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Joey
Joey

Reputation: 511

Advantages from Java JDK over JRE

Would someone be able to summarize all advantages from using Oracle Java JDK over JRE in a server environment (i.e. for Tomcat) for me? Using my prefered search engine I could only find fragments, which partially contradict themselves.

Upvotes: 0

Views: 476

Answers (2)

Kedar Mhaswade
Kedar Mhaswade

Reputation: 4695

My overall assessment of the situation is that what we get from these packages (JDK, JRE) is decided by the packaging team. To some extent, it is arbitrary. Let's see how, using the OpenJDK 7 packages on an Ubuntu system:

➜  ~  ls /usr/lib/jvm/java-7-openjdk-amd64/jre/bin
java  keytool  orbd  pack200  policytool  rmid  
rmiregistry  servertool  tnameserv  unpack200
➜  ~  ls /usr/lib/jvm/java-7-openjdk-amd64/bin    
appletviewer  idlj       java     javah         jcmd      jhat   jps         
jstack  keytool       pack200     rmid         serialver   unpack200  
xjc apt           jar        javac    javap         jconsole  jinfo  
jrunscript  jstat   native2ascii  policytool  rmiregistry  servertool  
wsgen extcheck      jarsigner  javadoc  java-rmi.cgi  jdb       jmap   
jsadebugd   jstatd  orbd          rmic        schemagen    tnameserv    
wsimport

The first location is because of the package openjdk-7-jre (Java Runtime Environment), whereas the second location is because of openjdk-7-jdk (Java Development Kit) package. The java in second listing is actually a symbolic link to the java file from the first listing.

You can thus see what the JDK team thinks is the difference between the JRE and JDK is by comparing the programs (executables) that you get as part of these packages.

For a long long time, I have been rather confused by the choice of programs that are part of these packages. For instance, I have always missed the excellent serviceability tools like jps, jstack, and jhat, jmap when I installed only the JRE. These tools are very useful to diagnose a Java runtime and yet, they are not a part of the JRE. One has to, rather inexplicably, install the JDK in order to get these tools. Like others have pointed out, javac, the Java compiler definitely belongs to the JDK.

In general, I have come to the conclusion that one should install the JDK (the superset) and not the JRE on the target system, unless there are some space issues.

Upvotes: 1

Matteo Baldi
Matteo Baldi

Reputation: 5828

Tomcat has a bundled java compiler, so it works fine with just JRE. And less things you have on your server, the safer you are.

Upvotes: 0

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