Parthiban Malayandi

Hi All,

I'm new to spring, I'm confused about primary attribute and autowire-candidate attribute.

Could someone explain me ?

Thanks,
Parthiban

Hi Rohit,

Thanks for your reply, I tried to retrieve a record using a primary key (id), which is supposed to return a unique record,still I'm getting the same exception .

Basically if I have more than one record in DB and when I retrieve a record I'm getting that exception.

Since it's a one to one mapping is Am I making a mistake ?

Hi All,

I'm learning Hibernate Framework

I did an simple example of One to One Mapping and when I try to select a row I'm getting an exception

Please find the programs I'm using


package com.example.chapter17; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; @Entity public class Exam { private Long id; private String shortName; private ExamDetail detail; @Id @GeneratedValue public Long getId() { return id; } public String getShortName() { return shortName; } @OneToOne(cascade=CascadeType.ALL) public ExamDetail getDetail() { return detail; } public void setId(Long id) { this.id = id; } public void setShortName(String shortName) { this.shortName = shortName; } public void setDetail(ExamDetail detail) { this.detail = detail; } @Override public String toString() { // TODO Auto-generated method stub return getShortName()+" : "+getDetail().getNoOfQuestions()+" : "+getDetail().getPassPercentage(); } }
package com.example.chapter17; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; @Entity(name="exam_detail") public class ExamDetail { private Long id; private int noOfQuestions; private int passPercentage; @Id @GeneratedValue public Long getId() { return id; } public int getNoOfQuestions() { return noOfQuestions; } public int getPassPercentage() { return passPercentage; } public void setId(Long id) { this.id = id; } public void setNoOfQuestions(int noOfQuestions) { this.noOfQuestions = noOfQuestions; } public void setPassPercentage(int passPercentage) { this.passPercentage = passPercentage; } }
package com.example.chapter17; import org.hibernate.Criteria; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.Example; import org.hibernate.service.ServiceRegistryBuilder; import org.hibernate.tool.hbm2ddl.SchemaExport; public class AssociationTester { public static void main(String[] args) { Configuration config = new Configuration(); config.addAnnotatedClass(Exam.class); config.addAnnotatedClass(ExamDetail.class); config.configure(); org.hibernate.service.ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()) .buildServiceRegistry(); SessionFactory factory = config.buildSessionFactory(serviceRegistry); Session session = factory.getCurrentSession(); ExamDetail examDetail = new ExamDetail(); examDetail.setNoOfQuestions(62); examDetail.setPassPercentage(65); Exam exam = new Exam(); exam.setShortName("SCJA"); exam.setDetail(examDetail); //SchemaExport export = new SchemaExport(config); //export.create(true,true); session.beginTransaction(); //Save the object Long pKey = (Long)session.save(exam); System.out.println("prima "+pKey); //Retrieve the object /*String queryString = "from Exam where shortName= :sName"; Query query = session.createQuery(queryString); query.setString("sName","SCJA"); Exam e = (Exam)query.uniqueResult(); System.out.println("Exam -> "+e);*/ // Using Criteria API Exam exObj = new Exam(); exObj.setId(1L); Example example = Example.create(exObj); Criteria criteria = session.createCriteria(Exam.class); criteria.add(example); Exam e1 = (Exam)criteria.uniqueResult(); System.out.println("Exam "+e1 ); session.getTransaction().commit(); } }

The Exception I'm getting is
Hibernate: insert into exam_detail (noOfQuestions, passPercentage) values (?, ?) Hibernate: insert into Exam (detail_id, shortName) values (?, ?) prima 2 Hibernate: select this_.id as id1_0_1_, this_.detail_id as detail3_0_1_, this_.shortName as shortNam2_0_1_, examdetail2_.id as id1_1_0_, examdetail2_.noOfQuestions as noOfQues2_1_0_, examdetail2_.passPercentage as passPerc3_1_0_ from Exam this_ left outer join exam_detail examdetail2_ on this_.detail_id=examdetail2_.id where (1=1) Exception in thread "main" org.hibernate.NonUniqueResultException: query did not return a unique result: 2 at org.hibernate.internal.AbstractQueryImpl.uniqueElement(AbstractQueryImpl.java:914) at org.hibernate.internal.CriteriaImpl.uniqueResult(CriteriaImpl.java:396) at com.example.chapter17.AssociationTester.main(AssociationTester.java:65)

How ever I'm not getting that exception if I un comment the following the tester program


//SchemaExport export = new SchemaExport(config);
//export.create(true,true);

Can somebody let me know what is the problem ?

