Gradle : how to use BuildConfig in an android-library with a flag that gets set in an app - android-gradle-plugin

My (gradle 1.10 and gradle plugin 0.8)-based android project consists of a big android-library that is a dependency for 3 different android-apps
In my library, I would love to be able to use a structure like this
if (BuildConfig.SOME_FLAG) {
callToBigLibraries()
}
as proguard would be able to reduce the size of the produced apk, based on the final value of SOME_FLAG
But I can't figure how to do it with gradle as :
* the BuildConfig produced by the library doesn't have the same package name than the app
* I have to import the BuildConfig with the library package in the library
* The apk of an apps includes the BuildConfig with the package of the app but not the one with the package of the library.
I tried without success to play with BuildTypes and stuff like
release {
// packageNameSuffix "library"
buildConfigField "boolean", "SOME_FLAG", "true"
}
debug {
//packageNameSuffix "library"
buildConfigField "boolean", "SOME_FLAG", "true"
}
What is the right way to builds a shared BuildConfig for my library and my apps whose flags will be overridden at build in the apps?

As a workaround, you can use this method, which uses reflection to get the field value from the app (not the library):
/**
* Gets a field from the project's BuildConfig. This is useful when, for example, flavors
* are used at the project level to set custom fields.
* #param context Used to find the correct file
* #param fieldName The name of the field-to-access
* #return The value of the field, or {#code null} if the field is not found.
*/
public static Object getBuildConfigValue(Context context, String fieldName) {
try {
Class<?> clazz = Class.forName(context.getPackageName() + ".BuildConfig");
Field field = clazz.getField(fieldName);
return field.get(null);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
To get the DEBUG field, for example, just call this from your Activity:
boolean debug = (Boolean) getBuildConfigValue(this, "DEBUG");
I have also shared this solution on the AOSP Issue Tracker.

Update: With newer versions of the Android Gradle plugin publishNonDefault is deprecated and has no effect anymore. All variants are now published.
The following solution/workaround works for me. It was posted by some guy in the google issue tracker:
Try setting publishNonDefault to true in the library project:
android {
...
publishNonDefault true
...
}
And add the following dependencies to the app project that is using the library:
dependencies {
releaseCompile project(path: ':library', configuration: 'release')
debugCompile project(path: ':library', configuration: 'debug')
}
This way, the project that uses the library includes the correct build type of the library.

You can't do what you want, because BuildConfig.SOME_FLAG isn't going to get propagated properly to your library; build types themselves aren't propagated to libraries -- they're always built as RELEASE. This is bug https://code.google.com/p/android/issues/detail?id=52962
To work around it: if you have control over all of the library modules, you could make sure that all the code touched by callToBigLibraries() is in classes and packages that you can cleave off cleanly with ProGuard, then use reflection so that you can access them if they exist and degrade gracefully if they don't. You're essentially doing the same thing, but you're making the check at runtime instead of compile time, and it's a little harder.
Let me know if you're having trouble figuring out how to do this; I could provide a sample if you need it.

