Not knowing how to catch Errors

[Maganti Suryanarayana Murthy]

Hi, I am using drools i.e., a fire engine. Instead of writing the business logic in java i am using text based rules. Everything is fine but i have doubt how to assign the error messages or warning messages to the corresponding object which i am inserting in session. I want to set the error messages to the pojo class so that in UI i can display it. Please find the code below.

Message.java

package com.rmn.eoodu.service.message;

import java.util.List;

/**
 * @author suryanarayanam
 *
 */
public interface Message {
	public enum Type {
		ERROR, WARNING
	}
	/**
	 * @return type of this message
	 */
	Type getType();
	/**
	 * @return key of this message
	 */
	String getMessageKey();
	/**
	 * objects in the context must be ordered from the least
	 * specific to most specific
	 * @return list of objects in this message's context
	 */
	List<Object> getContextOrdered();
}

DefaultMessage.java

package com.rmn.eoodu.service.messageImpl;

import java.io.Serializable;
import java.util.List;

import com.rmn.eoodu.service.message.Message;

public class DefaultMessage implements Message, Serializable{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private Message.Type type;
	private String messageKey;
	private List<Object> context;
	public DefaultMessage(Message.Type type, String messageKey,List<Object> context) {
		if (type == null || messageKey == null) {
			throw new IllegalArgumentException("Type and messageKey cannot be null");
		}
		this.type = type;
		this.messageKey = messageKey;
		this.context = context;
	}
	@Override
		public String getMessageKey() {
		return messageKey;
	}
	@Override
	public Message.Type getType() {
		return type;
	}
	@Override
	public List<Object> getContextOrdered() {
		return context;
	}
	/* (non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 */
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result
		+ ((context == null) ? 0 : context.hashCode());
		result = prime * result
		+ ((messageKey == null) ? 0 : messageKey.hashCode());
		result = prime * result + ((type == null) ? 0 : type.hashCode());
		return result;
	}
	/* (non-Javadoc)
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		DefaultMessage other = (DefaultMessage) obj;
		if (context == null) {
			if (other.context != null)
				return false;
		} else if (!context.equals(other.context))
			return false;
		if (messageKey == null) {
			if (other.messageKey != null)
				return false;
		} else if (!messageKey.equals(other.messageKey))
			return false;
		if (type != other.type)
			return false;
		return true;
	}
	/* (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return "DefaultMessage [type=" + type + ", messageKey="
		+ messageKey + ", context=" + context + "]";
	}


}

ValidationReport.java

package com.rmn.eoodu.service.message;

import java.util.Set;

/**
 * @author suryanarayanam
 *
 */
public interface ValidationReport {
	/**
	 * @return all messages in this report
	 */
	Set<Message> getMessages();
	/**
	 * @return all messages of specified type in this report
	More free*/
	Set<Message> getMessagesByType(Message.Type type);
	/**
	 * @return true if this report contains message with
	 * specified key, false otherwise
	 */
	boolean contains(String messageKey);
	/**
	 * adds specified message to this report
	 */
	boolean addMessage(Message message);
}

DefaultValidationReport.java

package com.rmn.eoodu.service.messageImpl;

import java.io.Serializable;
import java.util.Collections;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.HashMap;

import com.rmn.eoodu.service.message.Message;
import com.rmn.eoodu.service.message.ValidationReport;

public class DefaultValidationReport implements ValidationReport,Serializable{

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	protected Map<Message.Type, Set<Message>> messagesMap =	new HashMap<Message.Type, Set<Message>>();
	
	@Override
	public Set<Message> getMessages() {
		Set<Message> messagesAll = new HashSet<Message>();
		for (Set<Message> messages : messagesMap.values()){
			messagesAll.addAll(messages);
		}
		return messagesAll;
	}
	
	@Override
	public Set<Message> getMessagesByType(Message.Type type) {
		if (type == null)
			return Collections.emptySet();
		Set<Message> messages = messagesMap.get(type);
		if (messages == null)
			return Collections.emptySet();
		else
			return messages;
	}
	
	@Override
	public boolean contains(String messageKey) {
		for (Message message : getMessages()) {
			if (messageKey.equals(message.getMessageKey())) {
				return true;
			}
		}
		return false;
	}
	
	@Override
	public boolean addMessage(Message message) {
		if (message == null)
			return false;
		Set<Message> messages =messagesMap.get(message.getType());
		if (messages == null) {
			messages = new HashSet<Message>();
			messagesMap.put(message.getType(), messages);
		}
		return messages.add(message);
	}
}

ReportFactory.java

package com.rmn.eoodu.service.message;

/*
 * Its an factory class
 */
public interface ReportFactory {
	ValidationReport createValidationReport();
	Message createMessage(Message.Type type, String messageKey,Object... context);
	}

DefaultReportFactory.java

package com.rmn.eoodu.service.messageImpl;

import java.util.Arrays;

import com.rmn.eoodu.service.message.Message;
import com.rmn.eoodu.service.message.ReportFactory;
import com.rmn.eoodu.service.message.ValidationReport;

public class DefaultReportFactory implements ReportFactory{
	@Override
		public Message createMessage(Message.Type type,String messageKey, Object... context) {
		return new DefaultMessage(type, messageKey, Arrays.asList(context));
	}
	@Override
	public ValidationReport createValidationReport() {
		return new DefaultValidationReport();
	}
}