Thanks in advance

Hi Santhosh,

The mistake I made was
config.addClass(User.class); instead of
config.addAnnotatedClass(User.class);


I changed It and it works fine now.Thanks

Hi All,

I'm following book "Hibernate made easy" book and trying to compile my first Hibernate program.

I have configured classpath and path with appropriate library files and I'm not getting any compilation errors but I'm getting the below error when I try to run it

My config file
=========
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-configuration SYSTEM "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.dialect"> org.hibernate.dialect.MySQLDialect </property> <property name="hibernate.connection.driver_class"> com.mysql.jdbc.Driver </property> <!-- Assume test is the database name --> <property name="hibernate.connection.url"> jdbc:mysql://localhost/examscam </property> <property name="hibernate.connection.username"> root </property> <property name="hibernate.connection.password"> root </property> <!-- List of XML mapping files --> </session-factory> </hibernate-configuration>

Simple Class

package com.example; import javax.persistence.*; import org.hibernate.cfg.AnnotationConfiguration; import org.hibernate.tool.hbm2ddl.SchemaExport; @Entity public class User { public Long id; public String password; @Id @GeneratedValue public Long getId(){ return id; } public String getPassword() { return password; } public void setId(long id){ this.id=id; } public void setPassword(String password){ this.password=password; } public static void main(String[] args) { System.out.println("Hello!!! from Hibernate !!!"); AnnotationConfiguration config = new AnnotationConfiguration(); config.addClass(User.class); config.configure(); new SchemaExport(config).create(true,true); } }

Runtime Error

D:\Prg Files\classes>java com.example.User May 07, 2013 8:21:01 PM org.hibernate.annotations.common.Version <clinit> INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final} May 07, 2013 8:21:01 PM org.hibernate.Version logVersion INFO: HHH000412: Hibernate Core {4.1.12.Final} May 07, 2013 8:21:01 PM org.hibernate.cfg.Environment <clinit> INFO: HHH000206: hibernate.properties not found May 07, 2013 8:21:01 PM org.hibernate.cfg.Environment buildBytecodeProvider INFO: HHH000021: Bytecode provider name : javassist May 07, 2013 8:21:01 PM org.hibernate.cfg.Configuration addClass INFO: HHH000221: Reading mappings from resource: com/example/User.hbm.xml May 07, 2013 8:21:01 PM org.hibernate.cfg.Configuration addResource INFO: HHH000221: Reading mappings from resource: com/example/User.hbm.xml Exception in thread "main" org.hibernate.MappingNotFoundException: resource: com/example/User.hbm.xml not found at org.hibernate.cfg.Configuration.addResource(Configuration.java:702) at org.hibernate.cfg.AnnotationConfiguration.addResource(AnnotationConfiguration.java:111) at org.hibernate.cfg.AnnotationConfiguration.addResource(AnnotationConfiguration.java:46) at org.hibernate.cfg.Configuration.addClass(Configuration.java:747) at org.hibernate.cfg.AnnotationConfiguration.addClass(AnnotationConfiguration.java:129) at com.example.User.main(User.java:36)

Could you guys please let me know what is the problem ?

Thanks in advance

Hi all,

I have just started to learn Spring MVC and learned about formBackingObject method.

I have wrote a simple program to understand the concept .

