JDK7 on non-RPM based Linux

JDK 7出來已經有一段時日了，官方網頁也貼心的提供了rpm的套件可以直接安裝，只可惜沒有deb可以下載。雖然如此，我們還是可以省略掉一些手法來同時使用系統提供的jdk6以及網路下載的jdk7--利用update-alternatives工具來達成。但是為了方便作說明，還是先安裝系統套件庫所提供的jdk6吧：

aptitude install sun-java6-jdk

下載適合自己的版本 x86或是x86_64之後，查看自己的java版本以及安裝在何處：

ls -l `which java`

發現原來是連結到/etc/alternatives裡：

lrwxrwxrwx 1 root root 22 2011-10-24 21:39 /usr/bin/java -> /etc/alternatives/java

利用update-alternatives來幫助我們作版本控制，使我們不用手動設定變數等複雜設定，也統一了管理介面。

ls -l /etc/alternatives/java

lrwxrwxrwx 1 root root 36 2011-10-24 21:39 /etc/alternatives/java -> /usr/lib/jvm/java-6-sun/jre/bin/java

所以結果揭曉：/usr/bin/java是來自於/etc/alternatives的一個軟連結，而這個軟連結源自於真正的java位置。所以我們看看他的狀態：

update-alternatives --display java

輸出結果可能會是：

java - auto mode
  link currently points to /usr/lib/jvm/java-6-sun/jre/bin/java
/usr/lib/jvm/java-6-sun/jre/bin/java - priority 63
  slave java.1.gz: /usr/lib/jvm/java-6-sun/jre/man/man1/java.1.gz
Current 'best' version is '/usr/lib/jvm/java-6-sun/jre/bin/java'.

所以我們也可以如法泡製，把下載來的jdk7放在/usr/lib/jvm底下。 請至oracle網站下載最新版本的jdk，假設是jdk-7u25-linux-x64.tar.gz

sudo tar zxvf jdk-7u25-linux-x64.tar.gz -C /usr/lib/jvm/

但此時update-alternatives的cache裡並不會自己發現有jdk的存在，這是安裝一個deb檔的postinst程序才會執行的部份。我們自己試著新增一個，語法如下：

