Answers are directly available on [documentation][1]


&gt; I realize it can help make my DAOs work with a plain JDO PersistenceManagerFactory. 

Yes.
TransactionAwarePersistenceManagerFactoryProxy proxy allows DAOs to work with a plain JDO PersistenceManagerFactory reference, while still participating in Spring&#39;s (or a J2EE server&#39;s) resource and transaction management.
You can surely use it in your app. But without knowing your exact needs, we can&#39;t confirm any further.


&gt; Can I still use it to access my factory to create a transaction aware persistence manager

DAOs could seamlessly switch between a JNDI PersistenceManagerFactory and this proxy for a local PersistenceManagerFactory.


&gt; If the object managed by the factory is a singleton, does this change things? Why not just access the PersistenceManagerFactory directly? 

It is usually preferable to write your JDO-based DAOs with Spring&#39;s JdoTemplate, offering benefits such as consistent data access exceptions instead of JDOExceptions at the DAO layer. However, Spring&#39;s resource and transaction management (and Dependency Injection) will work for DAOs written against the plain JDO API as well.


  [1]: http://static.springsource.org/spring/docs/3.0.x/api/org/springframework/orm/jdo/TransactionAwarePersistenceManagerFactoryProxy.html

The [last example of jQuery&#39;s `focus()` documentation][1] states

    $(&#39;#id&#39;).focus()

should make the input focused (active). I can&#39;t seem to get this working.

Even in the console on this site, I&#39;m trying it for the search box

    $(&#39;input[name=&quot;q&quot;]&#39;).focus()

and I&#39;m getting nothing. Any ideas?


  [1]: http://api.jquery.com/focus/

$.focus() not working

When I tried to install **WAMP**, that popped up the following alert,
![MSVCR100.dll is missing][2]

I clicked **OK**, it continued to install WAMP. When I start, the WAMP logo is always &#39;yellow&#39;. It isn&#39;t turning &#39;green&#39;, meaning there&#39;s something wrong. What exactly is the `MSVCR100.dll` file? How do I obtain it and fix this error?

  [2]: http://i.stack.imgur.com/C1dkH.png

WAMP shows error &#39;MSVCR100.dll&#39; is missing when install

I am trying to use the `org.springframework.orm.jdo.TransactionAwarePersistenceManagerFactoryProxy` in my Spring project, but I am not sure how to use it or whether it&#39;s exactly what I am looking for. I realize it can help make my DAOs work with a plain JDO `PersistenceManagerFactory`. Another question is: what happens if the proxy doesn&#39;t get made properly? Can I still use it to access my factory to create a transaction aware persistence manager? If the object managed by the factory is a singleton, does this change things? Why not just access the PersistenceManagerFactory directly? Perhaps `PersistenceManagerFactoryUtils.getPersistenceManager` would be more suited to my needs? Can `getObject` return null?

Unsure if I understand TransactionAwarePersistenceManagerFactoryProxy

<p>I am trying to use the <code>org.springframework.orm.jdo.TransactionAwarePersistenceManagerFactoryProxy</code> in my Spring project, but I am not sure how to use it or whether it's exactly what I am looking for. I realize it can help make my DAOs work with a plain JDO <code>PersistenceManagerFactory</code>. Another question is: what happens if the proxy doesn't get made properly? Can I still use it to access my factory to create a transaction aware persistence manager? If the object managed by the factory is a singleton, does this change things? Why not just access the PersistenceManagerFactory directly? Perhaps <code>PersistenceManagerFactoryUtils.getPersistenceManager</code> would be more suited to my needs? Can <code>getObject</code> return null?</p>


Recently I started exploring Java 8 and I can&#39;t quite understand the concept of &quot;functional interface&quot; that is essential to Java&#39;s implementation of lambda expressions. There is a [pretty comprehensive guide][1] to lambda functions in Java, but I got stuck on [the chapter that gives definition to the concept of functional interfaces][2]. The definition reads:

&gt; More precisely, a functional interface is defined as any interface that has exactly one abstract method.

