JSP custom tag library -- select tag

Catalog

1. Write helper classes （ Need to splice ）：

2. To write tld file ：

3. Entity class and collection class （ You can refer to my last chapter foreach label ）：

4. Run on the page ：

---

1. Write helper classes （ Need to splice ）：

package com.zking.mymvc.tag;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.List;

import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;

import org.apache.commons.beanutils.BeanUtils;

import com.mysql.jdbc.StringUtils;

public class SelectTag extends BodyTagSupport {
	
	private String id;
	
	private String name;
	
	private String cssClass;
	
	private String cssStyle;
	
	private List<?> items;
	
	private String value;
	
	private String text;
	
	private String selectedVal;

	public void setId(String id) {
		this.id = id;
	}

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

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

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

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

	public void setValue(String value) {
		this.value = value;
	}

	public void setText(String text) {
		this.text = text;
	}

	public void setSelectedVal(String selectedVal) {
		this.selectedVal = selectedVal;
	}
	
	@Override
	public int doStartTag() {
		
		JspWriter out = this.pageContext.getOut();
		
		try {
			out.print(toHTML());
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		return SKIP_BODY;
	}
	
	
	private String toHTML() throws Exception {
		
		StringBuilder sb = new StringBuilder();
		sb.append("<select id='"+this.id+"' name='"+this.name+"'");
		
		if(!StringUtils.isNullOrEmpty(this.cssClass)) {
			sb.append(" class='"+this.cssClass+"'");
		}
		if(!StringUtils.isNullOrEmpty(this.cssStyle)) {
			sb.append(" style='"+this.cssStyle+"'");
		}
		sb.append(">");
		
		for(Object obj: this.items) {
			Object val = BeanUtils.getProperty(obj, this.value);
			Object text = BeanUtils.getProperty(obj, this.text);
			
			if(this.selectedVal != null && this.selectedVal.equals(val)) {
				sb.append("<option value='"+val+"' selected>" + text + "</option>");
			} else {
				sb.append("<option value='"+val+"'>" + text + "</option>");
			}
		}
		
		sb.append("</select>");
		
		return sb.toString();
	}
	
	
}

2. To write tld file ：

<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
   "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!--  Tag library descriptor  -->
<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>out</name>
		<tag-class>com.zking.mymvc.tag.OutTag</tag-class>
		<body-content>empty</body-content>
		<attribute>
			<name>val</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<description>out label val attribute , For output val Value </description>
		</attribute>
		<attribute>
			<name>defaultVal</name>
			<required>false</required>
			<rtexprvalue>false</rtexprvalue>
			<description> Used to define default values </description>
		</attribute>
	</tag>
	
	<tag>
		<name>if</name>
		<tag-class>com.zking.mymvc.tag.IfTag</tag-class>
		<body-content>jsp</body-content>
		<attribute>
			<name>test</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<description>if label </description>
		</attribute>
	</tag>
	
	<tag>
		<name>foreach</name>
		<tag-class>com.zking.mymvc.tag.ForeachTag</tag-class>
		<body-content>jsp</body-content>
		<attribute>
			<name>items</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>var</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
	</tag>
	
	<tag>
		<name>select</name>
		<tag-class>com.zking.mymvc.tag.SelectTag</tag-class>
		<body-content>empty</body-content>
		<attribute>
			<name>id</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>name</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>cssClass</name>
			<required>false</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>cssStyle</name>
			<required>false</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>items</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>value</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>text</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
		<attribute>
			<name>selectedVal</name>
			<required>false</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
	</tag>
	
</taglib>

3. Entity class and collection class （ You can refer to my last chapter foreach label ）：

4. Run on the page ：

<%@page import="com.zking.mymvc.model.*,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>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

	<%
		request.setAttribute("name", "");
		List<Book> books = TestData.getBooks();
		request.setAttribute("books", books);
	%>
	<!-- out  label  -->
	<z:out val="${name}" defaultVal="--"/>
	
	
	<z:if test="${100 == 100}">
		 test if(100 == 100)
	</z:if>
	
	<z:if test="${100 != 200}">
		 test if(100 != 200)
	</z:if>
	
	<hr>
	<z:foreach items="${books}" var="book">
		${book.id} -- ${book.name} <br>
	</z:foreach>
	
	<select id="test" name="test" class="" style="width:100%;">
		<option value=id> Unpaid </option>
		<option value=2 selected> Paid </option>
		<option value=3> Shipped </option>
	</select>
	
	<z:select id="test02" name="test02" 
	 items="${books}"  value="id" text="name" selectedVal="3"/>
	
</body>
</html>