To access the ValueStack from third-party JSP taglibs, expose property values to JSP using the <saf<s:set tag.
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| xml:title | Set a request scoped parameter 'a' to list of integers |
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| language | xml |
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| title | Set a request scoped parameter 'a' to list of integers |
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<saf<s:set name="'a'" value="{ 1, 2, 3, 4 }" scope="request"/>
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can be used in a text or inside of tag attributes:
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a[0] = ${a[0]}
<sample:tag value="${a[1]}"/>
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There is a simple, if not elegant, solution available in JSP 2.0 EL, for exposing ValueStack to OGNL. It is possible to create custom functions that can be called from EL expressions. Functions have to be 'public static' and specified in a TLD file.
To use a function, import the TLD in a JSP file where you've want to use a function. For example, you could access Action properties by evaluating OGNL expression by a function 'vs' (for valuestack) in EL.
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<%@ taglib uri="/WEB-INF/tld/wwel.tld" prefix="x" %>
a[0] = ${x:vs('a[0]')}
a[0] * 4 = ${x:vs('a[0] * 4')}
Current action name: ${x:name()}
Top of ValueStack: ${x:top()}
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If someone were interested, it would be helpful for a developer (like you!) to define a set of functions that we could include in a future release of the framework. |
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xml| language | xml | | title | wwel.tld |
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<?xml version="1.0"?>
<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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>
This taglib enables access to the ValueStack
from JSP 2.0 Expression Language
</description>
<tlib-version>1.0</tlib-version>
<short-name>wwel</short-name>
<function>
<name>vs</name>
<function-class>com.nmote.wwel.Functions</function-class>
<function-signature>
java.lang.Object findOnValueStack(java.lang.String)
</function-signature>
</function>
<function>
<name>name</name>
<function-class>com.nmote.wwel.Functions</function-class>
<function-signature>
java.lang.Object getActionName()
</function-signature>
</function>
<function>
<name>top</name>
<function-class>com.nmote.wwel.Functions</function-class>
<function-signature>
java.lang.Object getTopOfValueStack()
</function-signature>
</function>
</taglib>
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java| language | java | | title | Functions.java |
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package com.nmote.wwel;
import com.opensymphony.xwork.ActionContext;
/**
* Utility functions for accessing value stack and action context
* from JSP 2.0 EL taglibs.
*/
public class Functions {
public static Object findOnValueStack(String expr) {
ActionContext a = ActionContext.getContext();
Object value = a.getValueStack().findValue(expr);
return value;
}
public static Object getTopOfValueStack() {
ActionContext a = ActionContext.getContext();
Object value = a.getValueStack().peek();
return value;
}
public static Object getActionName() {
ActionContext a = ActionContext.getContext();
Object value = a.getName();
return value;
}
}
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