openjdk编译
最近在学习java虚拟机的技术，尝试下手动编译openjdk
准备工作
- CentOS7 环境
- openjdk8 源码
- bootstrap jdk源码（我用的是openjdk 7）
注意事项：
-
目标jdk版本号比bootstrap jdk 大1
-
准备可能需要安装各种编译工具
```code
yum -y install build-essential gawk m4 libasound2-print-dev binutils libmotif3 libmotif-dev ant
yum install libX*
## 准备目标`jdk`和`bootstrap jdk`
```code
## 目标jdk，openjdk8
unzip openjdk-8-src-b132-03_mar_2014.zip
解压完成会得到一个openjdk文件夹，里面目录如下：
[root@localhost openjdk8]# ll
total 348
-rwxrwxrwx. 1 root root 1503 Mar 4 2014 ASSEMBLY_EXCEPTION
drwxr-xr-x. 3 root root 89 Oct 22 14:03 build
drwxrwxrwx. 6 root root 61 Mar 4 2014 common
-rwxrwxrwx. 1 root root 1235 Mar 4 2014 configure
drwxrwxrwx. 5 root root 157 Mar 4 2014 corba
-rwxrwxrwx. 1 root root 1384 Mar 4 2014 get_source.sh
drwxrwxrwx. 7 root root 182 Mar 4 2014 hotspot
drwxrwxrwx. 6 root root 232 Mar 4 2014 jaxp
drwxrwxrwx. 6 root root 232 Mar 4 2014 jaxws
drwxrwxrwx. 6 root root 169 Mar 4 2014 jdk
drwxrwxrwx. 6 root root 169 Mar 4 2014 langtools
-rwxrwxrwx. 1 root root 19263 Mar 4 2014 LICENSE
drwxrwxrwx. 6 root root 189 Mar 4 2014 make
-rwxrwxrwx. 1 root root 6430 Mar 4 2014 Makefile
drwxrwxrwx. 12 root root 275 Mar 4 2014 nashorn
-rwxrwxrwx. 1 root root 1549 Mar 4 2014 README
-rwxrwxrwx. 1 root root 129333 Mar 4 2014 README-builds.html
drwxrwxrwx. 2 root root 22 Mar 4 2014 test
-rwxrwxrwx. 1 root root 178445 Mar 4 2014 THIRD_PARTY_README
我这里为了方便区分，改名字成openjdk8
bootstrap jdk如下：
## openjdk7
[root@localhost java]# cd jdk1.7.0_80/
[root@localhost jdk1.7.0_80]# ll
total 19780
drwxr-xr-x. 2 10 143 4096 Apr 11 2015 bin
-r--r--r--. 1 10 143 3339 Apr 11 2015 COPYRIGHT
drwxr-xr-x. 4 10 143 122 Apr 11 2015 db
drwxr-xr-x. 3 10 143 132 Apr 11 2015 include
drwxr-xr-x. 5 10 143 185 Apr 11 2015 jre
drwxr-xr-x. 5 10 143 250 Apr 11 2015 lib
-r--r--r--. 1 10 143 40 Apr 11 2015 LICENSE
drwxr-xr-x. 4 10 143 47 Apr 11 2015 man
-r--r--r--. 1 10 143 114 Apr 11 2015 README.html
-rw-r--r--. 1 10 143 499 Apr 11 2015 release
-rw-r--r--. 1 10 143 19947513 Apr 11 2015 src.zip
-rw-r--r--. 1 10 143 110114 Mar 17 2015 THIRDPARTYLICENSEREADME-JAVAFX.txt
-r--r--r--. 1 10 143 173571 Apr 11 2015 THIRDPARTYLICENSEREADME.txt
[root@localhost jdk1.7.0_80]#
编译检查
进入openjdk8文件夹，执行命令./configure --with-boot-jdk=/root/java/jdk1.7.0_80 这里要指定编译的bootstrap jdk
进行编译检查
检查结束可能需要安装CCache：
wget https://www.samba.org//ftp/ccache/ccache-3.6.tar.xz
tar -xvf ccache-3.6.tar.xz
cd ccache-3.6
./configure -prefix=/var/ccache
make -j8
make install
ln -s /var/ccache/bin/ccache /usr/bin/ccache
再次执行编译检查
然后执行编译命令make all
等待40分钟，结果如下： 
测试编译出来的jdk是否可用
编译出来的jdk在目录如下中
/root/java/openjdk8/build/linux-x86_64-normal-server-release/images/j2sdk-image/bin
执行测试
[root@localhost bin]# ./java -version
openjdk version "1.8.0-internal"
OpenJDK Runtime Environment (build 1.8.0-internal-root_2019_10_22_14_11-b00)
OpenJDK 64-Bit Server VM (build 25.0-b70, mixed mode)
[root@localhost bin]#
搞一个HelloWorld
public class Hello{
public static void main(String[] args){
System.out.println("Hello");
}
}
编译运行
[root@localhost testjdk]# javac Hello.java
[root@localhost testjdk]# java Hello
Hello
[root@localhost testjdk]#
总结要点
- Building JDK 8 requires use of a version of JDK 7 that is at Update 7 or newer. JDK 8 developers should not use JDK 8 as the boot JDK, to ensure that JDK 8 dependencies are not introduced into the parts of the system that are built with JDK 7.
- 下载源码极度困难
- 编译耗时长
- 官方文档
- 官方文档
下载链接统一整理：
全部： 链接：https://pan.baidu.com/s/1V41RPhDKCq7jK8PVxBIVWQ 提取码：5ccy