.YEAR, Integer
                                                .parseInt(year));
                                gregorianCalendar.set(gregorianCalendar.MONTH, Integer
                                                .parseInt(month) - 1);
                        }
                        int maxDay = gregorianCalendar
                                        .getActualMaximum(gregorianCalendar.DAY_OF_MONTH);
                        gregorianCalendar.set(gregorianCalendar.DAY_OF_MONTH, 1);
                        int space = gregorianCalendar.get(gregorianCalendar.DAY_OF_WEEK);
                        int counter = space - 1;
                        String[] days = new String[counter + maxDay];

                        for (int i = 0; i < counter; i++) {
                                days[i] = " ";
                        }
                        for (int i = counter; i < counter + maxDay; i++) {
                                days[i] = myformat.format(j);
                                j++;
                        }
                        pageContext.getOut().print("<table>");
                        pageContext.getOut().print("<tr class='headerStyle'>");
                        pageContext
                                        .getOut()
                                        .print(
                                                        "<td>日</td><td>一</td><td>二</td><td>三</td><td>四</td><td>五</td><td>六</td>");
                        pageContext.getOut().print("</tr>");
                        pageContext.getOut().print("<tr class='textStyle'>");
                        int m = 1;
                        for (int i = 0; i < counter + maxDay; i++) {
                                pageContext.getOut().print("<td>" + days[i] + "</td>");
                                if ((m++) % 7 == 0)
                                        pageContext.getOut().print("</tr><tr class='textStyle'>");
                        }
                        pageContext.getOut().print("</tr>");
                        pageContext.getOut().print("</table>");
                } catch (Exception e) {
                        throw new JspException(e.toString());
                }
                return EVAL_PAGE;
        }

}

网页：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>

2、利用属性传递变量名称
标签类：
package taglib;

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

public class CalendarTag extends TagSupport {
        String style = "";
        String cssFilePath = "";
        String year = "";
        String msky"))
                        cssFilePath = "css1.css";
                else
                        cssFilePath = "css2.css";
        }

        public void setYear(String year) {
                this.year = year;
        }

        public void setMonth(String month) {
                this.month = month;
        }

        public int doEndTag() throws JspException {
                try {
                        String year = pageContext.getRequest().getParameter(this.year);
                        String month = pageContext.getRequest().getParameter(this.month);
                        pageContext.getOut().print(
                                        "<link rel=stylesheet href='" + cssFilePath
                                                        + "' type='text/css'>");
                        java.text.DecimalFormat myformat = new java.text.DecimalFormat("00");//
                        java.util.GregorianCalendar gregorianCalendar = new java.util.GregorianCalendar();
                        int j = 1;
                        if (year != null && month != null) {
                                gregorianCalendar.set(gregorianCalendar.YEAR, Integer
                                                .parseInt(year));
                                gregorianCalendar.set(gregorianCalendar.MONTH, Integer
                                                .parseInt(month) - 1);
                        }
                        int maxDay = gregorianCalendar
                                        .getActualMaximum(gregorianCalendar.DAY_OF_MONTH);
                        gregorianCalendar.set(gregorianCalendar.DAY_OF_MONTH, 1);
                        int space = gregorianCalendar.get(gregorianCalendar.DAY_OF_WEEK);
                        int counter = space - 1;
                        String[] days = new String[counter + maxDay];

}

标签描述文件：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
        <tlibversion>1.0</tlibversion>
        <jspversion>1.2</jspversion>
        <shortname></shortname>
        <uri></uri>
        <info></info>
        <tag>
                <name>calendar</name>
                <tagclass>taglib.CalendarTag</tagclass>
                <attribute>
                        <name>style</name>
                        <rtexprvalue>true</rtexprvalue>
                </attribute>
                <attribute>
                        <name>year</name>
                        <rtexprvalue>true</rtexprvalue>
                </attribute>
                <attribute>
                        <name>month</name>
                        <rtexprvalue>true</rtexprvalue>
                </attribute>
        </tag>
</taglib>

网页：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>

3、利用属性传递变量值
标签类：
package taglib;

