Natalie Ap

Hi Rahul,

Thanks for the quick response.

Tell you what..This code worked fine till Thurs. On Friday, I was tinkering around a bit trying to learn how to enable the Hibernate caching and connection pooling. After that, this weird error started appearing for ALL queries in my code.. So I changed my hibernate config file to what it was before. The DB was not touched, not was the code. But this error ha been coming and I cannot figure out what to do about it.


Any clues anyone? Please help!

Thanks,
Natalie

Rahul Babbar wrote:Hi,

Most of the things seem right...
Is the User table is already present in your database or are you trying to create it using Hibernate.

I have a suggestion...change the table name in your hbm and the database to a name other than 'USER'..
to
<class name="User" table="USER_LOGIN">
or something like that..and make sure the table name in your DB is USER_LOGIN(or something else, but not USER)

I vaguely remember that sometime back, i was getting some weird error by using Hibernate with MySQL while trying to name the table name as USER....and hibernate complained...and changing the table name did the trick...
It sounds silly, but is true..(as far as i remember)

Hi all,

I am stuck with this since a very long time. I am getting this error for an HQL or a native sql query in hibernate. I

request you to help me. I am unable to find the post where this has been discussed before. Kindly help!


Error
INFO: Not binding factory to JNDI, no JNDI name configured Aug 14, 2009 7:04:57 PM org.hibernate.impl.SessionFactoryImpl checkNamedQueries INFO: Checking 0 named queries Hibernate: select user0_.USERNAME from USER user0_ Aug 14, 2009 7:04:58 PM org.hibernate.util.JDBCExceptionReporter logExceptions WARNING: SQL Error: 0, SQLState: S0022 Aug 14, 2009 7:04:58 PM org.hibernate.util.JDBCExceptionReporter logExceptions SEVERE: Column 'col_0_0_' not found. Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not execute query at org.hibernate.exception.ErrorCodeConverter.handledNonSpecificException(ErrorCodeConverter.java:92) at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:80) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43) at org.hibernate.loader.Loader.doList(Loader.java:1518) at org.hibernate.loader.Loader.list(Loader.java:1498) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:369) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:266) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:788) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74) at myapp.test.dao.HibernateDAO.validatePassword(HibernateDAO.java:41) at myapp.test.dao.HibernateDAO.main(HibernateDAO.java:468) Caused by: java.sql.SQLException: Column 'col_0_0_' not found. at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910) at com.mysql.jdbc.ResultSet.findColumn(ResultSet.java:970) at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5613) at org.hibernate.type.StringType.get(StringType.java:16) at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:77) at org.hibernate.type.NullableType.nullSafeGet(NullableType.java:68) at org.hibernate.loader.hql.QueryLoader.getResultColumnOrRow(QueryLoader.java:320) at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:313) at org.hibernate.loader.Loader.doQuery(Loader.java:387) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:206) at org.hibernate.loader.Loader.doList(Loader.java:1515) ... 7 more

Code
public User validatePassword(String username, String password){ String QUERY = "select username from User"; Query query = session.createQuery(QUERY); session = HibernateInitializer.getSession(); List<Object[]> data = (List<Object[]>)query.list(); Iterator<Object[]> it = data.iterator(); User user = null; try { while(it.hasNext()) { Object[] row = (Object[]) it.next(); user = new User(); user.setUsername((String)row[0]); } } catch (Exception e) { e.printStackTrace(); } finally { session.flush(); session.close(); } return user; }

xml files

<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test</property> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">root</property> <property name="hibernate.connection.pool_size">10</property> <property name="show_sql">true</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <mapping resource="user.hbm.xml"/> </session-factory> </hibernate-configuration>

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="User" table="USER"> <id name="username" column="USERNAME"> </id> </class> </hibernate-mapping>

Hi all,

We are building a web application that would use the following technologies:
1) Spring
2) Hibernate
3) Tomcat
4) MySQL database

The site would have 120K to 140 K users. We need to build a scalable server that can support so many users and one that has a good
response time. Can anyone please pool in suggestions, tips, etc on how to go about this.
Which design patterns we could use, what sort f optimizations can be applied while building the site?
Thanks,

Hi Rob,

I tried doing that. But my output is as follows:

FirstThread
FirstThread
FirstThread
FirstThread
FirstThread
FirstThread
FirstThread
SecondThread
SecondThread
SecondThread
SecondThread
SecondThread
SecondThread

Why does the Second thread enter the method at all when it is a synchronized method and when there is an infinite loop within it!