MyCustomFormController

package org.mypackage; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.springframework.stereotype.Controller; import org.springframework.validation.BindException; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.mvc.SimpleFormController; public class MyCustomFormController extends SimpleFormController { public MyCustomFormController() { setCommandClass(Person.class); setCommandName("person"); } @Override protected Object formBackingObject(HttpServletRequest request) throws Exception { System.out.println("::: FormBackingObject is called :::"); System.out.println(super.formBackingObject(request) instanceof Person? "Yes " + "formBackingObject is a Person ":" No, It's something else"); System.out.println("formBackingObject sysout ::: **--> "+(Person)super.formBackingObject(request)); return ((Person)super.formBackingObject(request)); } @Override protected ModelAndView onSubmit(Object command, BindException errors) throws Exception { System.out.println("::: onSubmit is called :::"); System.out.println("formBackingObject sysout ::: --> "+(Person)command); return new ModelAndView("listpersons","person",(Person)command); } }

Person Class

package org.mypackage; public class Person { private String name; private String age; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAge() { return age; } public void setAge(String age) { this.age = age; } @Override public String toString() { return "Name -> "+name+" Age -> "+age; } }

I came to know that formBackingObject is called twice ( first time when form is loaded with GET request and when it is submitted with POST method) but every time I'm getting null values
when I print the Person object where as I'm getting values in onSubmit method.

Can you please explain what is the significance of formBackingObject method ?

Thanks in advance

Hi all,

I learned about cookie so tried to create a one and found that getMaxAge is not worked as I expected.

I setMaxAge to two minutes and I expect when I call getMaxAge it will return two but it didn't instead it always returns -1 .

What is wrong with my code ?
//Cookie example package c6; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class CookieExample extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException, IOException { PrintWriter out = resp.getWriter(); Cookie myCookie = new Cookie("username","Parthiban M"); myCookie.setMaxAge(60*2);//2 minutes HttpSession session = req.getSession(); if(!session.isNew()){ Cookie[] availableCookies =req.getCookies(); for(Cookie cookie : availableCookies){ out.println("Cookie "+cookie.getName()+" has value "+cookie.getValue()+" and it's age is "+cookie.getMaxAge()); } }else{ out.println("New Session"); } resp.addCookie(myCookie); } }

Output
=====
Cookie username has value Parthiban M and it's age is -1 Cookie JSESSIONID has value 0A215A80C0889AEF59B1359CB4617948.worker1 and it's age is -1


Please clarify me why it always returns -1

Hi AJ,

Thanks for your reply.First of all sorry for the delayed response from my side. I tried as you said(Implementing Serializable interface in HttpSessionActivationListener class) and I'm getting "SessionDidActivated" message but not when I expected.

Here's the Scenario when I'm getting SessionDidActivated
=====================================

When I stop Tomcat instance (say for example currently "Tomcat Instance 1" is serving the request) after hitting "SessionExample" Servlet (mapped as "/sessiontest.do") as I said I'm getting "SessionWillPassivate " message . When I start the same Tomcat instance again I'm getting "SessionDidActivated" message.

What I Thought
==========

After stopped the Tomcat instance I reloaded the same page expecting this time it will served by another Tomcat instance(say "Tomcat Instance 2" and I will get "SessionDidActivated" message since the session will be migrated.

As I expected the page is served by another Tomcat instance but the session is not migrated and I'm not getting "SessionDidActivated" in the new Tomcat instance.

I also created a new Servlet named as (Servlet3) and modified SessionExample.java so that It contains button and when it clicked it will hit a new Servlet(Servlet 3) to test this instead of reloading the same page but it also doesn't help.


