I have a small application written in Java that was tested and ran on a JRE_1.6. Now I need to run it against a JRE_1.5. I altered the source code I had to match Java 1.5 requirements and the project compiled fine.
The problem is that it uses a number of precompiled libraries like opencsv-2.3 and those were compiled with Java 1.6, so calling any of their classes results in a java.lang.UnsupportedClassVersionError.
Most of them are com.apache libs + opencsv-2.3 + org.jdom
How can I figure out which libraries exactly need to be replaced? How can I replace the libraries that need it?
Upd: the how can I replace part actually stands for "what can be done if there is no older library?" Is there a way to downgrade a compiled library or do I need to find a similar solution on 1.5 and rewrite the code?
I suggest you look in the manifest for each library for lines like
Bundle-RequiredExecutionEnvironment: J2SE-1.3
X-Compile-Target-JDK: 1.5
Build-Jdk: 1.5.0_22
Created-By: 1.6.0_21-b07 (Sun Microsystems Inc.)
I would only take the create by if no other option appears.
The only way to know for sure is to example a class in the library (assuming all classes where built for the same version)
javap -v -classpath net\sf\trove4j\trove4j\3.0.2\trove4j-3.0.2.jar gnu/trove/list/TLongList | grep version
minor version: 0
major version: 49
A table of versions are
major minor Java platform version
45 3 1.0
45 3 1.1
46 0 1.2
47 0 1.3
48 0 1.4
49 0 1.5
50 0 1.6
51 0 1.7
52 0 1.8
For more details http://en.wikipedia.org/wiki/Java_class_file