| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN""http://www.w3.org/TR/REC-html40/loose.dtd"> |
| <!--NewPage--> |
| <HTML> |
| <HEAD> |
| <!-- Generated by javadoc on Fri Aug 22 03:43:54 EDT 2003 --> |
| <TITLE> |
| org.apache.struts.taglib.logic (Apache Struts API Documentation) |
| </TITLE> |
| <META NAME="keywords" CONTENT="org.apache.struts.taglib.logic package"> |
| <LINK REL ="stylesheet" TYPE="text/css" HREF="../../../../../stylesheet.css" TITLE="Style"> |
| </HEAD> |
| <SCRIPT> |
| function asd() |
| { |
| parent.document.title="org.apache.struts.taglib.logic (Apache Struts API Documentation)"; |
| } |
| </SCRIPT> |
| <BODY BGCOLOR="white" onload="asd();"> |
| |
| <!-- ========== START OF NAVBAR ========== --> |
| <A NAME="navbar_top"><!-- --></A> |
| <TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"> |
| <TR> |
| <TD COLSPAN=3 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> |
| <A NAME="navbar_top_firstrow"><!-- --></A> |
| <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> |
| <TR ALIGN="center" VALIGN="top"> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> |
| <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Package</B></FONT> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <FONT CLASS="NavBarFont1">Class</FONT> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-use.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> |
| </TR> |
| </TABLE> |
| </TD> |
| <TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM> |
| </EM> |
| </TD> |
| </TR> |
| |
| <TR> |
| <TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> |
| <A HREF="../../../../../org/apache/struts/taglib/html/package-summary.html"><B>PREV PACKAGE</B></A> |
| <A HREF="../../../../../org/apache/struts/taglib/nested/package-summary.html"><B>NEXT PACKAGE</B></A></FONT></TD> |
| <TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> |
| <A HREF="../../../../../index.html" TARGET="_top"><B>FRAMES</B></A> |
| <A HREF="package-summary.html" TARGET="_top"><B>NO FRAMES</B></A> |
| |
| <SCRIPT> |
| <!-- |
| if(window==top) { |
| document.writeln('<A HREF="../../../../../allclasses-noframe.html" TARGET=""><B>All Classes</B></A>'); |
| } |
| //--> |
| </SCRIPT> |
| <NOSCRIPT> |
| <A HREF="../../../../../allclasses-noframe.html" TARGET=""><B>All Classes</B></A> |
| </NOSCRIPT> |
| </FONT></TD> |
| </TR> |
| </TABLE> |
| <!-- =========== END OF NAVBAR =========== --> |
| |
| <HR> |
| <H2> |
| Package org.apache.struts.taglib.logic |
| </H2> |
| The "struts-logic" tag library contains tags that are useful in managing |
| conditional generation of output text, looping over object collections |
| for repetitive generation of output text, and application flow management. |
| <P> |
| <B>See:</B> |
| <BR> |
| <A HREF="#package_description"><B>Description</B></A> |
| <P> |
| |
| <TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"> |
| <TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"> |
| <TD COLSPAN=2><FONT SIZE="+2"> |
| <B>Class Summary</B></FONT></TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="CompareTagBase.html">CompareTagBase</A></B></TD> |
| <TD>Abstract base class for comparison tags.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ConditionalTagBase.html">ConditionalTagBase</A></B></TD> |
| <TD>Abstract base class for the various conditional evaluation tags.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="EmptyTag.html">EmptyTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is empty for this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="EqualTag.html">EqualTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| and value are equal.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ForwardTag.html">ForwardTag</A></B></TD> |
| <TD>Perform a forward or redirect to a page that is looked up in the |
| configuration information associated with our application.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="GreaterEqualTag.html">GreaterEqualTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| is greater than or equal to the specified value.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="GreaterThanTag.html">GreaterThanTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| is greater than the specified value.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="IterateTag.html">IterateTag</A></B></TD> |
| <TD>Custom tag that iterates the elements of a collection, which can be |
