I'm using com.sun.tools.attach from jdk's tools.jar and it need an specified java.library.path env pointing to attach.dll at startup to properly instatiate provider such as WindowsAttachProvider. For some reasons I need to dynamic loading one of bundled attach.dll. I'm try to use some like this:
public static void main(String[] args) throws Exception {
Path bin = Paths.get(System.getProperty("user.dir"),"bin").toAbsolutePath();
switch (System.getProperty("os.arch")) {
case "amd64":
bin = bin.resolve("win64");
break;
default:
bin = bin.resolve("win32");
}
// Dynamic setting of java.library.path only seems not sufficient
System.setProperty("java.library.path", System.getProperty("java.library.path") + File.pathSeparator + bin.toString());
// So I try to manual loading attach.dll. This is not sufficient too.
System.load(bin.resolve("attach.dll").toString());
// I'm using com.sun.tools.attach in my app
new myApp();
}
If I run this out of jdk (in normall jre) it's report to me:
java.util.ServiceConfigurationError: com.sun.tools.attach.spi.AttachProvider:
Provider sun.tools.attach.WindowsAttachProvider could not be instantiated:
java.lang.UnsatisfiedLinkError: no attach in java.library.path
Exception in thread "main" com.sun.tools.attach.AttachNotSupportedException:
no providers installed
at com.sun.tools.attach.VirtualMachine.attach(...
How to install attach provider without specifying -Djava.library.path to point attach.dll at startup?
The API you are using is using loadLibrary(String). It seems you cannot successfully pre-empt (cause it to succeed) this by invoking the more explicit load(String) first.
So you must to specify the path in java.library.path.
That System property is set once early in JVM lifecycle and is not modifiable by standard means.
So the conventional solution will be to pass an appropriate java.library.path when you launch the JVM.
Alternatively, you could look into the hacks to change this property after JVM startup using reflection. I have not tried any of these.
For example, see here:
System.setProperty( "java.library.path", "/path/to/libs" );
Field fieldSysPath = ClassLoader.class.getDeclaredField( "sys_paths" );
fieldSysPath.setAccessible( true );
fieldSysPath.set( null, null );
BTW, I would recommend pre-pending your custom path to the existing path, rather than replacing it.
Related
Has anyone tried the plugin to build an executable war/jar using Tomcat 9?
I attempted to do so however ran into:
Exception in thread "main" java.lang.NoSuchMethodError: org.apache.catalina.startup.Catalina.setConfig(Ljava/lang/String;)V
at org.apache.tomcat.maven.runner.Tomcat7Runner.run(Tomcat7Runner.java:240)
at org.apache.tomcat.maven.runner.Tomcat7RunnerCli.main(Tomcat7RunnerCli.java:204)
I looked at the source and changed Catalina.setConfig() to Catalina.setConfigFile() based on docs here. After doing so the .extract dir is just empty:
use extractDirectory:.extract populateWebAppWarPerContext
warValue:ROOT.war|ROOT populateWebAppWarPerContext
contextValue/warFileName:ROOT/ROOT.war webappWarPerContext entry
key/value: ROOT/ROOT.war expand to file:.extract/webapps/ROOT.war
Exception in thread "main" java.lang.Exception: FATAL: impossible to
create directories:.extract/webapps at
org.apache.tomcat.maven.runner.Tomcat7Runner.extract(Tomcat7Runner.java:586)
at
org.apache.tomcat.maven.runner.Tomcat7Runner.run(Tomcat7Runner.java:204)
at
org.apache.tomcat.maven.runner.Tomcat7RunnerCli.main(Tomcat7RunnerCli.java:204)
.... although there is a ROOT.war, server.xml, web.xml in the *-exec-war.jar.
Is there a better way to be creating exec-jars with embedded tomcat 9?
For those looking for a solution it was fairly straight forward to checkout the code for the plugin and make a few changes to get this to work. Namely:
Update POM to change the depends to Tomcat 9
Fix compile errors which generally stem from deprecated methods. The lookup on these methods can be found here. For example:
- container.setConfig( serverXml.getAbsolutePath() );
+ container.setConfigFile( serverXml.getAbsolutePath() );
... and ...
- staticContext.addServletMapping( "/", "staticContent" );
+ staticContext.addServletMappingDecoded( "/", "staticContent" );
There are a few others but generally not difficult to resolve. After doing so I updated my app's pom to use the modified version and was able to generate a Tomcat 9 exec jar.
I would love to hear what others are doing here. I know some are programmatically initializing Tomcat via a new Tomcat() instance however curious what other solutions exist ready made. Thanks
For future searchs, one solution is to use the DirResourceSet or JarResourceSet.
String webAppMount = "/WEB-INF/classes";
WebResourceSet webResourceSet;
if (!isJar()) {
webResourceSet = new DirResourceSet(webResourceRoot, webAppMount, getResourceFromFs(), "/");
} else {
webResourceSet = new JarResourceSet(webResourceRoot, webAppMount, getResourceFromJarFile(), "/");
}
webResourceRoot.addJarResources(webResourceSet);
context.setResources(webResourceRoot);
public static boolean isJar() {
URL resource = Main.class.getResource("/");
return resource == null;
}
public static String getResourceFromJarFile() {
File jarFile = new File(System.getProperty("java.class.path"));
return jarFile.getAbsolutePath();
}
public static String getResourceFromFs() {
URL resource = Main.class.getResource("/");
return resource.getFile();
}
When add the webapp, use root path "/" for docBase:
tomcat.addWebapp("", "/")
Credits for:
https://nkonev.name/post/101
I am running a servlet program to read an image using opencv,
getting error :
java.lang.UnsatisfiedLinkError: Native Library C:\opencv\build\java\x64\opencv_java300.dll already loaded in another classloader . When restarting the IDE it works fine.
