Question

我现在不在IDE的前面，只看API规范。

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

我想确定一个类来自哪个JAR文件。这是这样做的吗？

Answer 1

是。它适用于除bootstrap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");

因为notnoop指出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$1.class

getProtectionDomain().getCodeSource().getLocation()方法返回jar文件或CLASSPATH

的位置

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

Answer 2

从Lombok Patcher LiveInjector.java查看LiveInjector.findPathJar()。请注意，特殊情况下文件实际上并不存在于jar中，您可能希望更改它。

/**
 * 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.");
    }
}

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();
    }


}

Answer 4

使用

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

如果其中包含多个条目，请执行一些子字符串操作。

Answer 5

在 Linux 中，我使用一个小脚本来帮助我找到可以在 find -exec 中使用的类位于哪个 jar 中：

findclass.sh：

unzip -l "$1" 2>/dev/null | grep $2 >/dev/null 2>&1 && echo "$1"

基本上，由于 jars 是 zip，unzip -l 将打印类资源列表，因此您必须将 . 转换为 /。您可以在脚本中使用 tr 执行替换，但在调用脚本时自己完成并不会太麻烦。

这个想法是在类路径的根目录上使用 find 来定位所有 jar，然后在所有找到的 jar 上运行 findclass.sh 以查找匹配项。

它不处理多目录，但如果你仔细选择根目录，你可以让它工作。

现在，找出包含类 org.apache.commons.lang3.RandomUtils 的 jar 以取消对项目的优化 (...)：

$ find ~/.m2/repository/ -type f -name '*.jar' -exec findclass.sh {} org/apache/commons/lang3/RandomUtils \;

.m2/repository/org/apache/commons/commons-lang3/3.7/commons-lang3-3.7.jar
.m2/repository/org/apache/commons/commons-lang3/3.6/commons-lang3-3.6.jar
.m2/repository/org/apache/commons/commons-lang3/3.6/commons-lang3-3.6-sources.jar
$

确定类来自哪个JAR文件

5 个答案: