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How to load ResourceBundles within loaded JAR

I have a problem with loading resource bundles in loaded jars. The main program is loading jars from a folder with a plugin manager. When an object of the main class of a jar is initialized by the plugin manager, resource bundles of this jar can be loaded. By this, I mean in a static block or in a constructor. Otherwise, an MissingResourceException is thrown. Like when you call a method on that object, that tries to load an existing resource-bundle
Currently, I use a static block at the beginning of the main class of a jar to load all resource bundles of the plugin with possible locales. Because of this, the resource bundles will be cached for some time. Also, my current way seems to work out for sub-loaded jars the same way as for the loaded jar
public class PluginMain implements PluginInterface {
static {
for (Locale availableLocale : getAvailableLocales()) {
try {
ResourceBundle resourceBundle = ResourceBundle.getBundle(BUNDLE_PATH, availableLocale);
} catch (MissingResourceException e) {
e.printStackTrace();
}
}
}
...
}
I think it's about the classLoader that is loading the resource-bundle. Still i cannot find a good solution.
I already tried to find some solutions. The best i could find fitting is Loading with ResourceBundle from inside a jar, but that did not work out.
Edit: I load my jars like this
public class PluginManagerImpl implements PluginManager {
private final List<PluginInterface> loadedPlugins = new ArrayList<>();
private final String path;
public PluginManagerImpl(String path) {
File pluginsDir = new File(path, "plugins");
this.path = pluginsDir.getPath();
if (pluginsDir.exists()) {
//pluginsfolder exists
File[] files = pluginsDir.listFiles();
if (files != null) {
for (File f : files)
if (!f.isDirectory()) {
loadPlugin(f);
}
}
} else {
//pluginsfolder does not exist
if (pluginsDir.mkdir()) {
Output.WriteLine("Dictionary created: " + pluginsDir.getPath());
}
}
}
#Override
public void loadPlugin(File file) {
URL urlFile;
//trying to load file, convert it first to URI and then to URL
try {
urlFile = file.toURI().toURL();
} catch (MalformedURLException e) {
Output.WriteLineProblem(e.getMessage(), 4);
return;
}
//trying to create JAR-file from file
try (
//use JarFIle and URLClassLoader as auto-closable
JarFile jarFile = new JarFile(file);
//use classloader of this class as parent classLoader
URLClassLoader classLoader = new URLClassLoader(new URL[]{urlFile}, this.getClass().getClassLoader())
) {
//load manifest
Manifest manifest = jarFile.getManifest();
//read attributes from manifest
Attributes attributes = manifest.getMainAttributes();
//get main class from attributes
String main = attributes.getValue(Attributes.Name.MAIN_CLASS);
if (main == null) {
Output.WriteLineProblem(file.getName() + " has no main specified");
return;
}
String title = attributes.getValue(Attributes.Name.IMPLEMENTATION_TITLE);
if (title == null) {
//https://maven.apache.org/shared/maven-archiver/index.html
Output.WriteLineProblem(file.getName() + " has no implementation title specified");
return;
}
//https://javapapers.com/core-java/java-class-loader/
//load class with classLoader of jarFile
