自定义标签（二）

原创 于 2019-06-01 23:49:10 发布 · 118 阅读 · 0 ·
CC 4.0 BY-SA版权
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。

自定义标签

1. UI标签:out select checkbox
2. 控制标签 if forEach
3. 数据标签 set

1. UI标签:out select
有设置就有输出接下来让我们先写一下set 与out的的自定义标签
Set标签有var和value两个属性，Out标签只有value一个属性，所以我们先定义它们助手类

	public class SetTag  extends BodyTagSupport{

	    	private static final long serialVersionUID = 1L;
	    	
	    	private String var;
	    	private Object value;
	    	
	    	@Override
	    	public int doStartTag() throws JspException {
	    		//内置对象
	    		pageContext.setAttribute(var, value);
	    		return SKIP_BODY;//跳过主体
	    	}
	    	
	    	public String getVar() {
	    		return var;
	    	}
	    	public void setVar(String var) {
	    		this.var = var;
	    	}
	    	public Object getValue() {
	    		return value;
	    	}
	    	public void setValue(Object value) {
	    		this.value = value;
	    	}
	  }

public class OutTag extends BodyTagSupport {

	
	private static final long serialVersionUID = 1L;//防止报空指针异常
	private  Object value;//Objiec 打印的可能是任何类型
	
	public Object getValue() {
		return value;
	}
	public void setValue(Object value) {
		this.value = value;
	}
	

	@Override
	public int doStartTag() throws JspException {
		JspWriter out= pageContext.getOut();//输出流
		try {
			out.print(value.toString());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return SKIP_BODY;
	}
}

配置tld文件

<tag>
    <name>set</name>
    <tag-class>com.xyx.jsp2.SetTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
    	<name>var</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>value</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

  <tag>
    <name>out</name>
    <tag-class>com.xyx.jsp2.OutTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
    	<name>value</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

输出:

	<z:set var="name" value="zs"></z:set>
	<z:out value="${name }"></z:out>

***2. 控制标签 if ***
if标签只有一个属性值test
助手类：

public class IfTag extends BodyTagSupport {

	
	private static final long serialVersionUID = -8477321984637500253L;
	private boolean test;
	public boolean isTest() {
		return test;
	}
	public void setTest(boolean test) {
		this.test = test;
	}
	
	
	@Override
	public int doStartTag() throws JspException {
		return test ? EVAL_BODY_INCLUDE : SKIP_BODY;//三目运算符 
	}

}

配置tld文件：

<tag>
    <name>if</name>
    <tag-class>com.xyx.jsp2.IfTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
    	<name>test</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>

输出：

	<z:if test="true">lisi</z:if>//出现结果
	<z:if test="false">wangwu</z:if>//不出想

2.1 控制标签 foreach
foreach 有两个属性值一个是var 一个是集合items
助手类：

public class ForeachTag extends BodyTagSupport {
	
	private static final long serialVersionUID = 1L;
	private String var;
	private List<Object> items=new ArrayList<>();
	
	/**
	 * 执行完这个的时候，var代表的指针一定要向下移动一位；
	 */
	@Override
	public int doStartTag() throws JspException {
		if(items.size()==0) {//如果items的长度大于0
			return SKIP_BODY;//跳过主体
		} else {
			//pageContext只限于当前界面
			Iterator<Object> it = items.iterator();//迭代器
			pageContext.setAttribute(var, it.next());//第一个对象
			pageContext.setAttribute("it", it);//把迭代器往下传 if=1时
			return EVAL_BODY_AGAIN;//在循环一次
		}
	}
	
	
	@Override
	public int doAfterBody() throws JspException {
		Iterator<Object> it=(Iterator<Object>)pageContext.getAttribute("it");//获得上面的迭代器
		if(it.hasNext()){//迭代器继续循环  如果还有下一个
			pageContext.setAttribute(var, it.next());//往下移
			pageContext.setAttribute("it", it);
			return EVAL_BODY_AGAIN;
		}
			return EVAL_PAGE;
	}

	public String getVar() {
		return var;
	}


	public void setVar(String var) {
		this.var = var;
	}


	public List<Object> getItems() {
		return items;
	}


	public void setItems(List<Object> items) {
		this.items = items;
	}
	

}

配置tld文件：

<tag>
    <name>foreach</name>
    <tag-class>com.xyx.jsp2.ForeachTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
    	<name>var</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>items</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

