Motivation:
When system property is empty, the default value should be used.
Modification:
- Correctly use the default value in all cases
- Add unit tests
Result:
Correct behaviour
Motivation:
At the moment there is not way for the user to know if resolving a domain was failed because the domain was unkown or because of an IO error / timeout. If it was caused by an timeout / IO error the user may want to retry the query. Also if the query was failed because of an IO error / timeout we should not cache it.
Modifications:
- Add DnsNameResolverTimeoutException and include it in the UnkownHostException if the domain could not be resolved because of an timeout. This will allow the user to retry the query when inspecting the cause.
- Do not cache IO errors / timeouts
- Add unit test
Result:
Easier for users to implement retries for DNS querys and not cache IO errors / timeouts.
Motivation:
At the moment there is not way for the user to know if resolving a domain was failed because the domain was unkown or because of an IO error / timeout. If it was caused by an timeout / IO error the user may want to retry the query. Also if the query was failed because of an IO error / timeout we should not cache it.
Modifications:
- Add DnsNameResolverTimeoutException and include it in the UnkownHostException if the domain could not be resolved because of an timeout. This will allow the user to retry the query when inspecting the cause.
- Do not cache IO errors / timeouts
- Add unit test
Result:
Easier for users to implement retries for DNS querys and not cache IO errors / timeouts.
Motivation:
DefaultHttpHeader.names() exposes HTTP header names as a Set<String>. Converting the resulting set to an array using toArray(String[]) throws an exception: java.lang.ArrayStoreException: io.netty.util.AsciiString.
Modifications:
- Remove our custom implementation of toArray(...) (and others) by just extending AbstractCollection.
- Add unit test
Result:
Fixes [#7428].
Motivation:
HttpConversionUtil#toHttp2Headers has special code to filter the TE header name. However this filtering code may result in adding the <TE, TRAILERS> tuple in scenarios that are not appropriate. For example if a value containing trailers is seen it will be added, but the value could not actually be equal to trailers. Also CSV values are not supported.
Modifications:
- Account for CSV header values
- Account for the value containing 'trailers' but not actually being equal to 'trailers'
Result:
More robust parsing of the TE header.
Motivation:
For debugging/logging purpose, it would be convenient to have
HttpHeaders#toString implemented.
DefaultHeaders does implement toString be the implementation is suboptimal and allocates a Set for the names and Lists for values.
Modification:
* Introduce HeadersUtil#toString that provides a convenient optimized helper to implement toString for various headers implementations
* Have DefaultHeaders#toString and HttpHeaders#toString delegate their toString implementation to HeadersUtil
Result:
Convenient HttpHeaders#toString. Optimized DefaultHeaders#toString.
Motivation:
To better isolate OS system calls we should not call getsockopt directly but use our netty_unix_socket_getOption0 function. See is a followup of f115bf5.
Modifications:
Export netty_unix_socket_getOption0 by declaring it in the header file and use it
Result:
Better isolation of system calls.
Motivation:
Its possible that cleanup() will throw if invalid data is passed into the wrapped EmbeddedChannel. We need to ensure we still call channelInactive(...) in this case.
Modifications:
- Correctly forward Exceptions caused by cleanup()
- Ensure all content is released when cleanup() throws
- Add unit tests
Result:
Correctly handle the case when cleanup() throws.
Motivation:
https://github.com/netty/netty/issues/7418 reported an issue with writing a LastHttpContent with trailers set.
Modifications:
Add unit test to ensure this issue is fixed in latest netty release.
Result:
Ensure code is correct.
Modifications:
HttpConversionUtil#toLowercaseMap requires an intermediate List to be allocated. This can be avoided with the recently added value iterator methods.
Modifications:
- Use HttpHeaders#valueCharSequenceIterator instead of getAll
Result:
Less intermediate object allocation and copying.
Motivation:
Minor cleanup from 844d804 just to reduce the conditional statements and indentation level.
Modifications:
- combine the else + if into an else if statement
Result:
Code cleaned up.
Motivation:
HttpMethod#valueOf shows up on profiler results in the top set of
results. Since it is a relatively simple operation it can be improved in
isolation.
