J2EE —— 第 15 章 JSP 页中的自定义标签

J2EE—— 第 15 章JSP 页中的自定义标签

什么是自定义标签可以：在隐式对象上操作、处理表单、访问数

据库和其它企业服务、实现流控制可以用 JSP 语言或 Java 语言编写标签处理程序还可以：

通过从调用页传递的属性进行定制把变量传递回调用页访问 JSP 页可用的所有对象彼此通信：创建和初始化 bean 、在一个标签中创建

引用该 bean 的 EL 变量、在另一个标签中使用该 bean

彼此进行嵌套，并通过私有变量进行通信

示例 JSP 页

标签的类型<tt:tag>body</tt:tag> 或 <tt:tag /> 或 <tt:tag></tt:tag> 简单属性 <sc:catalog bookDB ="${bookDB}" color="#cccccc"> 段属性<sc:catalog bookDB ="${bookDB}" color="#cccccc"> <jsp:attribute name="normalPrice"> <fmt:formatNumber value="${price}" type="currency"/> </jsp:attribute> <jsp:attribute name="onSale"> <fmt:formatNumber value="${price}“ type="currency"/> <fmt:formatNumber value="${salePrice}“ type="currency"/> </jsp:attribute></sc:catalog> 动态属性 <colored:colored color1="red" color2="yellow" color3

="blue"/>

jsp:attribute 元素和具有体的标签

<c:if test="${param.Clear}"> <font color="#ff0000" size="+2"><strong> You just cleared your sho

pping cart! </strong><br> <br></font> </c:if> <tt:parameter name="title" direct="true"> <jsp:attribute name="value" > <fmt:message key="TitleBookCatalog"/> </jsp:attribute> <jsp:body> the tag body </jsp:body> </tt:parameter>

定义变量的标签和标签之间的通信<tlt:iterator var="departmentName" type="java.lang.String"group="${myorg.departmentNames}"><tr><td><a href="list.jsp?deptName=${departmentName}">${departmentName}</a></td></tr></tlt:iterator>

<c:set var="aVariable" value="aValue" /><tt:anotherTag attr1="${aVariable}" />

<tt:outerTag> <tt:innerTag /> </tt:outerTag>

用标签文件封装可重用内容 response.tag<%@ attribute name="greeting" required="true" %><%@ attribute name="name" required="true" %><h2><font color="black">${greeting}, ${name}!</font></h2> greeting.jsp<%@ taglib tagdir="/WEB-INF/tags" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %> <c:set var="greeting" value="Hello" /> <form method="get"> <input type="text" name="username" size="25"><input type="submit" value="Submit"></form><c:if test="${fn:length(param.username) > 0}" > <h:response greeting="${greeting}“ name="${param.username}"/></c:if>

标签文件位置和标签文件指令 /WEB-INF/tags 及其子目录 ,./WEB-INF/lib 的 jar

文件打包的标签文件要求标签库描述符 .tld 文件标签文件指令

taglib include tag （类似 JSP 中的 page ） attribute variable

tag 指令属性 display-name body-content dynamic-attributes small-icon large-icon description example language import pageEncoding isELIgnored

attribute 指令 (IN 参数 ) 属性 description name required rtexprvalue type fragment

variable 指令 (OUT 参数 ) 属性

description name-given 或 name-from-attribute alias variable-class declare scope

变量同步－ AT_BEGIN 作用域<%-- callingpage.jsp --%><c:set var="x" value="1"/>${x} <%-- (x == 1) --%><my:example>${x} <%-- (x == 2) --%></my:example>${x} <%-- (x == 4) --%><%-- example.tag --%><%@ variable name-given="x" scope="AT_BEGIN" %>${x} <%-- (x == null) --%><c:set var="x" value="2"/><jsp:doBody/>${x} <%-- (x == 2) --%><c:set var="x" value="4"/>

变量同步－ NESTED 作用域<%-- callingpage.jsp --%><c:set var="x" value="1"/>${x} <%-- (x == 1) --%><my:example>${x} <%-- (x == 2) --%></my:example>${x} <%-- (x == 1) --%><%-- example.tag --%><%@ variable name-given="x" scope="NESTED" %>${x} <%-- (x == null) --%><c:set var="x" value="2"/><jsp:doBody/>${x} <%-- (x == 2) --%><c:set var="x" value="4"/>

