Reading my own Jar s Manifest

Question

I need to read the Manifest file  which delivered my class  but when I use   getClass   getClassLoader   getResources        I get the MANIFEST from the first  jar loaded into the Java Runtime  My app will be running from an applet or a webstart  so I will not have access to my own  jar file  I guess   I actually want to read the Export-package attribute from the  jar which started the Felix OSGi  so I can expose those packages to Felix  Any ideas

User · Answer

I believe the most appropriate way to get the manifest for any bundle (including the bundle which loaded a given class) is to use the Bundle or BundleContext object.

// If you have a BundleContext
Dictionary headers = bundleContext.getBundle().getHeaders();

// If you don't have a context, and are running in 4.2
Bundle bundle = FrameworkUtil.getBundle(this.getClass());
bundle.getHeaders();

Note that the Bundle object also provides getEntry(String path) to look up resources contained within a specific bundle, rather than searching that bundle's entire classpath.

In general, if you want bundle-specific information, do not rely upon assumptions about the classloaders, just use the OSGi APIs directly.

User · Answer

You can find the URL for your class first  If it s a JAR  then you load the manifest from there  For example   Class clazz   MyClass class  String className   clazz getSimpleName       class   String classPath   clazz getResource className  toString    if   classPath startsWith  jar           Class not from JAR   return    String manifestPath   classPath substring 0  classPath lastIndexOf        1           META-INF MANIFEST MF   Manifest manifest   new Manifest new URL manifestPath  openStream     Attributes attr   manifest getMainAttributes    String value   attr getValue  Manifest-Version

User · Answer

I will admit up front that this answer does not answer the original question  that of generally being able to access the Manifest  However if what is really required is to read one of a number of  standard  Manifest attributes  the following solution is much simpler than those posted above  So I hope that the moderator will allow it  Note that this solution is in Kotlin  not Java  but I would expect that a port to Java would be trivial   Although I admit I don t know the Java equivalent of    package     In my case I wanted to read the attribute  Implementation-Version  so I started with the solutions given above to obtain the stream and then read it to obtain the value  While this solution worked  a coworker reviewing my code showed me an easier way to do what I wanted  Note that this solution is in Kotlin  not Java   val myPackage   MyApplication  class java  package  val implementationVersion   myPackage implementationVersion   Once again note that this does not answer the original question  in particular  Export-package  does not seem to be one of the supported attributes  That said  there is a myPackage name that returns a value  Perhaps someone who understands this more than I can comment on whether that returns the value the original poster is requesting

User · Answer

A simpler way to do this is to use getPackage    For example  to get Implementation-Version  Application class getPackage   getImplementationVersion

User · Answer

You can use getProtectionDomain   getCodeSource   like this    URL url   Menu class getProtectionDomain   getCodeSource   getLocation    File file   DataUtilities urlToFile url   JarFile jar   null  try       jar   new JarFile file       Manifest manifest   jar getManifest        Attributes attributes   manifest getMainAttributes        return attributes getValue  Built-By      finally       jar close

User · Answer

I have used the solution from Anthony Juckel but in the MANIFEST MF the key have to start with uppercase   So my MANIFEST MF file contain a key like   Mykey  value  Then in the activator or another class you can use the code from Anthony to read the MANIFEST MF file and the the value that you need      If you have a BundleContext  Dictionary headers   bundleContext getBundle   getHeaders        If you don t have a context  and are running in 4 2  Bundle bundle    FrameworkUtil getBundle this getClass      bundle getHeaders

User · Answer

Why are you including the getClassLoader step  If you say  this getClass   getResource    you should be getting resources relative to the calling class  I ve never used ClassLoader getResource    though from a quick look at the Java Docs it sounds like that will get you the first resource of that name found in any current classpath

User · Answer

You can use Manifests from jcabi-manifests and read any attribute from any of available MANIFEST MF files with just one line   String value   Manifests read  My-Attribute      The only dependency you need is    lt dependency gt     lt groupId gt com jcabi lt  groupId gt     lt artifactId gt jcabi-manifests lt  artifactId gt     lt version gt 0 7 5 lt  version gt   lt  dependency gt    Also  see this blog post for more details  http   www yegor256 com 2014 07 03 how-to-read-manifest-mf html