An then he proceeds to examples, one of which is `Comparator` interface:

&gt;     public interface Comparator&lt;T&gt; {
&gt;         int compare(T o1, T o2);
&gt;         boolean equals(Object obj);
&gt;     } 

I was able to test that I can use a lambda function in place of Comparator argument and it works(i.e. `Collections.sort(list, (a, b) -&gt; a-b)`). 

But in the Comparator interface both `compare` and `equals` methods are abstract, which means it has **two abstract methods**. So how can this be working, if the definition requires an interface to have **exactly one abstract method**? What am I missing here?


  [1]: http://www.lambdafaq.org/
  [2]: http://www.lambdafaq.org/what-is-a-functional-interface/

Precise definition of &quot;functional interface&quot; in Java 8

When upgrading from Surefire 2.6 to Surefire 2.13, I get a `TypeNotPresentExceptionProxy` when running my unit tests.

    java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy
        at sun.reflect.annotation.AnnotationParser.parseClassArray(AnnotationParser.java:653)
        at sun.reflect.annotation.AnnotationParser.parseArray(AnnotationParser.java:460)
        at sun.reflect.annotation.AnnotationParser.parseMemberValue(AnnotationParser.java:286)
        at sun.reflect.annotation.AnnotationParser.parseAnnotation(AnnotationParser.java:222)
        at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:69)
        at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:52)
        at java.lang.Class.initAnnotationsIfNecessary(Class.java:3070)
        at java.lang.Class.getAnnotation(Class.java:3029)
        at org.apache.maven.surefire.common.junit4.JUnit4TestChecker.isValidJUnit4Test(JUnit4TestChecker.java:64)

In `JUnit4TestChecker`, line 64 looks like this:

&lt;!-- language: lang-java --&gt;

    Annotation runWithAnnotation = testClass.getAnnotation( runWith );
    
So Surefire inspects the `@RunWith` annotation to make sure its type is valid. Our tests use Spring, so `@RunWith` looks like this in our test classes:

&lt;!-- language: lang-java --&gt;

    @RunWith(SpringJUnit4ClassRunner.class)

It seems like Surefire isn&#39;t finding the `SpringJUnit4ClassRunner` class. I&#39;m not sure why since under Surefire 2.6, the tests run fine.

Any ideas?

TypeNotPresentExceptionProxy

Can somebody explain this to me please :

    Intent intent = new Intent(Context, AlarmReceiver.class);

I never understood and I seriously think I never will if somebody doesn&#39;t try to explain this to me in depth. This whole context thing is so confusing to me. Sometimes it works like this :

		

    Intent intent = new Intent(getBaseContext(), AlarmReceiver.class);

Sometimes it wont work like that but it accepts only :

		Intent intent = new Intent(context, AlarmReceiver.class);

Sometimes its :

    Intent intent = new Intent(this, AlarmReceiver.class);

etc. etc. and many other.

I understand basics of context but how many are there? And why does eclipse throw me an error once and another time its fine? Why do we need to declare context sometimes? :

    Context context;

I&#39;m unable to find the right context for all situations how do I know what is the right one in every situation?

Android Intent Context Confusing

I am trying to create a folder for each username a user logs in as. Currently I have

    private String destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
    File theFile = new File(destination + username); // will create a sub folder for each user 

but the `File theFile` bit does not create a new folder for the username. How would I do this ?

I have tried 

    private String destination;

    public void File() 
    {
        destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
        File theFile = new File(destination + username); // will create a sub folder for each user (currently does not work, below hopefully is a solution) 
        theFile.mkdirs();
    }

but I need to use the destination later on in the program, how would I do that?

