Java 7u4发布,JRockit功能融合完毕

本文为WebLogic中文博客原创,禁止转载。日期:2012-04-29

美国时间2012年4月26日,甲骨文发布了Java 7u4(Java SE 7 Update 4),同时发布的还有JavaFX 2.1,该版本可通过网址http://www.oracle.com/technetwork/java/javase/downloads/index.html下载。至此,JRockit虚拟机的功能已经完整的融入到新的单一版本Oracle JVM中。

官方新闻地址:Oracle Releases Java SE 7 Update 4 and JavaFX 2.1 http://www.oracle.com/us/corporate/press/1603497

Java™ SE 7 Update 4

此次发布的更新包内部版本号为1.7.0_04-b20 (“b” 的含义是”build”). 外部版本号是7u4.

亮点

· Oracle JDK 正式支持 Mac OS X

· 新的JVM (Java HotSpot Virtual Machine, 版本 23)

· 新增垃圾收集器: Garbage First (G1)

· JavaFX 2.1 运行时将会在 JRE 7 自动更新时捆绑安装

· JAXP 升级至1.4.6

· Java DB 升级至10.8.2.2

· 针对SPARC T4 在安全领域进行了优化

· 解锁商业版功能的新参数

完整的更新内容可以查看 http://www.oracle.com/technetwork/java/javase/7u4-relnotes-1575007.html

关注下其中的新JVM(含JRockit功能),G1和Commercial Features:

New JVM (Java HotSpot Virtual Machine, version 23)

HotSpot 23 features JRockit JVM feature convergenceHotSpot 23已经完整的提供了JRockit JVM的功能集合). Some of the value-add features of the JRockit JVM are re-implemented in the HotSpot JVM. These features include:

· Text dumps with buffered data: buffered JVM state information available in text crash dumps and core/mdmp

· Diagnostics command framework (jcmd) and diagnostic commands

· Enhanced JMX Agent

Parallel Old GC (-XX:+UseParallelOldGC) is now enabled by default whenever -XX:+UseParallelGC is enabled. To revert to the previous default behavior, use the option -XX:-UseParallelOldGC on the java command line.

According to specification, the JVM should not maintain any particular order of methods being returned by reflection. In previous versions, the JVM used to return the methods in the declaration order and some user code may have relied on this behavior. Starting from Java SE 7, the JVM no longer guarantees constant order of methods and JMX MBeanInfo no longer guarantees equality of MBeanInfo between two identical MBeans.

New Supported Garbage Collector: Garbage First (G1)

Starting in Java SE 7u4 the Garbage First Collector is fully supported. The G1 collector is targeted for applications that fully utilize the large amount of memory available in today’s multiprocessor servers, while still keeping garbage collection latencies under control. Applications that require a large heap, have a big active data set, have bursty or non-uniform workloads or suffer from long Garbage Collection induced latencies should benefit from switching to G1. For more detailed information about G1 see the G1 documentation page and command line options.

Performance Tuning Examples

The following examples show how to use experimental tuning flags to optimize either throughput or faster response time.

Tuning for Higher Throughput

java -d64 -server -XX:+AggressiveOpts -XX:+UseLargePages -Xmn10g  -Xms26g -Xmx26g

Tuning for Lower Response Time

java -d64 -XX:+UseG1GC -Xms26g Xmx26g -XX:MaxGCPauseMillis=500 -XX:+PrintGCTimeStamps

New flag to unlock Commercial Features

The Java SE 7 Update 4 release introduces a new flag, -XX:+UnlockCommercialFeatures. This flag enables Oracle Java SE users to control when licensed features are allowed to run. All commercial features started or controlled via the command line or dynamically during execution will be gated by this flag. By default, commercial features are not allowed to execute, and any usage requires an active unlocking either on the command line or dynamically during runtime, to help remove any accidental usage.

For information on command line flags, see the command line documentation for Windows andSolaris/Linux platforms. For information about commercial features in Oracle Java SE and the license requirement please refer to Oracle Java SE Advanced and Suite, and the Binary Code License.

其它值得注意的是用户应尽快升级到Java 7,因为Oracle将在明年年底终止对JDK 6的支持:

Oracle Java SE Support Roadmap*


Major
Release

GA Date

Premier Support
Until**

Extended Support
Until**

Sustaining
Support


1.4

Feb 2002

Feb 2010

Feb 2013

Indefinite


5.0

May 2004

May 2011

May 2014

Indefinite


6

Dec 2006

Dec 2013

Dec 2016

Indefinite


7

July 2011

July 2016

July 2019

Indefinite


* Oracle Java SE commercial offering EOL dates are provided here as examples to illustrate the Oracle Java SE Support, Oracle Java SE Advanced, and Oracle Java SE Suite EOL Policy. Customers should refer to Oracle Lifetime Support policy for the most up-to-date information.

** Oracle will honor the support periods for legacy contracts with the dates stated in those contracts.

参考文档:

http://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html

http://docs.oracle.com/javase/7/docs/technotes/tools/solaris/java.html

http://www.oracle.com/technetwork/java/javase/terms/products/index.html

http://docs.oracle.com/javase/7/docs/technotes/guides/vm/index.html

Java Platform, Standard Edition

Java at Oracle

Java SE Downloads on OTN

Java SE 7 Update 4 Release Notes

JavaFX

JavaFX on OTN

OpenJDK Community

Planet JDK (JDK developer blogs)

Java Source Blog

Henrik on Java

The JavaFX Blog

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