1.使用标签输出客户机IP
1.1编写一个是实现tag接口的Java类（继承TagSupport类）
public class ViewTag extends TagSupport {
@Override
public int doEndTag() throws JspException {
HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
JspWriter out = this.pageContext.getOut();
String ip=request.getRemoteAddr();
try {
out.write(ip);
} catch (Exception e) {
throw new RuntimeException(e);
}
return super.doEndTag();
}
}1.2.在tld文件中对标签处理器类进行描述（tld文件的位置WEB-INF下，可以抄tomcat webapps下文件
<?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>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>viewtag</short-name>
<uri>www.scong.cn</uri>
<tag>
<name>viewIP</name>
<tag-class>cn.scong.web.tag.ViewTag</tag-class>
<body-content>empty</body-content>
</tag>
</taglib>1.3.在jsp页面中导入和使用自定义标签
<%@ taglib uri="www.scong.cn" prefix="viewtag" %>
<body>
您的ip是：
<viewtag:viewIP/>
</body>2.自定义标签功能扩展
2.1控制jsp页面某一部分内容是否执行
2.2控制整个jsp页面是否执行
2.3控制jsp页面内容重复执行
2.4修改jsp页面内容输出
2.5 tld文件中的四种标签体类型: empty JSP scriptless tagdepentend
例1：控制jsp页面某一部分内容是否执行（Tag接口）
public class TagDemo1 extends TagSupport {
@Override
public int doStartTag() throws JspException {
return Tag.SKIP_BODY;
//return Tag.EVAL_BODY_INCLUDE;
}
}tld：
<tag>
<name>demo1</name>
<tag-class>cn.scong.web.tag.TagDemo1</tag-class>
<body-content>JSP</body-content>
</tag>jsp：
<body>
<viewtag:demo1>
This is my JSP page.
</viewtag:demo1>
</body>例2.控制整个jsp页面是否执行（Tag接口）
public class TagDemo2 extends TagSupport{
@Override
public int doEndTag() throws JspException {
return Tag.SKIP_PAGE;
}
}tld:
<tag>
<name>demo2</name>
<tag-class>cn.scong.web.tag.TagDemo2</tag-class>
<body-content>empty</body-content>
</tag>jsp：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="www.scong.cn" prefix="viewtag"%>
<viewtag:demo2/>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>用标签控制整个页面是否输出</title>
</head>
<body>
This is my JSP page. <br>
</body>
</html>例3：控制jsp页面内容重复执行（IterationTag ）
public class TagDemo3 extends TagSupport {
int x=10;
@Override
public int doStartTag() throws JspException {
return Tag.EVAL_BODY_INCLUDE;
}
@Override
public int doAfterBody() throws JspException {
x--;
if (x>0) {
return IterationTag.EVAL_BODY_AGAIN;
}else {
return IterationTag.SKIP_BODY;
}
}
}tld：
<tag>
<name>demo3</name>
<tag-class>cn.scong.web.tag.TagDemo3</tag-class>
<body-content>JSP</body-content>
</tag>jsp：
<body>
<viewtag:demo3>
This is my JSP page. <br>
</viewtag:demo3>
</body>例4：修改jsp页面内容输出 （BodyTag）
public class TagDemo4 extends BodyTagSupport {
@Override
public int doStartTag() throws JspException {
return BodyTag.EVAL_BODY_BUFFERED;
}
@Override
public int doEndTag() throws JspException {
BodyContent bc = this.bodyContent;
String content = bc.getString();
content=content.toUpperCase();
JspWriter out = this.pageContext.getOut();
try {
out.write(content);
} catch (IOException e) {
throw new RuntimeException(e);
}
return Tag.EVAL_PAGE;
}
}tld：
</tag>
<tag>
<name>demo4</name>
<tag-class>cn.scong.web.tag.TagDemo4</tag-class>
<body-content>JSP</body-content>
</tag>jsp：
<body>
<viewtag:demo4>
my name is scong
</viewtag:demo4>
</body>JSP2.0使用SimpleTatSupport扩展标签库功能
例1：使用simpletagsupport控制jsp页面某一部分内容是否执行
public class SimpleTagDemo1 extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
//jf.invoke(this.getJspContext().getOut());
}
}tld:
<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>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>simpletag</short-name>
<uri>www.song.cn</uri>
<tag>
<name>demo1</name>
<tag-class>cn.scong.web.simpletag.SimpleTagDemo1</tag-class>
<body-content>scriptless</body-content>
</tag>
</taglib>jsp:
<body>
<simpletag:demo1>
This is my JSP page. <br>
</simpletag:demo1>
</body>例2：使用simpletagsupport控制jsp页面内容重复执行
public class SimpleTagDemo2 extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