This is my whole code:


    /*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */
    package richard.fileupload;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import javax.annotation.PostConstruct;
    import javax.faces.application.FacesMessage;
    import javax.faces.context.FacesContext;
    import javax.faces.event.ActionEvent;
    import javax.faces.application.FacesMessage;
    import javax.faces.bean.ManagedBean;
    import javax.faces.bean.ViewScoped;
    import javax.faces.context.FacesContext;
    import java.io.File;
    import org.primefaces.event.FileUploadEvent;
    
    @ViewScoped
    @ManagedBean(name = &quot;fileUploadController&quot;)
    public class FileUploadController {
    
        /*
         public void handleFileUpload(FileUploadEvent event) {
         System.out.println(&quot;called&quot;);
         FacesMessage msg = new FacesMessage(&quot;Succesful&quot;, event.getFile().getFileName() + &quot; is uploaded.&quot;);
         FacesContext.getCurrentInstance().addMessage(null, msg);
         }
         }
         */
        private String username;
        private String destination;
    
        @PostConstruct
        public void init() {
            System.out.println(&quot;called get username&quot;);
            username = FacesContext.getCurrentInstance().getExternalContext().getRemoteUser();
        }
        
        public void File() {
        destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
        File theFile = new File(destination + username); // will create a sub folder for each user (currently does not work, below hopefully is a solution) 
        theFile.mkdirs();
    }
    
        public File getDirectory(String destination, String username) {
            System.out.println(&quot;called get directory&quot;);
            // currently not working, is not calling the username or destination 
            //set the user directory from the destinarion and the logged user name
            File directory = new File(destination, username);
            //check if the location exists
            if (!directory.exists()) {
                //let&#39;s try to create it
                try {
                    directory.mkdir();
                } catch (SecurityException secEx) {
                    //handle the exception
                    secEx.printStackTrace(System.out);
                    directory = null;
                }
            }
            return directory;
        }
    
        public void handleFileUpload(FileUploadEvent event) {
            System.out.println(&quot;called handle file&quot;);
            FacesMessage msg = new FacesMessage(&quot;Succesful&quot;, event.getFile().getFileName() + &quot; is uploaded.&quot;); //Displays to user on the webpage
            FacesContext.getCurrentInstance().addMessage(null, msg);
            try {
                copyFile(event.getFile().getFileName(), event.getFile().getInputstream());
            } catch (IOException e) {
                //handle the exception
                e.printStackTrace();
            }
        }
    
        public void copyFile(String fileName, InputStream in) {
            try {
    
    
                // write the inputStream to a FileOutputStream
                OutputStream out = new FileOutputStream(new File(destination + fileName)); // cannot find path when adding username atm
                System.out.println(&quot;Called CopyFile&quot;); //testing 
                System.out.println(destination + fileName);
    
                int read = 0;
                byte[] bytes = new byte[1024];
    
                while ((read = in.read(bytes)) != -1) {
                    out.write(bytes, 0, read);
                }
    
                in.close();
                out.flush();
                out.close();
    //make sure new file is created, (displays in glassfish server console not to end user)
                System.out.println(&quot;New file created!&quot;);//testing
            } catch (IOException e) {
                e.printStackTrace();
    
                FacesMessage error = new FacesMessage(&quot;The files were not uploaded!&quot;);
                FacesContext.getCurrentInstance().addMessage(null, error);
            }
        }
    }


FINAL EDIT (Hopefully)

     public void copyFile(String fileName, InputStream in) {
            try {
    
                destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
                File theFile = new File(destination + &quot;/&quot; + username); 
                theFile.mkdirs();// will create a sub folder for each user (currently does not work, below hopefully is a solution) (DOES NOW WORK)
                
                System.out.println(&quot;Completed File&quot;);
                // write the inputStream to a FileOutputStream
                OutputStream out = new FileOutputStream(new File(destination + fileName)); // cannot find path when adding username atm
                System.out.println(&quot;Called CopyFile&quot;); //testing 
                System.out.println(destination + fileName);
    
                int read = 0;
                byte[] bytes = new byte[1024];
    
                while ((read = in.read(bytes)) != -1) {
                    out.write(bytes, 0, read);
                }
    
                in.close();
                out.flush();
                out.close();
    //make sure new file is created, (displays in glassfish server console not to end user)
                System.out.println(&quot;New file created!&quot;);//testing
            } catch (IOException e) {
                e.printStackTrace();
    
