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Creating Custom JSP Tag Libraries

Creating Custom JSP Tag Libraries. http://java.sun.com/products/jsp/taglibraries.html#tutorials Taken from Core Servlets and JavaServer Pages from Prentice Hall and Sun Microsystems Press, http://www.coreservlets.com/. © 2000 Marty Hall; may be freely used or adapted.

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Creating Custom JSP Tag Libraries

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  1. Creating Custom JSP Tag Libraries • http://java.sun.com/products/jsp/taglibraries.html#tutorials • Taken from Core Servlets and JavaServer Pages • from Prentice Hall and Sun Microsystems Press, • http://www.coreservlets.com/. • © 2000 Marty Hall; • may be freely used or adapted.

  2. JSP & Komponenten Java Entwickler Anwendungs Logik Daten Präsentation DB Daten Zugriff WEB Designer

  3. Beans • <jsp:useBean id="wobs" class="jspcr.beans.weather.Observation"> • <jsp:setProperty • name="wobs" • property="airportCode" • value="<%= airportCode %>"/> • </jsp:useBean>

  4. Custom Tags Aktion starten • <jax:example /> Simple Tag • <jax:debug> Body Tag • …. • </jax:debug> • + Kompaktere Syntax • + Inhalte bearbeiten • Arbeitsaufwendiger Aktion starten Inhalt bearbeiten Aktion starten

  5. Installieren und starten • Customtags benötigen folgende Elemente: • csajsp-taglib.tld Taglib Definition • SimpleExample.jsp JSP • ExampleTag.java Java Klasse • Pfad

  6. Custom Tags • Ein Tag ist eine Klasse, die • javax.servlet.jsp.tagext.Tag Interface implementiert.

  7. Hello World Kochrezept • 1. File HelloWorldTag.java im ../tag Ordner erstellen • 2. import Anweisungen: • package com.jax.tag • import javax.servlet.jsp.*;import javax.servlet.jsp.tagext.*; • 3. Implementierung javax.servlet.jsp.tagext.Tag Interface: • public class HelloWorldTag implements Tag { • 4. Container Variablen; • private PageContext pageContext;private Tag parent; • 5. Constructor: • public HelloWorldTag(){ • super(); • }

  8. Hello World Kochrezept • 6. Diese Methode wird beim Start-Tag ausgeführt: • public int doStartTag() throws javax.servlet.jsp.JspTagException { • return SKIP_BODY; • } • 7. Diese Methode wird beim End-Tag ausgeführt: • public int doEndTag() throws javax.servlet.jsp.JspTagException { • try{ • pageContext.getOut().write("Hello World!"); • }catch(java.io.IOException e){ • throw new JspTagException("IO Error: " + e.getMessage()); • }return EVAL_PAGE; // Den Rest der Seite weiterverarbeiten.}

  9. Hello World Kochrezept • 8. Es braucht noch weitere Methoden: • public void release() {} • 9. … • public void setPageContext(final javax.servlet.jsp.PageContext pageContext) {this.pageContext=pageContext; • } • 10. … • public void setParent(final javax.servlet.jsp.tagext.Tag parent) {this.parent=parent;} • 11. Finally, this method has to be implemented: • public javax.servlet.jsp.tagext.Tag getParent() { • return parent; • }

  10. Einfacher (extend TagSupport) • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • public class ExampleTag extends TagSupport { • public int doStartTag() { • try { • JspWriter out = pageContext.getOut(); • out.print("Hello World" + • "(Hello World)"); • } catch(IOException ioe) { • System.out.println("Error in ExampleTag: " + ioe); • } • return(SKIP_BODY); • } • }

  11. pageContext Methoden • getOut • getRequest • getResponse • getServletContext • getSession • JspWriter out = pageContext.getOut();

  12. SimpleExample.jsp • <HTML><HEAD> • <%@ taglib uri="csajsp-taglib.tld" prefix="jax" %> • <TITLE><jax:example /></TITLE></HEAD> • <BODY> • <H1><jax:example /></H1> • <jax:example /> • </BODY> • </HTML>

