Package com.alibaba.dcm

Class DnsCacheManipulator

java.lang.Object

com.alibaba.dcm.DnsCacheManipulator

@ParametersAreNonnullByDefault
@ReturnValuesAreNonnullByDefault
public final class DnsCacheManipulator
extends Object

DNS cache manipulator for querying/setting dns(in fact dns cache).

Throw DnsCacheManipulatorException if operation fail for all methods.

Author:

Jerry Lee (oldratlee at gmail dot com)

See Also:

DnsCache, DnsCacheEntry, DnsCacheManipulatorException

Method Summary

Modifier and Type	Method	Description
static void	clearDnsCache()	Clear whole dns cache entries(including cache and negative cache), cause lookup dns server for all host after.
static List<DnsCacheEntry>	getAllDnsCache()	Deprecated. this method name is confused: method name is "all" but without negative cache.
static DnsCacheEntry	getDnsCache(String host)	Get a dns cache entry by host.
static int	getDnsCachePolicy()	Get JVM DNS cache policy.
static int	getDnsNegativeCachePolicy()	JVM DNS negative cache policy.
static DnsCache	getWholeDnsCache()	Get whole dns cache info DnsCache including cache and negative cache.
static List<DnsCacheEntry>	listDnsCache()	Get dns cache entries, without negative cache.
static List<DnsCacheEntry>	listDnsNegativeCache()	Get dns negative cache entries.
static void	loadDnsCacheConfig()	Load dns config from properties file dns-cache.properties on classpath, then set to dns cache.
static void	loadDnsCacheConfig(String propertiesFileName)	Load dns config from the specified properties file on classpath, then set dns cache.
static void	removeDnsCache(String host)	Remove dns cache entry(including cache and negative cache), cause lookup dns server for host after.
static void	setDnsCache(long expireMillis, String host, String... ips)	Set a dns cache entry.
static void	setDnsCache(String host, String... ips)	Set a never expired dns cache entry.
static void	setDnsCache(Properties properties)	Set dns cache entries by properties.
static void	setDnsCachePolicy(int cacheSeconds)	Set JVM DNS cache policy.
static void	setDnsNegativeCachePolicy(int negativeCacheSeconds)	Set JVM DNS negative cache policy.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

setDnsCache

public static void setDnsCache(String host,
                               String... ips)

Set a never expired dns cache entry.

Parameters:

host - host

ips - ips

Throws:

DnsCacheManipulatorException - Operation fail

See Also:

setDnsCache(long, java.lang.String, java.lang.String...)

setDnsCache

public static void setDnsCache(long expireMillis,
                               String host,
                               String... ips)

Set a dns cache entry.

Parameters:

expireMillis - expire time in milliseconds.

host - host

ips - ips

Throws:

DnsCacheManipulatorException - Operation fail

setDnsCache

public static void setDnsCache(Properties properties)

Set dns cache entries by properties.

Parameters:

properties - input properties.
e.g. www.example.com=42.42.42.42,
or value is multiply ips seperated by comma www.example.com=42.42.42.42,43.43.43.43

Throws:

DnsCacheManipulatorException - Operation fail

loadDnsCacheConfig

public static void loadDnsCacheConfig()

Load dns config from properties file dns-cache.properties on classpath, then set to dns cache.

dns-cache.properties can be reset/customized by JVM -D option dcm.config.filename

Throws:

DnsCacheManipulatorException - Operation fail

See Also:

setDnsCache(java.util.Properties), loadDnsCacheConfig(java.lang.String)

loadDnsCacheConfig

public static void loadDnsCacheConfig(String propertiesFileName)

Load dns config from the specified properties file on classpath, then set dns cache.

Parameters:

propertiesFileName - specified properties file name on classpath.

Throws:

DnsCacheManipulatorException - Operation fail

See Also:

setDnsCache(java.util.Properties)

getDnsCache

@Nullable
public static DnsCacheEntry getDnsCache(String host)

Get a dns cache entry by host.

Returns:

dns cache. return null if no entry for host or dns cache is expired.