                FacesMessage error = new FacesMessage(&quot;The files were not uploaded!&quot;);
                FacesContext.getCurrentInstance().addMessage(null, error);
            }
        }
    }

Just how can i print out the new destination and use this later on as currently it creates the new folder but does not select it to use


EDIT SOLVED THIS TOO :


        NewDestination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot; + username;

Added the above code and now it all works


Create intermediate folders if one doesn&#39;t exist

&gt; **Possible Duplicate:**  
&gt; [List all files from a directory recursively with Java](https://stackoverflow.com/questions/2534632/list-all-files-from-a-directory-recursively-with-java)  

&lt;!-- End of automatically inserted text --&gt;

How can i return a file array that include all files on the folder and also sub folders my method just work for folder and it doesn&#39;t include sub folders .


	public File[] listf(String directoryName) {
		
		// .............list file
		File directory = new File(directoryName);
		
		// get all the files from a directory
		File[] fList = directory.listFiles();
		
		for (File file : fList) {
			if (file.isFile()) {
				System.out.println(file.getAbsolutePath());
			} else if (file.isDirectory()) {
				listf(file.getAbsolutePath());
			}
		}
		System.out.println(fList);
		return fList;
	}                        

list all files in the folder and also sub folders

I&#39;m using Spring 3.1.1.RELEASE, JUnit 4.8.1 and the HSQL 2.7.7 in-memory database.  I have one test class annotated as

	@RunWith(SpringJUnit4ClassRunner.class)
	@ContextConfiguration({ &quot;classpath:test-trainingSessionServiceContext.xml&quot; })
	@DirtiesContext(classMode = ClassMode.AFTER_EACH_TEST_METHOD)
	public class TrainingSessionServiceTest  
	{

The problem is, when I run &quot;mvn clean test&quot;, it seems that all test classes run after the above class fail because the in-memory database is destroyed and not re-created.  I get errors like

	org.hibernate.exception.SQLGrammarException: user lacks privilege or object not found: CB_ORGANIZATION&quot; type=&quot;javax.persistence.PersistenceException&quot;&gt;javax.persistence.PersistenceException: 	org.hibernate.exception.SQLGrammarException: user lacks privilege or object not found: CB_ORGANIZATION
        at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1360)
        at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:817)
        at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:771)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
        at $Proxy46.find(Unknown Source)
        at org.mainco.subco.organization.repo.OrganizationDaoImpl.findById(OrganizationDaoImpl.java:77)
        at org.mainco.subco.pd.repo.LinkDaoTest.createDummyLink(LinkDaoTest.java:686)
        at org.mainco.subco.pd.repo.LinkDaoTest.testSaveLink(LinkDaoTest.java:67)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)

Here is how I setup the test class (run after the above class) that gives the exceptions …

	@RunWith(SpringJUnit4ClassRunner.class)
	@ContextConfiguration({ &quot;classpath:test-context.xml&quot; })
	public class LinkDaoTest extends AbstractTransactionalJUnit4SpringContextTests
	{

Is there any way I can restore my application context to its original state before each test class is run?  I don&#39;t want to make the &quot;TrainingSessionServiceTest&quot; class extend AbstractTransactionalJUnit4SpringContextTests.  Here is the relevant part of my application context:

	&lt;bean id=&quot;dataSource&quot; class=&quot;org.springframework.jdbc.datasource.DriverManagerDataSource&quot;&gt;
        &lt;property name=&quot;driverClassName&quot; value=&quot;org.hsqldb.jdbcDriver&quot;/&gt;
        &lt;property name=&quot;url&quot; value=&quot;jdbc:hsqldb:mem:pd&quot; /&gt;
        &lt;property name=&quot;username&quot; value=&quot;sa&quot; /&gt;
        &lt;property name=&quot;password&quot; value=&quot;&quot; /&gt;
    &lt;/bean&gt;
    