Class<?> cl = classLoader.loadClass(main);
//get implemented interfaces of class
Class<?>[] interfaces = cl.getInterfaces();
//iterate over interfaces and check for PluginInterface.class
boolean isPlugin = false;
for (Class<?> anInterface : interfaces) {
if (anInterface.equals(PluginInterface.class)) {
isPlugin = true;
break;
}
}
if (isPlugin) {
//load all classes in jar file
loadClassesOfjarFile(jarFile, cl.getClassLoader());
//add the pluginfile
PluginInterface plugin = (PluginInterface) cl.getConstructor().newInstance();
plugin.calledAfterInstancing(new File(path, title).getPath());
Output.WriteLine("Loaded Plugin " + title);
loadedPlugins.add(plugin);
}
} catch (Exception e) {
Output.WriteLineProblem("Error on checking " + file.getName() + " for plugin");
e.printStackTrace();
}
}
public static void loadClassesOfjarFile(JarFile jarFile, ClassLoader classLoader) {
jarFile.entries().asIterator().forEachRemaining(jarEntry -> {
String jarEntryName = jarEntry.getName();
if ((jarEntryName.endsWith(".class"))) {
String className = jarEntry.getName().replaceAll("/", "\\.");
String myClass = className.substring(0, className.lastIndexOf('.'));
try {
Class<?> clazz = classLoader.loadClass(myClass);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
} else if (jarEntryName.endsWith(".xml")) {
String resourceName = jarEntry.getName().replaceAll("/", "\\.");
classLoader.getResourceAsStream(jarEntry.getName());
}
});
}
}
Edit 2: Here a sample project to test
The resource bundles are contained in the the resource folder of the plugin.
Hierarchy of the project
Sample for the main program:
package main;
public class Main {
public static final String DEFAULT_PATH = FileSystems.getDefault().getPath("").toAbsolutePath().toString();
public static void main(String[] args) {
PluginManager plugins = new PluginManager(DEFAULT_PATH);
List<PluginInterface> loadedPlugins = plugins.getLoadedplugins();
for (PluginInterface loadedPlugin : loadedPlugins) {
loadedPlugin.loadResourceBundle(Locale.ENGLISH);
}
}
}
Sample for plugin:
package plugin;
public class Main implements PluginInterface {
static {
Locale locale = Locale.ENGLISH;
ResourceBundle main = ResourceBundle.getBundle("mainLoadedInStatic", locale);
//only uncomment to check, that it would work if loaded in static
// ResourceBundle mainNotLoadedInStatic = ResourceBundle.getBundle("mainNotLoadedInStatic", locale);
}
#Override
public void loadResourceBundle(Locale locale) {
ResourceBundle mainLoadedInStatic = ResourceBundle.getBundle("mainLoadedInStatic", locale);
ResourceBundle mainNotLoadedInStatic = ResourceBundle.getBundle("mainNotLoadedInStatic", locale);
}
}
The error should be:
Exception in thread "main" java.util.MissingResourceException: Can't find bundle for base name mainNotLoadedInStatic, locale en
at java.base/java.util.ResourceBundle.throwMissingResourceException(ResourceBundle.java:2045)
at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1683)
at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1586)
at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1549)
at java.base/java.util.ResourceBundle.getBundle(ResourceBundle.java:932)
at plugin.Main.loadResourceBundle(Main.java:19)
at main.Main.main(Main.java:18)

