Java_11_10课堂总结

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案例：

一、开发<c:if>标签

IfTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.JspFragment;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class IfTag extends SimpleTagSupport {

private boolean test;

public void setTest(boolean test) {

this.test = test;

}

@Override

public void doTag() throws JspException, IOException {/ if(test){

//处理标签体

JspFragment jf=this.getJspBody();

jf.invoke(null);

}

TestIf.jsp

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>

<%@ taglib uri="/c" prefix="c" %>

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>My JSP 'TestIf.jsp' starting page</title>

<!--

-->

</head>

<body>

session.setAttribute("user","zhangsan");

<c:if test="${user!=null}">

aaa---aaa

</c:if>

</body>

</html>

c.tld

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN""http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">

<tlib-version>1.0</tlib-version>

<jsp-version>1.2</jsp-version>

<short-name>c</short-name>

<tag>

<tag-class>com.hbsi.web.tag.IfTag</tag-class>

<body-content>scriptless</body-content>

</attribute>

</tag>

</taglib>

二、开发<c:if><c:else>标签

案例分析：

<c:if test=””>aaa</c:if>------IfTag.java

<c:else>bbb</c:else>--------ElseTag.java

共享一个boolean变量

<c:choose>---------ChooseTag.java

<c:when test=””>aaa</c:when>---------WhenTag.java

<c:otherwise>bbb</c:otherwise>---------OtherTag.java

</c:choose>

TestIf.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

<%@ taglib uri="/c" prefix="c" %>

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>My JSP 'TestIf.jsp' starting page</title>

<!--

-->

</head>

<body>

session.setAttribute("user","zhangsan");

<c:if test="${user!=null}">

aaa---aaa

</c:if>

----------------------------------------

<c:choose>

<c:when test="${user!=null}">aaa</c:when>

<c:otherwise>bbb</c:otherwise>

</c:choose>

</body>

</html>

IfTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.JspFragment;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class IfTag extends SimpleTagSupport {

private boolean test;

public void setTest(boolean test) {

this.test = test;

}

@Override

public void doTag() throws JspException, IOException {

if(test){

//处理标签体

JspFragment jf=this.getJspBody();

jf.invoke(null);

}

ChooseTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.JspFragment;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class ChooseTag extends SimpleTagSupport {

private boolean flag=false;

public boolean isFlag() {

return flag;

}

public void setFlag(boolean flag) {

this.flag = flag;

}

@Override

public void doTag() throws JspException, IOException {

JspFragment jf=this.getJspBody();

jf.invoke(null);

}

WhenTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class WhenTag extends SimpleTagSupport {

private boolean test;

public void setTest(boolean test) {

this.test = test;

}

@Override

public void doTag() throws JspException, IOException {

//获取父标签对象

ChooseTag parent=(ChooseTag) this.getParent();

if(test && !parent.isFlag()){

//处理该标签体

this.getJspBody().invoke(null);

parent.setFlag(true);

}

OtherwiseTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class OtherwiseTag extends SimpleTagSupport {

@Override

public void doTag() throws JspException, IOException {

ChooseTag parent=(ChooseTag) this.getParent();

if(!parent.isFlag()){

this.getJspBody().invoke(null);

parent.setFlag(true);

}

c.tld描述符文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN""http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">

<tlib-version>1.0</tlib-version>

<jsp-version>1.2</jsp-version>

<short-name>c</short-name>

<tag>

<tag-class>com.hbsi.web.tag.IfTag</tag-class>

<body-content>scriptless</body-content>

</attribute>

</tag>

<tag>

<name>choose</name>

<tag-class>com.hbsi.web.tag.ChooseTag</tag-class>

<body-content>scriptless</body-content>

</tag>

<tag>

<tag-class>com.hbsi.web.tag.WhenTag</tag-class>

<body-content>scriptless</body-content>

</attribute>

</tag>

<tag>

<name>otherwise</name>

<tag-class>com.hbsi.web.tag.OtherwiseTag</tag-class>

<body-content>scriptless</body-content>

</tag>

</taglib>

三、开发迭代标签

List list=new ArrayList();

list.add(“aaa”);

list.add(“bbb”);

list.add(“ccc”);

list.add(“ddd”);

list.add(“eee”);

request.setAttribute(“list”,list);

Jsp

<c:foreach items=”${list}” var=”str”> -----ForEachTag.java-----对象赋值---doTag() pageContext对象中设置了一个属性：str=”aaa”

${str}

</c:foreach>

ForEachTag.java

package com.hbsi.web.tag;

import java.io.IOException;

import java.lang.reflect.Array;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

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 {

// TODO Auto-generated method stub

//List list=(List)items;

//Iterator it=list.iterator();

Collection collection=null;

if(items instanceof Map){

Map map=(Map)items;

//两列得集合转换成单列

collection=map.entrySet();

}else if(items instanceof Collection){

collection=(Collection)items;

}/*else if(items instanceof Object[]){

Object[] objs=(Object[])items;

collection=Arrays.asList(objs);

}else if(items instanceof int[]){

}*/

else if(items.getClass().isArray()){

collection=new ArrayList();

int length=Array.getLength(items);

for(int i=0;i<length;i++){

collection.add(Array.get(items, i));

}

Iterator it=collection.iterator();

while(it.hasNext()){

Object obj=it.next();//一个元素

this.getJspContext().setAttribute(var,obj);

this.getJspBody().invoke(null);

}

TextForEach.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

<%@ taglib uri="/c" prefix="c" %>

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>My JSP 'TestForEach.jsp' starting page</title>

<!--

-->

</head>

<body>

List list=new ArrayList();

list.add("aaa");

list.add("bbb");

list.add("ccc");

list.add("ddd");

list.add("eee");

request.setAttribute("list",list);

<c:foreach items="${list}" var="str">

${str }

</c:foreach>

----------------------------------

Map map=new HashMap();

map.put("aa","zhangsan");

map.put("bb","lisi");

map.put("cc","wangwu");

request.setAttribute("map",map);

<c:foreach items="${map}" var="name" >

${name }

</c:foreach>

---------------------------------

Integer[] num={1,2,3,4,5};

request.setAttribute("num",num);

<c:foreach items="${num}" var="i">

${i}

</c:foreach>

----------------------------------------

int[] arr={6,7,8,9,10};

request.setAttribute("arr",arr);

<c:foreach items="${arr}" var="index">

${index}

</c:foreach>

</body>

</html>

c.tld

<tag>

<name>foreach</name>

<tag-class>com.hbsi.web.tag.ForEachTag</tag-class>

<body-content>scriptless</body-content>

<name>items</name>

</attribute>

<rtexprvalue>false</rtexprvalue>

</attribute>

</tag>

四、打包标签库

jar包:标签处理器以及（META-INF）tld文件打成一个jar包

第一种方法：

命令提示状态下：

D:(选择任一个盘符)

cd mytag

jar cvf mytag.jar .

要导入到第三方直接copy到第三方的WEB-INF下的lib下就可以，它会自动进行配制

在第三方中，可以使用此包中的自定义标签

第二种方法：建一个JAVA项目，把源文件（也就是包）直接COPY到此项目的src中，再把所有的tld文件，考备到META-INF中，导出到java中的JAR文件，classpath project不选。

第三种方法：（最简单的方法）直接压缩。