变量同步－ AT_END 作用域<%-- callingpage.jsp --%><c:set var="x" value="1"/>${x} <%-- (x == 1) --%><my:example>${x} <%-- (x == 1) --%></my:example>${x} <%-- (x == 4) --%><%-- example.tag --%><%@ variable name-given="x" scope="AT_END" %>${x} <%-- (x == null) --%><c:set var="x" value="2"/><jsp:doBody/>${x} <%-- (x == 2) --%><c:set var="x" value="4"/>

变量同步－ AT_BEGIN 和 name-from-attribute<%-- callingpage.jsp --%><c:set var="x" value="1"/>${x} <%-- (x == 1) --%><my:example var="x">${x} <%-- (x == 2) --%>${result} <%-- (result == null) --%><c:set var="result" value="invisible"/></my:example>${x} <%-- (x == 4) --%>${result} <%-- (result == ‘invisible’) --%><%-- example.tag --%><%@ attribute name="var" required="true" rtexprvalue="false"%><%@ variable alias="result" name-from-attribute="var“ scope="AT_B

EGIN" %>${x} <%-- (x == null) --%> ${result} <%-- (result == null) --%><c:set var="x" value="ignored"/><c:set var="result" value="2"/><jsp:doBody/>${x} <%-- (x == ‘ignored’) --%>${result} <%-- (result == 2) --%><c:set var="result" value="4"/>

简单属性示例<%@ taglib prefix="sc" tagdir="/WEB-INF/tags" %><sc:shipDate shipping="${param.shipping}" />

<%@ attribute name="shipping" required="true" %> <jsp:useBean id="now" class="java.util.Date" /> <jsp:useBean id="shipDate" class="java.util.Date" /> <c:choose> <c:when test="${shipping == 'QuickShip'}"><c:set var="days" value="2" /> </c:when> <c:when test="${shipping == 'NormalShip'}"><c:set var="days" value="5" /> </c:when> </c:choose> <jsp:setProperty name="shipDate" property="time" value="${now.time + 86400000 * days}" /> <fmt:formatDate value="${shipDate}" type="date" dateStyle="full"/>

简单和段属性及变量示例 catalog.tag<%@ attribute name="bookDB" required="true" type="database.BookDB"

%><%@ attribute name="color" required="true" %><%@ attribute name="normalPrice" fragment="true" %><%@ attribute name="onSale" fragment="true" %><%@ variable name-given="price" %><%@ variable name-given="salePrice" %><c:forEach var="book" begin="0" items="${bookDB.books}"><c:set var="salePrice" value="${book.price * .85}" /><c:set var="price" value="${book.price}" /><c:choose> <c:when test="${book.onSale}"><jsp:invoke fragment="onSale"/> </c:wh

en> <c:otherwise><jsp:invoke fragment="normalPrice"/></c:otherwise></c:choose>

简单和段属性及变量示例 bookcatalog.jsp

<sc:catalog bookDB ="${bookDB}" color="#cccccc"> <jsp:attribute name="normalPrice"> <fmt:formatNumber value="${price}" type="currency"/> </jsp:attribute> <jsp:attribute name="onSale"> <strike> <fmt:formatNumber value="${price}" type="currency"/> </strike><br/> <font color="red"> <fmt:formatNumber value="${salePrice}" type="currency"/> </font> </jsp:attribute></sc:catalog>

动态属性示例<%@ tag dynamic-attributes="colorMap"%><ul><c:forEach var="color" begin="0“ tems="${colorMap}"> <li>${color.key} = <font color="${color.value}">${color.value}</font><li> </c:forEach> </ul>

标签库描述符<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/webjsptaglibrary_2_0.xsd" version="2.0">

<tlib-version>1.0</tlib-version> <short-name>bar-baz</short-name> <tag-file> <name>d</name> <path>/WEB-INF/tags/bar/baz/d.tag</path> </tag-file> </taglib> 标签库描述符文件 *.tld 在 /WEB-INF 目录中打包到 .jar 文件中，在 META-INF 目录标签文件在 /WEB-INF/tags 目录， Web 容器自动生成 .tld 文件打包在 jar 中的标签文件在 /META-INF/tags 目录，需要定义 tl

d

声明标签处理程序<tag> <name>present</name> <tag-class>condpkg.IfSimpleTag</tag-class> <body-content>scriptless</body-content> ... <attribute> <name>test</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> ...</tag>

