问题
I've just downloaded Oracle's Server JRE for Java SE 7 (link) The file I downloaded was server-jre-7u45-linux-x64.tar.gz. When I extracted this file I was surprised to find a directory named jdk1.7.0_45 was created containing the full java JDK. Not what I expected from a JRE install. What is going on here?
回答1:
The answer is in the description of the packages on the parent page:
JDK: (Java Development Kit). For Java Developers. Includes a complete JRE plus tools for developing, debugging, and monitoring Java applications.
Server JRE: (Server Java Runtime Environment) For deploying Java applications on servers. Includes tools for JVM monitoring and tools commonly required for server applications, but does not include browser integration (the Java plug-in), auto-update, nor an installer.
JRE: (Java Runtime Environment). Covers most end-users needs. Contains everything required to run Java applications on your system.
In the Server JRE case, "tools commonly required for server applications" includes some of the JDK tools. For instance, a web container (like Tomcat) needs to turn JSPs into compiled Java servlets, and this requires a callable Java compiler.
IMO, the benefit of using Server JRE is in what it DOES NOT include; i.e. the Java plugin which is a security nightmare (!) and auto-update which is bad for production service stability.
来源：https://stackoverflow.com/questions/21057365/oracles-server-jre-contains-jdk