I use a static BuildConfigHelper class in both the app and the library, so that I can have the packages BuildConfig set as final static variables in my library.
In the application, place a class like this:
package com.yourbase;
import com.your.application.BuildConfig;
public final class BuildConfigHelper {
public static final boolean DEBUG = BuildConfig.DEBUG;
public static final String APPLICATION_ID = BuildConfig.APPLICATION_ID;
public static final String BUILD_TYPE = BuildConfig.BUILD_TYPE;
public static final String FLAVOR = BuildConfig.FLAVOR;
public static final int VERSION_CODE = BuildConfig.VERSION_CODE;
public static final String VERSION_NAME = BuildConfig.VERSION_NAME;
}
And in the library:
package com.your.library;
import android.support.annotation.Nullable;
import java.lang.reflect.Field;
public class BuildConfigHelper {
private static final String BUILD_CONFIG = "com.yourbase.BuildConfigHelper";
public static final boolean DEBUG = getDebug();
public static final String APPLICATION_ID = (String) getBuildConfigValue("APPLICATION_ID");
public static final String BUILD_TYPE = (String) getBuildConfigValue("BUILD_TYPE");
public static final String FLAVOR = (String) getBuildConfigValue("FLAVOR");
public static final int VERSION_CODE = getVersionCode();
public static final String VERSION_NAME = (String) getBuildConfigValue("VERSION_NAME");
private static boolean getDebug() {
Object o = getBuildConfigValue("DEBUG");
if (o != null && o instanceof Boolean) {
return (Boolean) o;
} else {
return false;
}
}
private static int getVersionCode() {
Object o = getBuildConfigValue("VERSION_CODE");
if (o != null && o instanceof Integer) {
return (Integer) o;
} else {
return Integer.MIN_VALUE;
}
}
#Nullable
private static Object getBuildConfigValue(String fieldName) {
try {
Class c = Class.forName(BUILD_CONFIG);
Field f = c.getDeclaredField(fieldName);
f.setAccessible(true);
return f.get(null);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
Then, anywhere in your library where you want to check BuildConfig.DEBUG, you can check BuildConfigHelper.DEBUG and access it from anywhere without a context, and the same for the other properties. I did it this way so that the library will work with all my applications, without needing to pass a context in or set the package name some other way, and the application class only needs the import line changed to suit when adding it into a new application
Edit: I'd just like to reiterate, that this is the easiest (and only one listed here) way to get the values to be assigned to final static variables in the library from all of your applications without needing a context or hard coding the package name somewhere, which is almost as good as having the values in the default library BuildConfig anyway, for the minimal upkeep of changing that import line in each application.

For the case where the applicationId is not the same as the package (i.e. multiple applicationIds per project) AND you want to access from a library project:
Use Gradle to store the base package in resources.
In main/AndroidManifest.xml:
android {
applicationId "com.company.myappbase"
// note: using ${applicationId} here will be exactly as above
// and so NOT necessarily the applicationId of the generated APK
resValue "string", "build_config_package", "${applicationId}"
}
In Java:
public static boolean getDebug(Context context) {
Object obj = getBuildConfigValue("DEBUG", context);
if (obj instanceof Boolean) {
return (Boolean) o;
} else {
return false;
}
}
private static Object getBuildConfigValue(String fieldName, Context context) {
int resId = context.getResources().getIdentifier("build_config_package", "string", context.getPackageName());
// try/catch blah blah
Class<?> clazz = Class.forName(context.getString(resId) + ".BuildConfig");
Field field = clazz.getField(fieldName);
return field.get(null);
}

use both
my build.gradle
// ...
productFlavors {
internal {
// applicationId "com.elevensein.sein.internal"
applicationIdSuffix ".internal"
resValue "string", "build_config_package", "com.elevensein.sein"
}
production {
applicationId "com.elevensein.sein"
}
}
I want to call like below
Boolean isDebug = (Boolean) BuildConfigUtils.getBuildConfigValue(context, "DEBUG");
BuildConfigUtils.java
public class BuildConfigUtils
{
public static Object getBuildConfigValue (Context context, String fieldName)
{
Class<?> buildConfigClass = resolveBuildConfigClass(context);
return getStaticFieldValue(buildConfigClass, fieldName);
}
public static Class<?> resolveBuildConfigClass (Context context)
{
int resId = context.getResources().getIdentifier("build_config_package",
"string",
context.getPackageName());
if (resId != 0)
{
// defined in build.gradle
return loadClass(context.getString(resId) + ".BuildConfig");
}
// not defined in build.gradle
// try packageName + ".BuildConfig"
return loadClass(context.getPackageName() + ".BuildConfig");
}
private static Class<?> loadClass (String className)
{
Log.i("BuildConfigUtils", "try class load : " + className);
try {
return Class.forName(className);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return null;
}
private static Object getStaticFieldValue (Class<?> clazz, String fieldName)
{
try { return clazz.getField(fieldName).get(null); }
catch (NoSuchFieldException e) { e.printStackTrace(); }
catch (IllegalAccessException e) { e.printStackTrace(); }
return null;
}
}

