////
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
////

Try performing some basic CRUD (Create/Read/Update/Delete) operations.


=== Create


To create a domain class use Map constructor to set its properties and call <<ref-domain-classes-save,save>>:

[source,groovy]
----
def p = new Person(name: "Fred", age: 40, lastVisit: new Date())
p.save()
----

The <<ref-domain-classes-save,save>> method will persist your class to the database using the underlying Hibernate ORM layer.


=== Read


Grails transparently adds an implicit `id` property to your domain class which you can use for retrieval:

[source,groovy]
----
def p = Person.get(1)
assert 1 == p.id
----

This uses the <<ref-domain-classes-get,get>> method that expects a database identifier to read the `Person` object back from the database.
You can also load an object in a read-only state by using the <<ref-domain-classes-read,read>> method:

[source,groovy]
----
def p = Person.read(1)
----

In this case the underlying Hibernate engine will not do any dirty checking and the object will not be persisted. Note that
if you explicitly call the <<ref-domain-classes-save,save>> method then the object is placed back into a read-write state.

In addition, you can also load a proxy for an instance by using the <<ref-domain-classes-load,load>> method:

[source,groovy]
----
def p = Person.load(1)
----

This incurs no database access until a method other than getId() is called. Hibernate then initializes the proxied instance, or
throws an exception if no record is found for the specified id.


=== Update


To update an instance, change some properties and then call <<ref-domain-classes-save,save>> again:

[source,groovy]
----
def p = Person.get(1)
p.name = "Bob"
p.save()
----


=== Delete


To delete an instance use the <<ref-domain-classes-delete,delete>> method:

[source,groovy]
----
def p = Person.get(1)
p.delete()
----