输出

<%
	List list=new ArrayList();
	list.add(new Student("001","xiaocheng"));
	list.add(new Student("002","xiaohua"));
	list.add(new Student("003","xiaolv"));
	request.setAttribute("stus", list);
	
	%>
	
	<z:foreach items="${stus }" var="stu">
		${stu.id },${stu.name }<br>
	</z:foreach>


注：在这里需要写一个学生实体类，这个实体类属性有学号与姓名

注：导包不要导错了

/**
 * 1.值得传递  id,name
 * 2.数据源 iteams
 * 3.展示列与数据存储列与实体列的对应关系  textKey  textVal
 * 4.数据回显 selectedVal
 * 5.可能下拉框默认值（投标签） headerTextKey  headerTextVal
 * 
 * @author XYX
 *
 */

public class SelectTag extends BodyTagSupport {

	private static final long serialVersionUID = 1L;

	private String id;
	private String name;
	private List<Object> items=new ArrayList<>();
	private String textKey;
	private String textVal;
	private String selectedVal;
	private String headerTextKey;
	private String headerTextVal;
	
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out= pageContext.getOut();
		try {
			try {
				out.print(toHTML());
			} catch (NoSuchFieldException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (SecurityException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalArgumentException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalAccessException 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 (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	//用字符串拼接起来

	private String toHTML() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
		StringBuffer sb=new StringBuffer();//相当于String安全一些
		sb.append("<select id='"+id+"' name='"+name+"'>");//拼接
		if(!(headerTextKey==null|| "".equals(headerTextKey) ||
				headerTextVal==null||"".equals(headerTextVal))) {
			sb.append("<option selected value='"+headerTextKey+"'>"+headerTextVal+"</option>");
		}
		
		String value;//存到数据库里面的
		String html;//内容
		for (Object obj : items) {
			//<option value=''></option>
			//反射  第一种方式   
			Field field=obj.getClass().getDeclaredField(textKey);//从前台传来  获取它的属性名
			field.setAccessible(true);//打开访问权限
			value=(String) field.get(obj);
			
			//第一种方式 
			html=(String) PropertyUtils.getProperty(obj, textVal);//需要导包  与上面的代码意思一致
			if(value.equals(selectedVal)) {
				sb.append("<option selected value='"+value+"'>"+html+"</option>");
			}else {
				sb.append("<option value='"+value+"'>"+html+"</option>");
			}
			
			
		}
		sb.append("</select>");
		return sb.toString();
	}

	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public List<Object> getItems() {
		return items;
	}
	public void setItems(List<Object> items) {
		this.items = items;
	}
	public String getTextKey() {
		return textKey;
	}
	public void setTextKey(String textKey) {
		this.textKey = textKey;
	}
	public String getTextVal() {
		return textVal;
	}
	public void setTextVal(String textVal) {
		this.textVal = textVal;
	}
	public String getSelectedVal() {
		return selectedVal;
	}
	public void setSelectedVal(String selectedVal) {
		this.selectedVal = selectedVal;
	}
	public String getHeaderTextKey() {
		return headerTextKey;
	}
	public void setHeaderTextKey(String headerTextKey) {
		this.headerTextKey = headerTextKey;
	}
	public String getHeaderTextVal() {
		return headerTextVal;
	}
	public void setHeaderTextVal(String headerTextVal) {
		this.headerTextVal = headerTextVal;
	}
	
}

配置tld文件

<tag>
    <name>select</name>
    <tag-class>com.xyx.jsp2.SelectTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
    	<name>id</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>name</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>items</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
    	<name>textKey</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>textVal</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>selectedVal</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
    	<name>headerTextKey</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
    	<name>headerTextVal</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>

输出：

`<%
	List list=new ArrayList();
	list.add(new Student("001","xiaocheng"));
	list.add(new Student("002","xiaohua"));
	list.add(new Student("003","xiaolv"));
	request.setAttribute("stus", list);
	%>
	