	&lt;bean id=&quot;entityManagerFactory&quot; class=&quot;org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean&quot;&gt;
        &lt;property name=&quot;jpaVendorAdapter&quot;&gt;
            &lt;bean class=&quot;org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter&quot;/&gt;
        &lt;/property&gt;
        &lt;property name=&quot;persistenceXmlLocation&quot; value=&quot;classpath:META-INF/test-persistence.xml&quot;/&gt;
        &lt;property name=&quot;persistenceUnitName&quot; value=&quot;testingDatabase&quot;/&gt;
        &lt;property name=&quot;dataSource&quot; ref=&quot;dataSource&quot;/&gt;
    &lt;/bean&gt;

	&lt;bean id=&quot;sharedEntityManager&quot; class=&quot;org.springframework.orm.jpa.support.SharedEntityManagerBean&quot;&gt;
       &lt;property name=&quot;entityManagerFactory&quot; ref=&quot;entityManagerFactory&quot;/&gt;
    &lt;/bean&gt;

	&lt;bean id=&quot;transactionManager&quot; class=&quot;org.springframework.orm.jpa.JpaTransactionManager&quot;&gt;
        &lt;property name=&quot;entityManagerFactory&quot; ref=&quot;entityManagerFactory&quot;/&gt;
    &lt;/bean&gt;

	&lt;tx:annotation-driven /&gt;

	&lt;jdbc:embedded-database id=&quot;embedded&quot; type=&quot;HSQL&quot;/&gt; 
	&lt;jdbc:initialize-database data-source=&quot;dataSource&quot;&gt;
		&lt;jdbc:script location=&quot;classpath:db-test-data.sql&quot;/&gt;	
	&lt;/jdbc:initialize-database&gt;  

How do you reset Spring JUnit application context after a test class dirties it?

I am new to Spring MVC - and I am trying to pass a date from my javascript as a request Param

My controller looks something like - 

    public @ResponseBody List&lt;RecordDisplay&gt; getRecords(
    			@RequestParam(value=&quot;userID&quot;) Long userID,
    			@RequestParam(value=&quot;fromDate&quot;) Date fromDate,
    			@RequestParam(value=&quot;toDate&quot;) Date toDate) {

The question I have is how do I make the call from javascript - as in what should the URL look like 

    for eg. - /getRecords?userID=1&amp;fromDate=06022013&amp;toDate=08022013&#39;

Do I need a way to parse the date so Spring can recognize it?


Passing date to request param in Spring MVC

I&#39;m trying to upgrade my spring mvc project to utilize the new annotations and get rid of my xml. Previously I was loading my static resources in my `web.xml` with the line:

    &lt;mvc:resources mapping=&quot;/resources/**&quot; location=&quot;/resources/&quot; /&gt; 

Now, I&#39;m utilizing the `WebApplicationInitializer` class and `@EnableWebMvc` annotation to startup my service without any xml files, but can&#39;t seem to figure out how to load my resources. 

Is there an annotation or new configuration to pull these resources back in without having to use xml?

Annotation Configuration Replacement for mvc:resources - Spring

All

I created a jar file with the following MANIFEST.MF inside:

    Manifest-Version: 1.0
    Ant-Version: Apache Ant 1.8.3
    Created-By: 1.6.0_25-b06 (Sun Microsystems Inc.)
    Main-Class: my.Main
    Class-Path: . lib/spring-core-3.2.0.M2.jar lib/spring-beans-3.2.0.M2.jar

In its root there is a file called my.config which is referenced in my spring-context.xml like this:

    &lt;bean id=&quot;...&quot; class=&quot;...&quot;&gt;
		&lt;property name=&quot;resource&quot; value=&quot;classpath:my.config&quot; /&gt;
	&lt;/bean&gt;

If I run the jar, everything looks fine escept the loading of that specific file:

    Caused by: java.io.FileNotFoundException: class path resource [my.config] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/D:/work/my.jar!/my.config
            at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:205)
        at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:52)
        at eu.stepman.server.configuration.BeanConfigurationFactoryBean.getObject(BeanConfigurationFactoryBean.java:32)
        at eu.stepman.server.configuration.BeanConfigurationFactoryBean.getObject(BeanConfigurationFactoryBean.java:1)
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:142)
        ... 22 more

- classes are loaded the from inside the jar
- spring and other dependencies  are loaded from separated jars
- spring context is loaded (new ClassPathXmlApplicationContext(&quot;spring-context/applicationContext.xml&quot;))
- my.properties is loaded into PropertyPlaceholderConfigurer (&quot;classpath:my.properties&quot;)
- if I put my .config file outside the file system, and change the resource url to &#39;file:&#39;, everything seems to be fine...