For me this is the ONLY ONE AND ACCEPTABLE* SOLUTION TO determine the ANDROID APPLICATION BuildConfig.class:
// base entry point
// abstract application
// which defines the method to obtain the desired class
// the definition of the application is contained in the library
// that wants to access the method or in a superior library package
public abstract class BasApp extends android.app.Application {
/*
* GET BUILD CONFIG CLASS
*/
protected Class<?> getAppBuildConfigClass();
// HELPER METHOD TO CAST CONTEXT TO BASE APP
public static BaseApp getAs(android.content.Context context) {
BaseApp as = getAs(context, BaseApp.class);
return as;
}
// HELPER METHOD TO CAST CONTEXT TO SPECIFIC BASEpp INHERITED CLASS TYPE
public static <I extends BaseApp> I getAs(android.content.Context context, Class<I> forCLass) {
android.content.Context applicationContext = context != null ?context.getApplicationContext() : null;
return applicationContext != null && forCLass != null && forCLass.isAssignableFrom(applicationContext.getClass())
? (I) applicationContext
: null;
}
// STATIC HELPER TO GET BUILD CONFIG CLASS
public static Class<?> getAppBuildConfigClass(android.content.Context context) {
BaseApp as = getAs(context);
Class buildConfigClass = as != null
? as.getAppBuildConfigClass()
: null;
return buildConfigClass;
}
}
// FINAL APP WITH IMPLEMENTATION
// POINTING TO DESIRED CLASS
public class MyApp extends BaseApp {
#Override
protected Class<?> getAppBuildConfigClass() {
return somefinal.app.package.BuildConfig.class;
}
}
USAGE IN LIBRARY:
Class<?> buildConfigClass = BaseApp.getAppBuildConfigClass(Context);
if(buildConfigClass !- null) {
// do your job
}
*there are couple of things need to be watched out:
getApplicationContext() - could return a context which is not an App ContexWrapper implementation - see what Applicatio class extends & get to know of the possibilities of context wrapping
the class returned by final app could be loaded by different class loaders than those who will use it - depends of loader implementation and some principals typical (chierarchy, visibility) for loaders
everything depends on the implemmentation of as in this case simple DELEGATION!!! - the solution could be more sophisticetaded - i wanted only to show here the usage of DELEGATION pattern :)
** why i downwoted all of reflection based patterns because they all have weak points and they all in some certain conditions will fail:
Class.forName(className); - because of not speciified loader
context.getPackageName() + ".BuildConfig"
a) context.getPackageName() - "by default - else see b)" returns not package defined in manifest but application id (somtimes they both are the same), see how the manifest package property is used and its flow - at the end apt tool will replace it with applicaton id (see ComponentName class for example what the pkg stands for there)
b) context.getPackageName() - will return what the implementaio wants to :P
*** what to change in my solution to make it more flawless
replace class with its name that will drop the problems wchich could appear when many classes loaded with different loaders accessing / or are used to obtain a final result involving class (get to know what describes the equality between two classes (for a compiler at runtime) - in short a class equality defines not a self class but a pair which is constituted by the loader and the class. (some home work - try load a inner class with different loader and access it by outer class loaded with different loader) - it would turns out that we will get illegal access error :) even the inner class is in the same package has all modificators allowing access to it outer class :) compiler/linker "VM" treats them as two not related classes...

Related

Is it possible to add completion items to a Microsoft Language Server in runtime?