  13. taglib.tld (ins gleiche Verzeichnis wie die JSP‘s) • <?xml version="1.0" encoding="ISO-8859-1" ?> • <!DOCTYPE taglib • PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" • "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> • <taglib> • <tlibversion>1.0</tlibversion> • <jspversion>1.1</jspversion> • <shortname>csajsp</shortname> • <uri></uri> • <info> • Beispiel Tags für die Vorlesung JAX, • http://www.ifi.unibas.ch • </info> • <tag> • <name>example</name> • <tagclass>customtag.tags.ExampleTag</tagclass> • <info>Simplest example: inserts one line of output</info> • <bodycontent>empty</bodycontent> // JSP Inhalt wird als JSP interpretiert • </tag> • </taglib>

  14. SimplePrimeTag.java • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • import java.math.*; • import customtag.Primes; • public class SimplePrimeTag extends TagSupport { • protected int len = 50; • public int doStartTag() { • try { • JspWriter out = pageContext.getOut(); • BigInteger prime = Primes.nextPrime(Primes.random(len)); • out.print(prime); • } catch(IOException ioe) { • System.out.println("Error generating prime: " + ioe); • } • return(SKIP_BODY); • } • }

  15. PrimeTag.java • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • import java.math.*; • import customtag.tags.*; • public class PrimeTag extends SimplePrimeTag { • public void setLength(String length) { • try { • len = Integer.parseInt(length); • } catch(NumberFormatException nfe) { • len = 50; • } • } • }

  16. taglib • <tag> • <name>simplePrime</name> • <tagclass>customtag.tags.SimplePrimeTag</tagclass> • <info>Outputs a random 50-digit prime.</info> • <bodycontent>empty</bodycontent> • </tag> • <tag> • <name>prime</name> • <tagclass>customtag.tags.PrimeTag</tagclass> • <info>Outputs a random N-digit prime.</info> • <bodycontent>empty</bodycontent> • <attribute> • <name>length</name> • <required>false</required> • </attribute> • </tag>

  17. HeadingTag.jsp I • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • public class HeadingTag extends TagSupport { • private String bgColor; // The one required attribute • private String color = null; • private String align="CENTER"; • private String fontSize="36"; • private String fontList="Arial, Helvetica, sans-serif"; • private String border="0"; • private String width=null; • public void setBgColor(String bgColor) { • this.bgColor = bgColor; • } • public void setColor(String color) { • this.color = color; • }

  18. HeadingTag.jsp II • public int doStartTag() { • try { • JspWriter out = pageContext.getOut(); • out.print("<TABLE BORDER=" + border + • " BGCOLOR=\"" + bgColor + "\"" + • " ALIGN=\"" + align + "\""); • if (width != null) { • out.print(" WIDTH=\"" + width + "\""); • } • out.print("><TR><TH>"); • out.print("<SPAN STYLE=\"" + • "font-size: " + fontSize + "px; " + • "font-family: " + fontList + "; "); • if (color != null) { • out.println("color: " + color + ";"); • } • out.print("\"> "); // End of <SPAN ...> • } catch(IOException ioe) { • System.out.println("Error in HeadingTag: " + ioe); • } • return(EVAL_BODY_INCLUDE); // Include tag body • }

  19. HeadingTag.jsp III • public int doEndTag() { • try { • JspWriter out = pageContext.getOut(); • out.print("</SPAN></TABLE>"); • } catch(IOException ioe) { • System.out.println("Error in HeadingTag: " + ioe); • } • return(EVAL_PAGE); // Continue with rest of JSP page • } • }

  20. HeadingExample.jsp • <HTML><HEAD><TITLE>Some Tag-Generated Headings</TITLE></HEAD> • <BODY><%@ taglib uri="csajsp-taglib.tld" prefix="jax" %> • <jax:heading bgColor="#C0C0C0"> • Default Heading • </jax:heading> • <P> • <jax:heading bgColor="BLACK" color="WHITE"> • White on Black Heading • </jax:heading> • <P> • <jax:heading bgColor="#EF8429" fontSize="60" border="5"> • Large Bordered Heading • </jax:heading> • <P> • <jax:heading bgColor="CYAN" width="100%"> • Heading with Full-Width Background • </jax:heading> • <P> • <jax:heading bgColor="CYAN" fontSize="60" • fontList="Brush Script MT, Times, serif"> • Heading with Non-Standard Font • </jax:heading> • <P></BODY></HTML>