Any tips?


File inside jar is not visible for spring

The more I read, the more confused I am. 

Note that all the question is related to how service and facades fit on the MVC pattern.

My understanding is that a Facade is not a super-smart object, it is simply a way of exposing a simple interface/api to perform a complex operation (example: perform a 10$ payment, it is a complex operation that involves a number of operations, but such complexity can be handled by a facade which will just call the corresponding object in a particular order...etc...)

Now, a service is a way to perform calls to several DAOs in order to get complex data structures (I am not too sure of this, but it is what I understand so far).

Question then is, what is the difference between a facade and a service? At the end of the day, the facade can perfectly access several DAOs in order to perform a complex operation by providing a simple interface, and a service seems to to something similar.

Same happens with transactions, I understand that a service is the place to start transactions, but I equally feel that they could also be placed on facades, after all, a facade may call several DAOs too. 

So which stack would make more sense

controller-facade-dao 
controller-service-dao

or maybe

controller-facadade-dao AND sometimes controller-facade-service-dao ??


Are the roles of a service and a fa&#231;ade similar?

What and when is the best scenario to use DiscriminatorValue annotation in hibernate?

When to use DiscriminatorValue annotation in hibernate

I have a doubt, because name attribute is there in both @Entity and @Table

For example, I&#39;m allowed to have same value for name attribute 

    @Entity(name = &quot;someThing&quot;)
    @Table(name = &quot;someThing&quot;)

and I can have different names as well for same class

  

     @Entity(name = &quot;someThing&quot;)
     @Table(name = &quot;otherThing&quot;)

Can anybody tell me what is the difference between these two and why we have same attribute in both?

Name attribute in @Entity and @Table

I am new to the Java world and JPA. I was studying JPA and came across many new terms like Entity, persistence. While reading, I could not understand the exact definition for **Persistence Context**.

Can anyone explain it in simple laymen terms? What is it to do with the data used in the `@Entity`?

For example, I find this definition too complicated to understand:
&gt; A persistence context is a set of entities such that for any persistent identity there is a unique entity instance.

What is Persistence Context?

In few project I have been successfully using 

    @PersistenceUnit(unitName = &quot;MiddlewareJPA&quot;)
    EntityManagerFactory emf;
    ...
    EntityManager entityManager = emf.createEntityManager();

to obtain `EntityManager` for Database connection, but some days ago I was trying to move my project to `Jboss EAP 6.2` and it couldn&#39;t create `EntityManager`. I was googling it and I found that I should try change `@PersistenceUnit` to

    @PersistenceContext(unitName = &quot;MiddlewareJPA&quot;)
    private EntityManager entityManager;
 
to obtain *EntityManager*. It worked but I don&#39;t know why. What is the difference bettween `PersistenceUnit` and `PersistenceContext`? What are pros and cons of each one? Where should we be using one of them? 


     

PersistenceUnit vs PersistenceContext

How do I persist changes made within the same object inheriting from `TestCase` in unitttest?

    from unittest import TestCase, main as unittest_main
    
    
    class TestSimpleFoo(TestCase):
        foo = &#39;bar&#39;
    
        def setUp(self):
            pass
    
        def test_a(self):
            self.assertEqual(self.foo, &#39;bar&#39;)
            self.foo = &#39;can&#39;
    
        def test_f(self):
            self.assertEqual(self.foo, &#39;can&#39;)
    
    
    if __name__ == &#39;__main__&#39;:
        unittest_main()

I.e.: I want those two tests above to pass

Persist variable changes between tests in unittest?