| either an attribute or the property of an attribute.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="IterateTei.html">IterateTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>iterate</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="LessEqualTag.html">LessEqualTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| is less than or equal to the specified value.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="LessThanTag.html">LessThanTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| is less than the specified value.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="MatchTag.html">MatchTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is a substring of the specified variable.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="MessagesNotPresentTag.html">MessagesNotPresentTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is not present for this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="MessagesPresentTag.html">MessagesPresentTag</A></B></TD> |
| <TD>Evalute to <code>true</code> if an <code>ActionMessages</code> class or a |
| class that can be converted to an <code>ActionMessages</code> class is in |
| request scope under the specified key and there is at least one message in the |
| class or for the property specified.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="NotEmptyTag.html">NotEmptyTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is not empty for this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="NotEqualTag.html">NotEqualTag</A></B></TD> |
| <TD>Evaluate the nested body content of this tag if the specified variable |
| and value are not equal.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="NotMatchTag.html">NotMatchTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is not a substring of the specified variable.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="NotPresentTag.html">NotPresentTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is not present for this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="PresentTag.html">PresentTag</A></B></TD> |
| <TD>Evalute the nested body content of this tag if the specified value |
| is present for this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="RedirectTag.html">RedirectTag</A></B></TD> |
| <TD>Generate a URL-encoded redirect to the specified URI.</TD> |
| </TR> |
| </TABLE> |
| |
| |
| <P> |
| <A NAME="package_description"><!-- --></A><H2> |
| Package org.apache.struts.taglib.logic Description |
| </H2> |
| |
| <P> |
| <p>The "struts-logic" tag library contains tags that are useful in managing |
| conditional generation of output text, looping over object collections |
| for repetitive generation of output text, and application flow management. |
| </p> |
| <a name="doc.Description"></a> |
| |
| <p> </p> |
| <div align="Center"> <a href="#doc.Introduction">[Introduction]</a> |
| <a href="#doc.Functionality">[Logic Functionality]</a> |
| <a href="#doc.Properties">[Logic Properties]</a> |
| <a href="#doc.Examples">[Logic Examples]</a> |
| </div> |
| |
| <p></p> |
| |
| <hr /=""> <a name="doc.Intro"></a> |
| |
| <h3>Introduction<a name="doc.Introduction"></a> |
| </h3> |
| |
| <p> The Logic library supplies tags that are useful for manipulating |
| presentation logic without the use of scriptlets.</p> |
| <p><br> |
| </p> |
| <div align="Center"><img src="doc-files/logicUML.gif" alt="Logic Tag UML" > |
| <br> |
| </div> |
| <p></p> |
| <a name="doc.Functionality"></a> |
| |
| <h3>Logic Tag Functionality<a name="doc.Functionality"></a> |
| </h3> |
| |
| <p> The functionality of the logic tags can be divided into four groups:</p> |
| |
| <p><b>Value Comparisons -</b> The purpose of these tags is to print out the |
| body of the tag if the comparison evaluates to <i>true. </i></p> |
| |
| <ul> |
| <li><b><a href="../../../../../../userGuide/struts-logic.html#equal">equal,</a> |
| <a href="../../../../../../userGuide/struts-logic.html#notEqual">notEqual</a> |
| </b> </li> |
| <li><b><a href="../../../../../../userGuide/struts-logic.html#greaterEqual">greaterEqual</a> |
| , <a href="../../../../../../userGuide/struts-logic.html#lessEqual">lessEqual</a> |
| </b></li> |
| <li><b><a href="../../../../../../userGuide/struts-logic.html#greaterThan">greaterThan</a> |
| ,<a href="../../../../../../userGuide/struts-logic.html#lessThan"> lessThan</a> |
| </b></li> |
| |
| </ul> |
| |
| <p><b>Substring Matching -</b> The purpose of these tags is to match substrings |
| inside of other Strings</p> |
| |
| <ul> |
| <li><b><a href="../../../../../../userGuide/struts-logic.html#match">match</a> |
| , <a href="../../../../../../userGuide/struts-logic.html#notMatch">notMatch</a> |
| </b></li> |
| |
| </ul> |
| |
| <p><b>Presentation Location -</b> The purpose of these tags is to change |
