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Fix build break when missing netty-dns-resolver #1547

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Merged
merged 1 commit into from
Dec 22, 2020
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Fix build break when missing netty-dns-resolver #1547

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15 changes: 9 additions & 6 deletions src/main/java/io/lettuce/core/resource/AddressResolverGroupProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,11 +29,10 @@ class AddressResolverGroupProvider {
static {
boolean dnsResolverAvailable = LettuceClassUtils.isPresent("io.netty.resolver.dns.DnsAddressResolverGroup");

// create addressResolverGroup instance via Supplier to avoid NoClassDefFoundError.
AddressResolverGroup<?> group;
if (dnsResolverAvailable) {
logger.debug("Starting with netty's non-blocking DNS resolver library");
group = AddressResolverGroupProvider.defaultDnsAddressResolverGroup();
group = DefaultDnsAddressResolverGroupWrapper.INSTANCE;
} else {
logger.debug("Starting without optional netty's non-blocking DNS resolver library");
group = DefaultAddressResolverGroup.INSTANCE;
Expand All @@ -51,10 +50,14 @@ static AddressResolverGroup<?> addressResolverGroup() {
return ADDRESS_RESOLVER_GROUP;
}

private static AddressResolverGroup<?> defaultDnsAddressResolverGroup() {
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@yueki1993 yueki1993 Dec 3, 2020 •
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Here causes NoClassDefError because there are upcasts DnsAddressResolverGroup -> AddressResolverGroup) and DefaultDnsCnameCache -> DnsCnameCache.
I moved these to internal static class.

return new DnsAddressResolverGroup(new DnsNameResolverBuilder().channelType(Transports.datagramChannelClass())
.socketChannelType(Transports.socketChannelClass().asSubclass(SocketChannel.class))
.cnameCache(new DefaultDnsCnameCache()).resolveCache(new DefaultDnsCache()));
// Wraps DnsAddressResolverGroup to avoid NoClassDefFoundError.
private static class DefaultDnsAddressResolverGroupWrapper {

static AddressResolverGroup<?> INSTANCE = new DnsAddressResolverGroup(
new DnsNameResolverBuilder().channelType(Transports.datagramChannelClass())
.socketChannelType(Transports.socketChannelClass().asSubclass(SocketChannel.class))
.cnameCache(new DefaultDnsCnameCache()).resolveCache(new DefaultDnsCache()));

}

}