NP

Rob Prime wrote:Both MyThread instances synchronize on itself - their synchronization is separated.

The following will work as you expect:
public class MyThread extends Thread { public MyThread(String name) { super(name); } public void run() { callMe(); } public synchronized void callMe() { while(true) { System.out.println(Thread.currentThread().getName()); } } } public class Test { public static void main(String args[]) { MyThread myThread = new MyThread("MyThread"); Thread t1 = new Thread(myThread, "FirstThread"); t1.start(); Thread t2 = new Thread(myThread, "SecondThread"); t2.start(); } }This is because the same MyThread instance is used (as a Runnable) in two different threads.

Hi all,

Please check the following code:

public class MyThread extends Thread{ public MyThread(String name) { super(name); } public void run() { callMe(); } public synchronized void callMe() { while(true) { System.out.println(this.getName()); } } } public class Test { public static void main(String args[]){ MyThread t1 = new MyThread("FirstThread"); t1.start(); MyThread t2 = new MyThread("SecondThread"); t2.start(); } }

Despite of the method callMe being synchronized, when I run the program, I get the following output:

FirstThread SecondThread FirstThread SecondThread FirstThread

I would expect one of the threads to enter the callMe() method and stall it, so that the second thread cannot enter it at all! Can someone please help me understand the output? Also, if there is something wrong here, how do I correct it so as to allow only one thread to enter the method?

Thanks,
NP

Hi all,

I have heard of scalability issues with a few applications where Hibernate is used. Please let me know in case anyone has faced any such issues. Also, please let me know of the possible cause for this.

Thanks

On my UI, I am displaying a list of objects:

Employee id: 1
Employee Name: xyz
Age : 28
Phone: 235325

Employee id: 2
Employee Name: abc
Age : 30

Employee id: 3
Employee Name: pqr
Age : 25
Phone: 363433

The above fields are editable (except employee id) and have been loaded dynamically on basis of a search mechnism (to load employees with specific properties.) Since they have been loaded dynamically, the names of all fields are the same on the UI. They look like this.

<input type = "text" name = "txtname" value ="xyz"> <input type = "text" name = "txtname" value ="abc"> <input type = "text" name = "txtname" value ="pqr"> <input type = "text" name = "txtage" value ="28"> <input type = "text" name = "txtage" value ="30"> <input type = "text" name = "txtage" value ="25">

Similarly for phone. But phone may or may not exist on the UI depending on whether an employee has a phone or not.


The entire form has one submit button, mapped to an updateAction to update the new details put in by the user.

My Action form contains a String[] array txtname, String[] array txtage and and String[] array txtphone. When the details on the UI are captured in the above properties, in order to decipher which employee name, age or phone corresponds to which employee id, I have appended the employee id to the values of the textboxes.

BUT I think there must be a way in which i could capture these details in a better manner (in objects). So, in the my ActionForm i could have a list of Employee objects, each of which would contain the details submitted from the UI. But i am not able to figure out how to go about this.

First of all, can my ActionForm contain an Employee List which could be populated automatically with details from the UI??

I am simply looking for a better way to do this. Please advise.

Thanks.

Hi all,

I am trying to run the following piece of code, but I am getting a javascript error "Object does not support property error!" and I am unable to understand what the problem might be.

There is a form called "updateForm" which I am trying to submit when i get the error. When I comment lines (1), (2), (3), the error does not get thrown. Please help me!!

Please let me know if you need any other information besides this.

