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| <H2> |
| Package org.apache.struts.taglib.bean |
| </H2> |
| The "struts-bean" tag library contains JSP custom tags useful in defining new |
| beans (in any desired scope) from a variety of possible sources, as well as a |
| tag to render a particular bean (or bean property) to the output response. |
| <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="CookieTag.html">CookieTag</A></B></TD> |
| <TD>Define a scripting variable based on the value(s) of the specified |
| cookie received with this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="CookieTei.html">CookieTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>cookie</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="DefineTag.html">DefineTag</A></B></TD> |
| <TD>Define a scripting variable based on the value(s) of the specified |
| bean property.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="DefineTei.html">DefineTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>define</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="HeaderTag.html">HeaderTag</A></B></TD> |
| <TD>Define a scripting variable based on the value(s) of the specified |
| header received with this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="HeaderTei.html">HeaderTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>header</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="IncludeTag.html">IncludeTag</A></B></TD> |
| <TD>Define the contents of a specified intra-application request as a |
| page scope attribute of type <code>java.lang.String</code>.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="IncludeTei.html">IncludeTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>include</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="MessageTag.html">MessageTag</A></B></TD> |
| <TD>Custom tag that retrieves an internationalized messages string (with |
| optional parametric replacement) from the <code>ActionResources</code> |
| object stored as a context attribute by our associated |
| <code>ActionServlet</code> implementation.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="PageTag.html">PageTag</A></B></TD> |
| <TD>Define a scripting variable that exposes the requested page context |
| item as a scripting variable and a page scope bean.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="PageTei.html">PageTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>page</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ParameterTag.html">ParameterTag</A></B></TD> |
| <TD>Define a scripting variable based on the value(s) of the specified |
| parameter received with this request.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ParameterTei.html">ParameterTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>parameter</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ResourceTag.html">ResourceTag</A></B></TD> |
| <TD>Define a scripting variable based on the contents of the specified |
| web application resource.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="ResourceTei.html">ResourceTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>resource</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="SizeTag.html">SizeTag</A></B></TD> |
| <TD>Define a scripting variable that will contain the number of elements |
| found in a specified array, Collection, or Map.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="SizeTei.html">SizeTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>size</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="StrutsTag.html">StrutsTag</A></B></TD> |
| <TD>Define a scripting variable that exposes the requested Struts |
| internal configuraton object.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="StrutsTei.html">StrutsTei</A></B></TD> |
| <TD>Implementation of <code>TagExtraInfo</code> for the <b>struts</b> |
| tag, identifying the scripting object(s) to be made visible.</TD> |
| </TR> |
| <TR BGCOLOR="white" CLASS="TableRowColor"> |
| <TD WIDTH="15%"><B><A HREF="WriteTag.html">WriteTag</A></B></TD> |
| <TD>Tag that retrieves the specified property of the specified bean, converts |
| it to a String representation (if necessary), and writes it to the current |
| output stream, optionally filtering characters that are sensitive in HTML.</TD> |
| </TR> |
| </TABLE> |
| |
| |
| <P> |
| <A NAME="package_description"><!-- --></A><H2> |
| Package org.apache.struts.taglib.bean Description |
| </H2> |
| |
| <P> |
| The "struts-bean" tag library contains JSP custom tags useful in defining new |
