Use argument in EL expression

Leave a Comment / java / By

There is couple ways about doing that, you could use JBoss EL expression implementation they support method calls with parameters check out Seam, or use similar approach as @digitaljoel suggested.
This is what I created for that purpose, you can call static and static methods, not a great solution but it does the job.

    <c:if  test="#{t:call(null, '@Util.SecurityUtility', 'isPanelWorkbookEnabledForUser','')}">
          Hello Panel    
      </c:if>

@Util is just an alias to com.mycomp.util where

**Example 2**

    <c:if test="#{item != null and  t:call(item, 'java.lang.String', 'indexOf', t:params(t:param('flash-alert',''))) == 0}">                
        #{t:call(session, 'org.apache.catalina.session.StandardSessionFacade', 'removeAttribute', t:params(t:param(item,'')))}      
    </c:if>

t:call, t:params, t:param are function defined in project-taglib.xml as so

    	<function>
		<function-name>call</function-name>
		<function-class>util.Functions</function-class>
		<function-signature>java.lang.Object call(java.lang.Object, java.lang.String, java.lang.String, java.lang.Object[])</function-signature>
	</function>
	<function>
		<function-name>param</function-name>
		<function-class>.util.Functions</function-class>
		<function-signature>java.lang.String param(java.lang.Object, java.lang.String)</function-signature>
	</function>	
 
	<function>
		<function-name>params</function-name>
		<function-class>util.Functions</function-class>
		<function-signature>java.lang.Object[] params(java.lang.String)</function-signature>
	</function>

Here is the implementation

    package mycompany.web.util;
 
import java.beans.XMLDecoder;
import java.beans.XMLEncoder;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.StringWriter;
import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
 
import javax.el.MethodNotFoundException;
 
 
public class Functions {
 
	private  static HashMap<String, String> alliasMap;
	static{
		alliasMap=new HashMap<String, String>();
		alliasMap.put("@DateUtil", "com.americanbanksystems.compliance.util.DateUtil");
		//Match anything following the dot(.)
		alliasMap.put("@Util.*", "com.americanbanksystems.compliance.util");
 
		alliasMap.put("@Application.*", "com.americanbanksystems.compliance.application");
 
	}
 
 
 
 
	public static String param(Object obj, String cls) {	
		//make sure that passed in object is not null
		if(obj==null){
			obj="";
		}
 
		ByteArrayOutputStream baut=new ByteArrayOutputStream();
		XMLEncoder encoder=new XMLEncoder( baut );
		//Bug in the JDK
		//http://bugs.sun.com/bugdatabase/view_bug.do;jsessionid=c993c9a3160fd7de44075a2a1fa?bug_id=6525396
		if(obj instanceof java.sql.Timestamp){
			Date o = new Date(((java.sql.Timestamp)obj).getTime());
			obj=o;
		}		
		//Checking if this is possible 
		if(String.class.isAssignableFrom(obj.getClass())){
			//removed trailing +" " because it was causing indexOf return invalid value
			//Unknown side effects
			obj=FacesUtil.get(obj.toString());			
		}
			encoder.writeObject( obj );
		encoder.close();
		return new String(baut.toByteArray());
	}
 
	private static Object decode(String str){
		ByteArrayInputStream bais=new ByteArrayInputStream(str.getBytes());
		XMLDecoder decoder=new XMLDecoder(bais);
		return decoder.readObject();
	}
 
	public static Object[] params(String str){
		// (?<=</java>)\s*(?=<?)
		String[] obj=str.split("(?<=</java>)\\s*(?=<?)");
		Object[] results=new Object[obj.length];
		for(int i=0;i<obj.length;i++){
			results[i]=decode(obj[i]);
		}
		return results;
	}
 
 
	@SuppressWarnings("unchecked")
	public static Object call(Object owningObject, String qualifiedClassname, String methodName, java.lang.Object... methodArguments) {
		if (null == methodName || methodName.equals("")) {
			throw new IllegalArgumentException("Method name can't be null or empty");
		}
		if (null == methodArguments) {
			methodArguments = new Object[0];
		}
 