SecurityRules.drl File

package com.rmn.eoodu.service.security.drools;

import com.rmn.eoodu.service.security.impl.UserLoginServiceImpl;
import com.rmn.eoodu.service.security.dos.UserLogin;

global com.rmn.eoodu.service.message.ValidationReport validationReport;
global com.rmn.eoodu.service.message.ReportFactory reportFactory;
global com.rmn.eoodu.service.security.impl.UserLoginServiceImpl userLoginServiceImpl;

import function com.rmn.eoodu.service.security.validation.ValidationHelper.error;
import function com.rmn.eoodu.service.security.validation.ValidationHelper.warning;
import function com.rmn.eoodu.service.utils.DroolsUtils.validatePassword;

/*
rule "CheckUserName" 
activation-group "validateForm"
lock-on-active true
salience 100
when
	UserLogin($user : userLogin)
   	eval ($user.length() < 8)
then
	 warning(kcontext);
end	
*/
rule "Checkingthelengthofname"
activation-group "validateForm"
lock-on-active true
salience 50
when
    $userlogin: UserLogin($pwd: password)
   	eval(validatePassword($pwd)==true)	
then
	warning(kcontext,$userlogin);
end

/*
rule "PasswordValidationone"
activation-group "validateForm"
lock-on-active true
salience 100
when
	UserLogin($pwd : password)	
	eval(checkNullOrEmpty($pwd)==true)	
then
	drlMessages.addErrorMessage("LoginForm_Password","InvalidPassword","Password should not be empty",5);
end


rule "PasswordValidationsaliencetwo"
activation-group "validateForm"
lock-on-active true
salience 50
when
	UserLogin($pwd : password)	
	eval(validatePassword($pwd)==true)	
then
	drlMessages.addErrorMessage("LoginForm_Password","InvalidPassword","Please check the length of the password once",5);
end

rule "UserNameandPasswordarenotequal"
activation-group "validateForm"
lock-on-active true
salience 25
when 	
    UserLogin($user : userLogin , $pwd : password)
   	eval(checkEquals($user,$pwd)==true)
then
   drlMessages.addErrorMessage("LoginForm_UserName_Password","Invlid UserName & Password","UserName and Password Cannot be Same",5);  
end */

ServiceImplementation class. The problem is here. I am not understanding how to set error messages to UserLogin Pojo class. I have written one logic please correct me. I think what i have written is not setting the error messages to pojo class.

public void saveOrUpdate(UserLoginDTO userLoginDTO)throws HibernateException 
	{
		userLoginObj = new UserLogin();
		BeanUtils.copyProperties(userLoginDTO, userLoginObj);	
		KnowledgeBase base=createKnowledgeBase(VALIDATE_SECURITY_LOGIN);
		StatefulKnowledgeSession session = base.newStatefulKnowledgeSession();
		ValidationReport validationReport=new DefaultValidationReport();
		session.setGlobal("validationReport", validationReport);
		ReportFactory reportFactory = new DefaultReportFactory();
		session.setGlobal("reportFactory", reportFactory);
		UserLoginServiceImpl userLoginServiceImpl=null;
		session.setGlobal("userLoginServiceImpl", userLoginServiceImpl);
		session.insert(userLoginObj);
		session.fireAllRules();
		session.dispose();
		reportFactory.createValidationReport();
		if(validationReport.getMessages().size()>0)
		{
			reportFactory.createValidationReport();
			Object vo=validationReport.getMessages().iterator().next().getContextOrdered();
			System.out.println("The value of object is "+vo);
			validationReport.getMessagesByType(Type.WARNING).iterator().next().getContextOrdered();
			System.out.println(validationReport.getMessagesByType(Type.WARNING));
			System.out.println(validationReport.getMessages());
			Set<Message> s= new HashSet<Message>();
			s=validationReport.getMessages();
			for(Message m: s)
			{
				m.getMessageKey();
				m.getContextOrdered();
				m.getType();
				System.out.println(m.getMessageKey());
				System.out.println(m.getContextOrdered());
				System.out.println(m.getType());
				List<Object> list=m.getContextOrdered();
				System.out.println(list);
			}

		}
		else
		{
			masterDao.saveOrUpdate(userLoginObj);
		}

the code is working fine. I am getting the errors also and i am uning the condition that if the size of errors > 0 dont call save or update method. Upto here no problem. The problem is how to set the error message to pojo class so that in UI i can display it.

[Prabaharan Gopalan]

I didn't go through the classes but I'm curious, why would you think this is a Java problem and not some configuration in Drools?

[dennis deems]

I don't recommend setting an attribute on the object that is passed to the service. Better to return a collection of Messages from the service method. Also create a custom exception class that allows you to set your Message objects on it -- but be careful to differentiate these from the message attribute on the Throwable class. When you throw an exception, throw your custom exception type with the messages populated.

[Maganti Suryanarayana Murthy]

I can able to return the collection of messages in the service class. But the problem is that i want to set those messages to Object as it should be passed to VO.