How do I update a certain field of a Model in Playframework?

问题

Suppose we have a User class, if I want to update it's name:

User user = User.findById(123); user.name = "someone"; user.save();

The generated SQL would be

update user as user0 set user0.name = ? user0.email = ? .....

That means Play didn't realize I just want to update a single field. Is there any way could make the generated SQL only update the specified fields ?

回答1:

Info: this is answer for Play 2 + Ebean! so it DOES NOT work with Play 1 + JPA

There are some options in Ebean's API, so you should check it and choose one:

• Update<T> - check in the sample for @NamedUpdates annotation
• Ebean.createUpdate(beanType, updStatement)
• SqlUpdate - you can just perform raw SQL update, without need for giving the entity type

回答2:

This is dependent on whether Play (or actually Avaje Ebean) actually tracks which of the fields are changed. It's simpler to update all of the fields instead.

This isn't an issue performance-wise either, so I wouldn't waste too much time looking for a solution.

回答3:

You can use hibernate's dynamic update feature : http://www.mkyong.com/hibernate/hibernate-dynamic-update-attribute-example/

But remember that this have negative impact on performance as database cannot cache statements. See here for others explanations : Hibernate : dynamic-update dynamic-insert - Performance Effects

来源：https://stackoverflow.com/questions/17439364/how-do-i-update-a-certain-field-of-a-model-in-playframework