<s:select headerTextKey="-1" headerTextVal="=====请选择=====" textVal="name" items="${stus }"`

page(pageContext)|request(…)|session(…)|application(…)
       存储和交换数据

checkbox
首先让我们先写助手类

public class CheckedTag extends BodyTagSupport{
	
	
	private static final long serialVersionUID = 1L;
	
	private String textKey;//传入值
	private String textVal;//显示值
	private List<Object> checkedVal=new ArrayList<>();//数据回显用于默认选中
	private List<Object> item=new ArrayList<>();//数据集合
	public String getTextKey() {
		return textKey;
	}
	public void setTextKey(String textKey) {
		this.textKey = textKey;
	}
	public String getTextVal() {
		return textVal;
	}
	public void setTextVal(String textVal) {
		this.textVal = textVal;
	}
	public List<Object> getCheckedVal() {
		return checkedVal;
	}
	public void setCheckedVal(List<Object> checkedVal) {
		this.checkedVal = checkedVal;
	}
	public List<Object> getItem() {
		return item;
	}
	public void setItem(List<Object> item) {
		this.item = item;
	}
	public CheckedTag(String textKey, String textVal, List<Object> checkedVal, List<Object> item) {
		super();
		this.textKey = textKey;
		this.textVal = textVal;
		this.checkedVal = checkedVal;
		this.item = item;
	}
	public CheckedTag() {
		super();
	}
//以上是实体类
	
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out=pageContext.getOut();//获取out
		try {
			try {
				out.print(toHTML());//再下面创建一个方法
			} catch (NoSuchFieldException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (SecurityException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalArgumentException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalAccessException 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 (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	
	
	
	
	
	private String toHTML() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {//记得要把数据类型改为String
		StringBuffer sb=new StringBuffer();//比String安全
		String value;//存到数据库里面的
		String html;//内容
		for (Object obj : item) {//遍历
			Field textKeyfield = obj.getClass().getDeclaredField(textKey);//获得属性值
			textKeyfield.setAccessible(true);//打开访问权限
			value=(String)textKeyfield.get(obj);//获取


			Field textValfield = obj.getClass().getDeclaredField(textVal);
			textValfield.setAccessible(true);
			html=(String)textValfield.get(obj);

			//html=(String) PropertyUtils.getProperty(obj, textVal);//需要导包  与上面的代码意思一致
			

			if(checkedVal.contains(value)) {//判断数据回显是否包含value  包含的化就默认
				sb.append("<input checked type='checkbox' value='"+value+"'/>"+html+"");
			}else {
				sb.append("<input type='checkbox' value='"+value+"'/>"+html+"");
			}
		}
		return sb.toString();//返回值要特别注意
	}
}

配置tld文件：

 <tag>
    <name>checkbox</name>
    <tag-class>com.zking.jsp.day02.CheckedTag</tag-class>
    <body-content>JSP</body-content>
    
     <attribute>
        <name>textKey</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
     </attribute>
     <attribute>
        <name>textVal</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
     </attribute>
      <attribute>
        <name>item</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
     </attribute>
     <attribute>
        <name>checkedVal</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
     </attribute>
     
  </tag>

//输出

<%
	List ls=new ArrayList();
	ls.add(new Student("001","xiaocheng"));
	ls.add(new Student("002","xiaohua"));
	ls.add(new Student("003","xiaolv"));
	List lis=new ArrayList();
	lis.add("001");
	lis.add("002");
	lis.add("003");
	request.setAttribute("ls", ls);
	request.setAttribute("lis", lis);
	%>
	
	<z:checkbox textVal="name" checkedVal="${lis}" item="${ls}" textKey="id"></z:checkbox>

结果如图：
在这里插入图片描述

爕藝響
关注
评论
添加红包

请填写红包祝福语或标题

个

红包个数最小为10个

元

红包金额最低5元

当前余额3.43元 前往充值 >
需支付：10.00元
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付元
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明：

1.余额是钱包充值的虚拟货币，按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载，可以购买VIP、付费专栏及课程。

余额充值