> Can I please get a review of this change which proposes to fix the issue > noted in https://bugs.openjdk.org/browse/JDK-8308184? > > When an application is launched, the `app` classloader internally uses a > `jdk.internal.loader.URLClassPath` to find and load the main class being > launched. The `URLClassPath` uses a list of classpath entries to find > resources. Depending on the classpath entry, the `URLClassPath` will use a > relevant loader. A couple of such loaders are `URLClassPath$FileLoader` (for > loading resources from directories) and `URLClassPath$JarLoader` (for loading > resources from jar files). > > `JarLoader` creates instances of `java.net.URL` to represent the jar file > being loaded. `java.net.URL` uses protocol specific > `java.net.URLStreamHandler` instance to handle connections to those URLs. > When constructing an instance of `URL`, callers can pass a protocol handler. > If it is not passed then the `URL` class looks for protocol handlers that > might have been configured by the application. The > `java.protocol.handler.pkgs` system property is the one which allows > overriding the protocol handlers (even for the `jar` protocol). When this > property is set, the `URL` class triggers lookup and classloading of the > protocol handler classes. > > The issue that is reported is triggered when the `java.protocol.handler.pkgs` > system property is set and the classpath has too many jar files. `app` > classloader triggers lookup of the main class and the `URLClassPath` picks up > the first entry in the classpath and uses a `JarLoader` (in this example our > classpath entries have a jar file at the beginning of the list). The > `JarLoader` instantiates a `java.net.URL`, which notices that the > `java.protocol.handler.pkgs` is set, so it now triggers lookup of a > (different) class using the same classloader and thus the same > `URLClassPath`. The `URLClassPath` picks the next classpath entry and then > calls into the `URL` again through the `JarLoader`. This sequence ends up > being re-entrant calls and given the large number of classpath entries, these > re-entrant calls end up with a `StackOverflowError` as shown in the linked > JBS issue. > > The commit in this PR fixes this issue by using the system provided protocol > handler implementation of the `jar` protocol in the `app` classloader. This > results in the `URL` instances created through the `JarLoader` to use this > specific handler instance. This allows the `app` classloader which is > responsible for loading the application's main class to reliably use th...
Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision: Alan's review suggestion - no need to pass jarHandler as a parameter to the URLClassPath ------------- Changes: - all: https://git.openjdk.org/jdk/pull/14395/files - new: https://git.openjdk.org/jdk/pull/14395/files/418dd36d..2fdb5679 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=14395&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14395&range=00-01 Stats: 15 lines in 2 files changed: 4 ins; 6 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/14395.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/14395/head:pull/14395 PR: https://git.openjdk.org/jdk/pull/14395