I discovered that closing the URLClassLoader (as autocloseable) in loadPlugin of PluginManagerImpl was causing the Problem.
The Resources are tried to be loaded with that URLClassLoader and if it is closed, it will fail.
Which effect would occur, if the URLClassLoader doesn't get closed at all? As far as i understand this could have a negativ effect because of an unclosed JarFile.

Spring Batch - Not Shutting down - Due to Static Method call

I have completed a spring batch (Standalone Jar) in Spring Boot + CommandLineRunner. But the JVM is not getting shutdown after completion. After doing some research initially I thought its not shutting down because of below reasons.
1 . I am not closing the spring application context at the end ofcommandline runner.
2 . Executor service is not shutdown properly which might have caused the JVM from shutting down.
I dont want to call system.exit which is a forceful shutdown.
I tried closing the application context and also verified executor service is shutdown using isShutdown method (returns true).
Then I found out the root cause, it is because I am calling a static method which is the culprit. When I commented the static method call, the job was shutting down gracefully even if I dont close the application context explicitly.
I am not sure why this behavior and do I need to convert everything to objects or is there something else I am missing here. Can someone please throw some light.
Main Class
#SpringBootApplication
#ComponentScan(basePackages = "com.acn.abp.printbatch")
#EnableTransactionManagement
#ImportResource({ "ABPBatchInfrastructure.xml", "financeBillPayAppConfig.xml" })
public class financeBillPayFileUploadApplication extends PrintBatchConstants implements CommandLineRunner {
#Autowired
private NotifyConfig notify;
#Autowired
private ApplicationContext ctx;
static final Logger logger = LoggerFactory.getLogger(financeBillPayFileUploadApplication.class);
public static void main(String[] args) {
SpringApplication application = new SpringApplication(financeBillPayFileUploadApplication.class);
application.setBannerMode(Banner.Mode.OFF);
application.run(args);
}
#Override
public void run(String... args) throws Exception {
logger.info(notify.getEnvironment());
JobLauncher jobLauncher = ctx.getBean(JobLauncher.class);
Job job = ctx.getBean(Job.class);
jobLauncher.run(job,
new JobParametersBuilder()
.addString(batchDocumentClass, "InvoiceStatementDocumentation")
.addString(batchType, "2020-06-04")
.addString(batchEmailID, notify.getSupportEmailId())
.addString(batchEnvironment, notify.getEnvironment())
.toJobParameters());
System.out.println("Here cxf");
((ConfigurableApplicationContext)ctx).close();
}
}
Below Class which is causing the problem. If I comment out below code then everything works perfectly.
populateItemDocuments(job, printConfig.geteCMObjectStore(), printConfig.geteCMUserId());
Class file where this method is called
#Component
public class DuplexWorker implements Callable {
static final Logger logger = LoggerFactory.getLogger(DuplexWorker.class);
#Autowired
private ManageFormService formgmtClient;
#Autowired
private PostScriptService postScriptService;
#Autowired
private BarcodeService barcodeService;
private static CfBatchPrintConfiguration printConfig;
private static CfPersistenceUtil dbUtilService;
private static FilenetDocumentRetrieval docmgmtClient;
#Autowired
public DuplexWorker(CfPersistenceUtil dbUtilService,CfBatchPrintConfiguration printConfig,FilenetDocumentRetrieval docmgmtClient) {
DuplexWorker.dbUtilService = dbUtilService;
DuplexWorker.printConfig = printConfig;
DuplexWorker.docmgmtClient=docmgmtClient;
}
private MailUtil mailUtil;
private NotifyConfig notify;
private List<PrintJobItem> printJobItems;
private List<String> groupIds;
private ArrayList duplexJobs;
private String groupId;
private CountDownLatch latch;
public DuplexWorker(ArrayList duplexJobs, String groupId,CountDownLatch latch) {
super();
this.latch=latch;
this.duplexJobs = duplexJobs;
this.groupId = groupId;
}