Modifications:
- Introduce a special case map which assigns each HttpMethod to a unique
index in an array and provides constant time lookup from a hash code
algorithm. When the bucket is matched we can then directly do equality
comparison instead of potentially following a linked structure when
HashMap has hash collisions.
Result:
~10% improvement in benchmark results for HttpMethod#valueOf
Benchmark Mode Cnt Score Error Units
HttpMethodMapBenchmark.newMapKnownMethods thrpt 16 31.831 ± 0.928 ops/us
HttpMethodMapBenchmark.newMapMixMethods thrpt 16 25.568 ± 0.400 ops/us
HttpMethodMapBenchmark.newMapUnknownMethods thrpt 16 51.413 ± 1.824 ops/us
HttpMethodMapBenchmark.oldMapKnownMethods thrpt 16 29.226 ± 0.330 ops/us
HttpMethodMapBenchmark.oldMapMixMethods thrpt 16 21.073 ± 0.247 ops/us
HttpMethodMapBenchmark.oldMapUnknownMethods thrpt 16 49.081 ± 0.577 ops/us
Motivation:
In order to determine if a header contains a value we currently rely
upon getAll(..) and regular expressions. This operation is commonly used
during the encode and decode stage to determine the transfer encoding
(e.g. HttpUtil#isTransferEncodingChunked). This operation requires an
intermediate collection and possibly regular expressions for the
CombinedHttpHeaders use case which can be expensive.
Modifications:
- Add a valuesIterator to HttpHeaders and specializations of this method
for DefaultHttpHeaders, ReadOnlyHttpHeaders, and CombinedHttpHeaders.
Result:
Less intermediate collections and allocation overhead when determining
if HttpHeaders contains a name/value pair.
Motivation:
DefaultHttp2FrameWriter#writeData allocates a DataFrameHeader for each write operation. DataFrameHeader maintains internal state and allocates multiple slices of a buffer which is a maximum of 30 bytes. This 30 byte buffer may not always be necessary and the additional slice operations can utilize retainedSlice to take advantage of pooled objects. We can also save computation and object allocations if there is no padding which is a common case in practice.
Modifications:
- Remove DataFrameHeader
- Add a fast path for padding == 0
Result:
Less object allocation in DefaultHttp2FrameWriter
Motivation:
DN resolution does not fall back to the "original name" lookup after search list is checked. This results in a failure to resolve any name (outside of search list) that has number of dots less than resolv.conf's ndots value (which, for example, is often the case in the context of Kubernetes where kubelet passes on resolv.conf containing "options ndots:5").
It also does not go through the search list in a situation described in resolv.conf man:
"The default for n[dots] is 1, meaning that if there are any dots in a name, the name will be tried first as an absolute name before any search list elements are appended to it."
Modifications:
DnsNameResolverContext::resolve was updated to match Go's https://github.com/golang/go/blob/release-branch.go1.9/src/net/dnsclient_unix.go#L338 logic.
Result:
DnsNameResolverContext::resolve will now try to resolve "original name" if search list yields no results when number of dots in the original name is less than resolv.conf's ndots value. It will also go through the search list in case "origin name" resolution fails and number of dots is equal or larger than resolv.conf's ndots value.
Motivation:
AbstractByteBuf#readSlice relied upon the bounds checking of the slice operation in order to detect index out of bounds conditions. However the slice bounds checking operation allows for the slice to go beyond the writer index, and this is out of bounds for a read operation.
Modifications:
- AbstractByteBuf#readSlice and AbstractByteBuf#readRetainedSlice should ensure the desired amount of bytes are readable before taking a slice
Result:
No reading of undefined data in AbstractByteBuf#readSlice and AbstractByteBuf#readRetainedSlice.
Motivation:
If the HttpUtil class is initialized before HttpHeaders or
EmptyHttpHeaders, EmptyHttpHeaders.INSTANCE will be null. This
can lead to NPEs in code that relies on this field being
non-null. One example is the
LastHttpContent.EMPTY_LAST_CONTENT.trailingHeaders method.
Modifications:
- Move HttpUtil.EMPTY_HEADERS to a private static final inner class
of EmptyHttpHeaders called InstanceInitializer.
- Add tests, that when run in isolation, validate the fix for the issue.
