Java obtains generic types

Java method for retrieving generic types: Generally, a generic type name is obtained, assembled, and a Bean is obtained from the spring container Based on the name. For example, [java] @ Service ("baseService ") public class BaseService <T> implements BaseMapper <T> {private String mapper; @ Override public int insert (T t) {BaseMapper <T> baseMapper = (BaseMapper) SysConfigHelper. getAppContext (). getBean (t. getClass (). getSimpleName (). toLowerCase () + "Mapper"); return baseMapper. insert (t) ;}}like the above T, you can get the T type value as User, that is, t. getClass (). getSimpleName (). the result of toLowerCase () + "Mapper" is [userMapper], but when the delete method is used, this method is not applicable to [java] <pre name = "code" class = "java"> @ Override public int deleteById (int id) {T t = null; baseMapper <T> baseMapper = (BaseMapper) SysConfigHelper. getAppContext (). getBean (t. getClass (). getSimpleName (). toLowerCase () + "Mapper"); return baseMapper. deleteById (id) ;}</pre> in this way, an exception is thrown, because t is nul. We can write [java] @ Override public int update (T t) {Type type = getClass (). getGenericSuperclass (); Type trueType = (ParameterizedType) type ). getActualTypeArguments () [0]; Class <T> entityClass = (Class <T>) trueType; System. out. println (type); System. out. println (trueType); System. out. println (entityClass. getSimpleName (); BaseMapper <T> baseMapper = (BaseMapper) SysConfigHelper. getAppContext (). getBean (entityClass. getSimpleName (). toLowerCase () + "Mapper"); return baseMapper. update (t);} The result printed on the console is: [java] com. zte. framework. jdbc. baseService <com. zte. user. domain. user> class com. zte. user. domain. the User obtains the generic T type. The value is [User]