public DuplexWorker(CountDownLatch latch, MailUtil mailUtil,NotifyConfig notify,List<PrintJobItem> findByPrintStatusEquals,List<String>groupIds) {
this.latch=latch;
this.mailUtil=mailUtil;
this.notify=notify;
this.printJobItems=findByPrintStatusEquals;
this.groupIds=groupIds;
}
#Override
public Object call() throws Exception {
try {
if ((duplexJobs != null) && (!duplexJobs.isEmpty())) {
String prevJobId = null;
int docCount = 0;
CvPrintJob consolidatedPrintJob = (CvPrintJob)duplexJobs.get(0);
ArrayList printItems = new ArrayList();
if (consolidatedPrintJob != null)
{
ArrayList items = consolidatedPrintJob.getPrintJobItems();
int numPages = 0;
if ((items != null) && (!items.isEmpty()))
{
CvPrintJobItem firstItem = (CvPrintJobItem)items.get(0);
numPages = CfBatchPrintUtil.getItemTotalPages(firstItem);
logger.info("Item Total Pages == " + numPages);
logger.info("Job Item Page Limit == " +
printConfig.getJobItemPageLimit());
consolidatedPrintJob.setSequence(firstItem.getSequence());
}
if (numPages <= printConfig.getJobItemPageLimit())
{
consolidatedPrintJob.setHasLargeItems(false);
logger.info("Item setHasLargeItems == false");
}
else
{
consolidatedPrintJob.setHasLargeItems(true);
logger.info("Item setHasLargeItems == true");
}
}
ArrayList startBannerDataList = new ArrayList();
ArrayList barcodeList = new ArrayList();
ArrayList barcodeCorresPageCount = new ArrayList();
ArrayList statementNumberList = new ArrayList();
for (int i = 0; i < duplexJobs.size(); i++)
{
CvPrintJob job = (CvPrintJob)duplexJobs.get(i);
if ((prevJobId == null) ||
(!prevJobId.equalsIgnoreCase(job.getJobId()))) {
docCount = 0;
}
populateItemDocuments(job, printConfig.geteCMObjectStore(), printConfig.geteCMUserId());
}
consolidatedPrintJob.setPrintJobItems(printItems);
}
else
{
logger.info("====================================================================");
logger.info("=================>> No DUPLEX jobs to process <<===================");
logger.info("====================================================================");
}
duplexJobs = null;
this.latch.countDown();
System.gc();
return null;
}catch(Exception e) {
e.printStackTrace();
return null;
}
}
public static void populateItemDocuments(CvPrintJob job, String objectStore, String userid)
throws CfException
{
logger.info("Enters populateItemDocuments");
try
{
ArrayList items = job.getPrintJobItems();
job.setIsProcess(true);
ArrayList modelDocList = null;
logger.info("Items size::::::" + items.size());
for (int i = 0; i < items.size(); i++)
{
modelDocList = new ArrayList();
CvPrintJobItem x = (CvPrintJobItem)items.get(i);
ArrayList guidList = x.getGuidList();
if ((guidList != null) && (!guidList.isEmpty())) {
modelDocList.addAll(guidList);
}
logger.info("guidList size::::::" + guidList.size());
CvRenderPayloadRequest cvRenderPayloadRequest = null;
if ((modelDocList != null) && (!modelDocList.isEmpty()))
{
cvRenderPayloadRequest = new CvRenderPayloadRequest();
logger.info("Before creating CvRenderPayloadRequest");
logger.info("Document Class::: " +
x.getDocumentClass());
cvRenderPayloadRequest.setDocumentClass(
x.getDocumentClass());
cvRenderPayloadRequest.setGuid(modelDocList);
cvRenderPayloadRequest.setUserId(userid);
logger.info("After creating the CvRenderPayloadRequest");
try
{
if (cvRenderPayloadRequest != null)
{
List pdfContents = docmgmtClient.retrieveDocument(cvRenderPayloadRequest.getGuid());
if ((pdfContents != null) &&
(!pdfContents.isEmpty()))
{
logger.info(
"PDF contents sizenew::::::::::::::" + pdfContents.size());
Iterator pdfItr = pdfContents.iterator();
while (pdfItr.hasNext())
{
byte[] contents = (byte[])pdfItr.next();
CvPrintJobItem item = (CvPrintJobItem)items.get(i);
item.addDocumentList(contents);
int filenetpagecount = 100;
item.setPageCountFromFileNet(filenetpagecount);
logger.info("PageCOunt from Filenet " + filenetpagecount);
}
}
}
}
catch (Exception e)
{
e.printStackTrace();
throw new CfException(" Error populating documents" + e);
}
}
}
}
catch (Exception e)
{
e.printStackTrace();
throw new CfException(" Error populating documents" + e);
}
logger.info("Exits populateItemDocuments");
}