| the location of the presentation page</p> |
| |
| <ul> |
| <li><a href="../../../../../../userGuide/struts-logic.html#forward"><b>forward</b></a> |
| </li> |
| <li><a href="../../../../../../userGuide/struts-logic.html#redirect"><b>redirect</b></a> |
| </li> |
| |
| </ul> |
| |
| <p><b>Collection Utilities -</b>The purpose of these tags is to handle Collections</p> |
| |
| <ul> |
| <li><a href="../../../../../../userGuide/struts-logic.html#iterate"><b>iterate</b></a> |
| </li> |
| |
| </ul> |
| |
| <h3>Logic Tag Properties<a name="doc.Properties"></a> |
| </h3> |
| |
| <p>Each of the four groups of logic tags have a common set of attributes |
| associated with them. :</p> |
| |
| <blockquote> |
| <p><b>Value Comparisons</b> (equal, notEqual, greaterEqual, lessEqual, |
| greaterThan, lessThan, present, notPresent)</p> |
| |
| <p>Each of the value comparison tags takes a <i>value</i> and compares |
| it to the value of a comparison attribute. If the value given can be |
| successfully converted to a <i>float</i> or <i>double</i>, then a number |
| comparison is performed on the value given and the value of the comparison |
| attribute. Otherwise a String comparison is performed. You have to specify |
| one of the comparison attributes: <i>cookie</i>, <i>header</i>, <i>parameter</i> |
| , <i>property</i> or <i>name. </i>For each of the examples, the tag "<i> |
| someComparisonTag"</i>can be replaced by any of the value comparison |
| tags.</p> |
| |
| <ul> |
| <li>value - the value to which this tag is going to compare, used in |
| conjunction with one of the comparison attributes: <i>cookie</i>, <i> |
| header</i>, <i>parameter</i>, <i>and property</i> and/or <i>name. </i></li> |
| <li>cookie - the name of the cookie to compare to <i>value</i> |
| |
| <ul> |
| <li>example: |
| <pre><logic:<i>someComparisonTag</i> value="someUserName" cookie="userName"><br> User Logged In<br></logic:<i>someComparisonTag</i>><br></pre> |
| </li> |
| |
| </ul> |
| </li> |
| <li>header - the name of the HTTP header to compare to <i>value</i> |
| |
| <ul> |
| <li>example: |
| <pre><logic:<i>someComparisonTag</i> value="en_US" header="Accept-Language"><br> Welcome English-speaking User*<br></logic:<i>someComparisonTag</i>><br></pre> |
| </li> |
| <li> |
| <p>*Note: See the section in the user's guide on <a href="../../../../../../userGuide/building_view.html#i18n"> |
| Internationalized Messages</a> |
| to do things like this better.</p> |
| </li> |
| |
| </ul> |
| </li> |
| <li>name - the variable to be compared to <i>value</i> is the JSP bean |
| specified by this attribute, if property is not specified, or the value |
| of the specified property of this bean, if property is specified. |
| |
| <ul> |
| <li>example: |
| <pre><%<br> String testString = "pantalones";<br> pageContext.setAttribute("testString", testString, PageContext.PAGE_SCOPE);<br>%><br><jsp:useBean id="testString" scope="page" type="java.lang.String" /><br><logic:<i>someComparisonTag</i> name="testString" value="pantalones"><br> Usted tiene pantalones!<br></logic:<i>someComparison</i>><br></pre> |
| </li> |
| |
| </ul> |
| </li> |
| <li>parameter - the name of the request parameter to compare to <i>value</i> |
| |
| <ul> |
| <li>example: |
| <pre><logic:<i>someComparisonTag</i> value="" parameter="username"><br> Error: a username must be specified<br></logic:<i>someComparisonTag</i>><br></pre> |
| </li> |
| |
| </ul> |
| </li> |
| <li>property - the variable to be compared with <i>value</i> is the |
| property (of the bean specified by the name attribute) specified by |
| this attribute. The property reference can be simple, nested, and/or |
| indexed. <i>property</i> is used in conjunction with <i>name</i> to |
| specify a property in the bean specified by <i>name</i>. For the type |
| of syntax used for property, see the users guide on the Bean Tags.</li> |
| <li>scope - the bean scope within which to search for the bean named |
| by the name property, or "any scope" if not specified. Possible values |
| are "page", "request", "session", "application", or "any scope" |
| </li> |
| |
| </ul> |
| |
| <p><b>Substring Matching</b> (match, notMatch)</p> |
| |
| <p>The substring matching tags take all the same arguments as the value |
| comparison tags. You compare the String specified by <i>value</i> to |
| any of the comparison values you give it, specified by <i>cookie</i>, |
| <i>header</i>, <i>parameter</i>, <i>property</i> or <i>name.</i> Note |
| that in the examples, <i>matchTag</i> corresponds either the <i>match |
| </i>or <i>notMatch</i> tag. Matching tags also have an additional <i> |
