Java 8新特性探究（八）精简的JRE详解

缺乏、安全感 2022-08-26 03:56 2阅读 0赞

摘要  详细解释compact profile相关知识,字面上翻译是紧凑的配置文件，但我认为紧凑的JRE更容易理解，或者精简的JRE

目录\[-\]

*  [好处][Link 1]
 *  [概念][Link 2]
 *  [使用javac根据profile编译应用程序][javac_profile]
 *  [使用工具开发的效果][Link 3]
 *  [JPEDS工具使用][JPEDS]
 *  [在linux上构建profile][linux_profile]
 *  [编译后compact大致的占用空间 ][compact]
 *  [总结][Link 4]

Oracle公司如期发布了Java 8正式版！没有让广大javaer失望。对于一个人来说，18岁是人生的转折点，从稚嫩走向成熟，法律意味着你是完全民事行为能力人，不再收益于未成年人保护法，到今年为止，java也走过了18年，java8是一个新的里程碑，带来了前所未有的诸多特性，lambda表达式，Stream API，新的Date time api，多核并发支持，重大安全问题改进等，相信java会越来越好，丰富的类库以及庞大的开源生态环境是其他语言所不具备的，说起丰富的类库，很多同学就吐槽了，java该减肥了，确实是该减肥，java8有个很好的特性，即JEP161([http://openjdk.java.net/jeps/161][http_openjdk.java.net_jeps_161] ),该特性定义了Java SE平台规范的一些子集，使java应用程序不需要整个JRE平台即可部署和运行在小型设备上。开发人员可以基于目标硬件的可用资源选择一个合适的JRE运行环境。

# 好处 #

1.更小的Java环境需要更少的计算资源。

2.一个较小的运行时环境可以更好的优化性能和启动时间。

3.消除未使用的代码从安全的角度总是好的。

4.这些打包的应用程序可以下载速度更快。

# 概念    #

紧凑的JRE分3种，分别是compact1、compact2、compact3，他们的关系是compact1<compact2<compact3,他们包含的API如下图所示

[![234651_o8nK_1028150.png][]][234651_o8nK_1028150.png]

# 使用javac根据profile编译应用程序 #

javac –bootclasspath, or javac –profile <profile>

如果不符合compact的api，则报错。

# 使用工具开发的效果    #

[![000844_kr6c_1028150.png][]][000844_kr6c_1028150.png]

# JPEDS工具使用 #

java8新增一个工具，用来分析应用程序所依赖的profile，有三个参数比较常用 -p，-v，-r

# 在linux上构建profile #

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# 编译后compact大致的占用空间  #

[![002445_qWal_1028150.png][]][002445_qWal_1028150.png]

# 总结 #

如今，物联网正风行一时。我们看到大量不同的设备在市场上出现，每一种的更新速度都越来越快。java需要一个占用资源少的JRE运行环境，紧凑的JRE特性的出现，希望能带来以后的物联网的发展，甚至还是会有大量的java应用程序出现在物联网上面。目前oracle也发布了针对raspberry pi的JRE了。

另外该特性也是为java9的模块化项目做准备，模块化特性是javaer所期待的特性。他是解决业务系统复杂度的一个利器，当然OSGI也是相当的出色。但osgi对于新学者来说未免太复杂了。

[Link 1]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_1
[Link 2]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_2
[javac_profile]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_3
[Link 3]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_4
[JPEDS]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_5
[linux_profile]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_6
[compact]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_7
[Link 4]: http://my.oschina.net/benhaile/blog/211804#OSC_h1_8
[http_openjdk.java.net_jeps_161]: http://openjdk.java.net/jeps/161
[234651_o8nK_1028150.png]: /images/20220824/2a1d0734beef4b1895978ba6f4296f8e.png
[000844_kr6c_1028150.png]: /images/20220824/7b60db6d75fd43babcc2bab02200f9b1.png
[002445_qWal_1028150.png]: /images/20220824/24f5173f593f418ebccc367c4ee02a55.png