First of all you are using Tomcat server that runs the application. If you want to make standalone spring application you can configure like below
#Configuration
public class ApplicationMain {
#Bean
public Stackoverflow stackoverflow() {
return new Stackoverflow ();
}
public static void main(String[] args) {
ConfigurableApplicationContext configurableApplicationContext = new AnnotationConfigApplicationContext(ApplicationMain.class);
System.out.println(configurableApplicationContext.getBean("stackoverflow"));
}
}
'JVM is not getting shutdown after completion.' is normal behavior for Tomcat server because it waits for request to handle.
You can give basepackage like below
new AnnotationConfigApplicationContext("com.example");
it will scan the package for you

Spring AOP logging thread method

Is there any way to implement AOP logging to public method of class that implements Runnable and ran by ExecutorService?
Thread class
#Component
#Scope("prototype")
public class FileProcessor implements Runnable {
private final LinkedBlockingQueue<File> filesQueue;
private final GiftCertificateMapper certificateMapper;
private final File errorFolder;
private static final ReentrantLock LOCK = new ReentrantLock();
private static final Logger LOGGER = LoggerFactory.getLogger(FileProcessor.class);
public FileProcessor(LinkedBlockingQueue<File> filesQueue, GiftCertificateMapper certificateMapper,
File errorFolder) {
this.filesQueue = filesQueue;
this.certificateMapper = certificateMapper;
this.errorFolder = errorFolder;
}
#Override
public void run() {
File file = null;
try {
while ((file = filesQueue.poll(100, TimeUnit.MILLISECONDS)) != null) {
processFile(file);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
LOGGER.warn("File thread was interrupted");
} catch (IOException e) {
LOGGER.error("Error processing file {} \n{}", file.getAbsolutePath(), e);
}
}
public void processFile(File file) throws IOException {
if (file != null) {
try {
ObjectMapper objectMapper = new ObjectMapper();
List<GiftCertificate> certificates = Arrays.asList(objectMapper.readValue(file, GiftCertificate[].class));
certificateMapper.insertList(certificates);
file.delete();
} catch (JsonParseException | UnrecognizedPropertyException | InvalidFormatException | DataIntegrityViolationException e) {
moveFileToErrorFolder(file);
}
}
}
private void moveFileToErrorFolder(File file) throws IOException {
try {
LOCK.lock();
Files.move(Paths.get(file.getAbsolutePath()), getPathForMovingFile(file), StandardCopyOption.ATOMIC_MOVE);
} finally {
LOCK.unlock();
}
}
private Path getPathForMovingFile(File fileForMove) {
File fileList[] = errorFolder.listFiles();
int filesWithSameNameCounter = 0;
if (fileList != null && fileList.length > 0) {
for (File file : fileList) {
if (file.getName().contains(fileForMove.getName())) {
filesWithSameNameCounter++;
}
}
}
return filesWithSameNameCounter > 0 ?
Paths.get(errorFolder.getAbsolutePath(), "(" + filesWithSameNameCounter + ")" + fileForMove.getName()) :
Paths.get(errorFolder.getAbsolutePath(), fileForMove.getName());
}
}
Aspect
#Aspect
#Component
#ConditionalOnProperty(
value = "file-processing.logging.enabled",
havingValue = "true",
matchIfMissing = true)
public class FileProcessingLoggingAspect {
private static final Logger LOGGER = LoggerFactory.getLogger(FileProcessingLoggingAspect.class);
#Pointcut("execution(* com.epam.esm.processor.FileProcessor.processFile(java.io.File))")
public void processFilePointcut() {
}
#Around("processFilePointcut()")
public Object logFileProcessing(ProceedingJoinPoint joinPoint) throws Throwable {
// File file = (File) joinPoint.getArgs()[0];
// long time = System.currentTimeMillis();
Object object = joinPoint.proceed();
// long resultTime = System.currentTimeMillis() - time;
LOGGER.info("Processing of file took milliseconds");
return object;
}
}