| beans (in any desired scope) from a variety of possible sources, as well as a |
| tag to render a particular bean (or bean property) to the output response. |
| <br><br> |
| <a name="doc.Description"></a> |
| <div align="center"> |
| <a href="#doc.Intro">[Introduction]</a> |
| <a href="#doc.Properties">[Bean Properties]</a> |
| <a href="#doc.Creation">[Bean Creation]</a> |
| <a href="#doc.Output">[Bean Output]</a> |
| </div> |
| |
| <hr> |
| |
| <a name="doc.Intro"></a> |
| <h3>Introduction</h3> |
| |
| <p>Much of the power of JavaServer Pages (JSP) technology comes from the simple |
| and powerful mechanisms by which the servlet that is generated automatically |
| from your JSP source page can interact with JavaBeans that represent the |
| computational state of your application. In standard JSP pages, the |
| <code><jsp:useBean></code> tag is used create a bean (if necessary), |
| as well as a "scripting variable" that can be used within scriptlets to refer |
| to these beans.</p> |
| |
| <p>The "struts-bean" tag library provides substantial enhancements to the |
| basic capability provided by <code><jsp:useBean></code>, as discussed |
| in the following sections:</p> |
| <ul> |
| <li><a href="#doc.Properties">Bean Properties</a> - Extended syntax to refer to |
| JavaBean properties with simple names (same as the standard JSP tags |
| <code><jsp:getProperty></code> and |
| <code><jsp:setProperty></code>), nested names (a property named |
| <code>address.city</code> returns the value retrieved by the Java |
| expression <code>getAddress().getCity()</code>), and indexed names |
| (a property named <code>address[3]</code> retrieves the fourth address |
| from the indexed "address" property of a bean).</li> |
| <li><a href="#doc.Creation">Bean Creation</a> - New JSP beans, in any scope, |
| can be created from a variety of objects and APIs associated with the |
| current request, or with the servlet container in which this page is |
| running.</li> |
| <li><a href="#doc.Output">Bean Output</a> - Supports the rendering of textual |
| output from a bean (or bean property), which will be included in the |
| response being created by your JSP page.</li> |
| </ul> |
| |
| <p>See the <a href="../../../../../../struts-bean.html">Bean Tags |
| Reference</a> for detailed information about the available tags in this |
| tag library, and the valid attributes for each tag.</p> |
| |
| |
| <a name="doc.Properties"></a> |
| <h3>Bean Properties</h3> |
| |
| <h5>Common Tag Attributes</h5> |
| |
| <p>The tags in the "struts-bean" tag library (and, generally, in all tag |
| libraries included with the Struts framework) share a common set of tag |
| attributes that have the same meaning, no matter what tag they are used on. |
| These common attributes include:</p> |
| <ul> |
| <li><em>id</em> - Names the scripting variable that will be |
| created by this custom tag, as well as the key value used to locate this |
| bean in the scope defined by the <code>scope</code> attribute.</li> |
| <li><em>name</em> - Defines the key value by which an existing bean will be |
| looked up in the scope defined by the <code>scope</code> attribute |
| (if any), or by searching through the various scopes in the standard |
| order (page, request, session, application).</li> |
| <li><em>property</em> - Defines the name of a JavaBeans property, of the JSP |
| bean identified by the <code>name</code> and (optional) <code>scope</code> |
| attributes, whose value is to be used by this custom tag. If not |
| specified, the bean identified by <code>name</code> is itself used |
| as the value of interest. See below for more discussion about how a |
| property can be referenced.</li> |
| <li><em>scope</em> - Identifies the JSP scope ("page", "request", "session", |
| or "application" within which a particular bean will be searched for |
| (under the key specified by the <code>name</code> attribute) or created |
| (under the key specified by the <code>id</code> attribute). If not |
| specified, beans will generally be searched for in the order listed above, |
| or created in page scope.</li> |
| </ul> |
| |
| <a name="doc.Properties.References"></a> |
| <h5>Property References</h5> |
| |
| <p>Struts tags that support the <code>property</code> tag generally also |
| recognize a rich syntax for getting and setting properties. There are three |
| types of references supported: simple, nested, and indexed.</p> |
| |
| <p><em>Simple References</em> - These are equivalent to the syntax you use with |