I loaded System.loadLibrary ( Core.NATIVE_LIBRARY_NAME ) ; in servlet only ones.
Can anybody suggest a solution for how to unload it. And also anybody know how to read an image from browser using opencv in java.?
It is because the library is not in the system path, it needs to first added to the system path, then load. First extract the OpenCV to C drive something like this c:\opencv\... then use this code below to during initializing, it will automatically load the OpenCV lib in windows environment.
public static void loadOpenCV_Lib() throws Exception {
String model = System.getProperty("sun.arch.data.model");
String libraryPath = "C:/opencv/build/java/x86/";
if(model.equals("64")) {
libraryPath = "C:/opencv/build/java/x64/";
}
System.setProperty("java.library.path", libraryPath);
Field sysPath = ClassLoader.class.getDeclaredField("sys_paths");
sysPath.setAccessible(true);
sysPath.set(null, null);
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
}
And also it will automatically detect the system model and load the lib according to the system model.
My current java project is using methods and variables from another project (same package). Right now the other project's jar has to be in the classpath to work correctly. My problem here is that the name of the jar can and will change because of increasing versions, and because you cannot use wildcards in the manifest classpath, it's impossible to add it to the classpath. So currently the only option of starting my application is using the -cp argument from the command line, manually adding the other jar my project depends on.
To improve this, I wanted to load the jar dynamically and read about using the ClassLoader. I read a lot of examples for it, however I still don't understand how to use it in my case.
What I want is it to load a jar file, lets say, myDependency-2.4.1-SNAPSHOT.jar, but it should be able to just search for a jar file starting with myDependency- because as I already said the version number can change at anytime. Then I should just be able to use it's methods and variables in my Code just like I do now (like ClassInMyDependency.exampleMethod()).
Can anyone help me with this, as I've been searching the web for a few hours now and still don't get how to use the ClassLoader to do what I just explained.
Many thanks in advance
(Applies to Java version 8 and earlier).
Indeed this is occasionally necessary. This is how I do this in production. It uses reflection to circumvent the encapsulation of addURL in the system class loader.
/*
* Adds the supplied Java Archive library to java.class.path. This is benign
* if the library is already loaded.
*/
public static synchronized void loadLibrary(java.io.File jar) throws MyException
{
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 java.lang.NoSuchMethodException |
java.lang.IllegalAccessException |
java.net.MalformedURLException |
java.lang.reflect.InvocationTargetException e){
throw new MyException(e);
}
}
I needed to load a jar file at runtime for both java 8 and java 9+. Here is the method to do it (using Spring Boot 1.5.2 if it may relate).
public static synchronized void loadLibrary(java.io.File jar) {
try {
java.net.URL url = jar.toURI().toURL();
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(Thread.currentThread().getContextClassLoader(), new Object[]{url});
} catch (Exception ex) {
throw new RuntimeException("Cannot load library from jar file '" + jar.getAbsolutePath() + "'. Reason: " + ex.getMessage());
}
}
I want to point my play application to a particular application config file based on the environment it is running in. There are three and they correspond to the standard Play states:
application.dev.conf
application.test.conf
application.prod.conf
A co-worker shared a method for doing this which requires setting an OS environment variable.
I'd like to eliminate the need to set an OS variable.
My preference is the use whatever Play uses at startup to know what mode it is in.
For example, if you execute play run from the command line, part of the output is "[info] play - Application started (Dev)"
I want to use this information in my Global.java where I override onLoadConfig like so:
public Configuration onLoadConfig(Configuration baseConfiguration, File f, ClassLoader loader) {
String playEnv=<some static method to get mode>;
Config additionalConfig = ConfigFactory.parseFile(new File(f,"conf/application."+playEnv+".conf"));
Config baseConfig = baseConfiguration.getWrappedConfiguration().underlying();
return new Configuration(baseConfig.withFallback(additionalConfig));
}
Everything that I find is how to do this after the application has been started i.e. using isDev(), isTest(), isProd().
Is there static method that provides the mode while I am overriding onLoadConfig in Global.java?
I think play run is dev, play start is prod.
EDIT: If you're looking to see what the current mode is, it's passed in through play.api.Play.current:
Play.current.mode match {
case Play.Mode.Dev => "dev"
case Play.Mode.Prod => "prod"
}
The issue appeared to be addressed in the latest Play (3.0.0). There is another onLoadConfig method added to Global witch has a mode: {Dev,Prod,Test} parameter.
public Configuration onLoadConfig(Configuration config, File path, ClassLoader classloader, Mode mode) {
return onLoadConfig(config, path, classloader); // default implementation
}
Play allows to specifying alternative configuration file with command line so no need for setting OS variables.
You can of course create some bash script / bat file to avoid writing it every time
I need to find a way to change the settings of proxy on the IE 9.
I know a way directly in the reg., but ie9 doesn't refresh after I set them.
I tried to use another solution with jna:
Invoke WinInet Functions Used Java + JNA
In my case I use only:
System.out.println("Set refreshed...");
if (!WinInet.INSTANCE.InternetSetOption(
hInternet, WinInet.INTERNET_OPTION_REFRESH, (Pointer) null, len)) {
System.out.println("InternetSetOption failed!:"
+ Kernel32.INSTANCE.GetLastError());
but I get this error:
Set refreshed...
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError:
com/sun/jna/platform/win32/WinDef$DWORD
I downloaded the lib jars from here:
http://java.net/projects/jna/downloads/directory/3.3.0
Thank you.
makesure you have platform-3.4.0.jar and jna-3.4.0.jar in your classpath