		//Check for aliases 
		if(qualifiedClassname.indexOf("@")>-1){
			String subpackage=qualifiedClassname;
			String originalClass=qualifiedClassname;
			//Split at the dot
			boolean isPackageAllias=false;
			String[] sp=subpackage.split("\\.");	
			if(sp.length>1){
				subpackage=sp[0]+".*";
				isPackageAllias=true;
			}
			if(alliasMap.containsKey(subpackage)){
				String value = alliasMap.get(subpackage);
				if(isPackageAllias){
					qualifiedClassname=subpackage.replace(sp[0], value);
					qualifiedClassname=qualifiedClassname.replace(".*", originalClass.replace(sp[0],""));
				}else{
					qualifiedClassname=value;
				}
			}else{
				throw new IllegalArgumentException("Allias name '"+qualifiedClassname+"' not found");
			}
		}
		Class clazz;
		try {
			clazz = Class.forName(qualifiedClassname);
			//Find method by methodName,Argument Types
			Class[] argumentTypes=new Class[methodArguments.length];	
 
			for(int i=0;i<methodArguments.length;i++){
				argumentTypes[i]=methodArguments[i].getClass();
				//Check if the passed in method argument is a string and if its represented as unicode char				
				//if it is then convert it into a char and reassign to the original parameter
				//example 1:  \u0022 == "
				//example 2:  \u0027 == '
				// Reason for this functionality is that we can't pass " and ' from within t:call method
				if (argumentTypes[i] == String.class && methodArguments[i].toString().indexOf("\\u") > -1) {
					String arg = methodArguments[i].toString();
					arg = arg.substring(2, arg.length());
					try {
						int outchar = Integer.parseInt(arg, 16);
						if (Character.isDefined(outchar)) {
							methodArguments[i] = String.valueOf((char) outchar);
						}
					} catch (NumberFormatException nfe) {
						// Suppress error and continue assuming this is a regular string
					}
				}
			}
 
			Method methodToInvoke = null;
			try{
				methodToInvoke  = clazz.getMethod(methodName, argumentTypes);
			}catch(NoSuchMethodException nsm){//Find by method name/ argument count
				for (Method method : clazz.getMethods()) {
					if (method.getName().equals(methodName)  && method.getParameterTypes().length == methodArguments.length) {
						if (null == owningObject) {
							owningObject = clazz.newInstance();
						}
						methodToInvoke=method;
						break;
					}
				}
			}
 
			if(methodToInvoke!=null){								
				return methodToInvoke.invoke(owningObject, methodArguments);
			}else{
				throw new InstantiationException("method not found :" + methodName);	
			}
 
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		} catch (InstantiationException e) {
			e.printStackTrace();
		}
		return null;
	}
 
 
	public static void main(String[] arg) {
		// StringBuffer buff=new StringBuffer();
		// buff.append("Gregs init");
		// Functions.call(java.lang.Class<T>, T, java.lang.String, java.lang.String, java.lang.Object...)
		/*
		 * Functions.call(StringBuffer.class, buff, "java.lang.StringBuffer","append"," Init ");
		 * Functions.call(StringBuffer.class, buff, "java.lang.StringBuffer","append"," greg ");
		 * System.out.println("output="+ buff);
		 */
 
		//#{t:call(null, ".util.DateUtil", "normalizeDate", t:parametize(editRiskActionPlan.riskActionPlan.completionDate,",","java.lang.Object"))}
	//	c(call(null, "util.DateUtil", "normalizeDate", new Date()));
 
		//	#{t:parametize(editRiskActionPlan.riskActionPlan.completionDate,",","java.lang.Object")}
		//parametize((new Date()).toString(),",","java.lang.Object");
		Date a=new Date();
 
		Date b=new Date();
 
		String rawString=param((Date)b, Date.class.toString() );					
		//System.out.println(rawString);
 
		//Replaced=#{t:call("Gregs ' car", 'java.lang.String', 'replace', t:params( parameter ))}
 
		String paramA=param("\\u0027","");
		String paramB=param("\\u0022","");
		String params=paramA+paramB;
		String in="I need to ' have a replaced single quote with double";
		String out=(String)call(in, "java.lang.String", "replace", params(params));
 
		System.out.println(out);
 
 
		/*
		Object[] obj=params(rawString);
		for(Object o:obj){
			System.out.println(o);
		}
		//c(call(null, "@DateUtil", "normalizeDate", obj));
 
		*/
 
	}
 
}

I hope this helps, btw this was copied/pasted from my project so not sure if I missed anything.

Leave a Comment

Your email address will not be published. Required fields are marked *