J2EE-JSP自定义标签（二）_小言_互联网的博客

J2EE-JSP自定义标签（二）

2020-04-17 08:16 302人阅读评论(0)

前言

基于jsp自定义标签我们上一篇已经讲解了一些基本的语法、属性、以及开发步骤和注意事项。
那么我们今天就开始来了解以及使用jsp自定义标签。

常用作用域来存取数据有四个：

pageContext
request
session
application

案例：z:foreach、z:if、 z:deptList 、 z:out 、z:select(基于rebel.tld)

<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
   "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!-- 标签库描述符 -->
<taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor">
	<tlib-version>1.0</tlib-version>
	<jsp-version>1.2</jsp-version>
	<short-name>Simple Tags</short-name>
	<uri>/zking</uri>
	<tag>
		<name>if</name>
		<tag-class>com.zking.IfTag</tag-class>
		<body-content>jsp</body-content>
	     <attribute>
	     <name>test</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute>
	</tag>

       <!--自定义out标签  -->
     <tag>
		<name>out</name>
		<tag-class>com.zking.OutTag</tag-class>
		<body-content>empty</body-content>
	     <attribute>
	     <name>value</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute>
	</tag>
	<!-- 自定义froeach标签 -->
	 <tag>
		<name>foreach</name>
		<tag-class>com.zking.ForeachTag</tag-class>
		<body-content>jsp</body-content>
	     <attribute>
	     <name>var</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
		     </attribute>
		     <attribute>
		     <name>items</name>
		     <required>true</required>
		     <rtexprvalue>true</rtexprvalue>
		     </attribute>
	</tag>
	
	  <!-- 自定义数据标签 -->
	  <tag>
		<name>deptList</name>
		<tag-class>com.zking.DeptlistTag</tag-class>
		<body-content>empty</body-content>
	    <attribute>
	     <name>var</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	</tag> 
	
	  <!-- 自定义下拉框标签 -->
	  <tag>
		<name>Select</name>
		<tag-class>com.zking.SelectTag</tag-class>
		<body-content>empty</body-content>
	    <attribute>
	     <name>name</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>cssStyle</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>cssClass</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>headValue</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>headText</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>valueProperty</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>textProperty</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>items</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>var</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	     <attribute>
	     <name>selectValue</name>
	     <required>true</required>
	     <rtexprvalue>true</rtexprvalue>
	     </attribute> 
	</tag> 
	

</taglib>

UI标签

（1） z:out
UI标签的展示方法：
注：JspWriter out = pageContext.getOut();
out.println(html)

public class OutTag  extends  BodyTagSupport{

	  private Object  value;
	  public OutTag() {}
	public Object getValue() {
		return value;
	}
	public void setValue(Object value) {
		this.value = value;
	}
	@Override
	public int doStartTag() throws JspException {
		System.out.println("doStartTag----------out");
		System.out.println("value="+value);
		JspWriter out = pageContext.getOut();
		try {
			out.print(value);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			throw new RuntimeException(e);
		}
		return super.doStartTag();
	}
}

（2）z:select
这里我们要用到俩个jar包。

String 属性值=BeanUtils.getProperty(对象, 属性名);
注：PropertyUtils.getProperty 反射取值。

public class SelectTag  extends  BodyTagSupport{

	private String name;//名称
	private String cssStyle;//样式
	private String cssClass;
	
	private String headValue="-1";//头value
	private String headText="----请选择----";//头文本
	private String valueProperty;//deptid:java对象属性名
	private String textProperty;//deptName：java对象属性名
	
	private List<Object> items;//数据源
	private String var;//保存当前数据到作用域的名字
	private String selectValue;
	
	public String getSelectValue() {
		return selectValue;
	}

	public void setSelectValue(String selectValue) {
		this.selectValue = selectValue;
	}

	public SelectTag() {}
	
	public String getName() {
		return name;
	}

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


	public String getCssStyle() {
		return cssStyle;
	}


	public void setCssStyle(String cssStyle) {
		this.cssStyle = cssStyle;
	}

	public String getCssClass() {
		return cssClass;
	}

	public void setCssClass(String cssClass) {
		this.cssClass = cssClass;
	}

	public String getHeadValue() {
		return headValue;
	}

	public void setHeadValue(String headValue) {
		this.headValue = headValue;
	}

	public String getHeadText() {
		return headText;
	}

	public void setHeadText(String headText) {
		this.headText = headText;
	}

	public String getValueProperty() {
		return valueProperty;
	}

	public void setValueProperty(String valueProperty) {
		this.valueProperty = valueProperty;
	}

	public String getTextProperty() {
		return textProperty;
	}

	public void setTextProperty(String textProperty) {
		this.textProperty = textProperty;
	}