I was going through a document and I came across a term called `DAO`. I found out that it is a Data Access Object. Can someone please explain me what this actually is? 

I know that it is some kind of an interface for accessing data from different types of sources, in the middle of this little research of mine I bumped into a concept called data source or data source object, and things got messed up in my mind. 

I really want to know what a `DAO` is programmatically in terms of where it is used. How it is used? Any links to pages that explain this concept from the very basic stuff is also appreciated.

Data access object (DAO) in Java

I have below code in my DAO:  

    String sql = &quot;SELECT COUNT(*) FROM CustomerData &quot; +
                 &quot;WHERE custId = :custId AND deptId = :deptId&quot;;
    Query query = session.createQuery(sql);
    query.setParameter(&quot;custId&quot;, custId);
    query.setParameter(&quot;deptId&quot;, deptId);
    long count = (long) query.uniqueResult(); // ERROR THROWN HERE
    
Hibernate throws  below exception at the marked line:
    
&gt; org.hibernate.NonUniqueResultException: query did not return a unique result: 
        
   I am not sure whats happening as `count(*)` will always return only one row. 

Also when i run this query on db directly, it return result as 1. So whats the issue?

org.hibernate.NonUniqueResultException: query did not return a unique result: 2?

I&#39;m trying my hand at using [Android Room][1] and after following [this tutorial][2] I&#39;m getting the following error when i try to build the app:

`Error:(23, 27) error: There is a problem with the query: [SQLITE_ERROR] SQL error or missing database (no such table: screen_items)`

The name is fine and should exist. After making my changes I cleaned the project and made sure it was completely uninstalled from the device.

In my `Activity` I&#39;m initialising the things in `onCreate` with this line:

    db = AppDatabase.getDatabase(getApplicationContext());

Here is my code:

**AppDatabase**

    @Database(entities = {PermitItem.class}, version = 1, exportSchema = false)
    public abstract class AppDatabase extends RoomDatabase {
      public static String DATABASE_NAME = &quot;my_database&quot;;
      public final static String TABLE_ITEMS = &quot;screen_items&quot;;

      private static AppDatabase INSTANCE;

      public abstract PermitItemDao permitItemModel();

      public static AppDatabase getDatabase(Context context) {
        if (INSTANCE == null) {
            INSTANCE = Room.databaseBuilder(context, AppDatabase.class, DATABASE_NAME).allowMainThreadQueries().build();
        }
        return INSTANCE;
      }

      public static void destroyInstance() {
        INSTANCE = null;
      }
    }

**PermitItem**

    @Entity
    public class PermitItem {
      @PrimaryKey(autoGenerate = true)
      public final int id;
      private String posX, posY, width, height, content, type;

      public PermitItem(int id, String posX, String posY, String width, String height, String content, String type) {
        this.id = id;
        this.posX = posX;
        this.posY = posY;
        this.width = width;
        this.height = height;
        this.content = content;
        this.type = type;
      }

      public static PermitItemBuilder builder(){
        return new PermitItemBuilder();
      }

      public static class PermitItemBuilder{
        int id;
        String posX, posY, width, height, content, type;


        public PermitItemBuilder setId(int id) {
            this.id = id;
            return this;
        }


        public PermitItemBuilder setPosX(String posX) {
            this.posX = posX;
            return this;
        }


        public PermitItemBuilder setPosY(String posY) {
            this.posY = posY;
            return this;
        }


        public PermitItemBuilder setWidth(String width) {
            this.width = width;
            return this;
        }


        public PermitItemBuilder setHeight(String height) {
            this.height = height;
            return this;
        }


        public PermitItemBuilder setContent(String content) {
            this.content = content;
            return this;
        }


        public PermitItemBuilder setType(String type) {
            this.type = type;
            return this;
        }

        public PermitItem build() {
            return new PermitItem(id, posX, posY, width, height, content, type);
        }
      }