I am trying to develop a IntelliJ plugin which provides a Language Server with help of lsp4intellij by ballerina.
Thing is, i've got a special condition: The list of completion items should be editable in runtime.
But I've not found any way to communicate new completionItems to the LanguageServer process once its running.
My current idea is to add an action to the plugin which builds a new jar and then restarts the server with the new jar, using the Java Compiler API.
The problem with that is, i need to get the source code from the plugin project including the gradle dependencies accessable from the running plugin... any ideas?
If your requirement is to modify the completion items (coming from the language server) before displaying them in the IntelliJ UI, you can do that by implementing the LSP4IntelliJ's
LSPExtensionManager in your plugin.
Currently, we do not have proper documentation for the LSP4IntelliJ's extension points but you can refer to our Ballerina IntelliJ plugin as a reference implementation, where it has implemented Ballerina LSP Extension manager to override/modify completion items at the client runtime in here.
For those who might stumble upon this - it is indeed possible to change the amount of CompletionItems the LanguageServer can provide during runtime.
I simply edited the TextDocumentService.java (the library I used is LSP4J).
It works like this:
The main function of the LanguageServer needs to be started with an additional argument, which is the path to the config file in which you define the CompletionItems.
Being called from LSP4IntelliJ it would look like this:
String[] command = new String[]{"java", "-jar",
"path\\to\\LangServer.jar", "path\\to\\config.json"};
IntellijLanguageClient.addServerDefinition(new RawCommandServerDefinition("md,java", command));
The path String will then be passed through to the Constructor of your CustomTextDocumentServer.java, which will parse the config.json in a new Timer thread.
An Example:
public class CustomTextDocumentService implements TextDocumentService {
private List<CompletionItem> providedItems;
private String pathToConfig;
public CustomTextDocumentService(String pathToConfig) {
this.pathToConfig = pathToConfig;
Timer timer = new Timer();
timer.schedule(new ReloadCompletionItemsTask(), 0, 10000);
loadCompletionItems();
}
#Override
public CompletableFuture<Either<List<CompletionItem>, CompletionList>> completion(CompletionParams completionParams) {
return CompletableFuture.supplyAsync(() -> {
List<CompletionItem> completionItems;
completionItems = this.providedItems;
// Return the list of completion items.
return Either.forLeft(completionItems);
});
}
#Override
public void didOpen(DidOpenTextDocumentParams didOpenTextDocumentParams) {
}
#Override
public void didChange(DidChangeTextDocumentParams didChangeTextDocumentParams) {
}
#Override
public void didClose(DidCloseTextDocumentParams didCloseTextDocumentParams) {
}
#Override
public void didSave(DidSaveTextDocumentParams didSaveTextDocumentParams) {
}
private void loadCompletionItems() {
providedItems = new ArrayList<>();
CustomParser = new CustomParser(pathToConfig);
ArrayList<String> variables = customParser.getTheParsedItems();
for(String variable : variables) {
String itemTxt = "$" + variable + "$";
CompletionItem completionItem = new CompletionItem();
completionItem.setInsertText(itemTxt);
completionItem.setLabel(itemTxt);
completionItem.setKind(CompletionItemKind.Snippet);
completionItem.setDetail("CompletionItem");
providedItems.add(completionItem);
}
}
class ReloadCompletionItemsTask extends TimerTask {
#Override
public void run() {
loadCompletionItems();
}
}
}

How to fill out Dynamic Dropdown in Hippo CMS with dynamic values?

I have document type which contains "Dynamic Dropdown" field, and I want to fill it with some dynamic data. I couldn't figure out how to do it (couldn't find any adequate information, documentation, example about this). From links that I found I was able to do following things:
1) I've created service called SitemapValueListProvider in /hippo:configuration/hippo:frontend/cms/cms-services, with following properties:
plugin.class = com.test.cms.components.SitemapService
valuelist.provider = service.valuelist.custom
2) In CMS project created class com.test.cms.components.SitemapService
public class SitemapService extends Plugin implements IValueListProvider {
private final static String CONFIG_SOURCE = "source";
public SitemapService(IPluginContext context, IPluginConfig config) {
super(context, config);
String name = config.getString(IValueListProvider.SERVICE, "service.valuelist.custom");
context.registerService(this, name);
}
#Override
public ValueList getValueList(String name, Locale locale) {
ValueList valuelist = new ValueList();
if ((name == null) || (name.equals(""))) {
System.out.println("No node name (uuid or path) configured, returning empty value list");
} else {
valuelist.add(new ListItem("custom4", "Custom Value 4"));
valuelist.add(new ListItem("custom5", "Custom Value 5"));
valuelist.add(new ListItem("custom6", "Custom Value 6"));
}
return valuelist;
}
#Override
public List<String> getValueListNames() {
List<String> list = new ArrayList<>(1);
list.add("values");
return list;
}
#Override
public ValueList getValueList(IPluginConfig config) {
if (config == null) {
throw new IllegalArgumentException("Argument 'config' may not be null");
}
return getValueList(config.getString(CONFIG_SOURCE));
}
#Override
public ValueList getValueList(String name) {
return getValueList(name, null/*locale*/);
}
}
3) In CMS project created class com.test.cms.components.TestPlugin
public class TestPlugin extends Plugin{
public TestPlugin(IPluginContext context, IPluginConfig config) {
super(context, config);
context.registerService(this, "service.valuelist.custom");
}
}
4) For field /hippo:namespaces/cms/TestItem/editor:templates/_default_/dynamicdropdown of document type provided following properties: (using console)
plugin.class = com.test.cms.components.TestPlugin
But still unable to obtain data dynamically. Nothing happens at all.
I'm using HippoCMS 10 Community Edition
you are totally on the right track and I can't spot any obvious reason why this is not working. Can you double check a few things?
look for an error in the logs, possibly at the early start of the CMS. Maybe there is an error during the bootstrap process.
activate the development mode in the CMS: this adds extra logging in the CMS.
http://www.onehippo.org/library/development/debug-wicket-ajax-in-the-cms.html
you can also try to break the configuration by putting the wrong class name: if you don't have a ClassNotFound then you know your configuration is wrong and/or not picked-up.
HTH.

