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Custom tags - JSP tag enhancements
2022-06-23 08:57:00 【An Li Jiu Ge】
Catalog
Two 、 Custom drop-down box labels
3、 ... and 、 Custom check box labels
Preface
Last time we shared custom tags --jsp Label Foundation , Today's sharing is about custom tags ——jsp Label enhancements .
One 、 Customize foreach label
1、 Define helper classes ForeachTag
analysis foreach Attributes required for the tag ：1. items 2.var
package com.zhw.tag;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
public class ForeachTag extends BodyTagSupport{
private List<Object> items;
private String var;
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 {
Iterator<Object> it = items.iterator();
pageContext.setAttribute(var, it.next());
pageContext.setAttribute("it", it);
return EVAL_BODY_INCLUDE;
}
@Override
public int doAfterBody() throws JspException {
Iterator<Object> it = (Iterator<Object>) pageContext.getAttribute("it");
if(it.hasNext()) {
pageContext.setAttribute(var, it.next());
pageContext.setAttribute("it", it);
return EVAL_BODY_AGAIN;
}else {
return EVAL_PAGE;
}
}
}
doStartTag():
@Override public int doStartTag() throws JspException { Iterator<Object> it = items.iterator(); pageContext.setAttribute(var, it.next()); pageContext.setAttribute("it", it); return EVAL_BODY_INCLUDE; }Because we are going to traverse the data , So we need to output the values in the set one by one , Then assign values one by one . Here we use iterator() That is, iterators . If there is a value in the iterator , Let's assign the value to var, That is, the value of traversal output defined by me . Be careful ： Here we can not directly in dostartTag Method to assign the current set , because dostartTag The method is just the beginning , It cannot directly handle the label body . So next we need to use the value of the iterator pageContext Store it , stay doAfterBody Method to be used
doAfterBody():
@Override public int doAfterBody() throws JspException { Iterator<Object> it = (Iterator<Object>) pageContext.getAttribute("it"); if(it.hasNext()) { pageContext.setAttribute(var, it.next()); pageContext.setAttribute("it", it); return EVAL_BODY_AGAIN; }else { return EVAL_PAGE; } }stay doAfterBody Method, we first need to get our stored iterator , Then you can start to determine whether there is still data in the iterator . If there's data , Just assign the data to var in , If not, end
Next into tld Compilation of documents .
2、 Definition tld file
<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>JSTL 1.1 core library</description>
<display-name>JSTL core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>z</short-name>
<uri>http://jsp.zhwLouis</uri>
<validator>
<validator-class>
org.apache.taglibs.standard.tlv.JstlCoreTLV
</validator-class>
</validator>
<tag>
<name>foreach1</name>
<tag-class>com.zhw.tag.ForeachTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>var</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>
</taglib>
3、 Use custom foreach label
<%@page import="com.zhw.tag.Teacher"%>
<%@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="http://jsp.zhwLouis" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!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>
<%
List<Teacher> t = new ArrayList<>();
t.add(new Teacher(1," Zhang San "));
t.add(new Teacher(2," Li Si "));
t.add(new Teacher(3," Wang Wu "));
t.add(new Teacher(4," Zhao Liu "));
request.setAttribute("t", t);
%>
<z:foreach1 items="${t }" var="t">
Hello, I am ${t.tname }
</z:foreach1>
</body>
</html>The operation results are as follows ：
Two 、 Custom drop-down box labels
1、 Define helper classes SelectTag
analysis ： Use select The tag is definitely a drop-down button , In the down button, we can set the style , You can set id, You can set name attribute , You can also set the default selected value . So these are our definitions select What needs to be considered in the label .
1、 Background to traverse -------- data source --------items
2、 An object attribute is required to represent the display content corresponding to the drop-down box ---------textVal
3、 An object attribute is required to represent the corresponding... Of the drop-down box Value value ---------textKey
4、 Default header options --------headerTextVal
5、 Default header value ---------headerTextKey
6、 Values stored in data , It is convenient for data echo -----------selectedVal
7、id
8、name
9、cssStyle
package com.zhw.tag;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.apache.commons.beanutils.PropertyUtils;
public class SelectTag extends BodyTagSupport{
private String id;
private String name;
private List<Object> items = new ArrayList<>();
private String textKey;
private String textVal;
private String headerTextKey;
private String headerTextVal;
private String selectedVal;
@Override
public int doStartTag() throws JspException {
JspWriter out = pageContext.getOut();
try {
out.print(toHTML());
} catch (Exception e) {
e.printStackTrace();
}
return SKIP_BODY;
}
private String toHTML() throws Exception {
StringBuffer sb = new StringBuffer();
sb.append("<select id='"+id+"' name='"+name+"'>");
if(headerTextVal != null && !"".equals(headerTextVal)) {
sb.append("<option value='"+headerTextKey+"'>"+headerTextVal+"</option>");
}
if (items.size() > 0) {
for (Object obj : items) {
Field f = obj.getClass().getDeclaredField(textKey);
f.setAccessible(true);
if(selectedVal != null && !"".equals(selectedVal) && selectedVal.equals(f.get(obj))) {
sb.append("<option selected value='"+f.get(obj)+"'>"+PropertyUtils.getProperty(obj, textVal)+"</option>");
}else {
sb.append("<option value='"+f.get(obj)+"'>"+PropertyUtils.getProperty(obj, textVal)+"</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 getHeaderTextKey() {
return headerTextKey;
}
public void setHeaderTextKey(String headerTextKey) {
this.headerTextKey = headerTextKey;
}
public String getHeaderTextVal() {
return headerTextVal;
}
public void setHeaderTextVal(String headerTextVal) {
this.headerTextVal = headerTextVal;
}
public String getSelectedVal() {
return selectedVal;
}
public void setSelectedVal(String selectedVal) {
this.selectedVal = selectedVal;
}
}
2、 Definition tld file
<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>JSTL 1.1 core library</description>
<display-name>JSTL core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>z</short-name>
