jsp 自定义标签【继承TagSupport类】【带有参数】 简单例子三
1。标签代码实现类：
package taglib;
import java.io.IOException;
import java.io.Writer;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import org.apache.log4j.Logger;
/**
*
* @author zwc
*
*/
@SuppressWarnings("serial")
public class StringLengthUtils extends TagSupport {
private String value;
private Logger logger = Logger.getLogger(StringLengthUtils.class);
@Override
public int doEndTag() throws JspException {
logger.info("输入字符串为：" + value);
int length = 0;
if(value != null){
length = value.length();
}
System.out.println("string:" + value + " length:" + length);
try {
pageContext.getOut().print(length);
} catch (IOException e) {
logger.warn("计算字符串长度有错" + value,e);
}
return EVAL_BODY_INCLUDE;
}
@Override
public int doStartTag() throws JspException {
return EVAL_PAGE;
}
public void setValue(String value) {
this.value = value;
}
注意：传递参数，那么就得给出，他的setter方法：
}
2。tld，标签说明文档
<?xml version="1.0" encoding="UTF-8" ?>
<!--
Copyright 2004 The Apache Software Foundation
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<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">
<tlib-version>1.0</tlib-version>
<uri>/test-1.0</uri>
<tag>
<name>getStringLength</name>
<tag-class>taglib.StringLengthUtils</tag-class>
<attribute>
<name>value</name> 注意：这里给出，参数名称，就是实现类里的，setter方法的名
<required>true</required> 是否是必须的，如果是必须的，那么在敲入前缀是，所对应的属性名，也会给出
<description>who is string length</description>
</attribute>
注意，这是配置的关键， </tag>
</taglib>
3。页面调用：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="test" uri="/test-1.0"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Error</title>
</head>
<body>
Error<br>
<jsp:useBean id="user" class="bean.User"/>
<jsp:setProperty property="name" value="abc" name="user"/>
<jsp:getProperty property="name" name="user"/>
<br>
Test: ${test:getStringLength("yuanfen860913")}
<br>
TestA:<test:getTime/>
<br>
TestB:<test:getStringLength value="yuanfen860913"/> 注意，这里的参数名，就是value了，并且是必须给出的。
</body>
</html>