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

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

	public String getVar() {
		return var;
	}

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

	@Override
	public int doStartTag() throws JspException {
		//获取到out
		JspWriter out = pageContext.getOut();
		try {
			//将下拉框输出到html上面显示
			out.print(toHtml());
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	public String toHtml() throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
		//定义StringBuffer拼接下拉框
		StringBuffer bf=new StringBuffer();
		bf.append("<select name='"+this.name+"' style='"+this.cssStyle+"' class='"+this.cssClass+"'>");
	    //判断下拉框的默认值
		if("".equals(this.headText)) {
			bf.append("<option value='"+this.headValue+"'>'"+this.headText+"'</option>");	
		}
		//判断数据源是否有值
		if(null!=items) {
			for (Object obj : items) {
				String deptId =BeanUtils.getProperty(obj, valueProperty);
				String deptName = BeanUtils.getProperty(obj, textProperty);
				if(deptId.equals(this.selectValue)) {
					bf.append("<option selected  value='"+deptId+"'>"+deptName+"</option>");
				}
				bf.append("<option value='"+deptId+"'>"+deptName+"</option>");
			}
		}
		bf.append("</select>");
		//返回拼接好的下拉框
		return bf.toString();
	}


}

控制标签

(1)z:if

public class IfTag extends  BodyTagSupport{
    private boolean  test;
    
    public IfTag() {}

	public boolean isTest() {
		return test;
	}

	public void setTest(boolean test) {
		this.test = test;
	}
    
	@Override
	public int doStartTag() throws JspException {
		System.out.println("doStartTag--------if");
		if(test) {
			return EVAL_BODY_INCLUDE;//计算主体并且包含到输出
		}
		return SKIP_BODY;
	}
}

(2)z:foreach

public class ForeachTag  extends BodyTagSupport{

	 private String var;//保存当前数据到作用域的一个key(键/名字)
	 private  List<Object> items;//数据源
	 
	 public ForeachTag() {}

	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;
	}
	 
	 @Override
	public int doStartTag() throws JspException {
		 if(null==items||0==items.size()) {
			 return SKIP_BODY;
		 }
		 Iterator<Object> it = items.iterator();
		 Object next = it.next();
		 pageContext.setAttribute(var, next);
		 //保存iterator的指针
		 pageContext.setAttribute("it", it);		 	 
		return EVAL_BODY_INCLUDE;//计算主体并且包含到输出
	}
	 @Override
	public int doAfterBody() throws JspException {
		 Iterator<Object> it =(Iterator<Object>) pageContext.getAttribute("it");
		 while(it.hasNext()) {
			 Object next = it.next();
			 pageContext.setAttribute(var, next);
		    return EVAL_BODY_AGAIN;//再次计算主体
		 }
		return SKIP_BODY;
	}
	
}

数据标签

(1）z:deptList

public class DeptlistTag  extends BodyTagSupport{

	private String var;//保存数据到作用域的名字
	private  DeptDAO deptDAO=new  DeptDAO();
	
	
	public  DeptlistTag() {}
	public String getVar() {
		return var;
	}
	public void setVar(String var) {
		this.var = var;
	}
	@Override
	public int doStartTag() throws JspException {
		List<Dept> list = deptDAO.list();
		pageContext.setAttribute(var, list);
		return SKIP_BODY;//跳过主体
	}
}

测试页面：

<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
    <%@taglib prefix="z" uri="/zking"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
	<style type="text/css">
	.c1{
	font-size: 30px;
	color:red;
	}
</style>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
		<body>
		<%
		List<String> list=new ArrayList<>();
		list.add("hello");
		list.add("大家好");
		list.add("我叫java");
		request.setAttribute("list",list);
		
		%>	
		<h1>自定义if标签</h1>
		<z:if test="true">自定义if值为真</z:if>
		
		<h1>自定义out标签</h1>
		<z:out value="我是自定义out标签"></z:out>
		<h1>自定义foreach标签</h1>
		<z:foreach items="${list }" var="v">
		<div>${v}</div>
		</z:foreach>
		
		<h1>自定义deptList标签</h1>
		<z:deptList var="deptList"></z:deptList>${deptList }
		
		<h1>自定义select标签</h1>
		<z:Select name="SelectName" valueProperty="deptId" textProperty="deptName" headText="~~~~请选择~~~~~" headValue="-1" items="${deptList}" cssStyle="width:400px" var="v" cssClass="c1" selectValue="5"/>
		</body>
</html>

输出结果：

哈哈！开心，今天的砖终于搬完了！

转载：https://blog.csdn.net/qq_45384482/article/details/105565979

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