update-alternatives --install <link> <name> <path> <priority>

通常priority大於1000比較有可能是首選。假設您下載了多個jdk7的版本且想要安裝到最新，可以利用下列script來達成：

#!/bin/bash ##setup-jdk.sh is going to help you install/remove current jdk. ## 2012.06.07 ## Author: Jim T. Tang (maxubuntu@gmail.com) arch=$(uname -m) if [ $arch == x86_64 ]; then ls -1 *x64.tar.gz || { echo "no target file was found."; exit 0; } target=$(ls *x64.tar.gz | tail -n1) ## decide newest version. subv=$(echo $target | awk -F- '{print $2}'| awk -Fu '{printf "%02d", $2}') ## decide subversion number. else ls -1 *i586.tar.gz || { echo "no target file was found."; exit 0; } target=$(ls *i586.tar.gz | tail -n1) ## decide newest version. subv=$(echo $target | awk -F- '{print $2}'| awk -Fu '{printf "%02d", $2}') ## decide subversion number. fi #------pre-define install function-------# doInstall(){ tar zxvf $target -C "/usr/lib/jvm" ##just install it... for items in appletviewer apt extcheck idlj jar jarsigner java javac javadoc \ javafxpackager javah javap java-rmi.cgi javaws jcmd jconsole jcontrol \ jdb jhat jinfo jmap jps jrunscript jsadebugd jstack jstat \ jstatd jvisualvm keytool native2ascii orbd pack200 policytool rmic rmid \ rmiregistry schemagen serialver servertool tnameserv unpack200 wsgen \ wsimport xjc; do ## alternatives --install <link> <name> <path> <priority> echo "update-alternatives --install /usr/bin/$items $items /usr/lib/jvm/jdk1.7.0_$subv/bin/$items 2000" update-alternatives --install /usr/bin/$items $items /usr/lib/jvm/jdk1.7.0_$subv/bin/$items 2000 done } #------pre-define remove function-------# doRemove(){ for items in appletviewer apt extcheck idlj jar jarsigner java javac javadoc \ javafxpackager javah javap java-rmi.cgi javaws jcmd jconsole jcontrol \ jdb jhat jinfo jmap jps jrunscript jsadebugd jstack jstat \ jstatd jvisualvm keytool native2ascii orbd pack200 policytool rmic rmid \ rmiregistry schemagen serialver servertool tnameserv unpack200 wsgen \ wsimport xjc; do ## alternatives --remove <name> <path> echo "update-alternatives --remove $items /usr/lib/jvm/jdk1.7.0_$subv/bin/$items" update-alternatives --remove $items /usr/lib/jvm/jdk1.7.0_$subv/bin/$items done rm -rf /usr/lib/jvm/jdk1.7.0_$subv } #------pre-define probe function-------# doProbe(){ [ -e "/usr/lib/jvm" ] || { ##/var/lib/jvm doesn't exits... mkdir "/usr/lib/jvm" doInstall; exit 0; } && { ##/var/lib/jvm do exist. check the subversion... lsubv=local subversion ##this test is for /var/lib/jvm do exist but /usr/lib/jvm/jdk1.7.0* doesn't. [ -e "$(ls -d /usr/lib/jvm/jdk1.7.0* 2>/dev/null)" ] && { lsubv=$(ls -d /usr/lib/jvm/jdk1.7.0*| awk -F_ '{print $2;}') } || { read -p "Do you wanna (I)nstall $target?" answer case $answer in I|i) doInstall;; *) echo "Do nothing."; exit 0;; esac exit 0; } ##if /usr/lib/jvm/jdk1.7.0* exists, check the subversion declare -i A=$(printf "%1d" $subv); declare -i B=$(printf "%1d" $lsubv); if [ "$A" -eq "$B" ]; then ## if same version of jdk... echo "jdk1.7.0_$subv has already being found." read -p "Do you wanna (I)nstall again or (R)emove it?" answer case $answer in I|i) doRemove && doInstall;; R|r) doRemove;; *) echo "Do nothing."; exit 0;; esac elif [ "$A" -gt "$B" ]; then ## if installed is newer...abort this installation echo "jdk1.7.0_$lsubv has being found newer than $target." read -p "Do you wanna (I)nstall anyway?" answer case $answer in I|i) doInstall;; *) echo "Do nothing."; exit 0;; esac else ## if installed is older...execute an installation echo "jdk1.7.0_$lsubv is not up-to-date. Install $target for you." doInstall; exit 0; fi } } #### main function#### if [ -z "$1" ]; then doProbe; elif [ "$1" == "-h" -o "$1" == "--help" ];then echo "$0 --remove to remove current version of JDK7." echo "$0 --help to print this help page." echo "$0 to execute an installation if jdk files were found." elif [ "$1" == "--remove" -o "$1" == "-r" ]; then doRemove; fi exit 0;

所以到此為止雖然我們都沒有透過dpkg或是aptitude來安裝jdk7，但是一樣可以作到版本控制，非常方便。

啟動Java plugins：
你可以點我有Java嗎？來測試Java plugin是否有安裝上去。在我的LinuxMint 11 amd64的版本裡，我即使安裝了sun-java6-plugin，無論是我的firefox 或是chrome都無法顯示成功啟動java plugin。
試試看這樣行不行得通：

cd /usr/lib/mozilla/plugins
ln -s /usr/lib/jvm/jdk1.7.0_25/jre/lib/amd64/libnpjp2.so .

如果是rpm-based linux，可以這麼做：

cd /usr/lib/mozilla/plugins
ln -s /usr/java/default/jre/lib/amd64/libnpjp2.so .

參考文章：
man update-alternatives

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