Result:
Any initialization order of HttpUtil, EmptyHttpHeaders or
HttpHeaders will result in EmptyHttpHeaders.INSTANCE being initialized
correctly.
Motivation:
Netty could handle "connection" or "te" headers more gently when
converting from http/1.1 to http/2 headers. Http/2 headers don't
support single-hop headers, so when we convert from http/1.1 to http/2,
we should drop all single-hop headers. This includes headers like
"transfer-encoding" and "connection", but also the headers that
"connection" points to, since "connection" can be used to designate
other headers as single-hop headers. For the "te" header, we can more
permissively convert it by just dropping non-conforming headers (ie
non-"trailers" headers) which is what we do for all other headers when
we convert.
Modifications:
Add a new blacklist to the http/1.1 to http/2 conversion, which is
constructed from the values of the "connection" header, and stop
throwing an exception when a "te" header is passed with a non-"trailers"
value. Instead, drop all values except for "trailers". Add unit tests
for "connection" and "te" headers when converting from http/1.1 to http/2.
Result:
This will improve the h2c upgrade request, and also conversions from
http/1.1 to http/2. This will simplify implementing spec-compliant
http/2 servers that want to share code between their http/1.1 and http/2
implementations.
[Fixes#7355]
Motivation:
We should not fire a SslHandshakeEvent if the channel is closed but the handshake was not started.
Modifications:
- Add a variable to SslHandler which tracks if an handshake was started yet or not and depending on this fire the event.
- Add a unit test
Result:
Fixes [#7262].
Motivation:
If a user calls EpollSocketChannelConfig.getOptions() and TCP_FASTOPEN_CONNECT is not supported we throw an exception.
Modifications:
- Just return 0 if ENOPROTOOPT is set.
- Add testcase
Result:
getOptions() works as epxected.
Motivation:
The behavior for SelectorFailureBehavior and SelectedListenerFailureBehavior enum values are not clear. Additional comments would clarify the expected behavior.
Modifications:
- Add comments for each value in SelectedListenerFailureBehavior and SelectorFailureBehavior which clarify the expected behavior
Result:
The behavior of SelectedListenerFailureBehavior and SelectorFailureBehavior are more clearly communicated.
Motivation:
According to RFC 7231 the server may choose to:
```
indicate a zero-length payload for the response by including a
Transfer-Encoding header field with a value of chunked and a message
body consisting of a single chunk of zero-length
```
https://tools.ietf.org/html/rfc7231#page-53
In such cases the exception below appears during decoding phase:
```
java.lang.IllegalArgumentException: invalid version format: 0
at io.netty.handler.codec.http.HttpVersion.<init>(HttpVersion.java:121)
at io.netty.handler.codec.http.HttpVersion.valueOf(HttpVersion.java:76)
at io.netty.handler.codec.http.HttpResponseDecoder.createMessage(HttpResponseDecoder.java:118)
at io.netty.handler.codec.http.HttpObjectDecoder.decode(HttpObjectDecoder.java:219)
```
Modifications:
HttpObjectDecoder.isContentAlwaysEmpty specifies content NOT empty
when 205 Reset Content response
Result:
There is no `IllegalArgumentException: invalid version format: 0`
when handling 205 Reset Content response with transfer-encoding
Motivation:
`FixedChannelPool` allows users to configure `acquireTimeoutMillis`
and expects given value to be greater or equal to zero when timeout
action is supplied. However, validation error message said that
value is expected to be greater or equal to one. Code performs
check against zero.
Modifications:
Changed error message to say that value greater or equal to
zero is expected. Added test to check that zero is an acceptable
value.
Result:
Exception with right error message is thrown.
Motivation:
We should not try to use UnixResolverDnsServerAddressStreamProvider when on Windows as it will log some error that will produce noise and may confuse users.
Modifications:
Just use DefaultDnsServerAddressStreamProvider if windows is used.
Result:
Less noise in the logs. This was reported in vert.x: https://github.com/eclipse/vert.x/issues/2204
Motivation:
`AbstractScheduledEventExecutor` uses a standard `java.util.PriorityQueue` to keep track of task deadlines. `ScheduledFuture.cancel` removes tasks from this `PriorityQueue`. Unfortunately, `PriorityQueue.remove` has `O(n)` performance since it must search for the item in the entire queue before removing it. This is fast when the future is at the front of the queue (e.g., already triggered) but not when it's randomly located in the queue.
