关键词位置、密度、处理

Attributes
total (required) - The total number of results to paginate
action (optional) - the name of the action to use in the link, if not specified the default action will be linked
controller (optional) - the name of the controller to use in the link, if not specified the current controller will be linked
id (optional) - The id to use in the link
params (optional) - A map containing request parameters
prev (optional) - The text to display for the previous link (defaults to "Previous" as defined by default.paginate.prev property in I18n messages.properties)
next (optional) - The text to display for the next link (defaults to "Next" as defined by default.paginate.next property in I18n messages.properties)
max (optional) - The number of records displayed per page (defaults to 10). Used ONLY if params.max is empty
maxsteps (optional) - The number of steps displayed for pagination (defaults to 10). Used ONLY if params.maxsteps is empty
offset (optional) - Used ONLY if params.offset is empty
source: ./checkout/grails/src/groovy/org/codehaus/groovy/grails/plugins/web/taglib/RenderTagLib.groovy (No such file or directory)

3，在jsp中加入代码：

<%@ taglib uri="http://jakarta.apache.org/taglibs/string-1.0" prefix="str" %>

<str:substring start="0" end="40"><c:out value="${messages}"/></str:substring>

因此JSTL内置了几个用于字符串操作的方法，可以直接在表达式中使用，大大的简化了代码，提供代码的可读性。在JSTL的表达是中要使用一个函数，其格式如下

${ns:methodName(args....)}

在使用这些函数之前必须在JSP中引入标准函数的声明

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

下面是JSTL中自带的方法列表以及其描述

函数名	函数说明	使用举例
contains	判断字符串是否包含另外一个字符串	<c:if test="${fn:contains(name, searchString)}">
containsIgnoreCase	判断字符串是否包含另外一个字符串(大小写无关)	<c:if test="${fn:containsIgnoreCase(name, searchString)}">
endsWith	判断字符串是否以另外字符串结束	<c:if test="${fn:endsWith(filename, ".txt")}">
escapeXml	把一些字符转成XML表示，例如<字符应该转为&lt;	${fn:escapeXml(param:info)}
indexOf	子字符串在母字符串中出现的位置	${fn:indexOf(name, "-")}
join	将数组中的数据联合成一个新字符串，并使用指定字符格开	${fn:join(array, ";")}
length	获取字符串的长度，或者数组的大小	${fn:length(shoppingCart.products)}
replace	替换字符串中指定的字符	${fn:replace(text, "-", "•")}
split	把字符串按照指定字符切分	${fn:split(customerNames, ";")}
startsWith	判断字符串是否以某个子串开始	<c:if test="${fn:startsWith(product.id, "100-")}">
substring	获取子串	${fn:substring(zip, 6, -1)}
substringAfter	获取从某个字符所在位置开始的子串	${fn:substringAfter(zip, "-")}
substringBefore	获取从开始到某个字符所在位置的子串	${fn:substringBefore(zip, "-")}
toLowerCase	转为小写	${fn.toLowerCase(product.name)}
toUpperCase	转为大写字符	${fn.UpperCase(product.name)}
trim	去除字符串前后的空格	${fn.trim(name)}

import Java.io.IOException;
import Java.util.Collection;
import Java.util.Iterator;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTagSupport;

public class IterateTag extends BodyTagSupport {

 private String name;  //代表了在pageContext中表示的一个属性的名字
 private Iterator it;     //代表要迭代的内容
 private String type;  //表示it中对象的类型
 
 public void setCollection(Collection collection){
  if(collection.size()>0){
   it=collection.iterator();
  }
 }
 
 public void setName(String name){
  this.name=name;
 }
 
 public void setType(String type){
  this.type=type;
 }

 @Override
 public int doAfterBody() throws JspException {
  // TODO Auto-generated method stub
  return continueNext(it);
 }