Thanks,



<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %> <%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %> <%@ taglib uri="/WEB-INF/struts-logic.tld" prefix = "logic" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <LINK REL=StyleSheet HREF="fonts.css" TYPE="text/css"> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>SQIIS</title> <script type="text/javascript"> var tagValStr = ""; var domValStr = ""; var actionType = -1; function updateRule(){ document.all.UpdateButton.name = "Save"; document.all.submit3.disabled = true; } function submitForm() { tagArr = document.all.tags; domArr = document.all.domConds; for(i=0; i<tagArr.length; i++) { tagValStr = tagValStr + ":" + (tagArr[i].value) ; } for(i=0; i><domArr.length; i++) { domValStr = domValStr + ":" + (domArr[i].value) ; } document.all.tagpredicateinput.value = tagValStr; document.all.domainconditions.value = domValStr; document.all.query.value = "dfg"; setActionType(3); document.all.actiontype.value = actionType; } function setActionType(x) { document.all.actiontype.value = x; actionType = x; } function addRule() { tagArr = document.all.tags; domArr = document.all.domConds; for(i=0; i><tagArr.length; i++) { tagValStr = tagValStr + ":" + (tagArr[i].value) ; } var domValStr = ""; for(i=0; i><domArr.length; i++) { domValStr = domValStr + ":" + (domArr[i].value) ; } document.all.tagpredicateinput.value = tagValStr; document.all.domainconditions.value = domValStr; document.all.query.value = "dfg"; setActionType(0); document.all.actiontype.value = actionType; alert(" value for query " + dml.elements[i].query.value); alert(" value for tags " + dml.elements[i].tagpredicateinput.value); alert(" value for domains " + document.elements[i].domainconditions.value); alert(" value for actionType " + document.elements[i].actiontype.value); document.forms.mainForm.action = submit1; if(document.forms.mainForm.onsubmit()) { document.forms.mainForm.submit(); } } function selectSomeOption(val){ alert(val); for (j = 0; j >< document.all.cmbupdateQualifier.length; j++){ if (document.all.cmbupdateQualifier.options[j].value == val){ var f = document.all.cmbupdateQualifier.options[j]; f.selected = true; alert("Value:" + f.value); return; } } } function makeFieldsEditable(buttonObj) { r = document.getElementsByTagName('div'); for(i=0; i< r.length; i++) { r[i].style.visibility = 'visible'; } document.all.UpdateAllRules.innerText = "Save Rules"; } function deleteRules() { arrChecked = document.getElementsByName("chkRuleId"); var rulesToBeDeletedList = ""; for(i=0; i<arrChecked.length; i++) { if(arrChecked[i].checked) { rulesToBeDeletedList = rulesToBeDeletedList + ":" + arrChecked[i].value; document.all.rulestobedeleted.value = rulesToBeDeletedList; alert(rulesToBeDeletedList); } } submitDelForm(); } function submitDelForm() { document.forms.deleteForm.submit(); } function updateForm() { document.forms.updateForm.submit(); } ></script> </head> <body> <center> <h2>Rule-Base Admin page</h2> <br><br><br><br><br><br> <form action="ruleadmin.do" name = "mainForm"> <table > <tr> <c:forEach var="tagListVar" items="${tagsList}" varStatus="curr"> <td ><c:out value="${tagListVar.tagName}"></c:out> <c:set var="a" value="text . ${curr.count}"></c:set> <!--<c:out value="${a}"></c:out>--> <input type="text" name = "tags" size="3" maxlength="3"> </td> </c:forEach> </tr> </table> <table > <tr> <c:forEach var="domain" items="${DomainList}"> <td ><c:out value="${domain.domainName}"></c:out> <input type="text" name = "domConds" size="8" maxlength="8"></td> </c:forEach> </tr> <tr><td><input name = "query" type="hidden" value ="Ssdf"></td></tr> <tr><td><input name = "tagpredicateinput" type="hidden" ></td></tr> <tr><td><input name = "domainconditions" type="hidden" ></td></tr> <tr><td><input name = "actiontype" type="hidden" ></td></tr> <tr><td><input type = "submit" tabindex="3" value=" Search " alt="Search for rule" id="submit1" name="submit1" onclick="submitForm()"></td> <td><input type = "submit" tabindex="3" value=" Add New Rule " alt="Add New Rule" id="submit2" name="submit2" onclick="addRule()"></td></tr> </table> </form> <!