Many servers will use `ScheduledFuture.cancel` on all requests, e.g., to manage a request timeout. As these cancellations will be happen in arbitrary order, when there are many scheduled futures, `PriorityQueue.remove` is a bottleneck and greatly hurts performance with many concurrent requests (>10K).
Modification:
Use netty's `DefaultPriorityQueue` for scheduling futures instead of the JDK. `DefaultPriorityQueue` is almost identical to the JDK version except it is able to remove futures without searching for them in the queue. This means `DefaultPriorityQueue.remove` has `O(log n)` performance.
Result:
Before - cancelling futures has varying performance, capped at `O(n)`
After - cancelling futures has stable performance, capped at `O(log n)`
Benchmark results
After - cancelling in order and in reverse order have similar performance within `O(log n)` bounds
```
Benchmark (num) Mode Cnt Score Error Units
ScheduledFutureTaskBenchmark.cancelInOrder 100 thrpt 20 137779.616 ± 7709.751 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 1000 thrpt 20 11049.448 ± 385.832 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 10000 thrpt 20 943.294 ± 12.391 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 100000 thrpt 20 64.210 ± 1.824 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 100 thrpt 20 167531.096 ± 9187.865 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 1000 thrpt 20 33019.786 ± 4737.770 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 10000 thrpt 20 2976.955 ± 248.555 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 100000 thrpt 20 362.654 ± 45.716 ops/s
```
Before - cancelling in order and in reverse order have significantly different performance at higher queue size, orders of magnitude worse than the new implementation.
```
Benchmark (num) Mode Cnt Score Error Units
ScheduledFutureTaskBenchmark.cancelInOrder 100 thrpt 20 139968.586 ± 12951.333 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 1000 thrpt 20 12274.420 ± 337.800 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 10000 thrpt 20 958.168 ± 15.350 ops/s
ScheduledFutureTaskBenchmark.cancelInOrder 100000 thrpt 20 53.381 ± 13.981 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 100 thrpt 20 123918.829 ± 3642.517 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 1000 thrpt 20 5099.810 ± 206.992 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 10000 thrpt 20 72.335 ± 0.443 ops/s
ScheduledFutureTaskBenchmark.cancelInReverseOrder 100000 thrpt 20 0.743 ± 0.003 ops/s
```
Motivation:
At the moment use loops to run SslHandler tests with different SslProviders which is error-prone and also make it difficult to understand with which provider these failed.
Modifications:
- Move unit tests that should run with multiple SslProviders to extra class.
- Use junit Parameterized to run with different SslProvider combinations
Result:
Easier to understand which SslProvider produced test failures
Motivation:
When calling CompositeBytebuf.copy() and copy(...) we currently use Unpooled to allocate the buffer. This is not really correct and may produce more GC then needed. We should use the allocator that was used when creating the CompositeByteBuf to allocate the new buffer which may be for example the PooledByteBufAllocator.
Modifications:
- Use alloc() to allocate the new buffer.
- Add tests
- Fix tests that depend on the copy to be backed by an byte-array without checking hasArray() first.
Result:
Fixes [#7393].
Motivation:
93130b172a introduced a regression where we not "converted" an empty HttpContent to ByteBuf and just passed it on in the pipeline. This can lead to the situation that other handlers in the pipeline will see HttpContent instances which is not expected.
Modifications:
- Correctly convert HttpContent to ByteBuf when empty
- Add unit test.
Result:
Handlers in the pipeline will see the expected message type.
Motivation:
When looking for a leak, its nice to be able to request at least a
number of leaks.
Modification:
* Made all leak records up to the target amoutn recorded, and only
then enable backing off.
* Enable recording more than 32 elements. Previously the shift
amount made this impossible.
Result:
Ability to record all accesses.
Motivation:
AbstractCoalescingBufferQueue#add accounts for void promises, but AbstractCoalescingBufferQueue#addFirst does not. These methods should be consistent.