声明标签处理程序的标签变量<tlt:iterator var="departmentName" type="java.lang.String" group

="${myorg.departmentNames}"> <tr> <td><a href="list.jsp?deptName=${departmentName}"> ${depar

tmentName}</a></td> </tr> </tlt:iterator>

<tag> <variable> <name-given>var</name-given> <variable-class>java.lang.String</variable-class> <declare>true</d

eclare> <scope>NESTED</scope> </variable></tag> TagExtraInfo类

编写简单标签处理程序简单标签处理程序是如何调用的ATag t = new ATag();t.setJSPContext(...);t.setParent(...);t.setAttribute1(value1);t.setAttribute2(value2);...t.setJspBody(new JspFragment(...))t.doTag(); 基本标签的标签处理程序public HelloWorldSimpleTag extends SimpleTagSupport { public void doTag() throws JspException, IOException{ getJspContext().getOut().write("Hello, world."); } }

具有属性的标签的标签处理程序<c:if test="${Clear}">public void setTest(boolean test) {this.test = test;} <attribute> <name>attr1</name> <required>true</required> <rtexprvalue>true</rtexprvalue></attribute>public class TwaTEI extends TagExtraInfo { public ValidationMessage[] validate(TagData data) { Object o = data.getAttribute("attr1"); if (o != null && o != TagData.REQUEST_TIME_VALUE) { if (((String)o).toLowerCase().equals("true") || ((String)o).toLowerCase().equals("false") ) return null; else return new ValidationMessage( data.getId(), "Invalid boolean value."); } else return null;}}

设置动态属性private ArrayList keys = new ArrayList(); private ArrayList values = new ArrayList(); public void setDynamicAttribute(String uri, String localName, Object va

lue ) throws JspException { keys.add( localName ); values.add( value ); }

public void doTag() throws JspException, IOException { JspWriter out = getJspContext().getOut(); for( int i = 0; i < keys.size(); i++ ) { String key = (String)keys.get( i ); Object value = values.get( i ); out.println( "<li>" + key + " = " + value + "</li>" ); }}

具有体的标签的标签处理程序public class IfSimpleTag extends SimpleTagSupport {private boolean test;public void setTest(boolean test) {this.test = test; } public void doTag() throws JspException, IOException { if(test){getJspBody().invoke(null);}}}

public class SimpleWriter extends SimpleTagSupport { public void doTag() throws JspException, IOException { StringWriter sw = new StringWriter(); getJspBody.invoke(sw); getJspContext().getOut().println(sw.toString().toUpperCase()); }}

定义变量的标签的标签处理程序public void doTag() throws JspException, IOException { if (iterator == null) return; while (iterator.hasNext()) { getJspContext().setAttribute(var, iterator.next()); getJspBody().invoke(null); } } public void setVar(String var) { this.var = var; } public void setGroup(Collection group) { this.group = group; if(group.size() > 0) iterator = group.iterator();}

对象的作用域

TagExtraInfo 类声明标签处理程序的标签变量package iterator;public class IteratorTEI extends TagExtraInfo { public VariableInfo[] getVariableInfo(TagData data) { String type = data.getAttributeString("type"); if (type == null) type = "java.lang.Object"; return new VariableInfo[] { new VariableInfo(data.getAttributeString("var"), type, true, VariableInfo.NESTED) };}}

<tei-class>iterator.IteratorTEI</tei-class>

协作标签 (1)public class QueryTag extends SimpleTagSupport { public int doTag() throws JspException { String cid = getConnectionId(); Connection connection; if (cid != null) { connection =(Connection)pageContext. getAttribute(cid); } else { ConnectionTag ancestorTag = (ConnectionTag)findAncestorWithClass(this, ConnectionTag.class); if (ancestorTag == null) { throw new JspTagException("A query without a connection attribute must be nested within a connection tag."); } connection = ancestorTag.getConnection();...}}}