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

public class CalendarTag extends TagSupport {
        String style = "";
        String cssFilePath = "";
        int year = -1;
        int month = -1;

        public void setYear(String year) {
                if (year != null)
                        this.year = Integer.parseInt(year);
        }

        public void setMonth(String month) {
                if (month != null)
                        this.month = Integer.parseInt(month);
        }

        public int doEndTag() throws JspException {
                try {
                        pageContext.getOut().print(
                                        "<link rel=stylesheet href='" + cssFilePath
                                                        + "' type='text/css'>");
                        java.text.DecimalFormat myformat = new java.text.DecimalFormat("00");//
                        java.util.GregorianCalendar gregorianCalendar = new java.util.GregorianCalendar();
                        int j = 1;
                        if (year != -1 && month != -1) {
                                gregorianCalendar.set(gregorianCalendar.YEAR, year);
                                gregorianCalendar.set(gregorianCalendar.MONTH, month - 1);
                        }
                        int maxDay = gregorianCalendar
                                        .getActualMaximum(gregorianCalendar.DAY_OF_MONTH);
                        gregorianCalendar.set(gregorianCalendar.DAY_OF_MONTH, 1);
                        int space = gregorianCalendar.get(gregorianCalendar.DAY_OF_WEEK);
                        int counter = space - 1;
                        String[] days = new String[counter + maxDay];

}

网页：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>

4、利用属性传递变量值（写成EL的写法）
为了防止开始参数无值带来的影响，将网页做成两个
标签类：
package taglib;

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

public class CalendarTag extends TagSupport {
        String style = "";
        String cssFilePath = "";
        int year = -1;
        int month = -1;

        public void setYear(String year) {
                if (year != null)
                        this.year = Integer.parseInt(year);
        }

        public void setMonth(String month) {
                if (month != null)
                        this.month = Integer.parseInt(month);
        }

}

网页index.jsp：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>

网页result.jsp：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>

5、利用JavaBean传递
JavaBean类：
package javabeans;

public class MyDate {
String year;
String month;

        public String getYear() {
                return year;
        }

        public void setYear(String year) {
                this.year = year;
        }

        public String getMonth() {
                return month;
        }

        public void setMonth(String month) {
                this.month = month;
        }
}

标签类：
package taglib;

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

public class CalendarTag extends TagSupport {
        String style = "";
        String cssFilePath = "";
        int year = -1;
        int month = -1;

        public void setYear(String year) {
                if (year != null)
                        this.year = Integer.parseInt(year);
        }

        public void setMonth(String month) {
                if (month != null)
                        this.month = Integer.parseInt(month);
        }

}

网页index.jsp：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<jsp:useBean id="md" class="javabeans.MyDate" scope="session"></jsp:useBean>
<div id="Layer1"
        style="position: absolute; width: 200px; height: 115px; z-index: 1; left: 284px; top: 158px;">
<form action="result.jsp"><select name='syear'>
        <option value=2007>2007</option>
        <option value=2008>2008</option>
        <option value=2009>2009</option>
        <option value=2010>2010</option>
        <option value=2011>2011</option>
        <option value=2012 selected>2012</option>
</select> <select name='smonth'>
        <option value=1 selected>1</option>
        <option value=2>2</option>
        <option value=3>3</option>
        <option value=4>4</option>
        <option value=5>5</option>
        <option value=6>6</option>
        <option value=7>7</option>
        <option value=8>8</option>
        <option value=9>9</option>
        <option value=10>10</option>
        <option value=11>11</option>
        <option value=12>12</option>
</select> <input type='submit' value='ok' name='submit'></form>
</div>
</body>
</html>

网页result.jsp：
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<%@page import="javabeans.MyDate"%>
<html>
<head>
</head>
<body>
<jsp:setProperty name="md" property="year" value='${param.syear}' />
<jsp:setProperty name="md" property="month" value='${param.smonth}' />
<div id="Layer1"
style="position: absolute; width: 200px; height: 115px; z-index: 1; left: 284px; top: 158px;">
<mytag:calendar style="sun" year='${md.year}'
m>
</mytag:calendar></div>
</body>
</html>

<%-- <mytag:calendar style="sun" year=<jsp:getProperty name="md" property="year"/>
month=<jsp:getProperty name="md" property="month"/>></mytag:calendar>--%>

主题：关于标签属性值的传递问题——以日历标签为例