Modifications:
- AbstractCoalescingBufferQueue#addFirst should account for void promises and share code with AbstractCoalescingBufferQueue#add
Result:
More correct void promise handling in AbstractCoalescingBufferQueue.
complete
Motivation:
SslHandler removes a Buffer/Promise pair from
AbstractCoalescingBufferQueue when wrapping data. However it is possible
the SSLEngine will not consume the entire buffer. In this case
SslHandler adds the Buffer back to the queue, but doesn't add the
Promise back to the queue. This may result in the promise completing
immediately in finishFlush, and generally not correlating to the
completion of writing the corresponding Buffer
Modifications:
- AbstractCoalescingBufferQueue#addFirst should also support adding the
ChannelPromise
- In the event of a handshake timeout we should immediately fail pending
writes immediately to get a more accurate exception
Result:
Fixes https://github.com/netty/netty/issues/7378.
Motivation:
For use cases that create headers, but do not need to modify them a read only variant of HttpHeaders would be useful and may be able to provide better iteration performance for encoding.
Modifications:
- Introduce ReadOnlyHttpHeaders that is backed by a flat array
Result:
ReadOnlyHttpHeaders exists for non-modifiable HttpHeaders use cases.
Motivation:
We need to set readPending to false when we detect a EOF while issue a read as otherwise we may not unregister from the Selector / Epoll / KQueue and so keep on receving wakeups.
The important bit is that we may even get a wakeup for a read event but will still will only be able to read 0 bytes from the socket, so we need to be very careful when we clear the readPending. This can happen because we generally using edge-triggered mode for our native transports and because of the nature of edge-triggered we may schedule an read event just to find out there is nothing left to read atm (because we completely drained the socket on the previous read).
Modifications:
Set readPending to false when EOF is detected.
Result:
Fixes [#7255].
Motivation:
SslHandler only supports ByteBuf objects, but will not release objects of other types. SslHandler will also not release objects if its internal state is not correctly setup.
Modifications:
- Release non-ByteBuf objects in write
- Release all objects if the SslHandler queue is not setup
Result:
Less leaks in SslHandler.
Motivation:
HTTP/2 allows writes of 0 length data frames. However in some cases EMPTY_BUFFER is used instead of the actual buffer that was written. This may mask writes of released buffers or otherwise invalid buffer objects. It is also possible that if the buffer is invalid AbstractCoalescingBufferQueue will not release the aggregated buffer nor fail the associated promise.
Modifications:
- DefaultHttp2FrameCodec should take care to fail the promise, even if releasing the data throws
- AbstractCoalescingBufferQueue should release any aggregated data and fail the associated promise if something goes wrong during aggregation
Result:
More correct handling of invalid buffers in HTTP/2 code.
This reverts commit 413c7c2cd8 as it introduced an regression when edge-triggered mode is used which is true for our native transports by default. With 413c7c2cd8 included it was possible that we set readPending to false by mistake even if we would be interested in read more.
Motivation:
7995afee8f introduced a change that broke special handling of WebSockets 00.
Modifications:
Correctly delegate to super method which has special handling for WebSockets 00.
Result:
Fixes [#7362].
Motivation:
HttpObjectEncoder and MessageAggregator treat buffers that are not readable special. If a buffer is not readable, then an EMPTY_BUFFER is written and the actual buffer is ignored. If the buffer has already been released then this will not be correct as the promise will be completed, but in reality the original content shouldn't have resulted in any write because it was invalid.
Modifications:
- HttpObjectEncoder should retain/write the original buffer instead of using EMPTY_BUFFER
- MessageAggregator should retain/write the original ByteBufHolder instead of using EMPTY_BUFFER
Result:
Invalid write operations which happen to not be readable correctly reflect failed status in the promise, and do not result in any writes to the channel.
infinite loop
Motivation:
If SslHandler sets jdkCompatibilityMode to false and ReferenceCountedOpenSslEngine sets jdkCompatibilityMode to true there is a chance we will get stuck in an infinite loop if the peer sends a TLS packet with length greater than 2^14 (the maximum length allowed in the TLS 1.2 RFC [1]). However there are legacy implementations which actually send larger TLS payloads than 2^14 (e.g. OpenJDK's SSLSessionImpl [2]) and in this case ReferenceCountedOpenSslEngine will return BUFFER_OVERFLOW in an attempt to notify that a larger buffer is to be used, but if the buffer is already at max size this process will repeat indefinitely.
