[Rev 07] RFR: 6656: Allow capturing field values with path syntax
kxu at openjdk.java.net
Tue Jan 14 17:18:05 UTC 2020
> This patch implements [JMC-6656: Allow capturing field values with path syntax](https://bugs.openjdk.java.net/browse/JMC-6656).
> In the xml configuration, a field capture looks like:
> <name>a field value</name>
> <description>a field value capture with a path syntax</description>
> See `org/openjdk/jmc/agent/test/jfrprobes_template.xml` for more examples.
> There are currently two limitations to pay attention to:
> 1. Instrumentation point cannot be in synthesized classes:
> Instrumented classes are first loaded by obtaining the bytecode and inspected reflectively to resolve typing information. This fails if the class load is unable to provide the bytecode when `ClassLoader.getResouce()` is called. The cases where it might fail are unlikely to be for classes like proxies or auxiliaries for Java frameworks that have no visible equivalent.
> 2. Instrumentation is unable to access nestmates' private fields:
> Before [nest-base access control](https://openjdk.java.net/jeps/181) was introduced in Java 11, accessing nestmates' private fields is, while lexically correct, forbidden by the JVM. The Java compiler works around by inserting synthetic getters/setters. However, it's not for a BCI agent since changing the class structure is not allowed during class transformation.
> Please let me know your thoughts. Thank you very much!
The pull request has been updated with 1 additional commit.
- 10e48d58: update license header year values
- all: https://git.openjdk.java.net/jmc/pull/20/files
- new: https://git.openjdk.java.net/jmc/pull/20/files/09abbb99..10e48d58
- full: https://webrevs.openjdk.java.net/jmc/20/webrev.07
- incr: https://webrevs.openjdk.java.net/jmc/20/webrev.06-07
Stats: 25 lines in 24 files changed: 0 ins; 0 del; 25 mod
Fetch: git fetch https://git.openjdk.java.net/jmc pull/20/head:pull/20
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