| the standard <code><jsp:getProperty></code> and |
| <code><jsp:setProperty></code> tags. A reference to a property named |
| "foo" is converted into a method call to <code>getFoo()</code> or |
| <code>setFoo(value)</code> (as appropriate), using the standard JavaBeans |
| Specification naming conventions for bean properties. Struts uses the |
| standard Java introspection APIs to identify the names of the actual property |
| getter and setter methods, so your beans can provided customized method names |
| through the use of a <code>BeanInfo</code> class. See the JavaBeans |
| Specification, available at <a href="http://java.sun.com/products/javabeans/"> |
| http://java.sun.com/products/javabeans/</a>, for more information.</p> |
| |
| <p><em>Nested References</em> - Nested references are used to access a |
| property through a hierarchy of property names separated by periods ("."), |
| similar to the way that nested properties are accessed in JavaScript. For |
| example, the following property reference in a getter (such as the |
| <code><bean:define></code> tag discussed below):</p> |
| <pre> |
| property="foo.bar.baz" |
| </pre> |
| <p>is translated into the equivalent the Java expression:</p> |
| <pre> |
| getFoo().getBar().getBaz() |
| </pre> |
| <p>If a nested reference is used in a setter (such as when an input form is |
| processed), the property setter is called on the <strong>last</strong> property |
| in the chain. For the above property reference, the equivalent Java |
| expression would be:</p> |
| <pre> |
| getFoo().getBar().setBaz(value) |
| </pre> |
| |
| <p><em>Indexed References</em> - Subscripts can be used to access individual |
| elements of properties whose value is actually an array, or whose underlying |
| JavaBean offers indexed getter and setter methods. For example, the following |
| property reference in a getter (such as the <code><bean:define></code> |
| tag discussed below):</p> |
| <pre> |
| property="foo[2]" |
| </pre> |
| <p>is translated into the equivalent of the Java expression:</p> |
| <pre> |
| getFoo(2); |
| </pre> |
| <p>while the same property reference in a setter would call the |
| equivalent of:</p> |
| <pre> |
| setFoo(2, value) |
| </pre> |
| <p>As you can see from the above translations, the subscripts used in indexed |
| references are <strong>zero relative</strong> (that is, the first element in |
| an array is <code>foo[0]</code>), just as is true in the Java language.</p> |
| |
| <p><em>Combined References</em> - Nesting and indexing can be combined in |
| arbitrary ways, so that expressions like <code>foo.bar[0].baz[2]</code> are |
| legal. You must be careful, of course, to ensure that the actual beans being |
| accessed by these references have properties of the appropriate names and |
| types. Otherwise, JSP runtime exceptions will be thrown.</p> |
| |
| <p>See the JavaDocs for |
| <a href="../../util/PropertyUtils.html">PropertyUtils</a> for more detailed |
| information about the mechanisms that Struts uses to access |
| properties in a general way, through Java reflection APIs.</p> |
| |
| <hr> |
| |
| <a name="doc.Creation"></a> |
| <h3>Bean Creation</h3> |
| |
| <h5>Introduction</h5> |
| |
| <p>New beans can be created, and introduced into one of the four standard |
| JSP scopes (page, request, session, and application) through a variety of |
| techniques. The following subsections describe the use of the following |
| approaches:</p> |
| <ul> |
| <li>Java Code in Action Classes</li> |
| <li>Java Code in Scriptlets</li> |
| <li>The Standard <code><jsp:useBean></code> Tag</li> |
| <li>The Struts <code><bean:define></code> Tag</li> |
| <li>Other Struts Copying Tags</li> |
| </ul> |
| |
| <h5>Java Code in Action Classes</h5> |
| |
| <p>Because the JSP pages are compiled into Servlets, your <code>Action</code> |
| classes that are invoked by the Struts controller servlet have convenient |
| access to three of the four standard JSP scopes (request, session, and |
| application). It is very common practice for the business logic contained in |
| your <code>Action</code> class to create results that are stored in request |
| or session scope, which will be used by a JSP page you forward control to in |
| rendering the next page of the user interface.</p> |
| |
| <p><em>Request Scope</em> - To store a bean in request scope under name "cust", |
| your <code>Action</code> class would execute code similar to this:</p> |
| <pre> |
| Customer customer = ... create or acquire a customer reference ...; |