[1] https://tools.ietf.org/html/rfc5246#section-6.2.1
[2] http://hg.openjdk.java.net/jdk8u/jdk8u/jdk/file/d5a00b1e8f78/src/share/classes/sun/security/ssl/SSLSessionImpl.java#l793
Modifications:
- Support TLS payload sizes greater than 2^14 in ReferenceCountedOpenSslEngine
- ReferenceCountedOpenSslEngine should throw an exception if a
BUFFER_OVERFLOW is impossible to rectify
Result:
No more infinite loop in ReferenceCountedOpenSslEngine due to
BUFFER_OVERFLOW and large TLS payload lengths.
Motivation:
ReferenceCountedOpenSslEngine.rejectRemoteInitiatedRenegotiation() is called in a finally block to ensure we always check for renegotiation. The problem here is that sometimes we will already shutdown the engine before we call the method which will lead to an NPE in this case as the ssl pointer was already destroyed.
Modifications:
Check that the engine is not destroyed yet before calling SSL.getHandshakeCount(...)
Result:
Fixes [#7353].
Motivation:
Some SSLEngine implementations (e.g. ReferenceCountedOpenSslContext) support unwrapping/wrapping multiple packets at a time. The SslHandler behaves differently if the SSLEngine supports this feature, but currently requires that the constructor argument between the SSLEngine creation and SslHandler are coordinated. This can be difficult, or require package private access, if extending the SslHandler.
Modifications:
- The SslHandler should inspect the SSLEngine to see if it supports jdkCompatibilityMode instead of relying on getting an extra constructor argument which maybe out of synch with the SSLEngine
Result:
Easier to override SslHandler and have consistent jdkCompatibilityMode between SSLEngine and SslHandler.
Motivation:
We should ensure we only try to load the netty-tcnative version that was compiled for the architecture we are using.
Modifications:
Include architecture into native lib name.
Result:
Only load native lib if the architecture is supported.
Motivation:
Linux kernel 4.11 introduced a new socket option,
TCP_FASTOPEN_CONNECT, that greatly simplifies making TCP Fast Open
connections on client side. Usually simply setting the flag before
connect() call is enough, no more changes are required.
Details can be found in kernel commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=19f6d3f3
Modifications:
TCP_FASTOPEN_CONNECT socket option was added to EpollChannelOption
class.
Result:
Netty clients can easily make TCP Fast Open connections. Simply
calling option(EpollChannelOption.TCP_FASTOPEN_CONNECT, true) in
client bootstrap is enough (given recent enough kernel).
This change allows to upgrade a plain HTTP 1.x connection to TLS
according to RFC 2817. Switching the transport layer to TLS should be
possible without removing HttpClientCodec from the pipeline,
because HTTP/1.x layer of the protocol remains untouched by the switch
and the HttpClientCodec state must be retained for proper
handling the remainder of the response message,
per RFC 2817 requirement in point 3.3:
Once the TLS handshake completes successfully, the server MUST
continue with the response to the original request.
After this commit, the upgrade can be established by simply
inserting an SslHandler at the front of the pipeline after receiving
101 SWITCHING PROTOCOLS response, exactly as described in SslHander
documentation.
Modifications:
- Don't set HttpObjectDecoder into UPGRADED state if
101 SWITCHING_PROTOCOLS response contains HTTP/1.0 or HTTP/1.1 in
the protocol stack described by the Upgrade header.
- Skip pairing comparison for 101 SWITCHING_PROTOCOLS, similar
to 100 CONTINUE, since 101 is not the final response to the original
request and the final response is expected after TLS handshake.
Fixes#7293.
Motivation:
Fix NullPointerExceptions that occur when running netty-tcnative inside the bootstrap class loader.
Modifications:
- Replace loader.getResource(...) with ClassLoader.getSystemResource(...) when loader is null.
- Replace loader.loadClass(...) with Class.forName(..., false, loader) which works when loader is both null and non-null.
Result:
Support running native libs in bootstrap class loader
