JVM DNS IP地址缓存（InetAddress）

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于 2016-01-01 17:20:52 发布 · 6.2k 阅读

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本文介绍了JVM如何缓存IP地址，包括默认策略和自定义策略。默认情况下，正确解析的IP地址将永久缓存，错误解析的IP地址缓存10秒。自定义策略可以通过修改`java.security`文件、JVM启动参数或运行时使用`System`类进行调整。此外，文章还提出了使用单例模式操作`InetAddress`作为最佳实践。

一、JVM IP地址缓存

1. JVM默认策略

IP地址解析后缓存，LDNS、浏览器以及OS的hosts文件都会解析后缓存，因为一次DNS解析相对而言还是很耗时的。为了提高性能，JVM也会这么干。java.net.InetAddress类是IP地址的抽象，因此JVM对IP地址的默认缓存策略可以参看该类的注释。

InetAddress Caching

The InetAddress class has a cache to store successful as well as unsuccessful host name resolutions.
By default, when a security manager is installed, in order to protect against DNS spoofing attacks, the result of positive host name resolutions are cached forever. When a security manager is not installed, the default behavior is to cache entries for a finite (implementation dependent) period of time. The result of unsuccessful host name resolution is cached for a very short period of time (10 seconds) to improve performance.

If the default behavior is not desired, then a