code: public void setCompileVersion(String version) {
          if (version == null || ClassUtils.isBeforeJava6(version)) {
              JavassistCompiler javassistCompiler = new JavassistCompiler();
              javassistCompiler.setLogger(logger);
              javassistCompiler.setCodeDirectory(codeDirectory);
              compiler = javassistCompiler;
          } else {
              JdkCompiler jdkCompiler = new JdkCompiler();
              jdkCompiler.setCompileVersion(version);
              jdkCompiler.setLogger(logger);
              jdkCompiler.setCodeDirectory(codeDirectory);
              compiler = jdkCompiler;
          }
      }
docs: httl.properties: compile.version=1.7