Adventures of a Software Engineer

Tag: java

  • Ant BuildException Cannot run program “..\src\protoc”

    Error that I am getting when trying to run mvn test on google protobuf library.

    [INFO] Executing tasks
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] An Ant BuildException has occured: Execute failed: java.io.IOException: Cannot run program "..\src\protoc": CreateProcess error=2, The system c
annot find the file specified

[INFO] ------------------------------------------------------------------------
[INFO] For more information, run Maven with the -e switch

    I did place protoc.exe in the src directory. As a side note this is running on windows machine.

    Quick solution that I found was to edit the pom.xml file and modify the Ant tast into

  • Ant BuildException Cannot run program “..\src\protoc”

    Error that I am getting when trying to run mvn test on google protobuf library.

    [INFO] Executing tasks
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] An Ant BuildException has occured: Execute failed: java.io.IOException: Cannot run program "..\src\protoc": CreateProcess error=2, The system c
annot find the file specified

[INFO] ------------------------------------------------------------------------
[INFO] For more information, run Maven with the -e switch

    I did place protoc.exe in the src directory. As a side note this is running on windows machine.

    Quick solution that I found was to edit the pom.xml file and modify the Ant tast into

  • No Dialect mapping for JDBC type: -4

    Yet another fun day with hibernate.
    While working on ResourcePhaseListener for JSF attachment problem I run into following problem while trying to retrieve BLOB from MySQL db.

    org.hibernate.MappingException: No Dialect mapping for JDBC type: -4 No Dialect mapping for JDBC type: -4

    Here is the offending code:

    SerializableBlob result= null;
Session hibSession=(Session) em.getDelegate();
result = (SerializableBlob)	
hibSession.createSQLQuery("Select DATA from Table")	
.addScalar("DATA", Hibernate.BLOB)			
.uniqueResult();

    Adding the mapping addScalar("DATA", Hibernate.BLOB) solved the problem.

  • Modulo based counters

    Sometimes we need counters that wrap around at certain intervals ex:

    1,2,3,1,2,3,1,2,3


    One way of doing this would be to increment our ‘counter’ and then reset it when it reaches our number 

    int N = 3;
int counter = 0;
if (counter == N){
  counter = 0;
}
counter++;

    But there are also couple other ways this same could be achieved.

    Modulus

    Using modulus operator ‘%’ we can divide the counter and get our wrapped value, where N is the value we will wrap at.

    counter = (counter+1) % N;

    Binary AND

    This is almost this same approach as modulus but we are ‘AND’ing the counter with a power of 2. ex 1, 2, 4, 8, 16 … 2^n . Only problem here is that we have to AND with a power of 2.

    counter = (counter+1) & 0x1;

    produces 0,1,0,1,0,1

    Test program

    /**
 * Test program  for testing Modulus, Binary AND increments
 * @author greg
 *
 */
public class ModulePowerCounter {

	private static final int MAX_LOOP = 100000000;
	private static final int N = 2;
	private static final int POWER_OF_2 = 0x1;
	
	public static void main(String[] args) {
		long modTime = modulo();
		long counterTime = counter();
		long po2Time = powerOf2();		
		
		System.out.println(String.format("modTime = %s", modTime));
		System.out.println(String.format("counterTime = %s", counterTime));
		System.out.println(String.format("po2Time = %s", po2Time));
	}
	
	private static long powerOf2(){
		long start = System.currentTimeMillis();
		int counter = 0;
		for (int i = 0; i < MAX_LOOP; i++) {
			counter = (counter+1) & POWER_OF_2;
		}				
		return System.currentTimeMillis() - start;
	}
	
	private static long modulo(){
		long start = System.currentTimeMillis();
		int counter = 0;
		for (int i = 0; i < MAX_LOOP; i++) {
			counter = (counter+1) % N;
		}				
		return System.currentTimeMillis() - start;
	}
	
	private static long counter(){
		long start = System.currentTimeMillis();
		int counter = 0;
		for (int i = 0; i < MAX_LOOP; i++) {
			if(counter == N)counter = 0;
			counter++;
		}				
		return System.currentTimeMillis() - start;
	}
}

    Performance

    This is the fun part, so we have 3 different ways to achieve same thing but how do they perform.

    Lets think about it, division is much more expensive than 'addition and test' which is more expensive than binary manipulation, our test program confirms our assumption.

    modTime = 1258
counterTime = 449
po2Time = 108

    As we see Power of 2 outperforms other methods by far, but its only for powers of 2, also our plain counter is almost 2.5 times faster than modulus as well. So why would we like to use modulus increments at all? Well in my opinion I think they provide a clean code and if used properly they are a great tool to know of.

  • Expanding Rich tree nodes programmatically

    I have found two different methods for expanding nodes in Rich tree  from code, they both take  advantage of component binding and component state.

