Ask Hibernate about your update history!

Firstload();

And then .update();

He doesn't care who you're going to change, because hibernate is manipulating objects directly, not database records, so who you're going to change, you're going to tell him about the record, so load or get so he knows which record you're going to do with.

First of all, you should provide an entity identifier that corresponds to the primary key in the relational database, see that your program seems to be running under c s, in addition, you also need to provide those corresponding fields in the database that cannot be empty, that is, you need to set the corresponding properties of this entity object, and then update.

The idea is that if you find this record first, then in Hibernate the record is an object, so you find this object first and then update it

It is better to load the value in the assignment first:

hql = "from user as u set ? where ?"

setparameter(0,setparameter(1,executeupdate();

First of all, understand what Hibernate does:

1. It is to store the things of the object model (entity class) in the relational model, 2. The class in the entity corresponds to a table in the relational library, 3. An attribute in the entity class corresponds to a column in the relational database table.

4. An instance of the entity class corresponds to a record in a relational database table.

Critical: %%Save object data to the database, read database data into the object

Secondly, understand the reason why Hibernate exists:

1. Solve the problem of impedance mismatch;

2. There is no complete object-oriented database (all of them are relational databases);

3. JDBC operation database is very cumbersome.

4. SQL statement writing is not object-oriented.

5. Associationss can be established between objects and relational tables to simplify programming.

Finally know the scope of use of hibernate:

1.For a certain object, it is more appropriate to simply load and modify it, and the modification is only for a single object (rather than modifying it in batches);

2.There is a clear relationship between objects (e.g., multiple users belong to a group (many-to-one), a group has multiple users (one-to-many));

3.Clustering operations: Hibernate is not suitable for batch addition and modification (o mapping frameworks are not suitable for use);

4.It is not suitable for use when specific functions in the database are required, because Hibernate does not use SQL statements;

As for what you said, then the mapping files, those are all dead, you just got started, it feels difficult, and when you write more, you will find that those things are basically fixed patterns, and you won't check them.