| location</i> attribute added:</p> |
| |
| <ul> |
| <li>location - has two possible values, "start" and "end". If |
| "start", the substring is attempted to be matched at the beginning |
| of the String, if "end", then the substring is attempted to be matched |
| to the end of the String |
| <ul> |
| <li>example: |
| <pre><logic:<i>matchTag</i> parameter="action" value="processLogin" location="start"><br> Processing Login....<br></logic:<i>matchTag</i>><br><br>In this example, a request parameter "action" was compared to see if<br>its value started with the String "processLogin". In this case,<br><i>matchTag</i> would have to be <logic:match>.<br></pre> |
| </li> |
| |
| </ul> |
| </li> |
| |
| </ul> |
| |
| <p><b>Presentation Location</b> (forward, redirect)</p> |
| |
| <p>The <i>redirect</i> tag is resposible for sending a re-direct to the |
| client's browser, complete with URL-rewriting if it's supported by the |
| container. Its attributes are consistent with the Struts HTML <a href="../../../../../../struts-html.html#link"><code> |
| link</code></a> |
| tag. The base URL is calculated based on which of the following attributes |
| you specify (you must specify exactly one of them):</p> |
| |
| <ul> |
| <li> forward - Use the value of this attribute as the name of a global |
| ActionForward to be looked up, and use the context-relative URI found |
| there. </li> |
| <li>href - Use the value of this attribute unchanged. </li> |
| <li>page - Use the value of this attribute as a context-relative URI, |
| and generate a server-relative URI by including the context path. </li> |
| |
| </ul> |
| |
| <p>The <i>forward</i> tag is responsible for either redirecting or forwarding |
| to a specified global action forward. To define a global ActionForward, |
| see The <a href="../../../../../../userGuide/building_controller.html#config"> |
| Action Mappings Configuration File</a> |
| . You can specify whether the forward re-directs or forwards when executed |
| in the config file. The forward tag has one attribute:</p> |
| |
| <ul> |
| <li>name - The logical name of the ActionForward to use</li> |
| |
| </ul> |
| |
| <p><b>Collection Utilities</b> (iterate)</p> |
| |
| <p>The <i>iterate</i> tag is responsible for executing its body content |
| once for every element inside of the specified Collection. There is one |
| required attribute:</p> |
| |
| <ul> |
| <li>id - The name of a page scope JSP bean that will contain the current |
| element of the collection on each iteration</li> |
| |
| </ul> |
| |
| <p>The other attributes allow for more flexibility on which Collection |
| to iterate and how to do it:</p> |
| |
| <ul> |
| <li>collection - a runtime expression that evaluates to a Collection |
| to be iterated |
| <ul> |
| <li>example: |
| <pre><%<br> java.util.Vector vector = new java.util.Vector();<br> vector.add(new Integer(12));<br> vector.add(new Integer(5));<br> %><br></pre> |
| </li> |
| |
| </ul> |
| </li> |
| |
| </ul> |
| |
| <blockquote> |
| <blockquote> |
| <pre><logic:iterate id="myCollectionElement" collection="<%= vector %>"><br><i> Do something with myCollectionElement</i> |
| </logic:iterate> |
| </pre> |
| </blockquote> |
| </blockquote> |
| |
| <ul> |
| <li>length - The maximum number of entries (from the underlying collection) |
| to be iterated through on this page. This can be either an integer |
| that directly expresses the desired value, or the name of a JSP bean |
| (in any scope) of type java.lang.Integer that defines the desired value. |
| If not present, there will be no limit on the number of iterations |
| performed</li> |
| <li>name - The name of the JSP bean containing the collection to be |
| iterated (if property is not specified), or the JSP bean whose property |
| getter returns the collection to be iterated (if property is specified). |
| |
| <ul> |
| <li>example: |
| <pre><%<br> |
| java.util.ArrayList list = new java.util.ArrayList(); |
| list.add("First"); |
| list.add("Second"); |
| list.add("Third"); |
| list.add("Fourth"); |
| list.add("Fifth"); |
| pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE); |
| %> |
| |
| <logic:iterate id="myCollectionElement" name="list"> |
| <i>Do something with myCollectionElement</i> |
| </logic:iterate></pre> |
| </li> |
| |
| </ul> |
| </li> |
| <li>offset - The zero-relative index of the starting point at which |
| entries from the underlying collection will be iterated through. This |
| can be either an integer that directly expresses the desired value, |
| or the name of a JSP bean (in any scope) of type java.lang.Integer |
| that defines the desired value. If not present, zero is assumed (meaning |
