[jira] [Work logged] (BCEL-317) Pluggable cache for ConstantUtf8

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BCEL-317?focusedWorklogId=253983&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-253983 ]

ASF GitHub Bot logged work on BCEL-317:
---------------------------------------

                Author: ASF GitHub Bot
            Created on: 04/Jun/19 19:34
            Start Date: 04/Jun/19 19:34
    Worklog Time Spent: 10m 
      Work Description: suztomo commented on pull request #26: [BCEL-317] Pluggable cache for ConstantUtf8
URL: https://github.com/apache/commons-bcel/pull/26
 
 
   
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 253983)
    Time Spent: 0.5h  (was: 20m)

> Pluggable cache for ConstantUtf8
> --------------------------------
>
>                 Key: BCEL-317
>                 URL: https://issues.apache.org/jira/browse/BCEL-317
>             Project: Commons BCEL
>          Issue Type: Improvement
>          Components: Main
>    Affects Versions: 6.3.1
>            Reporter: Tomo Suzuki
>            Priority: Minor
>         Attachments: 2644k_constantutf8_without_getCachedInstance.png, 621k_constantutf8_with_getCachedInstance.png
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> Follow-up of BCEL-186. This enhancement is to provide an option to cache ConstantUtf8 instances that have the same value.
>  
> Email thread: [bcel] Idea to share ConstantUtf8 of same value among JavaClass instances
> --------------------
>  We use BCEL library to inspect Java class. Thank you for the great library.
>   
>  When our tool checks classes in ~200 jar files, it creates more than 2 million BCEL ConstantUtf8 instances. I suspect many of them share the same values such as "java.lang.String".
>   
> Without cache, my tool created 2,6 million ConstantUtf8 instances (before failing OutOfMemoryError: GC overhead limit exceeded) to check ~200 jar files.
> !2644k_constantutf8_without_getCachedInstance.png!
>  
> With the cache, my tool created just 0.6 million ConstantUtf8 instances. It didn't throw the OutOfMemoryError.
> !621k_constantutf8_with_getCachedInstance.png!
>  
>  Old commit that made ConstantUtf8.getInstance [https://svn.apache.org/viewvc/commons/proper/bcel/trunk/src/main/java/org/apache/bcel/classfile/Constant.java?r1=1481383&r2=1481382&pathrev=1481383]
> The ConstantUtf8.getInstance has been unused in BCEL since BCEL-186 [http://svn.apache.org/viewvc/commons/proper/bcel/trunk/src/main/java/org/apache/bcel/classfile/ConstantUtf8.java?r1=1652541&r2=1652540&pathrev=1652541]
>  
> h1. How our project uses BCEL
>  - Our tool (Linkage Checker) creates BCEL's ClassPathRepository with around 200 JAR files as its input class path in ClassDumper.createClassRepository([source code URL|https://github.com/GoogleCloudPlatform/cloud-opensource-java/blob/239fb82e368b2c181e358359f758b33c0a122787/dependencies/src/main/java/com/google/cloud/tools/opensource/classpath/ClassDumper.java#L83])
> {code:java}
>   private static Repository createClassRepository(List<Path> paths) {
>     ClassPath classPath = new LinkageCheckClassPath(paths);
>     return new ClassPathRepository(classPath);   # This is BCEL API
>   }{code}
>  - reads JavaClasses one by one in ClassDumper.listClassesInJar ([source code URL|https://github.com/GoogleCloudPlatform/cloud-opensource-java/blob/239fb82e368b2c181e358359f758b33c0a122787/dependencies/src/main/java/com/google/cloud/tools/opensource/classpath/ClassDumper.java#L360]) through the ClassPathRepository.
> {code:java}
>   private ImmutableSet<JavaClass> listClassesInJar(Path jar) throws IOException {
>     ImmutableSet.Builder<JavaClass> javaClasses = ImmutableSet.builder();
>     for (String className : listClassNamesInJar(jar)) {
>       try {
>         JavaClass javaClass = classRepository.loadClass(className); # This is BCEL API. ConstantUtf8 is not cached.
>         javaClasses.add(javaClass);
>   ...(omit)
>     return javaClasses.build();
>   }{code}
>   Stacktrace from the ClassDumper.listClassesInJar to BCEL's ConstantUtf8.getInstance would look like this:
>   {code:java}
> ConstantUtf8.getInstance
> Constant.readConstant
> ConstantPool.<init>
> ClassParser.readConstantPool
> ClassParser.parse
> ClassPathRepository.loadClass
> ClassPathRepository.loadClass
> ClassDumper.listClassesInJar {code}
>  - Use the JavaClass instances to check if any symbol references (entries in constant pool [Java Virtual Machine Specification 4.4. The Constant Pool|https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4]: CONSTANT_Class, CONSTANT_Fieldref, CONSTANT_Methodref, and CONSTANT_InterfaceMethodref) has invalid referent in the class path.
>  
>  
>  



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