Chapter 3 JPA problems

[yiyinggang]

1. spring.jpa.defer-datasource-initialization=true needs to be added to application.properties, otherwise the data.sql will not be executed when spring boot starts.
2. Add drop table if exists {tablename} cascade; before every create table statement. Change {tablename} to the name of the table being created. This can avoid some problems caused by tables still existing in the memory.
3. The Type type field of Ingredient entity class should be annotated with @Enumerated(EnumType.STRING), otherwise you'll probably encounter NumberFormatException.