Adding parameters from a map to a URL tag
Solution 1
The Parameter tag populates parameters only to its direct antecessor. Wrappings an iterator tag around the parameter tag has no effect. :) To solve this you can easily write an alternative parameter tag wich can use a map direclty The tag may look like this.
package my.taglibs;
import java.io.Writer;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts2.components.Component;
import org.apache.struts2.views.jsp.ComponentTagSupport;
import com.opensymphony.xwork2.util.ValueStack;
public class ParamTag extends ComponentTagSupport {
private String map;
private static final long serialVersionUID = 2522878390854066408L;
Log log = LogFactory.getLog(ParamTag.class);
@Override
public Component getBean(ValueStack stack, HttpServletRequest req, HttpServletResponse res) {
return new Param(stack);
}
@Override
protected void populateParams() {
super.populateParams();
Param param = (Param) component;
param.setMap(map);
}
public void setMap(String map) {
this.map = map;
}
public class Param extends Component {
private String map;
public Param(ValueStack stack) {
super(stack);
}
@Override
public boolean end(Writer writer, String body) {
Component component = findAncestor(Component.class);
if (this.map == null) {
log.warn("Attribute map is mandatory.");
return super.end(writer, "");
}
Object o = findValue(this.map); //find map in vs
if(o == null) {
log.warn("map not found in ValueStack");
return super.end(writer, "");
}
if(!(o instanceof Map)) {
log.warn("Error in JSP. Attribute map must evaluate to java.util.Map. Found type: " + o.getClass().getName());
return super.end(writer, "");
}
component.addAllParameters((Map) o);
return super.end(writer, "");
}
public void setMap(String map) {
this.map = map;
}
}
}
And you need a corresponding tld-entry
<tag>
<description><![CDATA[Parametrize other tags]]></description>
<name>param</name>
<tag-class>my.taglibs.ParamTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>map</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<dynamic-attributes>false</dynamic-attributes>
</tag>
Solution 2
Maybe you can use JSTL tags like this
<c:url var="uri" value="${namespace}/${action}.action">
<c:forEach items="${parameters}" var="p">
<c:param name="${p.key}" value="${p.value}"/>
</c:forEach>
</c:url>
<a href="${uri}">Your Link</a>
I know there is some hesitation to mix EL with OGNL etc but this works...
Peter Kelley
Architecture Director working for Fujitsu Australia in Canberra ACT. I play modern boardgames and dabble in Groovy web applications in my spare time.
Updated on June 04, 2022Comments
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Peter Kelley almost 2 years
I want to add a variable list of parameters to a Struts2 URL tag. I have a map of the parameters (name value pairs) in an object in the session. I'm struggling to find a good approach to this. Here is the relevant JSP code:
<s:iterator value="%{#session['com.strutsschool.interceptors.breadcrumbs']}" status="status"> <s:if test="#status.index > 0"> » </s:if> <s:url id="uri" action="%{action}" namespace="%{nameSpace}"> <s:param name="parameters" value="%{parameters}"/> </s:url> <nobr><s:a href="%{uri}"><s:property value="displayName"/></s:a></nobr> </s:iterator>
The parameters variable is a Map that contains the params. This, of course does not work but I cannot see a way to approach this at the moment. I'm thinking at the moment that I might need a custom freemarker template for this. Can anyone suggest a better way?
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jjmontes almost 13 years+1 for the short, concise snippet and the adequate comment on how EL and OGNL don't fit sometimes. In any case, I don't see a problem with that.