| that the collection will be iterated from the beginning. </li> |
| <li>property - Name of the property, of the JSP bean specified by name, |
| whose getter returns the collection to be iterated. See the user's |
| guide for the bean tag library for the syntax of the property attribute</li> |
| <li>scope - The bean scope within which to search for the bean named |
| by the name property, or "any scope" if not specified. Possible values |
| are "page", "request", "session", "application", or "any scope" |
| </li> |
| <li>type - Fully qualified Java class name of the element to be exposed |
| through the JSP bean named from the id attribute. If not present, no |
| type conversions will be performed. NOTE: The actual elements of the |
| collection must be assignment-compatible with this class, or a request |
| time ClassCastException will occur. |
| <ul> |
| <li>example: |
| <pre><% java.util.ArrayList list = new java.util.ArrayList();<br>list.add("First");<br>list.add("Second");<br>list.add("Third");<br>list.add("Fourth");<br>list.add("Fifth");<br> pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);<br> %><br><br><logic:iterate id="myCollectionElement" name="list" type="java.lang.String"><br> <i>Do something with myCollectionElement</i> |
| </logic:iterate></pre> |
| </li> |
| |
| </ul> |
| </li> |
| |
| </ul> |
| </blockquote> |
| |
| <h3>Logic Examples</h3> |
| |
| <blockquote> |
| <p><b>Value Comparisons</b></p> |
| |
| <blockquote> |
| <p><u></u><u></u><u>Logic Equivalence Tags (equal, notEqual, greaterEqual, |
| lessEqual, lessThan, greaterThan)</u></p> |
| |
| <blockquote> |
| <p>You can compare these tags to the "==", "!=" ,">=", |
| "<=", "<", and ">"logic operators in most languages. |
| Their usage is fairly straightforward for numbers. For an example, |
| we'll create a small "Guess That Number" game that uses request parameters |
| from a form input to play. The number will be hardcoded as "7", because |
| this is just an example. Note that this is actually putting application |
| logic inside of jsp pages, and isn't the recommended development |
| method for Struts. It's just an easy way to show how these tags are |
| used:</p> |
| |
| <p>The first step is to develop the form that will call on the |
| processing jsp page. This form will use the "GET" method so that |
| you can see the request parameter in the URL. The POST method can |
| also be used with no problem or changes.</p> |
| |
| <p>[numberGuess.jsp]</p> |
| |
| <pre><form action="numberProcess.jsp" method="GET"><br>Please Enter a Number From 1-10: <input type="text" name="number" /><br /><br> <center><br> <input type="submit" name="Guess Number" /><br> </center><br></form><br></pre> |
| The next step is to create the processing page. It uses the struts-logic |
| taglib. For information on how to set this tag library up in your application |
| to use, see <a href="../../../../../../userGuide/building_controller.html#dd_config"> |
| The Web Application Deployment Descriptor</a> |
| |
| <p>[numberProcess.jsp]</p> |
| |
| <pre><%@ page language="java" %><br><%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %><br></pre> |
| |
| <pre><!-- Is the number guess right? --><br><logic:equal parameter="number" value="7"><br> You guessed right! You win a high speed blender!<br></logic:equal><br></pre> |
| |
| <pre><!-- If the number guessed was wrong --><br><logic:notEqual parameter="number" value="7"><br> <!-- Less Than --><br> <logic:lessThan parameter="number" value="7"><br> A little higher...<br> </logic:lessThan><br> <!-- Greater Than --><br> <logic:greaterThan parameter="number" value="7"><br> A little lower...<br> </logic:greaterThan><br></logic:notEqual><br></pre> |
| |
| <p>Basically, the numberProcess.jsp page uses the equal tag to |
| check if the guess is 7, and if so, prints out a congratulatory message. |
| If the number isn't equal, specified by the use of the <logic:notEqual> |
| tag, it uses the greaterThan and lessThan tags to check if the number |
| is higher or lower than 7, and prints out a hint. As said before, |
| this is a horribly designed small application, with no validity checks |
| on the number input, but shows the basic usage of the logic equal |
| tags</p> |
| |
| <p>For String comparisons, the equal tags use the java.lang.String.compareTo() |
| method. See the javadocs on the compareTo() method for more information, |
| located <a href="http://www.javasoft.com/products/jdk/1.2/docs/api/java/lang/String.html#compareTo%28java.lang.Object%29"> |
| here</a> |
| .</p> |
| </blockquote> |
| |