--The following form is not getting submitted!--> <form action="updateAction.do" name = "updateForm"> <input type = "submit" name="Update Rules" value="Update All Rules" onClick="updateForm()"> <table border = "1" > <tr><td><button id = "UpdateAllRules" onclick="makeFieldsEditable(this)">Update Rules</button></td> </tr> <c:forEach var="op" items="${SearchOutput}"> <tr> <th >RuleId: <c:out value="${op.ruleId}"></c:out> Rule Weight: <c:out value="${op.ruleWt}"></c:out> <input type="checkbox" name = "chkRuleId" id = "chkRuleId" value=<c:out value="${op.ruleId}"></c:out>> <c:set var = "ruleIdU" value="${op.ruleId}"></c:set> <input name = "ruleid" type="hidden" value=<c:out value="${op.ruleId}"></c:out>> <input name = "actiontypedelete" type="hidden"> <input type = "button" tabindex="3" value=" Save Rule " alt=" Update Rule" id="SaveButton" name="SaveButton" > </th> </tr> <tr><td> <table id = "SearchResultsTable"> <tr> <td> <table> <tr> <th >Tag Name </th><th >Predicates</th> </tr> <c:forEach var="predicatesArrayList" items="${op.predicatesArrayList}" varStatus="curr"> <tr> <td ><c:out value="${predicatesArrayList.tagname}"></c:out></td> <td ><c:out value="${predicatesArrayList.qualifier}"></c:out> <c:out value="${predicatesArrayList.quantifier}"></c:out> <div id="EditableFields" style="visibility: hidden; display: compact"> Change current values to: <c:set var="valUpdQual" value="${op.ruleId}_${predicatesArrayList.tagname}_${predicatesArrayList.qualifier}"></c:set> <c:set var="valUpdQual" value="${op.ruleId}_${predicatesArrayList.tagname}_${predicatesArrayList.quantifier}"></c:set> <select name="cmbupdatequalifier"> <c:forEach var="allValidQualifiersVar" items="${allValidQualifiers}" varStatus="curr"> <option value=<c:out value="${allValidQualifiersVar}"></c:out>><c:out value="${allValidQualifiersVar}"></c:out></option> <!-- ******** (1) ********--> </c:forEach> </select> <c:set var="valUpdQuant" value="cmbupdateQuantifier${op.ruleId}"></c:set> <select name="cmbupdatequantifier" > <c:forEach var="validQuan" items="${validQuantifiers}"> <option value=<c:out value="${validQuan}"></c:out>><c:out value="${validQuan}"></c:out></option> <!-- ******** (2) ********--> </c:forEach> </select> <c:set var="valUpdQual" value=""></c:set> <c:set var="valUpdQuant" value=""></c:set> </div> </td> </tr> </c:forEach> </table> </td> <td > <table> <tr > <th>Domain Name </th><th>Confidence</th> </tr> <tr> <c:forEach var="domainsArrayList" items="${op.domainsArrayList}"> <tr ><td ><c:out value="${domainsArrayList.domainName}"></c:out></td> <td ><c:out value="${domainsArrayList.confidence}"></c:out></td></tr> <td > <div style="visibility: hidden; display: compact"> <input type = "text" name = "txtupdateconfidence" value="<c:out value="${op.ruleId}_${domainsArrayList.domainName}_${domainsArrayList.confidence}"></c:out>"> <!-- ******** (3) ********--> </div> </td> </c:forEach> </tr> </table> </td> </tr> </table> </td></tr> </c:forEach> <tr><td></td></tr> </table> </form> </center> </body> </html>

Hi,

I am trying to install Easy Struts plugin for Eclipse 3.3 or Europa.
I have copied the folder of the plugin into the plugin folder of Eclipse, but when i start eclipse, it does not appear to have been installed. Please help!!!