for (int i = 0; i <5; i++) {
//jf.invoke(this.getJspContext().getOut());
jf.invoke(null);
}
}
}tld:
<tag>
<name>demo2</name>
<tag-class>cn.scong.web.simpletag.SimpleTagDemo2</tag-class>
<body-content>scriptless</body-content>
</tag>jsp:
<body>
<simpletag:demo2>
This is my JSP page. <br>
</simpletag:demo2>
</bodypublic class SimpleTagDemo3 extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
//jf.invoke(this.getJspContext().getOut());
StringWriter sw = new StringWriter();
jf.invoke(sw);
String content = sw.toString();
content=content.toUpperCase();
this.getJspContext().getOut().write(content);
}
}tld：
<tag>
<name>demo3</name>
<tag-class>cn.scong.web.simpletag.SimpleTagDemo3</tag-class>
<body-content>scriptless</body-content>
</tag>jsp：
<body>
<simpletag:demo3>
This is my JSP page. <br>
</simpletag:demo3>
</body>例4：使用simpletagsupport控制整个jsp是否输出
public class SimpleTagDemo4 extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
throw new SkipPageException();
}
}tld：
<tag>
<name>demo4</name>
<tag-class>cn.scong.web.simpletag.SimpleTagDemo4</tag-class>
<body-content>empty</body-content>
</tag>jsp：
<simpletag:demo4/>3.开发带属性的标签
3.1.在自定义标签类中定义属性，并设置set方法
public class SimpleTagDemo5 extends SimpleTagSupport {
private int count;
private Date date;
public void setCount(int count) {
this.count = count;
}
public void setDate(Date date) {
this.date = date;
}
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
//jf.invoke(this.getJspContext().getOut());
this.getJspContext().getOut().write(date.toLocaleString());
for (int i = 0; i < count; i++) {
jf.invoke(null);
}
}
}3.2.在tld文件中，定义属性名称及属性标签
<tag>
<name>demo5</name>
<tag-class>cn.scong.web.simpletag.SimpleTagDemo5</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>count</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>date</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>3.3.在jsp文件中使用标签
<simpletag:demo5 count="90" date="<%=new Date() %>">
This is my JSP page. <br>
</simpletag:demo5>4.嵌套标签的使用
原理：定义一个父标签，在父标签类中定义个属性保存子标签状态。
ChooseTag类：
public class ChooseTag extends SimpleTagSupport {
private boolean isdo;
public boolean isIsdo() {
return isdo;
}
public void setIsdo(boolean isdo) {
this.isdo = isdo;
}
@Override
public void doTag() throws JspException, IOException {
this.getJspBody().invoke(null);
}
}WhenTag类：
public class WhenTag extends SimpleTagSupport{
private boolean test;
public void setTest(boolean test) {
this.test = test;
}
@Override
public void doTag() throws JspException, IOException {
ChooseTag parent = (ChooseTag) this.getParent();
if (test&&!parent.isIsdo()) {
this.getJspBody().invoke(null);
parent.setIsdo(true);
}
}
}OtherwiseTag类：
public class OtherwiseTag extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
ChooseTag parent = (ChooseTag) this.getParent();
if (!parent.isIsdo()) {
this.getJspBody().invoke(null);
parent.setIsdo(true);
}
}
}example.tld:
<?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>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>e</short-name>
<uri>/example</uri>
<tag>
<name>choose</name>
<tag-class>cn.scong.web.example.ChooseTag</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>when</name>
<tag-class>cn.scong.web.example.WhenTag</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>test</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>otherwise</name>
<tag-class>cn.scong.web.example.OtherwiseTag</tag-class>
<body-content>scriptless</body-content>
</tag>
</taglib>
jsp:
<body>
<e:choose>
<e:when test="${user==null }">
aaaaa
</e:when>
<e:otherwise>
bbbb
</e:otherwise>
</e:choose>
</body>5.自定义foreach标签
public class ForeachTag extends SimpleTagSupport{
private Object items;
private String var;
public void setItems(Object items) {
this.items = items;
}
public void setVar(String var) {