AspectJ, Intertype Definition

I am receiving this error when I compile
The type XXX must implement the inherited abstract method
I have three files
A default implementation [com.SafeReaderIMPL.java]
public class SafeReaderIMPL implements ISafeReader {
private boolean successfulRead;
public SafeReaderIMPL() {
successfulRead = true;
}
protected void fail() {
successfulRead = false;
}
#Override
public boolean isSuccessfulRead() {
return successfulRead;
}
}
An interface file [com.ISafeReader.java]
public interface ISafeReader {
public boolean isSuccessfulRead();
}
An apsect (using annotations) [com.SafeReaderAspect.java]
#Aspect
public class SafeReaderAspect {
#DeclareParents(value = "com.BadReader", defaultImpl = SafeReaderIMPL.class)
public ISafeReader implementedInterface;
#AfterThrowing(pointcut = "execution(* *.*(..)) && this(m)", throwing = "e")
public void handleBadRead(JoinPoint joinPoint, ISafeReader m, Throwable e) {
((SafeReaderIMPL)m).fail();
}
}
And a Test Class [com.BadReader]
public class BadReader {
public void fail() throws Throwable {
throw new Throwable();
}
}
I compile the first three files in a separate jar using
ajc -source 1.8 -sourceroots . -outjar aspectLib.jar
I then compile the second file using the aspectLib like so
ajc -source 1.8 -sourceroots . -aspectpath ./aspectLib.jar -outjar common.jar
When I go to compile the second jar I get the error. I am using the latest stable version of AspectJ 1.8.3
BadReader.java:10 [error] The type BadReader must implement the
inherited abstract method ISafeReader.isSuccessfulRead() public class
BadReader {
^^^^^^^^
The problem is not two-step compilation as such, but the fact that #DeclareParents in #AspectJ syntax in not 100% compatible with declare parents in native syntax. Actually, #DeclareParents for introducing default interface implementations is superseded by #DeclareMixin (see this bug ticket), but the downside of the mixin approach is that you do not have a real A implements B scenario there, i.e. you cannot cast as you wish in your after-throwing advice, so this is also not a good option in your case.
So what do you do if you want to keep the two-step compilation approach? Just use native syntax:
Interface:
package com;
public interface ISafeReader {
boolean isSuccessfulRead();
}
Default implementation:
package com;
public class SafeReaderIMPL implements ISafeReader {
private boolean successfulRead;
public SafeReaderIMPL() { successfulRead = true; }
public void fail() { successfulRead = false; }
#Override public boolean isSuccessfulRead() { return successfulRead; }
}
ITD aspect:
package com;
public aspect SafeReaderAspect {
declare parents : com.BadReader implements SafeReaderIMPL;
after(ISafeReader safeReader) throwing : execution(* *(..)) && this(safeReader) {
System.out.println(thisJoinPoint + " - calling 'fail()' before rethrowing error");
((SafeReaderIMPL) safeReader).fail();
}
}
ITD target class with sample main method:
package com;
public class BadReader {
public void doSomething() {
throw new RuntimeException("my error");
}
public static void main(String[] args) {
BadReader badReader = new BadReader();
System.out.println("badReader.isSuccessfulRead() = " + badReader.isSuccessfulRead());
try { badReader.doSomething(); }
catch(Throwable t) { System.out.println(t); }
System.out.println("badReader.isSuccessfulRead() = " + badReader.isSuccessfulRead());
}
}
Now you can use the two-stage compilation approach.
Console output:
badReader.isSuccessfulRead() = true
execution(void com.BadReader.doSomething()) - calling 'fail()' before rethrowing error
java.lang.RuntimeException: my error
badReader.isSuccessfulRead() = false
The problem is due to the two-step compilation. During the second step, ajc needs the source code of SafeReaderIMPL to be able to weave BadReader, but it cannot find it into aspectLib.jar
In fact, if you try compiling in a single step (I did), it compiles and runs.
Unfortunately I don't know a way to fix this without providing the source code during the second compile step, which I suppose would render the whole two-step approach a bit pointless.