In Spring AOP , internal method calls cannot be intercepted.
In the code shared , even though the method processFile() is public , it gets called from run(). This is a self reference / internal method call , which cannot be intercepted.
Details can be read in the documentation
Due to the proxy-based nature of Spring’s AOP framework, calls within
the target object are, by definition, not intercepted. For JDK
proxies, only public interface method calls on the proxy can be
intercepted
A pointcut expression to intercept all external method calls to a class implementing Runnable would be as follows
#Around("this(java.lang.Runnable) && within(com.epam.esm.processor..*)")
public Object logFileProcessing(ProceedingJoinPoint pjp) throws Throwable {
try {
return pjp.proceed();
} finally {
//log
System.out.println("****Logged");
}
}
Scoping designator within() limits the scope to apply the advice.
The point cut #Pointcut("execution(* com.epam.esm.processor.FileProcessor.processFile(java.io.File))") is valid and would work if an external method call happens to it.
Hope this helps.

JSP - Running a program with main method and nested static class

I'm a novice when it comes to JSPs and JAVA.
How do I get the output from the below code to display on a jsp, considering that it runs everything from the main and contains non-public methods, a nested static class etc?
I know that we are not supposed to use java code on jsp but my first step in this proof on concept exercise is to get the code running and returning data from a backend then I can set about using EL etc.
I can run the program, with the correct config settings, from within Eclipse and all works fine with the output appearing on the console but I'm really not sure how to access it from within a jsp.
How do I access the static class and static methods from a jsp if they aren't public?
All help greatly appreciated.
public class CustomDestinationDataProvider
{
static class MyDestinationDataProvider implements DestinationDataProvider
{
private DestinationDataEventListener eL;
private HashMap<String, Properties> secureDBStorage = new HashMap<String, Properties>();
public Properties getDestinationProperties(String destinationName)
{
try
{
//read the destination from DB
Properties p = secureDBStorage.get(destinationName);
if(p!=null)
{
//check if all is correct, for example
if(p.isEmpty())
throw new DataProviderException(DataProviderException.Reason.INVALID_CONFIGURATION, "destination configuration is incorrect", null);
return p;
}
return null;
}
catch(RuntimeException re)
{
throw new DataProviderException(DataProviderException.Reason.INTERNAL_ERROR, re);
}
}
public void setDestinationDataEventListener(DestinationDataEventListener eventListener)
{
this.eL = eventListener;
}
public boolean supportsEvents()
{
return true;
}
//implementation that saves the properties in a very secure way
void changeProperties(String destName, Properties properties)
{
synchronized(secureDBStorage)
{
if(properties==null)
{
if(secureDBStorage.remove(destName)!=null)
eL.deleted(destName);
}
else
{
secureDBStorage.put(destName, properties);
eL.updated(destName); // create or updated
}
}
}
} // end of MyDestinationDataProvider
//business logic
void executeCalls(String destName)
{
JCoDestination dest;
try
{
dest = JCoDestinationManager.getDestination(destName);
dest.ping();
System.out.println("Destination " + destName + " works");
step4WorkWithTable(dest);
}
catch(JCoException e)
{
e.printStackTrace();
System.out.println("Execution on destination " + destName+ " failed");
}
}
static Properties getDestinationPropertiesFromUI()
{
//adapt parameters in order to configure a valid destination
Properties connectProperties = new Properties();
// Add code here to set config settings
return connectProperties;
}
public static void main(String[] args)
{
MyDestinationDataProvider myProvider = new MyDestinationDataProvider();
//register the provider with the JCo environment;
//catch IllegalStateException if an instance is already registered
try
{
com.sap.conn.jco.ext.Environment.registerDestinationDataProvider(myProvider);
}
catch(IllegalStateException providerAlreadyRegisteredException)
{
//somebody else registered its implementation,
//stop the execution
throw new Error(providerAlreadyRegisteredException);
}
String destName = "????";
CustomDestinationDataProvider test = new CustomDestinationDataProvider();
//set properties for the destination and ...
myProvider.changeProperties(destName, getDestinationPropertiesFromUI());
//... work with it
test.executeCalls(destName);
}
public static void step4WorkWithTable(JCoDestination dest) throws JCoException
{
JCoFunction function = dest.getRepository().getFunction("BAPI_COMPANYCODE_GETLIST");
if(function == null)
throw new RuntimeException("BAPI_COMPANYCODE_GETLIST not found in SAP.");
try
{
function.execute(dest);
}
catch(AbapException e)
{
System.out.println(e.toString());
return;
}
JCoStructure returnStructure = function.getExportParameterList().getStructure("RETURN");
if (! (returnStructure.getString("TYPE").equals("")||returnStructure.getString("TYPE").equals("S")) )
{
throw new RuntimeException(returnStructure.getString("MESSAGE"));
}
JCoTable codes = function.getTableParameterList().getTable("COMPANYCODE_LIST");
for (int i = 0; i < codes.getNumRows(); i++)
{
codes.setRow(i);
System.out.println(codes.getString("COMP_CODE") + '\t' + codes.getString("COMP_NAME"));
}
//move the table cursor to first row
codes.firstRow();
for (int i = 0; i < codes.getNumRows(); i++, codes.nextRow())
{
function = dest.getRepository().getFunction("BAPI_COMPANYCODE_GETDETAIL");
if (function == null)
throw new RuntimeException("BAPI_COMPANYCODE_GETDETAIL not found in SAP.");
function.getImportParameterList().setValue("COMPANYCODEID", codes.getString("COMP_CODE"));
//We do not need the addresses, so set the corresponding parameter to inactive.
//Inactive parameters will be either not generated or at least converted.
function.getExportParameterList().setActive("COMPANYCODE_ADDRESS",false);
try
{
function.execute(dest);
}
catch (AbapException e)
{
System.out.println(e.toString());
return;
}
returnStructure = function.getExportParameterList().getStructure("RETURN");
if (! (returnStructure.getString("TYPE").equals("") ||
returnStructure.getString("TYPE").equals("S") ||
returnStructure.getString("TYPE").equals("W")) )
{
throw new RuntimeException(returnStructure.getString("MESSAGE"));
}
JCoStructure detail = function.getExportParameterList().getStructure("COMPANYCODE_DETAIL");
System.out.println(detail.getString("COMP_CODE") + '\t' +
detail.getString("COUNTRY") + '\t' +
detail.getString("CITY"));
}//for
}
}

