Develop Reference

Liferay transactional method

I want to call method filterFindByG_U from DLFileEntryUtil. The problem is, that the method in which I call filterFindBy must be transactional. But I dont know how to do this. I tried to write an annotation #Transactional before the method declaration but this didn't help. Can someone please give me some idea how to do this in Liferay 6.2? The method that should be transactional is:
public List<DLFileEntry> filterEntriesPermissions(User user) {
List<DLFileEntry> filtered = new ArrayList<DLFileEntry>();
try {
filtered = DLFileEntryUtil.filterFindByG_U(user.getGroupId(), user.getUserId());
} catch (SystemException | PortalException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return filtered;
}
I will be thankful for some help and explanation.

Try this method:
DLFileEntryLocalServiceUtil.getGroupFileEntries(user.getGroupId(), user.getUserId(), QueryUtil.ALL_POS, QueryUtil.ALL_POS);

Create instance of Generic class at runtime with getConstructor(): NoSuchMethodException()

am using generics and need to create an instance of a generic class at runtime, so I am trying to use getConstructor(). Unfortunately, I receive a NoSuchMethodException despite having the correct signature, so I am at a loss as to what is wrong. I will appreciate your suggestions so I can get beyond this issue. :) I've provided the constructors for CustomerAssembler. I need to create an instance of this class, dynamically, due to generics being used. I've included the snippet of code that I am using. In it, I called getConstructors() to see whether the constructors exist and their signatures. Both constructors exist and I have used the proper signature, so I don't know why I keep getting this exception. Arggg... Hopefully, you will see what I am doing wrong. :)
Thank you for your time and help,
Mike
// Here are the constructors for CustomerAssembler.
public CustomerAssembler()
{
super();
}
public CustomerAssembler(
Class<Customer> entityClass,
Class<CustomerPreviewDTO> entityPreviewDTOClass,
Class<CustomerDetailDTO> entityDetailDTOClass,
Class<CustomerUpdateDTO> entityUpdateDTOClass,
EntityManager entityManager)
{
super(entityClass, entityPreviewDTOClass, entityDetailDTOClass, entityUpdateDTOClass, entityManager);
}
Here is the exception: NoSuchMethodException:
java.lang.NoSuchMethodException: assemblers.CustomerAssembler.<init>(entities.Customer, dtos.CustomerPreviewDTO, dtos.CustomerDetailDTO, dtos.CustomerUpdateDTO, javax.persistence.EntityManager)
Here is the code...
try
{
Class<CustomerAssembler> customerAssemblerClass = CustomerAssembler.class;
Constructor<CustomerAssembler>[] lst = (Constructor<CustomerAssembler>[]) this.customerAssemblerClass.getConstructors();
/* See what the signature is for the non-default constructor, so I can make sure that
getConstructor() is configured properly. Here is what was reported in the debugger:
[0] = {java.lang.reflect.Constructor#10796}"public assemblers.CustomerAssembler()"
[1] = {java.lang.reflect.Constructor#10797}"public assemblers.CustomerAssembler(java.lang.Class,java.lang.Class,java.lang.Class,java.lang.Class,javax.persistence.EntityManager)"
signature = {java.lang.String#10802}"(Ljava/lang/Class<Lentities/Customer;>
Ljava/lang/Class<dtos/CustomerPreviewDTO;>
Ljava/lang/Class<dtos/CustomerDetailDTO;>
Ljava/lang/Class<dtos/CustomerUpdateDTO;>
Ljavax/persistence/EntityManager;)V"
*/
// Configure our constructor call... this.contactAssemblerClass
Constructor<CustomerAssembler> ca =
customerAssemblerClass.getConstructor(
Customer.class,
CustomerPreviewDTO.class,
CustomerDetailDTO.class,
CustomerUpdateDTO.class,
EntityManager.class);
// Create an instance here...
}
catch (NoSuchMethodException e)
{
e.printStackTrace();
}
catch (InstantiationException e)
{
e.printStackTrace();
}
catch (IllegalAccessException e)
{
e.printStackTrace();
}
catch (InvocationTargetException e)
{
e.printStackTrace();
}
catch (Exception e)
{
e.printStackTrace();
}

customerAssemblerClass.getConstructor(
Customer.class,
CustomerPreviewDTO.class,
CustomerDetailDTO.class,
CustomerUpdateDTO.class,
EntityManager.class);
This looks for a constructor that has the following signature:
CustomerAssemble(Customer c,
CustomerPreviewDTO cpDTO,
CustomerDetailDTO cdDTO,
CustomerUpdateDTO cuDTO,
EntityManager em)
Your constructor doesn't take that as argument. It takes 4 instances of Class, and an instance of EntityManager.
So the code should be
customerAssemblerClass.getConstructor(
Class.class,
Class.class,
Class.class,
Class.class,
EntityManager.class);