What is the reason that Policy.getPolicy() is considered as it will retain a static reference to the context and can cause memory leak

I just read some source code is from org.apache.cxf.common.logging.JDKBugHacks and also in
http://svn.apache.org/viewvc/tomcat/trunk/java/org/apache/catalina/core/JreMemoryLeakPreventionListener.java. In order to make my question clear not too broad. :)
I just ask one piece of code in them.
// Calling getPolicy retains a static reference to the context
// class loader.
try {
// Policy.getPolicy();
Class<?> policyClass = Class
.forName("javax.security.auth.Policy");
Method method = policyClass.getMethod("getPolicy");
method.invoke(null);
} catch (Throwable e) {
// ignore
}
But I didn't understand this comment. "Calling getPolicy retains a static reference to the context class loader". And they trying to use JDKBugHacks to work around it.
UPDATE
I overlooked the static block part. Here it is. This is the key. Actually it already has policy cached. So why cache contextClassLoader also? In comment, it claims #deprecated as of JDK version 1.4 -- Replaced by java.security.Policy.
I have double checked the code of java/security/Policy.java. It really removed the cached classloader. So my doubt is valid! :)
#Deprecated
public abstract class Policy {
private static Policy policy;
private static ClassLoader contextClassLoader;
static {
contextClassLoader = java.security.AccessController.doPrivileged
(new java.security.PrivilegedAction<ClassLoader>() {
public ClassLoader run() {
return Thread.currentThread().getContextClassLoader();
}
});
};
I also add the getPolicy source code.
public static Policy getPolicy() {
java.lang.SecurityManager sm = System.getSecurityManager();
if (sm != null) sm.checkPermission(new AuthPermission("getPolicy"));
return getPolicyNoCheck();
}
static Policy getPolicyNoCheck() {
if (policy == null) {
synchronized(Policy.class) {
if (policy == null) {
String policy_class = null;
policy_class = java.security.AccessController.doPrivileged
(new java.security.PrivilegedAction<String>() {
public String run() {
return java.security.Security.getProperty
("auth.policy.provider");
}
});
if (policy_class == null) {
policy_class = "com.sun.security.auth.PolicyFile";
}
try {
final String finalClass = policy_class;
policy = java.security.AccessController.doPrivileged
(new java.security.PrivilegedExceptionAction<Policy>() {
public Policy run() throws ClassNotFoundException,
InstantiationException,
IllegalAccessException {
return (Policy) Class.forName
(finalClass,
true,
contextClassLoader).newInstance();
}
});
} catch (Exception e) {
throw new SecurityException
(sun.security.util.ResourcesMgr.getString
("unable to instantiate Subject-based policy"));
}
}
}
}
return policy;
}
Actually I dig deeper, I find some interesting thing. Someone report a bug to apache CXF about the org.apache.cxf.common.logging.JDKBugHacks for this piece code recently.
In order for disabling url caching, JDKBugHacks runs:
URL url = new URL("jar:file://dummy.jar!/");
URLConnection uConn = url.openConnection();
uConn.setDefaultUseCaches(false);
When having the java.protocol.handler.pkgs system property set, that can lead to deadlocks between the system classloader and the file protocol Handler in particular situations (for instance if the file protocol URLStreamHandler is a signleton).
Besides that, the code above is really there for the sake of setting defaultUseCaches to false only, so actually opening a connection can be avoided, to speed up the execution.
So the fix is
URL url = new URL("jar:file://dummy.jar!/");
URLConnection uConn = new URLConnection(url) {
#Override
public void connect() throws IOException {
// NOOP
}
};
uConn.setDefaultUseCaches(false);
It's normal that JDK or apache cxf to have some minor bugs. And normally they will fix it.
javax.security.auth.login.Configuration has the same issues with Policy but it's not Deprecated.
The Policy class in java 6 contains a static reference to a classloader that is initialized to the current threads context classloader on the first access to the class:
private static ClassLoader contextClassLoader;
static {
contextClassLoader =
(ClassLoader)java.security.AccessController.doPrivileged
(new java.security.PrivilegedAction() {
public Object run() {
return Thread.currentThread().getContextClassLoader();
}
});
};
Tomcats lifecycle listener is making sure to to initialize this class from within a known environment where the context classloader is set to the system classloader. If this class was first accessed from within a webapp, it would retain a reference to the webapps classloader. This would prevent the webapps classes from getting garbage collected, creating a leak of perm gen space.