Modified Source codes
===============

Modified Listener class
-------------------------

package c6; import javax.servlet.http.*; import javax.servlet.*; import java.io.*; public class SessionMigrationTester implements HttpSessionActivationListener,Serializable { //Implemented Serializable Interface public void sessionDidActivate(HttpSessionEvent evt){ System.out.println("========================"); System.out.println("Session DID Activated --**-- Serializable"); System.out.println("========================"); } public void sessionWillPassivate(HttpSessionEvent evt){ System.out.println("========================"); System.out.println("Session WILL Passivate --**-- Serializable"); System.out.println("========================"); } }

Added in web.xml
---------------------

<servlet> <servlet-name>servlet3</servlet-name> <servlet-class>c6.Servlet3</servlet-class> </servlet> <servlet-mapping> <servlet-name>servlet3</servlet-name> <url-pattern>/servlet3.do</url-pattern> </servlet-mapping>
Modified SessionExample.java
-----------------------------------

package c6; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class SessionExample extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse resp)throws ServletException,IOException { System.out.println("Inside doGet method "); PrintWriter out = resp.getWriter(); resp.setContentType("text/html"); HttpSession session = req.getSession(false); out.println("<html>"); out.println("<head> "); out.println("</head>"); out.println("<body>"); out.println("<form >"); // Added a form to support if(session ==null){ System.out.println("No Session exists creating a new one ...."); session = req.getSession(true); String sessionID = session.getId(); if(session.isNew()){ session.setAttribute("hello",new SessionMigrationTester()); out.println("New session is created ID:- "+sessionID); System.out.println("New session is created ID:- "+sessionID); } }else { String sessionID = session.getId(); session.setAttribute("hello",new SessionMigrationTester()); out.println("Old session ID:- "+sessionID); System.out.println("Old session ID:- "+sessionID); } out.println("Modified ***<br/>"); // New added out.println("<input type='submit' value='click me' />"); out.println("<script lang='javascript'>"); out.println("document.forms[0].action ="+"\""+resp.encodeURL("servlet3.do")+"\""); out.println("</script>"); out.println("</form>"); // End of modification out.println("</body>"); out.println("</html>"); System.out.println("End of doGet"); } public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { doGet(req,resp); } }

Servlet3.java
---------------

package c6; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class Servlet3 extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { HttpSession session = req.getSession(false); if(session!=null){ System.out.println("Session Already Exists! "+session.getId()); }else{ System.out.println("Session doesn't exists!!!"); } } public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { doGet(req,resp); } }

I'm trying this in a single physical machine with two tomcat instance configured with Apache Http Server .

Is anything I'm missing ? Will it work ?

Thanks for your patience for reading lengthy post .

This is what I did


Servlet
=====
package c6; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class SessionExample extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse resp)throws ServletException,IOException { System.out.println("Inside doGet method "); PrintWriter out = resp.getWriter(); resp.setContentType("text/html"); HttpSession session = req.getSession(false); out.println("<html>"); out.println("<head> "); out.println("</head>"); out.println("<body>"); if(session ==null){ System.out.println("No Session exists creating a new one ...."); session = req.getSession(true); String sessionID = session.getId(); if(session.isNew()){ session.setAttribute("hello",new SessionMigrationTester()); out.println("New session is created ID:- "+sessionID); System.out.println("New session is created ID:- "+sessionID); } }else { String sessionID = session.getId(); session.setAttribute("hello",new SessionMigrationTester()); out.println("Old session ID:- "+sessionID); System.out.println("Old session ID:- "+sessionID); } out.println("<br/>"); out.println("</html>"); System.out.println("End of doGet"); } public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException { doGet(req,resp); } }
Listener ===== package c6; import javax.servlet.http.*; import javax.servlet.*; public class SessionMigrationTester implements HttpSessionActivationListener { public void sessionDidActivate(HttpSessionEvent evt){ System.out.println("========================"); System.out.println("Session DID Activated"); System.out.println("========================"); } public void sessionWillPassivate(HttpSessionEvent evt){ System.out.println("========================"); System.out.println("Session WILL Passivate"); System.out.println("========================"); } }


JSP File
======
<html> <head> <title> A Simple JSP to Understand URL Encoding - FIRST INSTANCE </title> <script language="javascript"> function dothis() { alert('here'); document.forms[0].action=<%= "\""+response.encodeURL("sessiontest.do")+"\"" %> alert(document.forms[0].action); document.forms[0].submit(); } </script> </head> <body> <form> <% Cookie[] ck = request.getCookies(); if(ck!= null&&ck.length>0) { for(Cookie c:ck) { %> <%= "Cookie Name "+c.getName()+" Cookie Value "+c.getValue()+"\n" %> <% } }else{ %> <%= "Cookies not Found !!! " %> <%} %> <input type="button" value="Click me To Encode this URL" onclick="dothis()"/> </form> </body> </html>


