Java 确定一个类来自哪个 JAR 文件

Determine which JAR file a class is from

提问by

I am not in front of an IDE right now, just looking at the API specs.

我现在不在 IDE 面前，只是在查看 API 规范。

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

I want to determine which JAR file a class is from. Is this the way to do it?

我想确定一个类来自哪个 JAR 文件。这是这样做的方法吗？

采纳答案by Chandra Patni

Yes. It works for all classes except classes loaded by bootstrap classloader. The other way to determine is:

是的。它适用于除引导类加载器加载的类之外的所有类。另一种确定方法是：

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

As notnoop pointed out klass.getResource()method returns the location of the class file itself. For example:

正如notnoop指出的那样，klass.getResource()方法返回类文件本身的位置。例如：

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

The getProtectionDomain().getCodeSource().getLocation()method returns the location of the jar file or CLASSPATH

该getProtectionDomain().getCodeSource().getLocation()方法返回jar文件的位置或CLASSPATH

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

回答by notnoop

Checkout the LiveInjector.findPathJar()from Lombok Patcher LiveInjector.java. Note that it special cases where the file doesn't actually live in a jar, and you might want to change that.

LiveInjector.findPathJar()从Lombok PatcherLiveInjector.java结帐。请注意，在文件实际上并不存在于 jar 中的特殊情况下，您可能想要更改它。

/**
 * 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.");
    }
}

回答by Don

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();
    }


}

回答by Abhishek Chatterjee

Use

用

String path = <Any of your class within the jar>.class.getProtectionDomain().getCodeSource().getLocation().getPath(); 

If this contains multiple entries then do some substring operation.

如果这包含多个条目，则执行一些子字符串操作。