Play 2 doesn't call provided action method in Global's onRequest

I'm trying to call different action methods depending on something I put in the session earlier. For this I override the onRequest method in Global like it's recommended in Play's tutorial. I use Java reflection to construct a new method with the same name and parameters but in a different class B. Class B and and the original class with the original actionMethod implement the same interface. So there shouldn't be a problem.
My onRequest in Global looks like:
#Override
public Action onRequest(Request request, final Method actionMethod) {
if (checkSomething) {
return super.onRequest(request, getNewActionMethod(actionMethod));
}
return super.onRequest(request, actionMethod);
}
private Method getNewActionMethod(Method oldActionMethod) {
String name = oldActionMethod.getName();
Class<?>[] parameterTypes = oldActionMethod.getParameterTypes();
Method newActionMethod = null;
try {
newActionMethod = B.class.getMethod(name, parameterTypes);
} catch (NoSuchMethodException | SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return newActionMethod;
}
The Problem here is that Play just ignores my new action method and keeps insisting to call the old one. Am I missing something?
I'm using Play framework 2.2.3.

How could I access a static class located at a package defined in a String?

To clarify: I am writing a plugin framework for my application. Both my application and the plugin are jar files. Currently, I use a script to merge the plugin files into the application jar, and the plugins end up in the package: com.crimson.server.plugins. I need to be able to access the plugin files, but I cant do hardcoded packages. For instance: com.crimson.server.plugins.nst.Plugin. The only other thing I can think of is to leave the plugins as jars and load them somehow. How could this be done?

You can use the reflection API. It is used to describe code which is able to inspect other code in the same system (or itself).
Here is an example how to create an instance of a class from a string.
import com.stakoverflow.plugin.MyPluginClass;
public class Main {
public static void main(String[] args) {
String myclass = "com.stakoverflow.plugin.MyPluginClass";
try {
Class clazz = Class.forName(myclass);
MyPluginClass myPlugin = (MyPluginClass) clazz.newInstance();
myPlugin.helloWorld();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
here is the definition of MyPluginClass:
package com.stakoverflow.plugin;
public class MyPluginClass {
public void helloWorld() {
System.out.println("Hello world!");
}
}
Of course in this example your class must be in the class path. Otherwise the classloader won't be able to find it. But it's possible to load dynamicaly a jar.

As #JEY mentioned you should use reflection API or existing module framework, such as OSGi.
In case of reflection, the classes you are interested in are ClassLoader and its descendants (URLClassLoader, which can load classes from jars). After you have a class loader you can use Class.forName(name, true, classLoader) to load classes and have access to them.
In case of OSGi you do so more declaratively, with Spring OSGi or use API directly.

Load a class from a jar

I´m trying to load a class from a jar, I´m using a classLoader.
I have this parts of code for prepare the classLoader:
private void loadClass(){
try{
JarFile jarFile = new JarFile( Path);
Enumeration e = jarFile.entries();
URL[] urls = { new URL("jar:file:" + Path +"!/") };
classLoader = URLClassLoader.newInstance(urls);
} catch (MalformedURLException ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Now I load a class, and I try to get a new instance
....
loadClass();
Class device = classLoader.loadClass( "org.myPackage.MyClass");
MyMotherClass Device = ( MyMotherClass) device.newInstance();
...
MyClass extends of MyMotherClass, and when I do classLoader.loadClass( "org.myPackage.MyClass"), the MyMotherClass it is in the classLoader.
At the moment, all right.
now, in device.newInstance(), I get a exception. The problem is the other classes that are used by MyClass, are not in the classpath.
What can i do?
I have a another method that load all the needed classes in the classLoader, but does not work when I get the new instance.
I can not change MyClass and the others

Here's some code I use to load a jar dynamically at run-time. I exploit reflection to circumvent the fact that you ain't really supposed to do this (that is, modify the class path after the JVM has started). Just change my.proprietary.exception to something sensible.
/*
* Adds the supplied library to java.class.path.
* This is benign if the library is already loaded.
*/
public static synchronized void loadLibrary(java.io.File jar) throws my.proprietary.exception
{
try {
/*We are using reflection here to circumvent encapsulation; addURL is not public*/
java.net.URLClassLoader loader = (java.net.URLClassLoader)ClassLoader.getSystemClassLoader();
java.net.URL url = jar.toURI().toURL();
/*Disallow if already loaded*/
for (java.net.URL it : java.util.Arrays.asList(loader.getURLs())){
if (it.equals(url)){
return;
}
}
java.lang.reflect.Method method = java.net.URLClassLoader.class.getDeclaredMethod("addURL", new Class[]{java.net.URL.class});
method.setAccessible(true); /*promote the method to public access*/
method.invoke(loader, new Object[]{url});
} catch (final NoSuchMethodException |
java.lang.IllegalAccessException |
java.net.MalformedURLException |
java.lang.reflect.InvocationTargetException e){
throw new my.proprietary.exception(e.getMessage());
}
}