协作标签 (2)<tt:connection cid="con01" ... >... </tt:connection> <tt:query id="balances" connectionId="con01"> SELECT account, balance FROM acct_table where customer_number = ? <tt:param value="${requestScope.custNumber}" /> </tt:query>

<tt:connection ... > <tt:query cid="balances"> SELECT account, balance FROM acct_table where customer_number = ? <tt:param value="${requestScope.custNumber}" /> </tt:query></tt:connection>

<tag>...<attribute><name>connectionId</name><required>false</required></attribute></tag>

示例－迭代标签－ JSP 页<%@ taglib uri="/tlt" prefix="tlt" %> <jsp:useBean id="myorg" class="myorg.Organization"/> <table border=2 cellspacing=3 cellpadding=3> <tlt:iterator var="departmentName" type="java.lang.String" group="${myorg.departmentNames}"> <tr> <td><a href="list.jsp?deptName=${departmentName}"> ${departmentName}</a></td> </tr> </tlt:iterator> </table>

示例－迭代标签－标签处理程序public void doTag() throws JspException, IOException { if (iterator == null) return; while (iterator.hasNext()) { getJspContext().setAttribute(var, iterator.next()); getJspBody().invoke(null); }}public void setVar(String var) {this.var = var; } public void setGroup(Collection group) { this.group = group; if(group.size() > 0) iterator = group.iterator();}

示例－模版标签库－ template.jsp

<%@ taglib uri="/tutorial-template" prefix="tt" %><%@ page errorPage="/template/errorinclude.jsp" %><%@ include file="/template/screendefinitions.jsp" %><html><head><title><tt:insert definition="bookstore" parameter="title"/></title></head><body bgcolor="#FFFFFF"><tt:insert definition="bookstore" parameter="banner"/><tt:insert definition="bookstore" parameter="body"/></body></html>

示例－模版标签库 screendefinitions.jsp

<tt:definition name="bookstore" screen="${requestScope['javax.servlet.forward.servlet_path']}">

<tt:screen id="/bookstore"> <tt:parameter name="title" value="Duke's Bookstore" direct="true"/> <tt:parameter name="banner" value="/template/banner.jsp" direct="false"/

> <tt:parameter name="body" value="/bookstore.jsp" direct="false"/></tt:screen><tt:screen id="/bookcatalog"> <tt:parameter name="title" direct="true"> <jsp:attribute name="value" ><fmt:message key="TitleBookCatalog"/> </jsp:attribute></tt:parameter> <tt:parameter name="banner" value="/template/banner.jsp" direct="false"/><tt:parameter name="body" value="/bookcatalog.jsp“ direct="false"/></tt:screen></tt:definition>

示例－模版标签库－ Dispatcher.javapublic class Dispatcher extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse r

esponse) { String selectedScreen = request.getServletPath(); if (selectedScreen.equals("/bookcatalog")) { bookId = request.getParameter("Add"); if (!bookId.equals("")) { book = bookDBAO.getBookDetails(bookId); cart.add(bookId, book); }else if (…) … } request.getRequestDispatcher("/template/template.jsp"). forward(request, response);}

示例－模版标签库－ DefinitionTag.java

public int doTag() { screens = new HashMap(); getJspBody().invoke(null); Definition definition = new Definition(); PageContext context = (PageContext)getJspContext(); ArrayList params = (ArrayList) screens.get(screenId); Iterator ir = null; if (params != null) { ir = params.iterator(); while (ir.hasNext()) {definition.setParam((Parameter)ir.next());} context.setAttribute(definitionName, definition, context.APPLICATION_SCOPE); } }

示例－模版标签库－ InsertTag.javapublic void doTag() throws JspTagException { Definition definition = null; Parameter parameter = null; boolean directInclude = false; PageContext context = (PageContext)getJspContext(); definition = (Definition)context.getAttribute( definitionName, context.APPLICATION_SCOPE); if (parameterName != null && definition != null) parameter = (Parameter) definition.getParam(parameterName); if (parameter != null) directInclude = parameter.isDirect(); if (directInclude && parameter != null) context.getOut().print(parameter.getValue()); else { if ((parameter != null) && (parameter.getValue() != null)) context.include(parameter.getValue()); } }

J2EE —— 第 15 章 JSP 页中的自定义标签

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