 @Override
 public int doEndTag() throws JspException {
  // TODO Auto-generated method stub
  try{
   if(bodyContent!=null){
    bodyContent.writeOut(bodyContent.getEnclosingWriter());
   }
  }catch(IOException e){
   throw new JspTagException("IO Error:"+e.getMessage());
  }
  return EVAL_PAGE;
 }

 @Override
 public int doStartTag() throws JspException {
  // TODO Auto-generated method stub
  if(it==null){
   return SKIP_BODY;
  }else{
   return continueNext(it);
  }
 }
 
 protected int continueNext(Iterator it)throws JspTagException{
  if(it.hasNext()){
   pageContext.setAttribute(name, it.next(), PageContext.PAGE_SCOPE);
   return EVAL_BODY_AGAIN;
  }else{
   return SKIP_BODY;
  }
 }
}
由于BodyTagSupport类实现了TagSupport，而TagSupport又实现了TterationTag接口。故在开发迭代标签时可以直接从BodyTagSupport继承。

package com.rain.tag;

import javax.servlet.jsp.tagext.TagData;
import javax.servlet.jsp.tagext.TagExtraInfo;
import javax.servlet.jsp.tagext.VariableInfo;

//TagExtraInfo用于提供一些在标签翻译时相关的信息
public class IterateTEI extends TagExtraInfo {

 public IterateTEI(){
  super();
 }

 @Override
 public VariableInfo[] getVariableInfo(TagData arg0) {
  // TODO Auto-generated method stub
  return new VariableInfo[]{
    new VariableInfo(arg0.getAttributeString("name"),
                     arg0.getAttributeString("type"),
                     true,
                     VariableInfo.NESTED)
  };
 }
}
需要说明的是VariableInfo的几个常数，如下所示：
1.NESTED：标签中的参数在starttag到endtag之间是有效的。
2.AT_BENGIN：标签中的参数在标签的开始到JSP页面结束是有效的。
3.AT_END：标签中的参数在标签的结束到JSP页面结束是有效的。

在标签的描述中，必须同时指定标签的实现类和IterateTEI类。
       <tag>
          <name>iterate</name>
            <tag-class>com.rain.tag.IterateTag</tag-class>
            <tei-class>com.rain.tag.IterateTEI</tei-class>
          <body-content>jsp</body-content>
          <attribute>
            <name>collection</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
          </attribute>
          <attribute>
            <name>name</name>
            <required>true</required>
          </attribute>
          <attribute>
            <name>type</name>
            <required>true</required>
          </attribute>
      </tag>

运行结果：
one
two
three

import Java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.BodyTagSupport;

/*
 * if tag
 * usage:<tag:if value=true>
 *       ...
 *       </tag:if>
 */
public class IfTag extends BodyTagSupport {

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

 @Override
 public int doEndTag() throws JspException {
  // TODO Auto-generated method stub
  try{
   if(bodyContent!=null){
    bodyContent.writeOut(bodyContent.getEnclosingWriter());
   }
  }catch(IOException e){
   throw new JspTagException("IO Error:"+e.getMessage());
  }
  return EVAL_PAGE;
 }

 @Override
 public int doStartTag() throws JspException {
  // TODO Auto-generated method stub
  if(value){
   System.out.println("value is true");
   return EVAL_BODY_INCLUDE;
  }else{
   System.out.println("value is false");
   return SKIP_BODY;
  }
 }
 
 
}

import Java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.TagSupport;

public class OutTag extends TagSupport {

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

 @Override
 public int doEndTag() throws JspException {
  // TODO Auto-generated method stub
  return EVAL_BODY_INCLUDE;
 }

 @Override
 public int doStartTag() throws JspException {
  // TODO Auto-generated method stub
  try{
   System.out.println(value);
   pageContext.getOut().write(value.toString());
  }catch(IOException e){
   throw new JspTagException("IO Error:"+e.getMessage());
  }
  return EVAL_PAGE;
 }
 