Throws:

DnsCacheManipulatorException - Operation fail

getWholeDnsCache

public static DnsCache getWholeDnsCache()

Get whole dns cache info DnsCache including cache and negative cache.

If you only need cache without negative cache use convenient method listDnsCache().

Returns:

dns cache entries

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.2.0

See Also:

listDnsCache()

listDnsCache

public static List<DnsCacheEntry> listDnsCache()

Get dns cache entries, without negative cache.

Same as getWholeDnsCache().getCache()

Returns:

dns cache entries

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.2.0

See Also:

getWholeDnsCache()

getAllDnsCache

@Deprecated
public static List<DnsCacheEntry> getAllDnsCache()

Deprecated.

this method name is confused: method name is "all" but without negative cache. use listDnsCache() instead.

Get dns cache entries, without negative cache.

Returns:

dns cache entries

Throws:

DnsCacheManipulatorException - Operation fail

listDnsNegativeCache

public static List<DnsCacheEntry> listDnsNegativeCache()

Get dns negative cache entries.

Same as getWholeDnsCache().getNegativeCache()

Returns:

dns negative cache entries

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.6.0

See Also:

getWholeDnsCache()

removeDnsCache

public static void removeDnsCache(String host)

Remove dns cache entry(including cache and negative cache), cause lookup dns server for host after.

Parameters:

host - host

Throws:

DnsCacheManipulatorException - Operation fail

See Also:

clearDnsCache()

clearDnsCache

public static void clearDnsCache()

Clear whole dns cache entries(including cache and negative cache), cause lookup dns server for all host after.

Throws:

DnsCacheManipulatorException - Operation fail

getDnsCachePolicy

public static int getDnsCachePolicy()

Get JVM DNS cache policy.

Returns:

cache seconds.

• InetAddressCachePolicy.FOREVER(-1) means never expired.(In effect, all negative value)
• InetAddressCachePolicy.NEVER(0) never cached.

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.3.0

See Also:

InetAddressCachePolicy.get(), InetAddressCachePolicy.FOREVER, InetAddressCachePolicy.NEVER, InetAddressCachePolicy.DEFAULT_POSITIVE

setDnsCachePolicy

public static void setDnsCachePolicy(int cacheSeconds)

Set JVM DNS cache policy.

NOTE: if Security Manage is turn on, JVM DNS cache policy set will not take effective. You can check by method getDnsCachePolicy().

Parameters:

cacheSeconds - set default dns cache time. Special input case:

• InetAddressCachePolicy.FOREVER(-1) means never expired.(In effect, all negative value)
• InetAddressCachePolicy.NEVER(0) never cached.

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.3.0

See Also:

InetAddressCachePolicy, InetAddressCachePolicy.cachePolicy, InetAddressCachePolicy.get(), InetAddressCachePolicy.FOREVER, InetAddressCachePolicy.NEVER, InetAddressCachePolicy.DEFAULT_POSITIVE

getDnsNegativeCachePolicy

public static int getDnsNegativeCachePolicy()

JVM DNS negative cache policy.

Returns:

negative cache seconds.

• InetAddressCachePolicy.FOREVER(-1) means never expired.(In effect, all negative value)
• InetAddressCachePolicy.NEVER(0) never cached.

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.3.0

See Also:

InetAddressCachePolicy.getNegative(), InetAddressCachePolicy.FOREVER, InetAddressCachePolicy.NEVER

setDnsNegativeCachePolicy

public static void setDnsNegativeCachePolicy(int negativeCacheSeconds)

Set JVM DNS negative cache policy.

Parameters:

negativeCacheSeconds - set default dns cache time. Special input case:

• InetAddressCachePolicy.FOREVER(-1) means never expired.(In effect, all negative value)
• InetAddressCachePolicy.NEVER(0) never cached.

Throws:

DnsCacheManipulatorException - Operation fail

Since:

1.3.0

See Also:

InetAddressCachePolicy, InetAddressCachePolicy.FOREVER, InetAddressCachePolicy.NEVER