      public long getId() {
        return id;
      }

      public String getPosX() {
        return posX;
      }

      public void setPosX(String posX) {
        this.posX = posX;
      }

      public String getPosY() {
        return posY;
      }

      public void setPosY(String posY) {
        this.posY = posY;
      }

      public String getWidth() {
        return width;
      }

      public void setWidth(String width) {
        this.width = width;
      }

      public String getHeight() {
        return height;
      }

      public void setHeight(String height) {
        this.height = height;
      }

      public String getContent() {
        return content;
      }

      public void setContent(String content) {
        this.content = content;
      }

      public String getType() {
        return type;
      }

      public void setType(String type) {
        this.type = type;
      }

      @Override
      public String toString() {
        return &quot;PermitItem{&quot; +
                &quot;id=&quot; + id +
                &quot;, posX=&#39;&quot; + posX + &#39;\&#39;&#39; +
                &quot;, posY=&#39;&quot; + posY + &#39;\&#39;&#39; +
                &quot;, width=&#39;&quot; + width + &#39;\&#39;&#39; +
                &quot;, height=&#39;&quot; + height + &#39;\&#39;&#39; +
                &quot;, content=&#39;&quot; + content + &#39;\&#39;&#39; +
                &quot;, type=&#39;&quot; + type + &#39;\&#39;&#39; +
                &#39;}&#39;;
      }


    }

**PermitItemDao**

    @Dao
    public interface PermitItemDao {

      @Insert(onConflict = OnConflictStrategy.REPLACE)
      long addPermitItem(PermitItem permitItem);

      @Query(&quot;select * from &quot; + TABLE_ITEMS)
      ArrayList&lt;PermitItem&gt; getAllPermitItems();

      @Query(&quot;select * from &quot; + TABLE_ITEMS + &quot; where id = :id&quot;)
      PermitItem getPermitItemById(int id);

      @Update(onConflict = OnConflictStrategy.REPLACE)
      void updatePermitItem(PermitItem permitItem);

      @Query(&quot;delete from &quot; + TABLE_ITEMS)
      void removeAllPermitItems();
    }


  [1]: https://developer.android.com/topic/libraries/architecture/room.html
  [2]: http://www.vogella.com/tutorials/AndroidSQLite/article.html

Android Room SQLite_ERROR no such table

    Error:Not sure how to convert a Cursor to this method&#39;s return type
    Error:Execution failed for task &#39;:app:compileDebugJavaWithJavac&#39;.
    Compilation failed; see the compiler error output for details.

Using `Room` I&#39;m getting this error and I&#39;d like to find out which method causes it.  

I have multiple `DAO`s, with approximately 60 methods in total, and this error just popped up after adding a method (copy&amp;pasted from another one that worked perfectly, just changed the field to set).  

I could post the whole class of `DAO`s, but **I&#39;m asking for a way to know which method failed**. I tried with `Run with --stacktrace`, `Run with --info` and `--debug option`, but none of these show any valuable information.

The method I added is a `@Query` `UPDATE` with `Int` return type, as suggested in the [documentation][1] 

&gt; UPDATE or DELETE queries can return void or int. If it is an int, the
value is the number of rows affected by this query.


EDIT: I&#39;d like to add that I tried deleting the method, bringing the DAO back to the working state, but it still gives me this error.

EDIT2: Adding gradle console output because unreadable in comments:

   
    error: Not sure how to convert a Cursor to this method&#39;s return type
    error: Not sure how to convert a Cursor to this method&#39;s return type
    2 errors

    :app:compileDebugJavaWithJavac FAILED

    FAILURE: Build failed with an exception.

    * What went wrong:
    Execution failed for task &#39;:app:compileDebugJavaWithJavac&#39;.
    Compilation failed; see the compiler error output for details.

    * Try:
    Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

    * Get more help at https://help.gradle.org

    BUILD FAILED in 22s

  [1]: https://developer.android.com/reference/android/arch/persistence/room/Query.html

Content Type	Original Author	Original Content on Stackoverflow
Question	megazord	View Question on Stackoverflow
Solution 1 - Java	Chand Priyankara	View Answer on Stackoverflow

Unsure if I understand TransactionAwarePersistenceManagerFactoryProxy

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