 
}

import Java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;

public class BodyTagExample extends BodyTagSupport {

 int counts;    //counts为迭代的次数
 
 public BodyTagExample(){
  super();
 }
 
 /*
  * 设置counts属性，这个方法由容器自动调用
  */
 public void setCounts(int c){
  this.counts=c;
 }
 
 @Override
 public int doAfterBody() throws JspException {
  // TODO Auto-generated method stub
  System.out.println("doAfterBody"+counts);
  if(counts>1){
   counts--;
   return EVAL_BODY_AGAIN;
  }else{
   return SKIP_BODY;
  }
 }

 @Override
 public int doEndTag() throws JspException {
  // TODO Auto-generated method stub
  System.out.println("doEndTag");
  try{
   if(bodyContent!=null){
    bodyContent.writeOut(bodyContent.getEnclosingWriter());
   }
  }catch(IOException e){
   throw new JspTagException("IO Error:"+e.getMessage());
  }
  return EVAL_PAGE;
 }

 @Override
 public void doInitBody() throws JspException {
  // TODO Auto-generated method stub
  System.out.println("doInitBody");
 }

 @Override
 public int doStartTag() throws JspException {
  // TODO Auto-generated method stub
  System.out.println("doStartTag");
  if(counts>0){
   return EVAL_BODY_AGAIN;
  }else{
   return SKIP_BODY;
  }
 }

 @Override
 public void setBodyContent(BodyContent arg0) {
  // TODO Auto-generated method stub
  System.out.println("setBodyContent");
  this.bodyContent=arg0;
 }
}

<?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 web-jsptaglibrary_2_0.xsd"
        version="2.0">
        <description>A tag library exercising SimpleTag handlers.</description>
        <tlib-version>1.0</tlib-version>
       
        <short-name>examples</short-name>
        <uri>/demotag</uri>
        <description>JSP应用开发</description>
        
          <tag>
          <name>loop</name>
          <tag-class>com.rain.tag.BodyTagExample</tag-class>
          <body-content>jsp</body-content>    Body-Content必须为JSP
          <attribute>
            <name>counts</name>                    定义中必须有setCounts(int counts)方法
            <required>true</required>               表示这个属性是必须的
            <rtexprvalue>true</rtexprvalue>       支持JSP表达式
          </attribute>
        </tag>
</taglib>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
 <taglib>
   <taglib-uri>/demotag</taglib-uri>
   <taglib-location>/WEB-INF/mytag.tld</taglib-location>
 </taglib>
</web-app>

<%@ page language="Java" contentType="text/html; charset=UTF-8"%>
<%@ taglib uri="/demotag" prefix="bodytag" %>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<bodytag:loop counts="5">
  现在时间是:<%=new Java.util.Date()%><br>
</bodytag:loop>
</body>
</html>

执行结果：
控制台打印出
doStartTag
setBodyContent
doInitBody
doAfterBody5
doAfterBody4
doAfterBody3
doAfterBody2
doAfterBody1
doEndTag
页面显示
现在时间是:Mon Jan 22 14:52:43 CST 2007
现在时间是:Mon Jan 22 14:52:43 CST 2007
现在时间是:Mon Jan 22 14:52:43 CST 2007
现在时间是:Mon Jan 22 14:52:43 CST 2007
现在时间是:Mon Jan 22 14:52:43 CST 2007

import Java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;

public class HelloTag implements Tag {

 private PageContext pageContext;
 private Tag parent;
 
 public HelloTag(){
  super();
 }
 public int doEndTag() throws JspException {
  // TODO Auto-generated method stub
  try{
   pageContext.getOut().write("Hello World!　你好");
  }catch(IOException e){
   throw new JspTagException("IO Error:"+e.getMessage());
  }
  return EVAL_PAGE;
 }

 public int doStartTag() throws JspException {
  // TODO Auto-generated method stub
  return SKIP_BODY;  //返回SKIP_BODY，表示不计算标签体
 }

 public Tag getParent() {
  // TODO Auto-generated method stub
  return this.parent;
 }

 public void release() {
  // TODO Auto-generated method stub
 }

 public void setPageContext(PageContext arg0) {
  // TODO Auto-generated method stub
  this.pageContext=arg0;
 }

 public void setParent(Tag arg0) {
  // TODO Auto-generated method stub
  this.parent=arg0;
 }