User · Answer

The easiest way is to use JarURLConnection class    String className   getClass   getSimpleName       class   String classPath   getClass   getResource className  toString    if   classPath startsWith  jar          return DEFAULT PROPERTY VALUE     URL url   new URL classPath   JarURLConnection jarConnection    JarURLConnection  url openConnection    Manifest manifest   jarConnection getManifest    Attributes attributes   manifest getMainAttributes    return attributes getValue PROPERTY NAME     Because in some cases    class getProtectionDomain   getCodeSource   getLocation    gives path with vfs    so this should be handled additionally

User · Answer

public static Manifest getManifest  Class lt   gt  cl         InputStream inputStream   null      try         URLClassLoader classLoader    URLClassLoader cl getClassLoader          String classFilePath   cl getName   replace            class         URL classUrl   classLoader getResource classFilePath         if   classUrl  null   return null        String classUri   classUrl toString          if    classUri startsWith  jar      return null        int separatorIndex   classUri lastIndexOf             if   separatorIndex lt  0   return null        String manifestUri   classUri substring 0 separatorIndex 2   META-INF MANIFEST MF         URL url   new URL manifestUri         inputStream   url openStream          return new Manifest  inputStream          catch   Throwable e              handle errors                 return null        finally         if   inputStream  null             try             inputStream close              catch   Throwable e                  ignore

User · Answer

The following code works with multiple types of archives  jar  war  and multiple types of classloaders  jar  url  vfs          public static Manifest getManifest Class lt   gt  clz        String resource         clz getName   replace               class       String fullPath   clz getResource resource  toString        String archivePath   fullPath substring 0  fullPath length   - resource length         if  archivePath endsWith    WEB-INF  classes      archivePath endsWith   WEB-INF classes            archivePath   archivePath substring 0  archivePath length   -   WEB-INF classes  length        Required for wars            try  InputStream input   new URL archivePath     META-INF MANIFEST MF   openStream            return new Manifest input         catch  Exception e          throw new RuntimeException  Loading MANIFEST for class     clz     failed    e

User · Answer

You can do one of two things    Call getResources   and iterate through the returned collection of URLs  reading them as manifests until you find yours   Enumeration lt URL gt  resources   getClass   getClassLoader      getResources  META-INF MANIFEST MF    while  resources hasMoreElements          try         Manifest manifest   new Manifest resources nextElement   openStream              check that this is your manifest and do what you need or get the next one                 catch  IOException E             handle          You can try checking whether getClass   getClassLoader   is an instance of java net URLClassLoader  Majority of Sun classloaders are  including AppletClassLoader   You can then cast it and call findResource   which has been known - for applets  at least - to return the needed manifest directly   URLClassLoader cl    URLClassLoader  getClass   getClassLoader    try     URL url   cl findResource  META-INF MANIFEST MF      Manifest manifest   new Manifest url openStream          do stuff with it         catch  IOException E         handle

User · Answer

I have this weird solution that runs war applications in a embedded Jetty server but these apps need also to run on standard Tomcat servers  and we have some special properties in the manfest   The problem was that when in Tomcat  the manifest could be read  but when in jetty  a random manifest was picked up  which missed the special properties   Based on Alex Konshin s answer  I came up with the following solution  the inputstream is then used in a Manifest class    private static InputStream getWarManifestInputStreamFromClassJar Class lt   gt  cl         InputStream inputStream   null      try           URLClassLoader classLoader    URLClassLoader cl getClassLoader            String classFilePath   cl getName   replace            class           URL classUrl   classLoader getResource classFilePath           if   classUrl  null   return null          String classUri   classUrl toString            if    classUri startsWith  jar      return null          int separatorIndex   classUri lastIndexOf               if   separatorIndex lt  0   return null          String jarManifestUri   classUri substring 0 separatorIndex 2           String containingWarManifestUri   jarManifestUri substring 0 jarManifestUri indexOf  WEB-INF    replace  jar file     file         MANIFEST FILE PATH          URL url   new URL containingWarManifestUri           inputStream   url openStream            return inputStream        catch   Throwable e                handle errors         LOGGER warn  No manifest file found in war file  e           return null

[java] Reading my own Jar's Manifest

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