在user.properties中，可以使用以下属性：
- search_paths
- user.classpath
- plugin_dependency_paths
search_paths：
List of paths (separated by ;) to search for additional JMeter plugin classes, for example new GUI elements and samplers. A path item can either be a jar file or a directory. Any jar file in such a directory will be automatically included, jar files in sub directories are ignored. The given value is in addition to any jars found in the lib/ext directory. Do not use this for utility or plugin dependency jars.
user.classpath：
List of paths that JMeter will search for utility and plugin dependency classes. Use your platform path separator to separate multiple paths. A path item can either be a jar file or a directory. Any jar file in such a directory will be automatically included, jar files in sub directories are ignored. The given value is in addition to any jars found in the lib directory. All entries will be added to the class path of the system class loader and also to the path of the JMeter internal loader. Paths with spaces may cause problems for the JVM
plugin_dependency_paths：
List of paths (separated by ;) that JMeter will search for utility and plugin dependency classes. A path item can either be a jar file or a directory. Any jar file in such a directory will be automatically included, jar files in sub directories are ignored. The given value is in addition to any jars found in the lib directory or given by the user.classpath property. All entries will be added to the path of the JMeter internal loader only. For plugin dependencies using plugin_dependency_paths should be preferred over user.classpath.