this.var = var;
}
@Override
public void doTag() throws JspException, IOException {
List list = (List) items;
Iterator it = list.iterator();
while (it.hasNext()) {
String value = (String) it.next();
this.getJspContext().setAttribute(var, value);
this.getJspBody().invoke(null);
}
}
}tld：
<tag>
<name>foreach</name>
<tag-class>cn.scong.web.example.ForeachTag</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>jsp：
<body>
<%
List list = new ArrayList();
list.add("aaa");
list.add("bbb");
list.add("ccc");
list.add("ddd");
request.setAttribute("list", list);
%>
<e:foreach var="str" items="${list }">
${str }<br/>
</e:foreach>
</body>6.模拟sum公司foreach标签开发
public class ForeachTag2 extends SimpleTagSupport {
private Object items;
private String var;
public void setItems(Object items) {
this.items = items;
if (items instanceof Collection) {
collection = (Collection) items;
}
if (items instanceof Map) {
Map map = (Map) items;
collection = map.entrySet();
}
if (items instanceof Object[]) {
Object object[] = (Object[]) items;
collection = Arrays.asList(object);
}
if (items.getClass().isArray()) {
this.collection = new ArrayList();
int length = Array.getLength(items);
for (int i = 0; i <length; i++) {
Object value =Array.get(items, i);
this.collection.add(value);
}
}
}
public void setVar(String var) {
this.var = var;
}
private Collection collection;
@Override
public void doTag() throws JspException, IOException {
Iterator it = this.collection.iterator();
while (it.hasNext()) {
Object value = it.next();
this.getJspContext().setAttribute(var, value);
this.getJspBody().invoke(null);
}
}
}tld:
</tag>
<tag>
<name>foreach2</name>
<tag-class>cn.scong.web.example.ForeachTag2</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>jsp:
<body>
<%
List list = new ArrayList();
list.add("aaa");
list.add("bbb");
list.add("ccc");
list.add("ddd");
request.setAttribute("list", list);
%>
<e:foreach2 var="str" items="${list }">
${str }<br/>
</e:foreach2>
<br>-----------------------------------------------<br>
<%
Map map = new HashMap();
map.put("1", "aaa");
map.put("2", "bbb");
map.put("3", "ccc");
request.setAttribute("map", map);
%>
<e:foreach2 items="${map }" var="entry">
${entry.key }=${entry.value }<br/>
</e:foreach2>
<br>-----------------------------------------------<br>
<%
Integer num[] = {1,2,3,4,5,6};
request.setAttribute("num", num);
%>
<e:foreach2 items="${num }" var="i">
${i }<br/>
</e:foreach2>
<br>-----------------------------------------------<br>
<%
double arr[] = {1,2,3,4,5,6};
request.setAttribute("arr", arr);
%>
<e:foreach2 items="${arr }" var="i">
${i }<br/>
</e:foreach2>
</body>7.html转译标签
filter方法在F:\Program Files\apache-tomcat-7.0.67\apache-tomcat-7.0.67\webapps\examples\WEB-INF\classes\util下可以找到
public class HtmlFliterTag extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
StringWriter sw =new StringWriter();
JspFragment jf = this.getJspBody();
jf.invoke(sw);
String content = sw.getBuffer().toString();
content = filter(content);
this.getJspContext().getOut().write(content);
}
public static String filter(String message) {
if (message == null)
return (null);
char content[] = new char[message.length()];
message.getChars(0, message.length(), content, 0);
StringBuilder result = new StringBuilder(content.length + 50);
for (int i = 0; i < content.length; i++) {
switch (content[i]) {
case '<':
result.append("<");
break;
case '>':
result.append(">");
break;
case '&':
result.append("&");
break;
case '"':
result.append(""");
break;
default:
result.append(content[i]);
}
}
return (result.toString());
}
}tld：
<tag>
<name>htmlfilter</name>
<tag-class>cn.scong.web.example.HtmlFliterTag</tag-class>
<body-content>scriptless</body-content>
</tagjsp：
<body>
<e:htmlfilter>
<a href="">点我</a>
</e:htmlfilter>
</body>