| request.setAttribute("cust", customer); |
| </pre> |
| |
| <p><em>Session Scope</em> - To store a bean in session scope under name "user" |
| (perhaps in a logon action), your <code>Action</code> class would execute code |
| similar to this:</p> |
| <pre> |
| User user = ... look up valid user in the database ...; |
| HttpSession session = request.getSession(); |
| session.setAttribute("user", user); |
| </pre> |
| |
| <p><em>Application Scope</em> - Generally, application scope beans are |
| initialized in the <code>init()</code> method of a startup servlet. However, |
| it is legal for an <code>Action</code> class to create such beans, if this is |
| appropriate, like this:</p> |
| <pre> |
| Foo foo = ... create a Foo ...; |
| servlet.getServletContext().setAttribute("foo", foo); |
| </pre> |
| |
| <h5>Java Code in Scriptlets</h5> |
| |
| <p>While it is not a recommended practice in Struts-based applications |
| (because developers will be tempted to mix business logic and presentation |
| logic in their JSP pages), it is legal for scriptlet code in a JSP page to |
| create new JavaBeans dynamically, and add them to any of the four possible |
| scopes, as demonstrated in the code examples below:</p> |
| |
| <p><em>Page Scope</em> - To store a bean in page scope under name "foo", |
| your scriptlet must execute code like this:</p> |
| <pre> |
| <% |
| Foo foo = ... create a foo ...; |
| pageContext.setAttribute("foo", foo, PageContext.PAGE_SCOPE); |
| %> |
| </pre> |
| |
| <p><em>Request Scope</em> - To store a bean in request scope under name "cust", |
| your scriplet must execute code like this:</p> |
| <pre> |
| <% |
| Customer customer = ... create or acquire a customer reference ...; |
| pageContext.setAttribute("cust", customer, PageContext.REQUEST_SCOPE); |
| %> |
| </pre> |
| |
| <p><em>Session Scope</em> - To store a bean in session scope under name "user", |
| (perhaps as a result of a validated login), your scriplet must execute code |
| like this:</p> |
| <pre> |
| <% |
| User user = ... look up valid user in the database ...; |
| pageContext.setAttribute("user", user, PageContext.SESSION_SCOPE); |
| %> |
| </pre> |
| |
| <p><em>Application Scope</em> - Generally, application scope beans are |
| initialized in the <code>init()</code> method of a startup servlet. However, |
| a scriptlet can create such beans, if appropriate, like this:</p> |
| <pre> |
| <% |
| Foo foo = ... create a Foo ...; |
| pageContext.setAttribute("foo", foo, PageContext.APPLICATION_SCOPE); |
| %> |
| </pre> |
| |
| <p><strong>NOTE</strong> - As mentioned above, using scriptlets in your JSP |
| pages is strongly discouraged in a Struts based application, unless you are |
| executing code that is <strong>only</strong> related to presentation of |
| existing data. In general, your application's processing logic should be |
| encapsulated in <code>Action</code> classes (or in beans or EJBs called by |
| those classes), rather than being intermixed in your JSP pages.</p> |
| |
| <h5>The Standard <code><jsp:useBean></code> Tag</h5> |
| |
| <p>JavaServer Pages (JSP) offers a standard tag, |
| <code><jsp:useBean></code> that can be used to create a new bean, or |
| introduce a reference to an existing bean, into a JSP page. Beans (or bean |
| references) introduced through this mechanism are completely interoperable |
| with beans created by any of the Struts creation techniques described in this |
| section.</p> |
| |
| <p>You <strong>must</strong> use <code><jsp:useBean></code> to introduce |
| a reference to an existing bean, if you wish to reference that bean with other |
| standard JSP tags (such as <code><jsp:getProperty></code> or |
| <code><jsp:setProperty></code>). If you only wish to reference such |
| beans with other Struts tags, use of <code><jsp:useBean></code> is not |
| required.</p> |
| |
| <p>For more information about the <code><jsp:useBean></code> tag, see |
| the JavaServer Pages Specification, available at |
| <a href="http://java.sun.com/products/jsp/download.html"> |
| http://java.sun.com/products/jsp/download.html</a>.</p> |
| |
| <h5>The Struts <code><bean:define></code> Tag</h5> |
| |
| <p>Struts provides a powerful, general purpose, tag |
| (<code><bean:define></code>) that can be used to create a new bean, |
| in any scope, by copying another bean (or the value of the property of |
| another bean). This tag supports the "property" attribute, and therefore |
| all the power of property references, as discused |