Load external properties files into EJB 3 app running on WebLogic 11

Am researching the best way to load external properties files from and EJB 3 app whose EAR file is deployed to WebLogic.
Was thinking about using an init servlet but I read somewhere that it would be too slow (e.g. my message handler might receive a message from my JMS queue before the init servlet runs).
Suppose I have multiple property files or one file here:
~/opt/conf/
So far, I feel that the best possible solution is by using a Web Logic application lifecycle event where the code to read the properties files during pre-start:
import weblogic.application.ApplicationLifecycleListener;
import weblogic.application.ApplicationLifecycleEvent;
public class MyListener extends ApplicationLifecycleListener {
public void preStart(ApplicationLifecycleEvent evt) {
// Load properties files
}
}
See: http://download.oracle.com/docs/cd/E13222_01/wls/docs90/programming/lifecycle.html
What would happen if the server is already running, would post start be a viable solution?
Can anyone think of any alternative ways that are better?
It really depends on how often you want the properties to be reloaded. One approach I have taken is to have a properties file wrapper (singleton) that has a configurable parameter that defines how often the files should be reloaded. I would then always read properties through that wrapper and it would reload the properties ever 15 minutes (similar to Log4J's ConfigureAndWatch). That way, if I wanted to, I can change properties without changing the state of a deployed application.
This also allows you to load properties from a database, instead of a file. That way you can have a level of confidence that properties are consistent across the nodes in a cluster and it reduces complexity associated with managing a config file for each node.
I prefer that over tying it to a lifecycle event. If you weren't ever going to change them, then make them static constants somewhere :)
Here is an example implementation to give you an idea:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.*;
/**
* User: jeffrey.a.west
* Date: Jul 1, 2011
* Time: 8:43:55 AM
*/
public class ReloadingProperties
{
private final String lockObject = "LockMe";
private long lastLoadTime = 0;
private long reloadInterval;
private String filePath;
private Properties properties;
private static final Map<String, ReloadingProperties> instanceMap;
private static final long DEFAULT_RELOAD_INTERVAL = 1000 * 60 * 5;
public static void main(String[] args)
{
ReloadingProperties props = ReloadingProperties.getInstance("myProperties.properties");
System.out.println(props.getProperty("example"));
try
{
Thread.sleep(6000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println(props.getProperty("example"));
}
static
{
instanceMap = new HashMap(31);
}
public static ReloadingProperties getInstance(String filePath)
{
ReloadingProperties instance = instanceMap.get(filePath);
if (instance == null)
{
instance = new ReloadingProperties(filePath, DEFAULT_RELOAD_INTERVAL);
synchronized (instanceMap)
{
instanceMap.put(filePath, instance);
}
}
return instance;
}
private ReloadingProperties(String filePath, long reloadInterval)
{
this.reloadInterval = reloadInterval;
this.filePath = filePath;
}
private void checkRefresh()
{
long currentTime = System.currentTimeMillis();
long sinceLastLoad = currentTime - lastLoadTime;
if (properties == null || sinceLastLoad > reloadInterval)
{
System.out.println("Reloading!");
lastLoadTime = System.currentTimeMillis();
Properties newProperties = new Properties();
FileInputStream fileIn = null;
synchronized (lockObject)
{
try
{
fileIn = new FileInputStream(filePath);
newProperties.load(fileIn);
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if (fileIn != null)
{
try
{
fileIn.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
properties = newProperties;
}
}
}
public String getProperty(String key, String defaultValue)
{
checkRefresh();
return properties.getProperty(key, defaultValue);
}
public String getProperty(String key)
{
checkRefresh();
return properties.getProperty(key);
}
}
Figured it out...
See the corresponding / related post on Stack Overflow.