    Tree Setup

    Only thing to note here is the binding attribute that we setup in our backing bean.

    	protected org.richfaces.component.UITree sampleTreeBinding;

    for both solutions after we changed the sampleTree we need to update the binding with new value whitch is
    value="#{ourbean.sampleTree}" 

    // Make sure that we set the new TreeModel on current binding
sampleTreeBinding.setValue(sampleTree);

    Solution 1 : Expanding all nodes

    TreeState componentState = (TreeState) sampleTreeBinding.getComponentState();
try {
	componentState.expandAll(sampleTreeBinding);
} catch (IOException e) {
	e.printStackTrace();
}

    This will expand all levels of the nodes.

    Solution 2 : Expanding only nodes that meet our criteria

    try {
	final TreeState state = (TreeState) sampleTreeBinding.getComponentState();
	sampleTreeBinding.walk(FacesContext.getCurrentInstance(), new DataVisitor(){
		@SuppressWarnings("unchecked")
		public void process(FacesContext context, Object rowKey, Object argument)
		throws IOException {
			TreeRowKey row = (TreeRowKey)rowKey;
			if(row.depth() == 1){
				state.expandNode(sampleTreeBinding, (TreeRowKey)rowKey);
			}
		}
	});
}
catch (IOException e) {
	e.printStackTrace();
}


    Here we are only expanding nodes at depth 1 but it could be anything. Idea is that we are walking the tree
    
and checking if we are interested in the doing something with that node if so then we can modify it here.
    

    I hope this helps.
    

			
    
		
		
	
  • 
		
		
    
			
			
    How to read the files placed in WEB-INF from JSF
    
			
    Reading files from WEB-INF  in JSF
    

    This no different than reading files from a Servlet except it involves a extra step of getting ServletContext from FacesContext
    

    

    FacesContext context = FacesContext.getCurrentInstance();
ExternalContext externalContext = context.getExternalContext();
ServletContext sc = (ServletContext)externalContext.getContext();
String sc.getRealPath("/WEB-INF/somefile.xml");

    

    Here we are getting the path to the file but you could read it if you like.
    

    
			
    
		
    
		
	
  • 
		
		
    
			
			
    UnsatisfiedLinkError: javaxpcomglue.dll: Can’t find dependent libraries
    
			
    While playing around with JavaXPCOM I have run into couple issues.  I am running on window 7 64 bit.
    

    When trying to initialize my GRE (Gecko Runtime Environment) I got following exception 
    

    Exception in thread "main" java.lang.UnsatisfiedLinkError: D:\xulrunner-sdk\bin\javaxpcomglue.dll: Can't find dependent libraries
	at java.lang.ClassLoader$NativeLibrary.load(Native Method)
	at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1803)
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1699)
	at java.lang.Runtime.load0(Runtime.java:770)
	at java.lang.System.load(System.java:1003)
	at org.mozilla.xpcom.internal.JavaXPCOMMethods.registerJavaXPCOMMethods(JavaXPCOMMethods.java:57)
	at org.mozilla.xpcom.internal.MozillaImpl.initialize(MozillaImpl.java:48)
	at org.mozilla.xpcom.Mozilla.initialize(Mozilla.java:668)
	at SampleBroswer.init(SampleBroswer.java:69)
	at SampleBroswer.main(SampleBroswer.java:45)

    

    What is strange on my other dev machine same configuration I don’t have this problem, very strange.
    

    Problem is that the file mozcrt19.dll can’t be found. So what I did is that I copied that file from xulrunner-sdk\bin to my C:\Windows\SysWOW64 folder and that fixed the problem. Still little puzzled over why my other machine is  not throwing this exception.
    

    
			
    
		
    
		
	
  • 
		
		
    
			
			
    Preventing ViewExpiredException in JSF
    
			
    When our page is idle for x amount of time the view will expire and throw  javax.faces.application.ViewExpiredException to prevent this from happening
    
one solution is to create CustomViewHandler that extends ViewHandler
    
and override restoreView method all the other methods are being delegated to the Parent
    

    import java.io.IOException;
import javax.faces.FacesException;
import javax.faces.application.ViewHandler;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
import javax.servlet.http.HttpServletRequest;

public class CustomViewHandler extends ViewHandler {
	private ViewHandler parent;

	public CustomViewHandler(ViewHandler parent) {
		//System.out.println("CustomViewHandler.CustomViewHandler():Parent View Handler:"+parent.getClass());
		this.parent = parent;
	}

    @Override public UIViewRoot restoreView(FacesContext facesContext, String viewId) {
	/**
	 * {@link javax.faces.application.ViewExpiredException}. This happens only  when we try to logout from timed out pages.
	 */
	UIViewRoot root =null; 
	root = parent.restoreView(facesContext, viewId);
	if(root == null) {			
		root = createView(facesContext, viewId);
	}
	return root;
 }
 
 @Override
	public Locale calculateLocale(FacesContext facesContext) {
		return parent.calculateLocale(facesContext);
	}