<uri>http://jsp.zhwLouis</uri>
<validator>
<validator-class>
org.apache.taglibs.standard.tlv.JstlCoreTLV
</validator-class>
</validator>
<tag>
<name>foreach1</name>
<tag-class>com.zhw.tag.ForeachTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>var</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>
<tag>
<name>select</name>
<tag-class>com.zhw.tag.SelectTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>id</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>name</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<!-- data source -->
<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>
<!-- Not data loaded from the database , The first option of the drop-down box value value -->
<attribute>
<name>headerTextKey</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<!-- Not data loaded from the database , The display value of the first option in the drop-down box -->
<attribute>
<name>headerTextVal</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<attribute>
<name>selectedVal</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
3、 Use
<%@page import="java.util.List"%>
<%@page import="com.zhw.tag.Teacher"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib prefix="z" uri="http://jsp.zhwLouis" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!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>
<%
List<Teacher> list = new ArrayList<>();
list.add(new Teacher("t1"," Zhang San "));
list.add(new Teacher("t2"," Li Si "));
list.add(new Teacher("t3"," Wang Wu "));
request.setAttribute("list", list);
%>
<z:foreach1 items="${list}" var="t">
Hello, I am ${t.tname }<br>
</z:foreach1>
<z:select selectedVal="t1" id="mySel" headerTextKey="-1" headerTextVal="=== Please select ===" items="${list }" textKey="tid" textVal="tname"></z:select>
</body>
</html>The operation results are as follows ：
3、 ... and 、 Custom check box labels
1、 Define helper classes
Ideas and select It's about the same
package com.zhw.tag;
import java.lang.reflect.Field;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.apache.commons.beanutils.PropertyUtils;
public class CheckTag extends BodyTagSupport{
// <input type="checkbox" value="">
private String id;
private String name;
private String textKey;
private String textVal;
private List<Object> items;
private String selectedVal;
@Override
public int doStartTag() throws JspException {
JspWriter out = pageContext.getOut();
try {
out.print(toHTML());
} catch (Exception e) {
e.printStackTrace();
}
return SKIP_BODY;
}
private String toHTML() throws Exception {
StringBuffer sb = new StringBuffer();
if (items.size() > 0) {
for (Object obj : items) {
Field f = obj.getClass().getDeclaredField(textKey);
f.setAccessible(true);
if(selectedVal != null && !"".equals(selectedVal) && selectedVal.contains((CharSequence) f.get(obj))) {
sb.append("<input type='checkbox' checked value='"+f.get(obj)+"'>"+PropertyUtils.getProperty(obj, textVal)+"");
}else {
sb.append("<input type='checkbox' value='"+f.get(obj)+"'>"+PropertyUtils.getProperty(obj, textVal)+"");
}
}
}
return sb.toString();
}
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 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 getSelectedVal() {
return selectedVal;
}
public void setSelectedVal(String selectedVal) {
this.selectedVal = selectedVal;
}
}
2、 Definition tld file
<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>JSTL 1.1 core library</description>
<display-name>JSTL core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>z</short-name>
<uri>http://jsp.zhwLouis</uri>
<validator>
<validator-class>
org.apache.taglibs.standard.tlv.JstlCoreTLV
</validator-class>
</validator>
<tag>
<name>foreach1</name>
<tag-class>com.zhw.tag.ForeachTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<!-- Identifies where the collection traversal is the pointer , Point to the current traversal object -->
<name>var</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>
<tag>
<name>select</name>
<tag-class>com.zhw.tag.SelectTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>id</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>name</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<!-- data source -->
<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>
<!-- Not data loaded from the database , The first option of the drop-down box value value -->
<attribute>
<name>headerTextKey</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<!-- Not data loaded from the database , The display value of the first option in the drop-down box -->
<attribute>
<name>headerTextVal</name>
<required>false</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
<attribute>
<name>selectedVal</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>check</name>
<tag-class>com.zhw.tag.CheckTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>id</name>
<required>false</required>
<rtexprvalue>true</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>
</tag>
</taglib>
3、 Use
<%@page import="com.zhw.tag.Hobby"%>
<%@page import="java.util.List"%>
<%@page import="com.zhw.tag.Teacher"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib prefix="z" uri="http://jsp.zhwLouis" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!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>
<%
List<Teacher> list = new ArrayList<>();
list.add(new Teacher("t1"," Zhang San "));
list.add(new Teacher("t2"," Li Si "));
list.add(new Teacher("t3"," Wang Wu "));
List<Hobby> ls = new ArrayList<>();
ls.add(new Hobby("lq"," Basketball "));
ls.add(new Hobby("zq"," football "));
ls.add(new Hobby("ppq"," Table Tennis "));
request.setAttribute("list", list);
request.setAttribute("ls", ls);
%>
<input type="checkbox" value="">
<z:foreach1 items="${list}" var="t">
Hello, I am ${t.tname }<br>
</z:foreach1>
<z:select selectedVal="t1" id="mySel" headerTextKey="-1" headerTextVal="=== Please select ===" items="${list }" textKey="tid" textVal="tname"></z:select>
<z:check selectedVal="lq" textVal="hname" items="${ls }" textKey="hid"></z:check>
</body>
</html>The operation results are as follows ：
summary
The content shared this time is the custom tag library enhancement , I hope it can help you , General page for next issue preview .
I'm nine songs , A programmer who likes programming .
If there is any mistake, please correct it , Thank you very much! .
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