My Web.xml File
===========

<web-app> <servlet> <servlet-name>SessionTest</servlet-name> <servlet-class>c6.SessionExample</servlet-class> </servlet> <servlet-mapping> <servlet-name>SessionTest</servlet-name> <url-pattern>/sessiontest.do</url-pattern> </servlet-mapping> </web-app>


http://thought-bytes.blogspot.com/2007/03/how-to-load-balance-tomcat-55-with.html

That is URL I used to configure Apache with Tomcat for Load balancing .

Please clarify me.

Hi all,

I studied about HttpSessionActivation Listener and in order understand it fully I created a simple program . I studied that the listener will be invoked whenever session attribute is migrated from one JVM to another .


The following was what I did to understand HttpSessionActivationListener

Created two instances of Tomcat in a single box.(Actually two services)

Configured Apache Http Server to point the two instances (Load balancing and fail over)

Created a small web application and deployed in two servers


Whenever I stop once instance I'm getting a message "Session Will Passivated "(which is what I have in overridden sessionWillPassivate method)

but I'm not getting "Session Did Activated" message (overridden in sessionDidActivated method) .

Please clarify me why I'm not getting Activated method message .

Thanks in advance

Vijitha, Thanks for your clarification

Hi Ulf,

Thanks for correcting my mistake and helped me to understood exactly what happens.

I understood that init() mehod not necessarily will be called just before service() method .

Rahul Kumar Tiwari wrote: I am calling distroy() method within the init() method but servlet service() method is running why ?

For Rahul the service method is called because he explicitly invoked a servlet(which is a request to a web container).
what I understood is correct ?

please clarify me.

Once again thanks for correcting my mistake.

Hi Rahual,

You are calling destroy() inside init but to use that, you are invoking servlet which is a REQUEST to a Web Container . so what happens is in order to respond to your request the servlet will be initalised(init) and service () method is invoked to do that. so the point is WHENEVER you are hitting a servlet means it is request, so service() method will be invoked to process your request .

Tim Hagberg wrote: My first assumption was that these servlets were being destroyed after every use, and thus the init method was being called every time one of the respective actions was performed, however I can't find any evidence of destroy methods being called. Has anyone seen anything like this, and are there easy ways to find out if a servlet is being destroyed before the container is shut down?

Hi Tim,

We have init and destroy methods which serves the purpose but it is invoked whenever a servlet instance is created (Only once if it's the FIRST Request since at that time we won't be having any instance for THAT servlet ) and destroyed .NOT for every servlet Request.

For every request the SAME servlet instance is used with a NEW Thread.

As same with init, destroy method will also be called only if don't have any request for that particular Servlet INSTANCE

Following is the extract form API
==========================
Destroy

Called by the servlet container to indicate to a servlet that the servlet is being taken out of service. This method is only called once all threads within the servlet's service method have exited or after a timeout period has passed. After the servlet container calls this method, it will not call the service method again on this servlet.

This method gives the servlet an opportunity to clean up any resources that are being held (for example, memory, file handles, threads) and make sure that any persistent state is synchronized with the servlet's current state in memory.

Hope this will clear your doubt.

Hi Ulf,

I found where is the problem . Actually I download Tomcat in zip format and used it. Later I created it as service in Windows (using 'sevice install' command ) to configure it to Apache Http Server.

When I use this as service with Apache Http server it's not serving the dynamic things(servlets and JSP) but If I start it as standalone Tomcat using batch file(startup.bat) It's works well.

I even tried logged as administrator but it didn't help .

I guess I need to add some permission to the service which I created for Tomcat.

Can you tell me how to add permissions for the Tomcat instance service in Windows ?