| <a href="#doc.Properties.References">above</a>. It can be used in a |
| variety of different ways, described further below. Unless you specify |
| the "toScope" attribute, all defined beans will be created in page scope.</p> |
| |
| <p><em>Introduce A String Constant</em> - You can create a new bean that has |
| a constant String value (or the result of calculating a runtime expression): |
| </p> |
| <pre> |
| <bean:define id="foo" value="This is a new String"/> |
| <bean:define id="bar" value='<%= "Hello, " + user.getName() %>'/> |
| <bean:define id="last" scope="session" |
| value='<%= request.getRequestURI() %>'/> |
| </pre> |
| |
| <p><em>Copy An Existing Bean</em> - You can create a new reference to an |
| existing bean object. You can specify the Java class or interface the new |
| bean is expected to conform to with the "type" attribute, or accept the |
| default type of <code>java.lang.Object</code> (this only affects the scripting |
| variable that is exposed to scriptlets, so it is not generally meaningful in |
| Struts-based applications).</p> |
| <pre> |
| <bean:define id="foo" name="bar"/> |
| <bean:define id="baz" name="bop" type="com.mycompany.MyBopClass"/> |
| </pre> |
| |
| <p><em>Copy An Existing Bean Property</em> - You can create a new bean that |
| is initialized to the value returned by a property getter. The value of the |
| "property" attribute can be any simple, nested, or indexed property reference |
| that follows the rules described earlier. In the first example below, we |
| also illustrate accessing the property of a request scope bean, and creating |
| the new bean in session scope (rather than the default page scope).</p> |
| <pre> |
| <bean:define id="foo" name="bar" property="baz" scope="request" |
| toScope="session"/> |
| <bean:define id="bop" name="user" property="role[3].name"/> |
| </pre> |
| |
| <h5>Other Struts Copying Tags</h5> |
| |
| <p>Struts offers a variety of bean creation tags that copy existing beans (or |
| bean properties) from the environment within which this page is running, and |
| the request that is currently being processed. Not all of the attributes |
| for each tag are illustrated in the examples below - see the |
| <a href="../../../../../../struts-bean.html">Bean Tags Reference</a> for |
| more information. Any bean created by these tags exists only in page |
| scope, for the remainder of the current page.</p> |
| |
| <p><em>Copy A Cookie</em> - You can create a new bean containing a |
| <code>javax.servlet.http.Cookie</code> that was included in the current |
| request. If no cookie of the specified name was included, a request time |
| expression will be thrown - therefore, it is common to nest the use of this |
| tag inside a <code><logic:present cookie="xxx"></code> tag to ensure |
| that the cookie was really included. If there is the possibility that more |
| than one cookie of the same name was included, specify the "multiple" |
| attribute (and the resulting bean will be an array of Cookies, instead of |
| a single Cookie).</p> |
| <pre> |
| <bean:cookie id="foo" name="cookiename"/> |
| <bean:cookie id="all" name="JSESSIONID" multiple="true"/> |
| </pre> |
| |
| <p><em>Copy A Request Header</em> - You can create a new bean containing the |
| value of an HTTP header included in this request. If no header of the |
| specified name was included, a request time exception will be thrown - |
| therefore, it is common to nest the use of this tag inside a |
| <code><logic:present header="xxx"></code> tag to ensure that the header |
| was really included. If there is the possibility that more than one header |
| of the same name was included, specify the "multiple" attribute (and the |
| resulting value bean will be an array of String values, instead of a |
| single String).</p> |
| <pre> |
| <bean:header id="agent" name="User-Agent"/> |
| <bean:header id="languages" name="Accept-Language" multiple="true"/> |
| </pre> |
| |
| <p><em>Copy A Dynamically Created Response</em> - You can generate an internal |
| request to the application you are running, and turn the response data that is |
| returned from that request into a bean (of type String). One possible use |
| for this technique is to acquire dynamically created XML formatted data that |
| will be stored in a bean and later manipulated (such as by applying an XSLT |
| stylesheet). If the current request is part of a session, the generated |
| request for the include will also include the session identifier (and thus be |
| considered part of the same session).</p> |