Let me know in case you know of any other plugin as well.

Thanks

Amit Ghorpade wrote:By making a variable transient, you indicate that the variable does not add to the object's state and hence should not be saved/serialized.
Now when restoring the same object, transient variable value is not available and it gets the same treatment as class variables get during initialization and gets assigned to default value.


Hope this helps

Thanks! I understood the concept of transient variables now!

Ankit Garg wrote:From where did the class Poddle come. You didn't show poddle class in your code...

Hi Ankit,

Sorry, Please consider the following code as an addition to thecode above:

class Poodle extends Dog {} class Labrador extends Dog {}

Hi all,

From Kathy and Sierra, from the Chapter Objects and Collections: The hashCode() Contract: i gather the following:

Suppose an object having 2 variables x and y is serialized. x is transient and y is not. While serializing the object, the value of x = 10, y = 9. After we deserialize this object, the value of the transient variable reset to the default value. So will x be = 0 after desrialization? Why does this happen?

Thanks

Hi all,

Another Generics question from me. Thanks to Vierda Mila for answering my last few queries!

class Cage<E> { private E el; public void setElement(E x) { el = x; } public E getElement() { return el; } } class Animal {} class Dog extends Animal{} class Cat extends Animal { } Cage<? extends Dog> cg11 = new Cage<Poodle>(); Object o11 = (Object)cg11.getElement(); Dog d11 = (Dog)cg11.getElement(); Poodle p11 = (Poodle)cg11.getElement(); Labrador l11 = (Labrador)cg11.getElement();

In the above case, <? extends Dog> indicates Cage can contain any subclass object of Dog. The RHS indicates that the object created of Cage needs to contain a type of class Poodle. Then why is it that any of the getElement() invocations do not show a compilation error.
According to my understanding, it is because, <? extends Poodle> allows addition of only null objects to the cage. Hence any retrieval using a getElement() expects a null object to be returned, which can be type-casted into any other class (Object/Dog/Poodle/Labrador). Please correct me if i am wrong.

Why i find this tough to understand is because i do not see a practical usage of the above syntax. Please let me know if there is any.

Vierda Mila wrote:Hi N path,

one rule you have to remember here that polymorphism is not apply for generic type.
if you provide as per below it will result compile error :

Cage<Animal> cg1 = new Cage<Dog>();

but these example is ok :

Cage <Animal> cg1 = new Cage <Animal>();
Cage<? extends Animal cg1 = new Cage <Dog>();

please check this one for further information

regards,
-Vierda-

Thanks for your reply Vierda.

But what exactly does the syntax mean then? If it is to be explained in simple english..
As in,
Cage<Animal> cg = new Cage<Animal>();

Cage<? extends Dog> cg1 = new Cage<Dog>();

According to this syntax, cg can contain an object of Animal class. Then what does the type in RHS signify?

In the first case, the type in LHS and RHS is the same. Why is it not the same in the second case? Why can't we write the following
Cage<? extends Dog> cg1 = new Cage<? extends Dog>();

This is a little tough to explain! But i hope you understand! All i mean to ask it, what do the types on each side indicate in plain English?

Hi all,


Given the following:

Animal class

Dog class extends Animal class


class Cage<E> { private E el; public void setElement(E x) { el = x; } public E getElement() { return el; } }


Please explain to me why the following is not allowed: (gives compilation error)

Cage<Animal> cg1 = new Cage<Dog>();

I always thought it means that LHS indicates that Cage may contain objects of Animal class. And by doing the instantiation in RHS, we are specifiying that the objects added would be of type Dog. Since Dog is a subclass of Animal, it should not matter even if Dog is added to the Cage.


Thanks