| <p><u>Match and Present Tags (match, notMatch, present, notPresent)</u></p> |
| |
| <blockquote> |
| <p>You use the match tags in conjunction with the present tags |
| in order to do substring matches. For an example using this we'll |
| use headers, specifically the "Referer" header. The HTTP referer |
| header gives the URL of the document that refers to the requested |
| URL. We'll use this to check if the user is coming from a link specified |
| by a <a href="http://www.google.com">Google</a> |
| search, and offer a personalized greeting, frightening users that |
| find our site through the search engine with our amazing intimate |
| knowledge of their browsing habits:</p> |
| |
| <p>[sneaky.jsp]</p> |
| |
| <pre><%@ page language="java" %><br><%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %><br><br><br><!-- Check to see if the "Referer" header is present --><br><logic:present header="Referer"><br> <logic:match header="Referer" value="google.com"><br> I see you found our site through Google... interesting.<br> </logic:match><br> <logic:notMatch header="Referer" value="google.com"><br> Welcome to the site, we're secretly logging what site you came from,<br> because we're shady...<br> </logic:notMatch><br></logic:present><br><br><!-- If the header is not present --><br><logic:notPresent header="Referer"><br> Hi, welcome to our site. Please fill out our<br> <a href="nonExistantForm.jsp">Form</a> and<br> tell us where you're coming from.<br></logic:notPresent></pre> |
| |
| <p>Note: Another interesting usage of these tags and headers |
| would be to use the "User-Agent" header to display browser-specific |
| javascript.</p> |
| </blockquote> |
| </blockquote> |
| |
| <p><b>Collection Utilities (iterate)</b></p> |
| |
| <blockquote> |
| <p>For an example of using the <logic:iterate> tag, |
| we'll use one of the previous examples given, in it's entirety. This |
| example uses the <bean:write> tag from the Bean Tag Library, |
| see the User's Guide on the bean tag library for more information on |
| it's usage:</p> |
| |
| <p>[iterate.jsp]</p> |
| |
| <pre><%@ page language="java" %><br><%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %><br><%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %><br></pre> |
| |
| <pre><%<br>java.util.ArrayList list = new java.util.ArrayList();<br> list.add("First");<br> list.add("Second");<br> list.add("Third");<br> list.add("Fourth");<br> list.add("Fifth");<br> pageContext.setAttribute("list", list, PageContext.PAGE_SCOPE);<br>%><br><br><logic:iterate id="myCollectionElement" name="list"><br> Element Value: <bean:write name="myCollectionElement" /><br /><br></logic:iterate></pre> |
| </blockquote> |
| </blockquote> |
| <P> |
| |
| <P> |
| <HR> |
| |
| <!-- ========== START OF NAVBAR ========== --> |
| <A NAME="navbar_bottom"><!-- --></A> |
| <TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"> |
| <TR> |
| <TD COLSPAN=3 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> |
| <A NAME="navbar_bottom_firstrow"><!-- --></A> |
| <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> |
| <TR ALIGN="center" VALIGN="top"> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> |
| <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Package</B></FONT> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <FONT CLASS="NavBarFont1">Class</FONT> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-use.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> |
| <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> |
| </TR> |
| </TABLE> |
| </TD> |
| <TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM> |
| </EM> |
| </TD> |
| </TR> |
| |
| <TR> |
| <TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> |
| <A HREF="../../../../../org/apache/struts/taglib/html/package-summary.html"><B>PREV PACKAGE</B></A> |
| <A HREF="../../../../../org/apache/struts/taglib/nested/package-summary.html"><B>NEXT PACKAGE</B></A></FONT></TD> |
| <TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> |
| <A HREF="../../../../../index.html" TARGET="_top"><B>FRAMES</B></A> |
| <A HREF="package-summary.html" TARGET="_top"><B>NO FRAMES</B></A> |
| |
| <SCRIPT> |
| <!-- |
| if(window==top) { |
| document.writeln('<A HREF="../../../../../allclasses-noframe.html" TARGET=""><B>All Classes</B></A>'); |
| } |
| //--> |
| </SCRIPT> |
| <NOSCRIPT> |
| <A HREF="../../../../../allclasses-noframe.html" TARGET=""><B>All Classes</B></A> |
| </NOSCRIPT> |
| </FONT></TD> |
| </TR> |
| </TABLE> |
| <!-- =========== END OF NAVBAR =========== --> |
| |
| <HR> |
| Copyright © 2000-2003 - Apache Software Foundation |
| </BODY> |
| </HTML> |