	@Override
	public String calculateRenderKitId(FacesContext facesContext) {
		String renderKitId = parent.calculateRenderKitId(facesContext);
		//System.out.println("CustomViewHandler.calculateRenderKitId():RenderKitId: "+renderKitId);
		return renderKitId;
	}

	@Override
	public UIViewRoot createView(FacesContext facesContext, String viewId) {
		return parent.createView(facesContext, viewId);
	}
	
	
    @Override
	public String getActionURL(FacesContext facesContext, String actionId) {
		return parent.getActionURL(facesContext, actionId);
	}

	@Override
	public String getResourceURL(FacesContext facesContext, String resId) {
		return parent.getResourceURL(facesContext, resId);
	}

	@Override
	public void renderView(FacesContext facesContext, UIViewRoot viewId) throws IOException, FacesException {
		parent.renderView(facesContext, viewId);

	}

	@Override
	public void writeState(FacesContext facesContext) throws IOException {
		parent.writeState(facesContext);
	}

	public ViewHandler getParent() {
		return parent;
	}

}

    

    Then you need to add it to your faces-config.xml
    

     		
com.demo.CustomViewHandler

    

    This will prevent you from getting ViewExpiredException’s 
    

    
			
    
		
    
		
	
  • 
		
		
    
			
			
    Use argument in EL expression
    
			
    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.
    

        
          Hello Panel    
      

    

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

    **Example 2**
    

                        
        #{t:call(session, 'org.apache.catalina.session.StandardSessionFacade', 'removeAttribute', t:params(t:param(item,'')))}      
    

    

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

        	
		call
		util.Functions
		java.lang.Object call(java.lang.Object, java.lang.String, java.lang.String, java.lang.Object[])
	
	
		param
		.util.Functions
		java.lang.String param(java.lang.Object, java.lang.String)
		
	
	
		params
		util.Functions
		java.lang.Object[] params(java.lang.String)
		

    

    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 alliasMap;
	static{
		alliasMap=new HashMap();
		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){
		// (?<=)\s*(?=)\\s*(?=-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 -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, 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.
    

    
			
    
		
    
		
	
  • 
		
		
    
			
			
    Display all managed-beans in JSF at runtime
    
			
    Sometimes we like to see whats going on under the hood of jsf application (Checkout my JSFConsole). One such task is being able to display all the registered managed-beans during runtime.
    
Here we can see all registered beans, including implicit object(cookie,header,param etc…)
    

    Result
    

         a4j
     a4jSkin
     ajaxContext
     ajaxHandler
     application
     applicationScope
     beeHive       --- My Managed bean
     cookie
     facesContext
     header
     headerValues
     initParam
     param
     paramValues
     request
     requestScope
     richSkin
     session
     sessionScope
     view

    

    Source
    

    /**
	 * Retrieve all registered beans for given {@link ScopeType}
	 * @param scopeType to search in
	 * @return List of beanNames
	 */
	public static List getRegisteredBeans(ScopeType scopeType){
		FacesContext facesContext=FacesContext.getCurrentInstance();
		ApplicationAssociate application = ApplicationAssociate.getInstance(facesContext.getExternalContext());
		BeanManager  beanManager = application.getBeanManager();
		Map beanMap=beanManager.getRegisteredBeans();
		Set>beanEntries=beanMap.entrySet();
		List registeredBeans=new ArrayList();
		for(Entry bean:beanEntries){
			String beanName=bean.getKey();
			if(!beanManager.isManaged(beanName)){
				continue;
			}			
			BeanBuilder builder=bean.getValue();
			Scope bScope=builder.getScope();
			if(scopeType==ScopeType.ALL || bScope.toString().equals(scopeType.toString())){
				registeredBeans.add(beanName+":"+bScope.toString());
			}
		}

		if(scopeType==ScopeType.ALL || scopeType==ScopeType.IMPLICIT){
			List implicitList=getProperties(new ImplicitObjectELResolver(), null);
			for(String implicitBeanName:implicitList){
				registeredBeans.add(implicitBeanName+":"+ScopeType.IMPLICIT.toString());
			}
		}

		Collections.sort(registeredBeans);
		return registeredBeans;
	}

    

    ScopeType is nothing more than an emun wrapper 
    

    
/**
 * Scope type with additional properties for all/implicit
 * @author devil
 *
 */
public enum ScopeType {
	//Really not a scope but a marker
	ALL("all"),
	IMPLICIT("implicit"),
	
	REQUEST("request"),
	SESSION("session"),
	APPLICATION("application");

	String scope;
	ScopeType(String scope) {
		this.scope = scope;
	}

	public String toString() {
		return scope;
	}

	
	/**
	 * Get Enum from value
	 * @param name
	 * @return
	 */
	public static ScopeType fromValue(String name) {
		name=name!=null?name.toUpperCase():"";
		for(ScopeType v:values()){
			if(v.name().equals(name)){
				return v;
			}
		}
		//By default return all scoped objects
		return ScopeType.ALL;
	}
}


    

    
			
    
		
    
		
	
    •