}

编写标签库描述

<?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 web-jsptaglibrary_2_0.xsd"
        version="2.0">
        <description>A tag library exercising SimpleTag handlers.</description>
        <tlib-version>1.0</tlib-version>
       
        <short-name>examples</short-name>
        <uri>/demotag</uri>
        <description>JSP应用开发</description>
       
        <tag>
          <description>Outputs Hello,World</description>
          <name>hello_int</name>
          <tag-class>com.rain.tag.HelloTag</tag-class>
          <body-content>empty</body-content>
        </tag>
</taglib>

使用自定义标签

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
 <taglib>
   <taglib-uri>/demotag</taglib-uri>
   <taglib-location>/WEB-INF/mytag.tld</taglib-location>
 </taglib>
</web-app>


<%@ page language="Java" contentType="text/html; charset=UTF-8"%>
<%@ taglib uri="/demotag" prefix="hello" %>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<p>以下的内容是从Taglib中显示的：</p>
<p><i><hello:hello_int/></i></p>
</body>
</html>

本实例是实现Tag接口，但为了在开发中方便简单，一般直接继承TagSupport类，只覆盖doStartTag和doEndTag两个方法就可以。TagSupport是Tag的子类。

1．  把数据保存在 Session 中（这是常见方式）；

2．  通过 Cookie ；

3．  通过隐含的表单把数据提交到下一个页面；

4．  通过 ServletContext 对象；

5．  通过 Application 对象；

6．  通过文件系统或者数据库。

在不同用户之间共享数据，通常用法是：

1．  通过 ServletContext 对象；

2．  通过 Application 对象；

3．  通过文件系统或者数据库。

        byte[] buff = new byte[2048];
        int bytesRead;

        while(-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
            bos.write(buff,0,bytesRead);
        }

    } catch(final IOException e) {
        System.out.println ( "出现IOException." + e );
    } finally {
        if (bis != null)
            bis.close();
        if (bos != null)
            bos.close();
    }
    return;
%>

<select name="kind1" id="kind1" onChange="onchange_kind1(this.value);">
         <%
         Vector myvector=null;
      myvector=kind1info.selectInfor();
      for(int i=0;i<myvector.size();i++)
      {
        kind1id=((kind1Unit)myvector.elementAt(i)).getID();
        kindname1=((kind1Unit)myvector.elementAt(i)).getKindName1();
      %>
                      <option value="<%=kind1id%>"><%=kindname1%></option>
                      <%
        }//循环结束
      %>
                    </select></td>
                    <td width="81%"><div id="divKind" name="divKind">
                      <select name="kind2" id="kind2">
                      </select>
                    </div>

<iframe id="frmcontent" name="frmcontent" width="400" height="40" src=""></iframe>

第二页面
<div id="divKind" name="divKind">
<select name="kind2" id="kind2" >
      <%
  Vector myvector=null;
  myvector=kind2info.selectInfor(kind1id);
  for(int i=0;i<myvector.size();i++)
     {
   kind2id=((kind2Unit)myvector.elementAt(i)).getID();
   kindname2=((kind2Unit)myvector.elementAt(i)).getKindName2();
  %>
  <option value="<%=kind2id%>"><%=kindname2%></option>
    <%
    }//循环结束
    %>
</select>
</div>

<script language="javascript">
  function getItem()
  {
    //alert(document.form1.kind2.innerHTML);
 //alert(parent.document.form1.kind2.innerHTML);
    parent.document.all.divKind.innerHTML = document.all.divKind.innerHTML;
 //alert(parent.document.form1.kind2.innerHTML); 
 //.innerText
  }
  getItem();
</script>