निर्धारित करें कि कौन सी जेएआर फ़ाइल एक कक्षा

Question

से है, मैं अभी एडीई के सामने नहीं हूं, बस एपीआई चश्मा देख रहा हूं।

CodeSource src = MyClass.class.getProtectionDomain().getCodeSource(); 
if (src != null) { 
    URL jar = src.getLocation(); 
} 

मैं यह निर्धारित करना चाहता हूं कि कौन सी जेएआर फ़ाइल कक्षा से है। क्या ऐसा करने का यह तरीका है?

Answer 1

हां। यह बूटस्ट्रैप क्लासलोडर द्वारा लोड की गई कक्षाओं को छोड़कर सभी वर्गों के लिए काम करता है। निर्धारित करने के लिए दूसरा रास्ता है:

Class klass = String.class; 
URL location = klass.getResource('/' + klass.getName().replace('.', '/') + ".class"); 

रूप notnoop ने बताया getProtectionDomain().getCodeSource().getLocation() विधि वर्ग फ़ाइल के ही स्थान देता है। उदाहरण के लिए:

jar:file:/jdk/jre/lib/rt.jar!/java/lang/String.class 
file:/projects/classes/pkg/MyClass$1.class 

klass.getResource() विधि जार फ़ाइल या CLASSPATH

file:/Users/home/java/libs/ejb3-persistence-1.0.2.GA.jar 
file:/projects/classes 

Answer 2

चेकआउट Lombok Patcher LiveInjector.java से LiveInjector.findPathJar() के स्थान देता है। ध्यान दें कि यह विशेष मामले हैं जहां फ़ाइल वास्तव में एक जार में नहीं रहती है, और आप इसे बदलना चाहेंगे।

/** 
* If the provided class has been loaded from a jar file that is on the local file system, will find the absolute path to that jar file. 
* 
* @param context The jar file that contained the class file that represents this class will be found. Specify {@code null} to let {@code LiveInjector} 
*    find its own jar. 
* @throws IllegalStateException If the specified class was loaded from a directory or in some other way (such as via HTTP, from a database, or some 
*        other custom classloading device). 
*/ 
public static String findPathJar(Class<?> context) throws IllegalStateException { 
    if (context == null) context = LiveInjector.class; 
    String rawName = context.getName(); 
    String classFileName; 
    /* rawName is something like package.name.ContainingClass$ClassName. We need to turn this into ContainingClass$ClassName.class. */ { 
     int idx = rawName.lastIndexOf('.'); 
     classFileName = (idx == -1 ? rawName : rawName.substring(idx+1)) + ".class"; 
    } 

    String uri = context.getResource(classFileName).toString(); 
    if (uri.startsWith("file:")) throw new IllegalStateException("This class has been loaded from a directory and not from a jar file."); 
    if (!uri.startsWith("jar:file:")) { 
     int idx = uri.indexOf(':'); 
     String protocol = idx == -1 ? "(unknown)" : uri.substring(0, idx); 
     throw new IllegalStateException("This class has been loaded remotely via the " + protocol + 
       " protocol. Only loading from a jar on the local file system is supported."); 
    } 

    int idx = uri.indexOf('!'); 
    //As far as I know, the if statement below can't ever trigger, so it's more of a sanity check thing. 
    if (idx == -1) throw new IllegalStateException("You appear to have loaded this class from a local jar file, but I can't make sense of the URL!"); 

    try { 
     String fileName = URLDecoder.decode(uri.substring("jar:file:".length(), idx), Charset.defaultCharset().name()); 
     return new File(fileName).getAbsolutePath(); 
    } catch (UnsupportedEncodingException e) { 
     throw new InternalError("default charset doesn't exist. Your VM is borked."); 
    } 
} 

Answer 3

private String resourceLookup(String lookupResourceName) { 



    try { 

     if (lookupResourceName == null || lookupResourceName.length()==0) { 
      return ""; 
     } 
     // "/java/lang/String.class" 

     // Check if entered data was in java class name format 
     if (lookupResourceName.indexOf("/")==-1) { 
      lookupResourceName = lookupResourceName.replaceAll("[.]", "/"); 
      lookupResourceName = "/" + lookupResourceName + ".class"; 
     } 

     URL url = this.getClass().getResource(lookupResourceName); 
     if (url == null) { 
      return("Unable to locate resource "+ lookupResourceName); 

     } 

     String resourceUrl = url.toExternalForm(); 

     Pattern pattern = 
      Pattern.compile("(zip:|jar:file:/)(.*)!/(.*)", Pattern.CASE_INSENSITIVE); 

     String jarFilename = null; 
     String resourceFilename = null; 
     Matcher m = pattern.matcher(resourceUrl); 
     if (m.find()) { 
      jarFilename = m.group(2); 
      resourceFilename = m.group(3); 
     } else { 
      return "Unable to parse URL: "+ resourceUrl; 

     } 

     if (!jarFilename.startsWith("C:")){ 
      jarFilename = "/"+jarFilename; // make absolute path on Linux 
     } 

     File file = new File(jarFilename); 
     Long jarSize=null; 
     Date jarDate=null; 
     Long resourceSize=null; 
     Date resourceDate=null; 
     if (file.exists() && file.isFile()) { 

      jarSize = file.length(); 
      jarDate = new Date(file.lastModified()); 

      try { 
       JarFile jarFile = new JarFile(file, false); 
       ZipEntry entry = jarFile.getEntry(resourceFilename); 
       resourceSize = entry.getSize(); 
       resourceDate = new Date(entry.getTime()); 
      } catch (Throwable e) { 
       return ("Unable to open JAR" + jarFilename + " "+resourceUrl +"\n"+e.getMessage()); 

      } 

      return "\nresource: "+resourceFilename+"\njar: "+jarFilename + " \nJarSize: " +jarSize+" \nJarDate: " +jarDate.toString()+" \nresourceSize: " +resourceSize+" \nresourceDate: " +resourceDate.toString()+"\n"; 


     } else { 
      return("Unable to load jar:" + jarFilename+ " \nUrl: " +resourceUrl); 

     } 
    } catch (Exception e){ 
     return e.getMessage(); 
    } 


}