Small class to allow a java program to auto-update itself

The goal is to have a simple Java class start a jar main-class. When the main-class finishes, it can be queried if it would like to be reloaded. By this method it can hot-update itself and re-run itself.
The Launcher is to load the jar via a URLClassloader and then unload/re-load the changed jar. The jar can be changed by a modification to Launcher, or by a provided dos/unix script that is called to swap the new jar into place of the old jar.
The entire program is below. Tested and it seems to work without a hitch.
java Launcher -jar [path_to_jar] -run [yourbatchfile] [-runonce]? optional]
1) Launcher looks for the "Main-Class" attribute in your jarfile so that it does not need to be giventhe actual class to run.
2) It will call 'public static void main(String[] args)' and pass it the remaining arguments that you provided on the command line
3) When your program finishes, the Launcher will call your programs method 'public static boolean reload()' and if the result is 'true' this will trigger a reload.
4) If you specified -runonce, then the program will never reload.
5) If you specified -run [batchfile] then the batchfile will run before reloading.
I hope this is helpful to some people.
Happy coding!
import java.io.File;
import java.io.IOException;
import java.lang.ProcessBuilder.Redirect;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.jar.Attributes;
import java.util.jar.Manifest;
public class Launcher {
public static void main(String[] args) {
new Launcher().run(new ArrayList<>(Arrays.asList(args)));
}
private void run(List<String> list) {
final String jar = removeArgPairOrNull("-jar", list);
final boolean runonce = removeArgSingle("-runonce", list);
final String batchfile = removeArgPairOrNull("-run", list);
if (jar == null) {
System.out.println("Please add -jar [jarfile]");
System.out.println("All other arguments will be passed to the jar main class.");
System.out.println("To prevent reloading, add the argument to -runonce");
System.out.println("To provide another program that runs before a reload, add -run [file]");
}
boolean reload;
do {
reload = launch(list.toArray(new String[0]), new String(jar), new String(batchfile), new Boolean(runonce));
System.out.println("Launcher: reload is: " + reload);
gc();
if (reload && batchfile != null) {
try {
System.err.println("Launcher: will attempt to reload jar: " + jar);
runBatchFile(batchfile);
} catch (IOException | InterruptedException ex) {
ex.printStackTrace(System.err);
System.err.println("Launcher: reload batchfile had exception:" + ex);
reload = false;
}
}
} while (reload);
}
private boolean launch(String[] args, String jar, String batchfile, boolean runonce) {
Class<?> clazz = null;
URLClassLoader urlClassLoader = null;
boolean reload = false;
try {
urlClassLoader = new URLClassLoader(new URL[]{new File(jar).toURI().toURL()});
String mainClass = findMainClass(urlClassLoader);
clazz = Class.forName(mainClass, true, urlClassLoader);
Method main = clazz.getMethod("main", String[].class);
System.err.println("Launcher: have method: " + main);
Method reloadMethod;
if (runonce) {
// invoke main method using reflection.
main.invoke(null, (Object) args);
} else {
// find main and reload methods and invoke using reflection.
reloadMethod = clazz.getMethod("reload");
main.invoke(null, (Object) args);
System.err.println("Launcher: invoked: " + main);
reload = (Boolean) reloadMethod.invoke(null, new Object[0]);
}
} catch (final Exception ex) {
ex.printStackTrace(System.err);
System.err.println("Launcher: can not launch and reload this class:" + ex);
System.err.println("> " + clazz);
reload = false;
} finally {
if (urlClassLoader != null) {
try {
urlClassLoader.close();
} catch (IOException ex) {
ex.printStackTrace(System.err);
System.err.println("Launcher: error closing classloader: " + ex);
}
}
}
return reload ? true : false;
}
private static String findMainClass(URLClassLoader urlClassLoader) throws IOException {
URL url = urlClassLoader.findResource("META-INF/MANIFEST.MF");
Manifest manifest = new Manifest(url.openStream());
Attributes attr = manifest.getMainAttributes();
return attr.getValue("Main-Class");
}
private static void runBatchFile(String batchfile) throws IOException, InterruptedException {
System.out.println("Launcher: executng batchfile: " + batchfile);
ProcessBuilder pb = new ProcessBuilder("cmd", "/C", batchfile);
pb.redirectErrorStream(true);
pb.redirectInput(Redirect.INHERIT);
pb.redirectOutput(Redirect.INHERIT);
Process p = pb.start();
p.waitFor();
}
private static String removeArgPairOrNull(String arg, List<String> list) {
if (list.contains(arg)) {
int index = list.indexOf(arg);
list.remove(index);
return list.remove(index);
}
return null;
}
private static boolean removeArgSingle(String arg, List<String> list) {
if (list.contains(arg)) {
list.remove(list.indexOf(arg));
return true;
}
return false;
}
private void gc() {
for (int i = 0; i < 10; i++) {
byte[] bytes = new byte[1024];
Arrays.fill(bytes, (byte) 1);
bytes = null;
System.gc();
System.runFinalization();
}
}
}

After debugging, I determined the original difficulty was that the Launcher was not isolating the UrlClassloader.
By putting the part of the program that starts the classloader in a seperate method, I was able to allow all the system to determine that no more references existed.
After reworking the code, it all works now :)