| <pre> |
| <bean:include id="text" name="/generateXml?param1=a¶m2=b"/> |
| </pre> |
| |
| <p><em>Copy A JSP Implicitly Defined Object</em> - You can create a bean that |
| is one of the JSP implicitly defined objects (see the JSP spec for more |
| details). This is useful if you wish to perform property getter actions |
| against the implicit object with a custom tag instead of a scriptlet.</p> |
| <pre> |
| <bean:page id="app" property="application"/> |
| <bean:page id="sess" property="session"/> |
| </pre> |
| |
| <p><em>Copy A Request Parameter</em> - You can create a new bean containing the |
| value of a parameter included in this request. If no parameter of the |
| specified name was included, a request time exception will be thrown - |
| therefore, it is common to nest the use of this tag inside a |
| <code><logic:present parameter="xxx"></code> tag to ensure that the |
| parameter was really included. If there is the possibility that more than |
| one parameter of the same name was included, specify the "multiple" attribute |
| (and the resulting value bean will be an array of String values, instead of a |
| single String).</p> |
| <pre> |
| <bean:parameter id="name" name="name"/> |
| <bean:header id="options" name="option" multiple="true"/> |
| </pre> |
| |
| <p><em>Copy a Web Application Resource</em> - You can create a new bean |
| containing either the value of a web application resource as a String, or |
| a <code>java.io.InputStream</code> for reading the content of that resource. |
| The resource is accessed with a context-relative path (beginning with "/"), |
| using the <code>ServletContext.getResource()</code> or |
| <code>ServletContext.getResourceAsStream()</code> methods on the underlying |
| application object.</p> |
| <pre> |
| <bean:resource id="deployment" name="/WEB-INF/web.xml"/> |
| <bean:resource id="stream" name="/WEB-INF/web.xml" |
| input="true"/> |
| </pre> |
| |
| <p><em>Copy A Struts Configuration Object</em> - You can create a new bean |
| containing one of the standard Struts framework configuration objects. Doing |
| this gives you access to the properties of the configuration object, if needed. |
| </p> |
| <pre> |
| <bean:struts id="form" formBean="CustomerForm"/> |
| <bean:struts id="fwd" forward="success"/> |
| <bean:struts id="map" mapping="/saveCustomer"/> |
| </pre> |
| |
| |
| <hr> |
| |
| <a name="doc.Output"></a> |
| <h3>Bean Output</h3> |
| |
| <p>None of the Struts Bean tags discussed so far render any output to the |
| response page that is being generated from this JSP page. They are executed |
| in order to make relevant Java objects visible as beans for further |
| manipulation. The following tags cause output to be written to the response, |
| and therefore made visible to the ultimate requester.</p> |
| |
| <p><em>Render An Internationalized Message</em> - You can specify a message |
| key (with optional parameter replacement objects) that are passed to a |
| <a href="../../util/MessageResources.html">MessageResources</a> object that |
| returns the corresponding message text. The message text will be copied to |
| the response currently being created. By default, messages are looked up in |
| the application resources bundle that is initialized for you (as an |
| application scope bean) by the Struts controller servlet, using the Locale |
| must recently stored in the user's session. These defaults can be overridden |
| by setting values for the "bundle" and "locale" attributes, as described in the |
| <a href="../../../../../../struts-bean.html#message">Bean Tags Reference</a>. |
| <pre> |
| <bean:message key="label.Cancel"/> |
| <bean:message key="message.hello" arg0='<%= user.getFullName() %>'/> |
| </pre> |
| |
| <p><em>Render A Bean or Bean Property</em> - The contents of a bean, or bean |
| property, are converted to a String and then copied to the response currently |
| being created. This tag understands the syntax for simple, nested, and |
| indexed property references described <a href="#doc.Properties.Reference"> |
| above</a>. Beans from any scope can be requested - by default, the scopes |
| are searched in expanding visibility order (page, request, session, and |
| application) to locate the requested bean.</p> |
| <pre> |
| <bean:write name="username"/> |
| <bean:write name="user" property="fullName"/> |
| <bean:write name="customer" property="orders[2].partNumber" |
| scope="session"/> |
| </pre> |
| <P> |
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