  21. Debug.jsp • <HTML><HEAD><TITLE>Using the Debug Tag</TITLE></HEAD> • <BODY> • <H1>Using the Debug Tag</H1> • <%@ taglib uri="csajsp-taglib.tld" prefix="jax" %> • Top of regular page. Blah, blah, blah. Yadda, yadda, yadda. • <P> • <jax:debug> • <B>Debug:</B> • <UL> • <LI>Current time: <%= new java.util.Date() %> • <LI>Requesting hostname: <%= request.getRemoteHost() %> • <LI>Session ID: <%= session.getId() %> • </UL> • </jax:debug> • <P>Bottom of regular page. Blah, blah, blah. Yadda, yadda, yadda. • </BODY></HTML>

  22. DebugTag.java • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • import javax.servlet.*; • public class DebugTag extends TagSupport { • public int doStartTag() { • ServletRequest request = pageContext.getRequest(); • String debugFlag = request.getParameter("debug"); • if ((debugFlag != null) && • (!debugFlag.equalsIgnoreCase("false"))) { • return(EVAL_BODY_INCLUDE); • } else { • return(SKIP_BODY); • } • } • }

  23. FilterTag.java • package customtag.tags; • import javax.servlet.jsp.*; • import javax.servlet.jsp.tagext.*; • import java.io.*; • import customtag.*; • public class FilterTag extends BodyTagSupport { • public int doAfterBody() { • BodyContent body = getBodyContent(); • String filteredBody = ServletUtilities.filter(body.getString()); • try { • JspWriter out = body.getEnclosingWriter(); • out.print(filteredBody); • } catch(IOException ioe) { • System.out.println("Error in FilterTag: " + ioe); • } • return(SKIP_BODY); • } • }

  24. FilterExample.jsp • <HTML><HEAD><TITLE>HTML Logical Character Styles</TITLE> • <BODY> • <H1>HTML Logical Character Styles</H1> • Physical character styles (B, I, etc.) are rendered consistently • in different browsers. Logical character styles, however, • may be rendered differently by different browsers. • Here's how your browser • (<%= request.getHeader("User-Agent") %>) • renders the HTML 4.0 logical character styles: • <P> • <%@ taglib uri="csajsp-taglib.tld" prefix="jax" %> • <TABLE BORDER=1 ALIGN="CENTER"> • <TR CLASS="COLORED"><TH>Example<TH>Result • <TR>

  25. FilterExample.jsp • <TD><PRE><jax:filter> • <EM>Some emphasized text.</EM><BR> • <STRONG>Some strongly emphasized text.</STRONG><BR> • <CODE>Some code.</CODE><BR> • <SAMP>Some sample text.</SAMP><BR> • <KBD>Some keyboard text.</KBD><BR> • <DFN>A term being defined.</DFN><BR> • <VAR>A variable.</VAR><BR> • <CITE>A citation or reference.</CITE> • </jax:filter></PRE> • <TD><EM>Some emphasized text.</EM><BR> • <STRONG>Some strongly emphasized text.</STRONG><BR> • <CODE>Some code.</CODE><BR> • <SAMP>Some sample text.</SAMP><BR> • <KBD>Some keyboard text.</KBD><BR> • <DFN>A term being defined.</DFN><BR> • <VAR>A variable.</VAR><BR> • <CITE>A citation or reference.</CITE> • </TABLE></BODY></HTML>

  26. Taglibs

  27. Praktikum • Frohe Festtage • Bean Übung beenden • Beispiele Customtags durchspielen • 3. Eine Taglib von Apache austesten • http://jakarta.apache.org/taglibs/index.html

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