code: public Class<?> getEntityClass(MappedStatement ms) {
          String msId = ms.getId();
          if (entityClassMap.containsKey(msId)) {
              return entityClassMap.get(msId);
          } else {
              Class<?> mapperClass = getMapperClass(msId);
              Type[] types = mapperClass.getGenericInterfaces();
              for (Type type : types) {
                  if (type instanceof ParameterizedType) {
                      ParameterizedType t = (ParameterizedType) type;
                      if (t.getRawType() == this.mapperClass || this.mapperClass.isAssignableFrom((Class<?>) t.getRawType())) {
                          Class<?> returnType = (Class<?>) t.getActualTypeArguments()[0];
                          //获取该类型后，第一次对该类型进行初始化
                          EntityHelper.initEntityNameMap(returnType, mapperHelper.getConfig());
                          entityClassMap.put(msId, returnType);
                          return returnType;
                      }
                  }
              }
          }
          throw new MapperException("无法获取 " + msId + " 方法的泛型信息!");
      }
docs: 获取返回值类型 - 实体类型
  
  @param ms
  @return